In a refrigeration system, normal discharge pressure is defined as the pressure at which condensation takes place as per the design
At the normal discharge pressure, it is assumed that the refrigeration would be most energy efficient and there would be no fouling in the condensing circuit. Operating a compressor at significantly away from the normal discharge pressure values might be detrimental to compressor’s health.
For a compressor to operate at normal discharge pressure, following must be fulfilled:
Right amount of refrigerant: The quantity of the refrigerant loaded must be correct. Too high a refrigerant load increases the discharge pressure and too low a refrigerant load decreases the discharge pressure.
Both suction and discharge valves of compressor must be leak proof: If the discharge valve is passing a part of refrigerant would sneak back into the cylinder and keep recirculating inside the compressor increasing the discharge temperature and reducing the discharge pressure.Similarly, if the suction valve is passing there will be malfunction in the compressor upstroke.
The compressor piston rings should not leak: IF the discharge gases leaks through the piston rings it leads to lower discharge pressure.
Condenser should not be in fouled condition: A fouled condenser leads to higher discharge pressure because of inefficient cooling
Sufficient cooling utility: Even if the condenser is fine, insufficient cooling water flow and temperature for a water cooled system and high ambient temperature for air cooled system may lead to higher than normal discharge temperatures.
What is Normal Discharge Pressure?
Normal discharge pressure is defined as the pressure at the discharge of refrigeration compressor, for which the refrigeration system is designed.
Since at the discharge of the refrigeration compressor the condenser is located, normal discharge pressure can also be defined as the pressure at which the refrigerant condenses with specified amount of sub-cooling at the available cooling utility.
Air Conditioning Cycle and Circuit Diagram;Image Credit: wikipedia
Thus, the normal discharge pressure depends upon the refrigeration system, which includes the refrigerant in use and temperature of cooling utility.
If cooling utility is air, the discharge pressure would depend on specified ambient air temperature and it cooling utility is water, then it shall depend upon the available cooling water temperature.
Vapor Compression Refrigeration Cycle; Image Credit: Credit: wikipedia
The discharge pressure would also depend upon the type of refrigerant use.
The efficiency of refrigeration system in terms of power consumption are highest when operating at normal discharge pressure providing optimum cooling capacity for which it is designed.
However, for example, normally the Ammonia based refrigeration systems are designed for normal discharge pressures of 95-100 Psig.
Normal Discharge Pressure Cause
Normal discharge pressure is the default pressure of a refrigeration system and it is more important to ponder what causes the discharge pressure to increase.
Speaking of normal discharge pressure, from energy conservation point of view it is however always preferred to have a discharge pressure lower than the normal. Lowering discharge pressure requires higher cooling duty to condense the refrigerant.
As a thumb rule for each °F decrease in condensing temperature, compressor power consumption decreases by 1%.
There are several causes that can lead to higher than normal discharge pressure. The primary and most common among them is the fouling of the condenser coils. Fouled condenser coils leads to lower cooling of refrigerant cause higher back pressure to the compressor.
The second common cause of higher discharge pressure, is topping up of higher than required refrigerant into the system. Higher refrigerant load makes a part of condenser ineffective by reducing the condensing area.
This leads to higher sub-cooling of refrigerant but higher back-pressure to compressor due to lower effective condensing surface area.
The third but less common condesnder malfunction leading to higher back-pressure to the compressor , is build-up of non-condensable in the refrigeration system.
Low suction pressure and Normal Discharge Pressure
The easiest way to detect low suction pressure in a refrigeration compressor is to look for frosting in the suction line.
The frosting in the suction line happens due to excessive cooling as a result of lower refrigerant flow. Lower refrigerant flow can also happen due to minor leaks in the system taking place over a long period of time.
There are other reasons too which may lead to lower suction pressure. If the suction line or liquid line is made too long or installation of these lines are such that it leads to a pressure drop large enough to cause the liquid flash upstream of the expansion valve.
The expansion valve is normally designed to allow liquid flow and if vapor is encountered instead, the amount of refrigerant would be lower than design thus reducing the suction pressure.
Similarly, an inadequately sized suction line can lead to lower suction pressure due to higher pressure drop.
Low suction pressure is also encountered because of low evaporator load. This may be because of fouling in air distribution system or circulating air being too cold.
How to calculate Discharge Pressure?
Discharge pressure or head pressure is the pressure generated on the output side of a gas compressor in a refrigeration or air conditioning system.
The discharge pressure of a refrigeration compressor can be calculated based on Cooling media availability and desired temperature drop of system being cooled.
For water cooled systems, the discharge pressure requirements are generally lower than air cooled systems for same indoor temperature.
Consider the case of a R-22 refrigerant system, where the ambient temperature is 95°F and indoor temperature to be maintained is 85°C. As a thumb rule, the condensing temperature can be considered to be 30° F + Amb = 125°F. The corresponding saturation pressure for R-22 refrigerant is 279 psi from the R-22 Pressure temperature chart.
Rack and pinion is a mechanical system that is widely used in various applications, ranging from steering systems in automobiles to industrial machinery. It is a simple yet effective mechanism that converts rotational motion into linear motion. In this section, we will explore the definition and function of rack and pinion, as well as its working principle.
Definition and function of Rack and Pinion
A rack and pinion is a type of gear mechanism that consists of a toothed bar, known as the rack, and a gear, known as the pinion. The rack has straight teeth that mesh with the teeth of the pinion, allowing for smooth and precise motion transfer.
The primary function of a rack and pinion system is to convert rotational motion into linear motion. When the pinion gear rotates, it engages with the teeth of the rack, causing the rack to move in a linear direction. This linear motion can be used to perform various tasks, such as steering a vehicle or moving a load in an industrial setting.
One of the most common applications of rack and pinion is in the steering systems of automobiles. In a rack and pinion steering system, the rotational motion of the steering wheel is transferred to the pinion gear, which then moves the rack back and forth. This motion is transmitted to the wheels, allowing the driver to control the direction of the vehicle.
Rack and pinion systems are also used in other applications, such as robotics, CNC machines, and conveyor systems. In these cases, the linear motion provided by the rack and pinion mechanism is utilized to move objects or perform specific tasks with precision and accuracy.
Working principle of Rack and Pinion
The working principle of a rack and pinion system is relatively straightforward. When the pinion gear rotates, its teeth engage with the teeth of the rack, causing the rack to move in a linear direction.
To understand this principle better, imagine a scenario where you have a rack and pinion mechanism with a stationary rack and a rotating pinion. As the pinion gear rotates, its teeth push against the teeth of the rack, causing the rack to move in the direction determined by the rotation of the pinion.
The direction of the linear motion depends on the orientation of the teeth on the rack and pinion. If the teeth are angled in a way that the pinion rotates clockwise, the rack will move in one direction. Conversely, if the teeth are angled in a way that the pinion rotates counterclockwise, the rack will move in the opposite direction.
The precision and smoothness of the motion in a rack and pinion system are determined by the quality of the gear teeth and the lubrication used. Proper maintenance and regular inspection of the rack and pinion mechanism are essential to ensure optimal performance and longevity.
Applications of Rack and Pinion
Rack and pinion systems are widely used in various applications due to their simplicity, efficiency, and reliability. Let’s explore some of the common areas where rack and pinion mechanisms find their application.
Steering Mechanism
One of the most well-known applications of rack and pinion is in the steering systems of vehicles. In this mechanism, the rack is a linear gear that meshes with a pinion gear attached to the steering column. As the driver turns the steering wheel, the pinion gear rotates, causing the rack to move linearly. This linear motion is then translated into the rotational motion of the vehicle’s wheels, allowing for precise control and maneuverability.
Rack and pinion steering systems offer several advantages over other steering mechanisms. They provide a direct and responsive steering feel, making it easier for drivers to navigate tight turns and parking spaces. Additionally, rack and pinion systems are compact, lightweight, and require minimal maintenance, making them ideal for a wide range of vehicles, from small cars to heavy-duty trucks.
Rack and pinion mechanisms are extensively used in various industrial machinery applications. These systems are commonly employed in machine tools, such as milling machines, lathes, and CNC routers, to convert rotary motion into linear motion. By coupling a pinion gear to a rack, these machines can accurately position and move their cutting tools or workpieces along a linear axis.
The precise and repeatable motion provided by rack and pinion systems makes them suitable for applications that require high accuracy and tight tolerances. Industries such as manufacturing, woodworking, metalworking, and automation heavily rely on rack and pinion mechanisms to achieve efficient and precise operations.
Transportation Systems
Rack and pinion systems also play a crucial role in various transportation systems, particularly in funicular railways and cable cars. In these systems, a rack railway is used to provide traction and control the movement of the vehicles. The pinion gear, driven by an electric motor or hydraulic system, engages with the rack, allowing the vehicles to ascend or descend steep slopes safely.
The use of rack and pinion in transportation systems ensures reliable and secure operation, even in challenging terrains. These mechanisms offer excellent traction, preventing slippage and ensuring the safety of passengers and cargo. Additionally, rack and pinion systems enable precise speed control and smooth acceleration and deceleration, enhancing the overall comfort and efficiency of the transportation system.
Other Applications
Apart from the aforementioned examples, rack and pinion mechanisms find applications in various other fields. Some notable examples include:
Robotics: Rack and pinion systems are often utilized in robotic arms and manipulators to achieve precise and controlled movements.
Elevators: Rack and pinion systems are employed in elevator mechanisms to facilitate vertical transportation in buildings and other structures.
Material Handling: Rack and pinion systems are utilized in conveyor systems, cranes, and hoists to move heavy loads efficiently and safely.
Stage and Theater Equipment: Rack and pinion mechanisms are commonly used in stage curtains, scenery movement, and other theatrical applications.
Advantages and Disadvantages of Rack and Pinion
Rack and pinion is a popular mechanism used in various applications, ranging from steering systems in automobiles to industrial machinery. This mechanism offers several advantages and disadvantages, which we will explore in this section.
Advantages
Rack and pinion systems provide numerous benefits that make them a preferred choice in many applications. Let’s take a closer look at some of these advantages:
Simplicity and Efficiency: One of the key advantages of rack and pinion is its simple design. The mechanism consists of a rack (a linear gear) and a pinion (a circular gear). This simplicity allows for easy installation and maintenance. Moreover, the direct transfer of motion from the pinion to the rack ensures high efficiency, minimizing energy loss.
Precise and Responsive: Rack and pinion systems offer excellent precision and responsiveness. The direct contact between the rack and pinion results in immediate and accurate motion transfer. This makes rack and pinion ideal for applications that require precise control, such as steering systems in vehicles.
Compact Size: Rack and pinion mechanisms are compact, making them suitable for applications with limited space. The linear motion of the rack allows for a more compact design compared to other types of gear systems. This advantage is particularly valuable in industries where space optimization is crucial.
Smooth Operation: Rack and pinion systems provide smooth and uniform motion. The teeth of the pinion engage with the rack, ensuring a consistent transfer of force. This smooth operation reduces noise and vibration, enhancing the overall user experience.
Versatility: Rack and pinion mechanisms find applications in a wide range of industries. From steering systems in automobiles to robotics, CNC machines, and even elevators, the versatility of rack and pinion makes it a popular choice across different sectors.
Disadvantages
While rack and pinion systems offer numerous advantages, they also have a few limitations. Let’s explore some of the disadvantages associated with this mechanism:
Limited Load Capacity: Rack and pinion systems may have limitations when it comes to handling heavy loads. The teeth of the pinion and rack can experience excessive wear and tear under high loads, leading to reduced lifespan and potential failure. In such cases, alternative mechanisms, such as ball screws or hydraulic systems, may be more suitable.
Backlash: Backlash refers to the slight play or clearance between the teeth of the rack and pinion. This can result in a small amount of lost motion or imprecision. While modern rack and pinion systems have minimized backlash, it can still be a concern in applications that require extremely precise positioning.
Maintenance: Although rack and pinion systems are relatively easy to install and maintain, they do require periodic lubrication to ensure smooth operation and prevent premature wear. Failure to perform regular maintenance can lead to increased friction, noise, and reduced lifespan of the mechanism.
Cost: Depending on the specific application and requirements, rack and pinion systems can be more expensive compared to other alternatives. Factors such as material quality, precision, and load capacity can influence the overall cost. It is important to carefully consider the cost-benefit ratio when choosing rack and pinion for a particular application.
Rack and pinion systems are widely used in various applications due to their simplicity and effectiveness. There are different types of rack and pinion mechanisms, each with its own unique characteristics and advantages. Let’s explore some of the most common examples:
Straight Teeth
One of the simplest and most commonly used types of rack and pinion is the straight teeth design. In this configuration, the pinion gear has straight teeth that mesh with a straight rack. This type of rack and pinion mechanism provides a smooth and efficient transfer of motion.
The straight teeth design is often used in applications where precision and accuracy are crucial, such as in CNC machines, robotics, and industrial automation. It offers excellent positioning capabilities and can handle heavy loads with ease. Additionally, the straight teeth design is relatively easy to manufacture and maintain.
Helical Teeth
Another popular variation of the rack and pinion mechanism is the helical teeth design. In this configuration, both the pinion gear and the rack have helical teeth that mesh together. The helical teeth are cut at an angle, allowing for a smoother and quieter operation compared to straight teeth.
The helical teeth design offers improved load-carrying capacity and higher efficiency due to the increased contact area between the gear and the rack. This makes it suitable for applications that require high-speed and high-torque operations, such as automotive steering systems and machine tools.
Roller Pinion
The roller pinion system is a unique variation of the rack and pinion mechanism that utilizes rollers instead of teeth. The rack consists of a series of rollers that engage with the pinion gear, which has matching grooves. This design provides a smooth and precise motion transfer with minimal backlash.
The roller pinion mechanism offers several advantages over traditional rack and pinion systems. It has a higher positional accuracy, lower friction, and longer lifespan due to reduced wear. This makes it ideal for applications that demand high precision and durability, such as in semiconductor manufacturing and medical equipment.
Design Considerations for Rack and Pinion
When it comes to designing a rack and pinion system, there are several important considerations to keep in mind. These considerations will help ensure that the system functions properly and efficiently. In this section, we will discuss two key design considerations: module and pitch, and pinion size and material.
Module and Pitch
The module and pitch of a rack and pinion system are crucial factors that determine the system’s performance and compatibility. The module refers to the size of the teeth on the gear, while the pitch is the distance between corresponding points on adjacent teeth. Let’s take a closer look at each of these considerations:
Module: The module of a rack and pinion system is determined by the size and strength requirements of the application. It is important to choose a module that can handle the load and torque requirements of the system. A larger module will generally result in a stronger and more durable system, but it may also increase the size and weight of the components. On the other hand, a smaller module can provide a more compact and lightweight system, but it may not be as robust. Therefore, it is crucial to strike a balance between strength and size when selecting the module for your rack and pinion system.
Pitch: The pitch of a rack and pinion system determines the smoothness of its operation. A smaller pitch will result in a finer resolution and smoother motion, but it may also reduce the system’s load-carrying capacity. Conversely, a larger pitch will provide a higher load-carrying capacity but may result in a less smooth motion. The pitch should be chosen based on the specific requirements of the application. For example, applications that require precise positioning, such as CNC machines, may benefit from a smaller pitch, while applications that require high load-carrying capacity, such as heavy machinery, may require a larger pitch.
Pinion Size and Material
The size and material of the pinion are also important considerations in rack and pinion system design. Let’s explore these factors in more detail:
Size: The size of the pinion is determined by the torque and load requirements of the system. A larger pinion can handle higher loads and torques, but it may also increase the size and weight of the system. On the other hand, a smaller pinion can provide a more compact and lightweight system, but it may have limitations in terms of load-carrying capacity. It is essential to select a pinion size that strikes a balance between the system’s requirements and the desired size and weight.
Material: The material of the pinion plays a crucial role in its durability and performance. Common materials used for pinions include steel, brass, and plastic. Steel pinions are known for their strength and durability, making them suitable for heavy-duty applications. Brass pinions offer good wear resistance and are often used in applications that require smooth and quiet operation. Plastic pinions, on the other hand, are lightweight and cost-effective, making them suitable for applications where weight and cost are important factors. The choice of pinion material should be based on the specific requirements of the application, considering factors such as load, speed, and environmental conditions.
Common Steering Rack Problems
The steering rack is a crucial component of a vehicle‘s steering system, responsible for converting the rotational motion of the steering wheel into the linear motion needed to turn the wheels. While rack and pinion steering systems are generally reliable, they can experience certain problems over time. In this section, we will explore some of the common steering rack problems that car owners may encounter.
1. Leaking Power Steering Fluid
One of the most common issues with a steering rack is a leak in the power steering system. Power steering fluid is essential for smooth and effortless steering, as it helps to reduce friction and provide hydraulic assistance. However, over time, the seals in the steering rack can wear out or become damaged, leading to fluid leakage.
When power steering fluid leaks from the rack, you may notice a puddle of fluid underneath your vehicle or a drop in the power steering fluid level. In addition, you may experience difficulty in steering, a whining noise when turning the wheel, or a jerky steering response. It is important to address a power steering fluid leak promptly, as low fluid levels can cause further damage to the steering system.
2. Excessive Play or Loose Steering
Another common problem with steering racks is excessive play or loose steering. This can occur due to wear and tear on the rack and pinion mechanism, which can lead to a gap between the teeth of the rack and the pinion gear. As a result, you may notice that the steering wheel feels loose or has a significant amount of play before the wheels respond to your input.
Excessive play in the steering can make the vehicle feel unstable and can affect your ability to control the direction of the vehicle. It is important to have this issue addressed by a qualified mechanic, as it may require replacing worn-out components or adjusting the steering system.
3. Uneven Tire Wear
A faulty steering rack can also cause uneven tire wear. When the steering rack is not functioning properly, it can result in the wheels being misaligned or not turning at the same rate. This can lead to uneven tire wear, with some tires wearing out faster than others.
Uneven tire wear not only affects the performance and handling of the vehicle but also reduces the lifespan of the tires. Regularly inspecting your tires for signs of uneven wear, such as excessive wear on the inner or outer edges, can help identify potential steering rack issues early on.
4. Steering Wheel Vibration
If you notice a vibration in the steering wheel while driving, it could be a sign of a problem with the steering rack. Steering wheel vibration can occur due to various reasons, including worn-out tie rod ends, misalignment, or a damaged steering rack.
A worn-out or damaged steering rack can cause the wheels to vibrate, especially at higher speeds. This vibration can be felt through the steering wheel, making the driving experience uncomfortable and potentially unsafe. It is important to have the steering system inspected and repaired if you experience steering wheel vibration.
5. Difficulty Turning or Stiff Steering
Difficulty turning the steering wheel or stiff steering is another common steering rack problem. This can be caused by various factors, such as a lack of power steering fluid, a malfunctioning power steering pump, or a worn-out steering rack.
If you find it challenging to turn the steering wheel, especially at low speeds or when parking, it is essential to have the steering system checked. Ignoring this issue can lead to further damage to the steering components and potentially compromise your safety on the road.
Examples of Rack and Pinion Gears in Everyday Life
Rack and pinion gears are widely used in various applications, ranging from car steering systems to industrial machinery. Let’s explore some common examples of how these gears are utilized in our everyday lives.
Car Steering Systems
One of the most well-known applications of rack and pinion gears is in car steering systems. In this setup, the steering wheel is connected to a pinion gear, which engages with a rack gear. As the driver turns the steering wheel, the pinion gear rotates, causing the rack gear to move either left or right. This motion is then transmitted to the car‘s wheels, allowing for precise control and maneuverability.
Elevators
Another example of rack and pinion gears in action can be found in elevators. Rack and pinion systems are often used to control the vertical movement of elevators. The pinion gear is connected to the elevator car, while the rack gear is fixed along the elevator shaft. When the pinion gear rotates, it moves the elevator car up or down along the rack gear, providing a smooth and reliable means of transportation between floors.
Measuring Instruments
Rack and pinion gears are also utilized in various measuring instruments, such as calipers and micrometers. These gears enable precise and accurate measurements by converting rotational motion into linear motion. By turning the pinion gear, the rack gear moves, allowing for precise adjustments and measurements to be made.
Industrial Machinery
In the realm of industrial machinery, rack and pinion gears play a crucial role in many applications. For example, they are commonly used in CNC machines, where they help control the movement of the cutting tool. By converting rotational motion into linear motion, rack and pinion gears enable precise and controlled movements, resulting in accurate machining operations.
Transportation Systems
Rack and pinion gears are also found in various transportation systems, such as funicular railways and tramways. These gears are used to control the movement of the vehicles along the tracks. The pinion gear engages with the rack gear, allowing for smooth and efficient transportation of passengers or goods.
Rack and pinion gears are often employed in gates and silos to control their opening and closing mechanisms. By rotating the pinion gear, the rack gear moves, enabling the precise positioning of gates or the controlled release of materials from silos. This ensures efficient operation and prevents any potential accidents or spillages.
Stair Lifts
Stair lifts, which are commonly used to assist individuals with mobility challenges, also rely on rack and pinion gears. These gears enable the smooth and controlled movement of the stair lift along the staircase. By turning the pinion gear, the rack gear moves, allowing for a safe and comfortable ascent or descent of the stairs.
Rack and pinion gears are frequently used in actuators, which are devices that convert electrical or hydraulic power into mechanical motion. These gears play a crucial role in translating the rotational motion of the actuator into linear motion, enabling precise control and movement in various applications, such as robotics and automation systems.
Woodworking and Metal Cutting Machines
In woodworking and metal cutting machines, rack and pinion gears are often employed to control the movement of the cutting tool or workpiece. By converting rotational motion into linear motion, these gears enable precise and controlled movements, resulting in accurate and efficient cutting operations.
How to Center a Rack and Pinion
If you’ve noticed that your vehicle’s steering feels off-center or imbalanced, it may be time to center your rack and pinion system. Centering the rack and pinion ensures that the steering wheel is aligned with the wheels, providing a smooth and controlled driving experience. Here are the steps to center the steering rack and pinion:
Locate the Adjustment Nut: Start by finding the adjustment nut on the rack and pinion assembly. This nut is typically located on the driver’s side of the vehicle, near the firewall. It may be covered by a rubber boot for protection.
Raise the Front Wheels: Use a jack to lift the front of the vehicle off the ground. Ensure that the vehicle is securely supported on jack stands before proceeding. This step is crucial to allow the wheels to move freely during the centering process.
Access the Adjustment Nut: Depending on the vehicle, you may need to remove any covers or panels to access the adjustment nut. Refer to the vehicle’s manual for specific instructions on how to access the nut.
Turn the Adjustment Nut: With the wheels off the ground and the adjustment nut accessible, use a wrench or socket to turn the nut. The direction in which you turn the nut will depend on the type of rack and pinion system in your vehicle. Consult the vehicle’s manual or a trusted mechanic for guidance.
Check the Steering Wheel Alignment: After making adjustments to the adjustment nut, lower the vehicle back to the ground. Sit in the driver’s seat and check the alignment of the steering wheel. It should now be centered and aligned with the wheels. If it is still off-center, repeat the adjustment process until the steering wheel is properly centered.
Test Drive: Take your vehicle for a test drive to ensure that the steering feels balanced and responsive. Pay attention to any unusual vibrations or noises, as these may indicate further issues with the rack and pinion system.
It’s important to note that centering a rack and pinion system requires precision and accuracy. If you’re unsure about performing this task yourself, it’s recommended to seek the assistance of a qualified mechanic. They have the expertise and specialized tools to ensure the rack and pinion is centered correctly.
By following these steps, you can effectively center your rack and pinion system, improving the overall steering performance of your vehicle. Remember to always prioritize safety and consult the vehicle’s manual for any specific instructions or precautions.
In order to understand how rack and pinion systems work, it’s important to have a grasp of the calculations involved in determining gear ratio and force transmission. Let’s take a look at an example calculation to illustrate these concepts.
Let’s say we have a rack and pinion mechanism that is being used in a steering system. The rack has 20 teeth, while the pinion has 4 teeth. We want to determine the gear ratio and the force transmitted when a force of 100 Newtons is applied to the pinion.
To calculate the gear ratio, we can use the formula:
Gear Ratio = Number of Teeth on Rack / Number of Teeth on Pinion
Plugging in the values from our example, the gear ratio would be:
Gear Ratio = 20 / 4 = 5
This means that for every revolution of the pinion, the rack will move 5 times.
Now let’s move on to calculating the force transmitted. The force transmitted can be determined using the formula:
Force Transmitted = Applied Force * Gear Ratio
Substituting the values from our example, we get:
Force Transmitted = 100 N * 5 = 500 N
Therefore, when a force of 100 Newtons is applied to the pinion, the rack will experience a force of 500 Newtons.
It’s important to note that these calculations are simplified examples and do not take into account factors such as friction and efficiency. In real-world applications, these factors need to be considered for accurate calculations.
By understanding these calculations, engineers and designers can determine the appropriate gear ratio and estimate the force that will be transmitted in a rack and pinion system. This knowledge is crucial in ensuring the system functions optimally and meets the desired requirements.
In the next section, we will explore some practical examples of rack and pinion applications in various industries.
Frequently Asked Questions
Q: Where can a rack and pinion be used?
A: A rack and pinion system can be used in various applications such as steering systems in automobiles, CNC machines, robotics, and industrial machinery.
Q: How does a rack and pinion system work?
A: In a rack and pinion system, a gear called a pinion meshes with a linear toothed component called a rack. When the pinion rotates, it translates the rotational motion into linear motion along the rack.
Q: How to center a steering rack and pinion?
A: To center a steering rack and pinion, you need to turn the steering wheel to its neutral position and adjust the tie rods until the wheels are straight and aligned.
A: In a rack and pinion system, the rack refers to the linear toothed component that meshes with the pinion gear. It converts rotational motion into linear motion.
Q: How to design a rack and pinion?
A: Designing a rack and pinion involves determining the required gear ratio, tooth profile, module, and pitch diameter based on the application requirements. It also involves considering factors such as load, speed, and backlash.
Q: What are the applications of rack and pinion?
A: Rack and pinion systems find applications in various fields, including automotive steering, industrial machinery, robotics, CNC machines, and even some household appliances.
Q: What are some common steering rack problems?
A: Common steering rack problems include leaks in the hydraulic system, worn-out or damaged rack bushings, loose or damaged tie rods, and excessive play in the steering wheel.
Q: Can you provide examples of rack and pinion gears in everyday life?
A: Sure! Some examples of rack and pinion gears in everyday life include power steering systems in cars, sliding gates, elevators, and even some exercise equipment like rowing machines.
Q: Can you list an example where the rack and pinion mechanism might be used?
A: One example where the rack and pinion mechanism might be used is in the steering system of a go-kart. The rack and pinion system provides precise and responsive steering control.
Q: What are the different types of rack and pinion?
A: The different types of rack and pinion include straight (spur) rack and pinion, helical rack and pinion, circular rack and pinion, and rack and pinion with a non-circular gear profile. Each type has its own advantages and applications.
Q: Can you provide an example sentence using “rack and pinion”?
A: “The rack and pinion steering system in the car ensured smooth and precise control while navigating tight corners.”
This article discusses about master cylinder diagram. Before moving towards master cylinder diagram, we will study about what is master cylinder.
If you have driven an automobile, be it a four wheeler or a two wheeler, you must have noticed that you do not need to apply much force on the braking pedal. Just a slight force stops the vehicle running at high speeds. Lets study more about master cylinder in below sections.
What is a master cylinder?
A master cylinder is a device that converts mechanical force to hydraulic force. A master cylinder finds its application in braking system of automobiles (of all types).
It is an integral part of braking system. It amplifies the force that we apply on braking pedal and with the help of hydraulic fluid it stops the vehicle that is running at very high speeds. Without a master cylinder, it would get very difficult to stop at emergency situations. A hydraulic brake is always better than a mechanical brake due to the emergency stopping advantage.
The most common types of master cylinders used in the braking systems are-
Single circuit master cylinder– The single circuit master cylinder uses only one cylinder in the braking circuit of the braking system. This way the braking force is distributed equally among all the wheels of the automobile. This type of circuit is quite unsafe and should be used only in light weighted four wheeler vehicles, two wheeler vehicles and e-auto rickshaws.
Tandem or dual circuit master cylinder- In Tandem circuit master cylinder, more than one cylinder is used (generally two). This way the braking system can be used independently in front wheels and rear wheels. This improves the safety feature in the design of braking system.
Master cylinder diagram
The master cylinder is an assembly of many parts. The main working parts of the master cylinder are shown in the diagram below-
The notable parts shown in the above diagram are- Reservoir, cylinder, piston, valve, spring and braking pedal. We shall study in detail about them in below sections.
Master cylinder parts
As discussed above, master cylinder is an assembly of many working parts. Let us discuss about the main working parts of the master cylinder-
Reservoir– Reservoir acts like a storage tank for braking fluid. Braking fluid rests inside the reservoir, when the braking pedal acts then certain amount of braking fluid is taken into the braking circuit.
Cylinder– Inside the cylinder, piston movement takes place. When the braking fluid exerts pressure, piston movement takes place inside the cylinder.
Piston– Piston transfers hydraulic force from the hydraulic fluid to the brakes. The application of brakes stops the vehicle running at high speeds. Piston rests inside the cylinder.
Returning spring– A spring generally stores potential energy inside it when a force is applied on it. This potential energy helps it to regain its original shape back. In a master cylinder, returning spring is used to bring back the piston and braking pedal to their original positions once the braking application is complete.
Valve– Valve acts like an outlet portion to which the braking line is attached. The compressed braking fluid passes to the caliper through this valve.
Braking pedal– The braking pedal is a lever on which the driver applies the braking force. Although the force applied by the driver is not equal to the actual force required for stopping the vehicle. The force applied on the pedal is transferred to the hydraulic fluid. This fluid exerts hydraulic force to the brakes. The brakes are actuated by this hydraulic force and so the braking application takes place.
Single circuit master cylinder working
The following steps take place while a braking force is applied on single circuit master cylinder.
When no braking force is applied, that is when the pedal is idle. The inlet valve is closed and no braking fluid flows through the circuit.
When the braking force is applied on the brakes, the inlet valve is opened and the braking fluid flows from the reservoir to the compression chamber.
When the braking fluid attains enough compression pressure, it flows through the braking lines and moves the brakes. This way the application of brakes takes place.
The master cylinder amplifies the braking force applied by the driver.
When the brake pedal is left idle again, the braking fluid returns back to the reservoir.
Tandem or dual circuit master cylinder working
The working of tandem circuit master cylinder is similar to that of single circuit master cylinder. Let us see about its working in detail below-
Similar to single circuit master cylinder, the application of braking force on braking pedal activates the primary cylinder or the compression chamber.
After the first cylinder is activated, the braking fluid flows through another cylinder also called as secondary cylinder. After the secondary cylinder is activated, another circuit also starts participating in braking application.
This way two cylinders participate in the braking application. This feature can also be used to make independent braking system for front wheel and rear wheel.
This type of circuit is also safer and is used in almost all four wheeler vehicles.
Need of a master cylinder
As we have discussed above, master cylinder uses hydraulic force for the application of brakes. Hydraulic force is always better than the mechanical force as it can be used in emergency situations with better efficiency.
The need of a master cylinder arises due to multiple reasons. They are-
It can allow independent braking systems for front and rear wheels.
They can be used in emergency situations with better efficiency.
They amplify the force applied on the braking pedal and make it equal to the actual braking force required to stop the vehicle.
It decreases the risk of failure because it can be used as independent systems for front and rear wheels.
In this given article we will briefly discuss about the topic of “Milling Machine Parts”. The milling machine parts are very useful and uses widely in the work of the production engineering.
In every milling machine tool in generally contain eleven parts.The parts which are carried by the milling machine tool is
The base is the part which is placed at the bottom of the milling machine tool. The whole parts of the machine tool are situated in the base.
The base is the foundation of the milling machine tool. The base should be enough rigid and the strength should be enough thus it could hold the whole machine tool.
Material used to make:
The body of the base made with cast iron.
Working Purpose:
1. To hold properly the machine parts of the milling machine tool.
2. Storage of the cutting fluid
3. To absorb the surroundings shocks.
Table:
Table is situated at the saddle’s top portion. The shape of the table is rectangular.
The table is control by the electric power in milling machine. But in common milling machine the milling machine is controlled by both man power and electric power and when the table is controlled by the manpower the hand crank is engaged longitudinally and when the table of the machine tool is controlled by the electric power that time control lever is engaged longitudinally.
Material used to make:
Table of the machine tool is made with cast iron.
Working Purpose:
1. The main purpose of the table is to grip the work piece and the work tool.
2. T slots are also placed in the table of the milling machine tool which are used to hold the work piece and work tool such as jigs and fixtures.
Arbor support:
In the milling machine the tool is support the arbor’s end portion with arbor support’s axle. The support of the arbor is pitch with the help of bearing.
In the milling machine tool general arbor support is categorized in two types. The one type is smaller diameter bearing which containing the hole diameter maximum up to 1 inch and the another one is bigger diameter bearing which containing the hole diameter is 5.75 inch.
Working Purpose:
1. The oil reservoir is placed in the arbor supports. Lubricate which is comes from the oil reservoir uses in the surface of the bearings.
2. In overhanging arm’s any places the arbor support can be clamped.
Knee:
The shape of the knee in the milling machine tool is almost looks like a human’s knee. The movement of the knee is vertically upon the face of the column. The knee can be moved upward and downward in the directions both.
Material used to make:
The knee of the milling machine tool is made with the help of grey cast iron.
Working Purpose:
1. Help to hold the feed mechanism which is situated in the table of the milling machine tool.
2. Also helps to grip the saddle.
3. By the help of the knee we could easily adjust the height of the column which is attached with the elevating screw.
Spindle:
The spindle is a machine tool which is act as an intermediate between the knee and table of the milling machine tool. The spindle is placed in the upper portion of the column.
It is actually a shaft which is work in the rotating motion. The spindle can be moved by both manpower and the electric power. The power of the machine tool such as gears, belt and clutches is received by the spindle.
Working Purpose:
1. To horizontally moves the workpiece.
2. The shaft of the spindle is act like as a supporter and positioned for the tool devices.
3. Support the column.
4. The spindle’s face is situated in the tapered machine of the table. The taper of the internal position is situated in the spindle’s face and only permits with arbor or the cutter which is in tapered.
Column:
The column of the milling machine tool is placed the vertical position of the base. The column is one of the most important part of the milling machine tool which carrying all the driving mechanism and also carry the motor.
In the column the v belt is used. The v belt is usually connected the motor and the driving mechanism. The driving mechanism is mainly used to control the speed. It is shaped like a box and all driving mechanisms are situated on it.
Material used to make:
Cast iron is used to make the column of the milling machine tool.
Working Purpose:
1. To hold the driving mechanism and motor.
Ram:
Ram can be defined as if the overhanging arm is present in the milling machine. The ram’s one ending part is attached with the column and other ending part is attached with the head of the milling machine tool.
By the help of the hand lever ram easily can be moved.
Motor:
The power is generated of the milling machine by the motor.
Head:
As the human body’s head the milling machine head is also situated at the top. The controlling mechanism is totally handle bf the milling head. The spindle and driven motor also placed in the head.
Machine tool:
The machine tool means the spindle carried the all the components by this the excess amount of material is removed to achieve the desired part.
Machine interface:
The meaning of the machine interface is the operator of the machine components used as machine program of the computer numerical control, load and initiate.
Saddle:
The saddle is placed in the knee and worked as a supporter of a table of the milling machine tool. The dovetail which is placed paralleled to the spindle’s axis. The saddle is present in the horizontal milling machine tool.
Working Purpose:
1. Guide the table with the help of the top portion of the saddle.
Front brace:
Front brace actually an additional support tool. By the help of the front brace the knee and overhanging arm get extra support.
Arbor:
The arbor of the milling machine meaning into the spindle when the component of the shaft is insert into the horizontal milling machine where tools of machine can be mounted. The component of the milling machine is in various sizes and diameters.
The arbor is present all most every milling machine that could be in end milling, normal milling machine, slitting saw milling cutter, screw, shell cutter arbors and milling cutter arbors.
Working Purpose:
1. Worked as the supporter of the cutters which are used in the milling machining tool.
2. Work tool can be easily hold and move by the arbor.
Milling machine:
In a production industry there a lots of machine and machine tools are present to do a wide range of operation in the work piece among them milling machine is one of the machine tool. By the help of the machine tool a wide range of cutting can be done in the work piece. A lots of operations which are in general very complicated to do on a work piece but with the help of the milling machine tool we can provide this complicated operation too. The operation we could easily do by the machine tool is,
Straddle milling
Indexing
End milling
Gang milling
Plain milling
Face milling
Side milling
Saw milling
Form milling
Angular milling or bevel milling
Spiral milling or helical milling
In industrial area the milling machine tool mainly used to produce the surfaces .The surfaces which are mainly in form of flat profiled. In other way the slots are made with the help of the tooth cutter which are revolving in multiple.
In the production engineering field there are different types of milling machine tools are present. The types of milling machine which are present in different form is named in the below section,
Solution: Jigs can be defined as the device which is helps to grip and locate workpiece of the milling machine tool and control the cutting tool that could be one or more than one.
In this article we will discuss about the topic of “Low Discharge Pressure” and also we will briefly discuss the others facts like types, causes, and how with the some several facts are directly related with the low discharge pressure.
Low discharge pressure can be defined as when the gases are discharges under the pressure of the gas in the range between some millitorr to very less than the atmospheric pressure. In the system if the pressure of suction side is increasing continuously then the phenomenon is increases inside the system.
The capacity of the compressor of the refrigeration system is decreases when the quantity of the inside temperature in increasing for some defects of the system. The benefit of the low discharge pressure is it’s required very less amount of power because the rate of the volume combination is less than the discharge substances.
The benefit of the low discharge superheat is the discharge is easily can be achieve uniformly .In the system only the plasma gas is flow in the plasma chamber when the air-conditioning system is pumped . The ionized gas present in the system is argon that is the big reason to break it very easily by chemically.
The phenomenon is of the air conditioning system can be easily resolve by following some steps. The coils in the refrigeration system carried dirt. When the dirt are mixed with the air which is flowing in the compressor’s suction line to the evaporator coils the temperature is increases and lower head pressure is appear inside the system.
The problem is mainly begins from the compressor of the refrigeration system. If we beginning of the process go through in the condition of the compressor and check the discharge valve of the compressor then the low discharge pressure can be avoided without any hassle.
Now the other process to control the low discharge valve into the refrigeration system is to check the inside condition of the valve of the evaporator. By the help of the evaporator coil the refrigerant is passes through from the compressor to the evaporator. In this situation to avoid the unwanted situation need to open the valve of the expansion.
And we should to check the condition of the evaporator in the refrigeration system.
The low discharge pressure easily can be check by the measuring instruments like Manometer and Bourdon tube gauge.
What is low discharge pressure?
When the excessive amount of refrigerant is present in the suction line of the compressor then the heat cannot flow properly across the coils of the evaporator in the refrigeration system.
In the air conditioning system simultaneously when the pressure is excessive lower than the normal pressure this condition called the low discharge pressure. In the low discharge pressure the temperature is excessive higher than the normal temperature and refrigerant is present in suction line of the compressor in a particular area.
The excessive amount of the refrigerant is present in the compressor’s suction line which is not suitable for the air conditioning system.
The coils which are used in the refrigeration system usually these are made with metal. The main reason using the metal is less power will be needed for generating the heat in the system.
The low discharge pressure is created unbalanced condition in the whole refrigeration system. In this condition the amount of pressurized refrigerant near about 65 – 75 pound per square. The refrigerant is pressurized in the compressor’s suction line and inside temperature is gradually an increase without any limitation. The low discharge pressure also slows down the refrigeration cycle.
In the refrigeration system inside the suction lime and the in the coils mainly metals are used. The metal is chosen for the systems which are good in heat conduction. The name of the metal is copper and alternatively the tungsten also can be used. With the help of the suction line the evaporator valve and the condenser’s whole unit are connected.
Low discharge pressure high suction pressure:
In this section we will discuss about the topic of low discharge pressure high suction pressure.
In the refrigeration system the low discharge pressure is generates for the bad condition of the equipment. The leakage is present in the return line of the oil separator, the piston’s condition of the compressor is not well or the discharge valve which is placed in the outside of the compressor is generate lower pressure than the regular pressure and increases unwanted temperature is excessive inside the system is appear low discharge pressure.
The condition for the low discharge pressure the capacity of the system became less.
Most of the discharges in the refrigeration system used in the industry related to the semiconductors.
Low discharge pressure type:
When the proper reason behind the low discharge pressure is not detect properly that time the pressure gauge can be used in the compressor of the refrigeration system.
The low discharge pressure for an air conditioning system is increases when the amount of insufficient compressor is more than the usual amount. So, the low discharge pressure cannot be classified only the range of the air conditioning system it can be only read by the measuring instruments.
The reading range of the air conditioning system where the low discharge pressure is appearing is between 155 PSI to 30 PSI.
The ranges of the reading for the air conditioning system is summarize briefly in below,
1. 250 PSI / 30 PSI – If the unwanted amount of air is present inside the air conditioning system then this range of reading is appearing.
2. 250 PSI / 50 PSI – From the range reading we can recognize the inside condition of the condenser. The condenser may be not cool as much it’s required or may be somewhere blocked.
3. 225 PSI / 80 PSI – This range of reading tell us that the refrigerant is present in excess amount in the compressor some leakage is present in the expansion valve and also the size is too large.
4. 200 PSI / 70 PSI – This range of reading directly shows some blockage definitely present in the refrigeration system or may be in device of the expansion.
5.160 PSI / 10 PSI – This range of reading denoted that frosting is happened inside the evaporator of the refrigeration system. This situation is happened when pressure is too low in the pipe or may be the clogged of the valve of the expansion. For resolve the problem need to check the evaporator or the evaporator valve.
6.150 PSI / 30 PSI – The range is appearing when in the cooling medium of the refrigeration cycle water is carry by the refrigeration system.
7.150 PSI / > 10 PSI – The range of reading of the air conditioning system helps to understand that, in the refrigeration system some leakage is must be present. The leakage can be easily detected by the technician. If the problem can be solve at beginning of the process then the low discharge pressure cannot be arise.
8.125 PSI / 30 PSI – The range for the refrigeration system gives us a clear concept that, the whole system is not carry the sufficient charged or may be excessive amount of oil is carry by the oil separator.
9.100 PSI / 100 PSI – The range is clearly gives us the clear concept about the condition of the compressor in the refrigeration system. In this range the compressor cannot be engage just because the brunt coil not transfers the power.
10. 50 PSI / 50 PSI – By this range of the reading we could understand the inside condition of the clutch for the refrigeration system.
Low discharge pressure cause:
In this portion of the article we will discuss about the causes of the of the low discharge pressure.
The reasons which are consider to as primary causes for the low discharge pressure is,
1. Malfunction of the thermostatic expansion valve
2. The condition of the refrigerant is when under the charge
The secondary reasons for the low discharge pressure is discuss in below section,
1. The leakage of the valve of the compressor: The common problem for the air conditioning system of the discharge valve of the compressor is the leakage. If we go through the air conditioning reading then the range of the reading is about 150 PSI. The condition in practically very hard to detects. Only the condition can be fixed by professional technician.
2. The compressor’s piston rings face the damage: The discharge gas is emitted by holes present in the compressor’s piston ring the pressure of the refrigeration cycle became low more than the regular pressure and low discharge pressure is happened in the system.
3. Leakage from oil separator to the return line:
4. Overcharged of the refrigerant:
The electronic expansion valve size is more than the normal size then the overfeeding is happened in the electronic expansion valve and the low discharge pressure is causes in the system.
5. Increasing the temperature:
When the air of the refrigeration system could not flow properly across the suction line of the compressor as a result excess amount of temperature is an increase which is not good for the system.
6. Size of the valve is excessive: The valves which are present in the air-conditioning system are larger than the regular size then the low discharge pressure is appearing.
“How to calculate Volume Flow Rate of a fluid?” is one of the most frequently faced question in an chemical industry for the smooth, safe and cost effective running of a process.
The movement of fluids through a pipe in an engineering plant has great importance especially to ensure the correct proportion of different chemicals for a reaction. Calculation of Volume Flow Rate from different entities play a major role.
Volumetric Flow Rate is the volume of a fluid flows through a tube, duct, channel or other this type of structure per unit time.
Volume Flow Rate, Q or V=Av
Where A= Cross sectional area of a section in m2
And v=Average velocity of the fluid throughout the section in m/s.
The unit ofVolume Flow Rate is m3/s(cubic meters/second), m3/h(cubic meter/hour), l/s (litre/second), l/min.(litre/minute),ml/s(millilitre/second) etc.
In case of very small flow rate(for example fluid inside a syringe), ml/s is preferred and for very large volume flow rate(for example flow of water in a river), it is expressed in m3/h.
How to calculate Volume Flow Rate from Volume and Time?
Volume Flow Rate is a common term associated with flow measurement especially in case of liquids and gases.
To calculate Volume Flow Rate of a fluid using the amount of fluid passing through (in cubic meter)a passage within a particular time period (in second), we can use the following formula:
Volume Flow Rate, Q=V/t
Volume Flow Rate of a fluid (gas and liquid)is the volume of fluid passing a given point within a given period of time. Units are litre/minute, cubic centimetres per minute etc. It is denoted by Q or
Here Volume of the Fluid =A.d
A is cross sectional area of the pipe in m2 and d is the distance traveled by the fluid in m
Q= Volume flow rate m3/s or L/s .
V=Volume of fluid in litre or cubic metre
=Average velocity of flow in m/s
Here we consider the average value of the velocity because due to frictional force velocity is less near the wall of the pipe than at the middle portion.
A=Cross sectional area occupied by the moving fluid m2
Hence,
How to find Volume Flow Rate with Pressure?
For the movement of a fluid through a duct there should be a pressure difference in between the two ends of the duct, which is termed as pressure gradient .
Hagen Poiseuille equation gives the relationship between pressure drop and flow rate of a fluid through a long cylindrical pipe. The equation is applied for laminar flow of incompressible liquid flowing through a pipe of constant cross sectional area.
Using Eq(2) we can determine the Volume Flow Rate from Pressure Gradient.
One of the common applicationof Hagen–Poiseuille equation( or Hagen–Poiseuille law)is observed in flow of liquid through a drinking straw. Here pressure drop is considered due to viscosity of the fluid.
In case of incompressible fluids like water we can apply Bernoulli’s equation to know the relationship between fluid flow and pressure. Here, fluid velocity of incompressible nonviscous flow is determined from the pressure measurements.
Flow through a pipe with different cross section
Mathematically, Bernoulli’s principle can be given as-
P = pressure
v = velocity
ρ = density of the fluid
g = gravity
h = height
How to find Volume Flow Rate without Velocity?
Volume Flow Rate is a common term associated with flow measurement especially in case of liquids and gases.
The equation to find Volume Flow Rate of a fluid without knowing its velocity is as follows:
Q=V/t
Where Q=Volume Flow Rate m3/s
V = Volume of the fluid passing through a particular cross sectional area in m3
t =Time taken by the fluid second
Volume Flow Rate
In the above figure, a fluid is passing through a duct, if V is the Volume of fluid crossed a unit cross sectional area A of the pipe within a time period of ‘t’, then Volume Flow Rate Q is given by
To calculate Volume Flow Rate of air we can use the following formula:
Q=Cross sectional area x Average velocity
Generally air velocity i.e. distance traveled by air per unit time is represented in feet per minute is not uniform at each portion of the duct.
The air velocity is lowest near the walls of the duct due to friction, considering this we can use an averaging Pitot tube having several number of sensing points to get average velocity more precisely.
If the dimension of the duct is known to us then we can easily calculate the cross sectional area of the duct and then multiplying it with average velocity, we can determine the Volume Flow rate, generally in cubic feet per minute.
The amount of water flowing through a duct or pipe within a particular time period which is known as Volume Flow Rate can be calculated using the following equation:
Q=Cross sectional area x Average velocity
Here we consider the average velocity of water since the speed of water is not uniform through out the whole pipe, speed is maximum at the centre of the pipe and minimum near the side portion.
Problem1:Water is flowing through a pipe of inner radius 10 cm with a volume flow rate of 0.50 m3/s. Calculate the speed of water through the pipe.
Solution: Data given are:
Radius of the pipe, r=10 cm=0.1m
Volume Flow Rate, Q=0.50m3/s
Now area of the pipe,A= πr2=3.14 x 0.01=0.0314m2
We know that,Q=v.A
Here v is the speed or velocity of water in m/s
Speed of water,v=Q/A=0.50/0.0314=15.92 m/s
Problem2: A nozzle with a radius of 0.150 cm is attached to a garden hose with a radius of 0.700 cm. The flow rate through hose and nozzle is 0.500 L/s. Determine the velocity of the water (a) in the hose and (b) in the nozzle.
Solution:
(a) velocity of the water in the hose
We know that,Q=v.A
Radius of the hose,r1=0.700cm=0.007m
Area of the hose A1=πr2=3.14 x 0.000049=.00015m2
Flow Rate,Q=0.500 L/s=0.0005 m3/s
Therefore the velocity of water in the hose,v1=Q/A1=.0005/.00015=3.33m/s
In this article we will discuss about the relationship of Mass Flow Rate to Velocity.
The concept of flow rate(Mass Flow rate and Volume Flow Rate) measurement in a industry is very much essential for accurate and cost effective running of a process. Velocity indicates how fast a fluid is moving a distance per unit time.
Whenever we calculate flow rate of a fluid flowing through a pipe line certain terms like mass flow rate, volumetric flow rate, Molar flow rate, velocity, density, volume ,temperature , pressure etc come into the picture.
Flow rates and all the above mentioned physical properties are inter related and we can determine one quantity from the other by using different formulas associated with them.
Accurate measurement of Mass flow rate is necessary in an industry to control the different operations smoothly. Efficiency of an equipment and product quality also depends on mass flow rate of a fluid.
Mass is neither created nor destroyed and Mass flow rate is not affected by temperature and pressure change during the process so in case of precision measurement mass flow measurement is always advisable.
Mass Flow Rate to Velocity relationship
Flow rate measurement of different fluids is an important aspect of pipe line industries.
Velocity is the measurement of how fast a fluid is moving per unit of time. Mass Flow Rate is associated with the amount of fluid passing through a passage per unit time.
Mass Flow Rate can be expressed as ṁ=mass/time=m/t Eq1
And Volume Flow rate can be expressed as Q= volume/time= V/t Eq2
From Eq(1), ṁ=mass/volume . volume/time Eq3
Now, mass/volume=Fluid density ρ
And volume/time=Volumetric Flow Rate=Q
From Eq(3) , ṁ= ρ.Q Eq4
The above equation relates Mass Flow rate and Volumetric Flow Rate of a fluid. If we know the density of the fluid and discharge through a pipe, then we can determine the amount of fluid passing through the pipe in terms of Kg/s i.e. mass flow rate of the fluid.
From the Continuity Equation applicable for incompressible fluid we can write,
Here A is the cross sectional area of the passage and bar(v) is the average velocity of the fluid.
So Eq(4) becomes,
From the Eq(5) it is clear that mass flow rate of a liquid is directly proportional to the density of the liquid, velocity of the liquid and the cross sectional area.
How to Calculate Mass Flow Rate from Velocity?
The Flow rates, velocity, pressure, density all these terms are interrelated to each other.
If we know the velocity(v)of a flow through a pipe of cross sectional area(A), then we can calculate the volume flow rate of the fluid by using following formula,
Where Q=Volume Flow rate
A= Cross sectional area of the pipe
= Average velocity of the fluid
Now Mass Flow Rate is the density ρ multiplied by the Volume Flow Rate
ṁ=ρ. Q or,
As per the law of conservation of mass, in case of incompressible fluid passing through a channel of non uniform cross sectional area, the Mass flow rate maintains a constant value.
Flow through a pipe with different cross section
In the above figure we can observe a pipe with different cross sectional area A1 and A2 (where A1>A2) through which water(incompressible in nature) is flowing.
Even though the diameter of the pipe is not same, due to continuity same amount of water is passing through the point 1 and 2. The speed of the fluid is less at the wider area of the passage than the speed at the narrow region to keep the flow constant.
At point 1 and 2,
Q_{1}=Q_{2} or,
This is the famous Continuity Equation applicable for Incompressible fluids.
Difference between Mass Flow Rate and Velocity
The difference between Mass Flow Rate and Velocity as follows:
Mass Flow Rate
Velocity
Volume Flow Rate(ṁ) is the amount of mass(m) of a fluid flows through a cross sectional area (A) per unit time (t).
Velocity bar(v) of a fluid is defined as the distance(d) travelled by a fluid within a time period( t).
Mathematically, ṁ= m/t
Mathematically, bar(v)=d/t
Units: kg/s( SI unit), gm/s(CGS unit)
Units: m/s(SI unit), cm/s(CGS unit)
Problems Related to Mass Flow Rate
Problem 1: A fluid with density 650 kg/m3 is flowing through a duct of inner cross sectional area 25 cm2 with a velocity of 30 m/s. Find the mass flow rate of the fluid.
Solution: Here, Density, ρ=650kg/m3
Cross sectional Area, A=25 cm2=0.25m2
Velocity, v=30m/s
The formula for calculating mass flow rate ṁ= ρVA
\dot{m}= 650× 30 × 0.25m = 8400 kg/s
The mass flow rate m for the above-given data is 4875 kg/s
Problem 2:The mass flow rate of a fluid flowing through a circular pipe is 3600 kg/s, the velocity of the flow is 25 m/s and cross sectional area of the pipe is 10 cm2. Calculate the density of the fluid inside the pipe.
Solution:
From the given data,
\dot{m}= 3600 kg/s,
Velocity,v = 25 m/s and
Area of the cross section,A = 10 cm2 = 0.10m2
To determine the density of thefluid from the above-given values, we can use the formula,
Density ρ= m/vA
ρ = 3600 / ( 25 * 0.10 ) = 3600 / 2.5
ρ = 1440 kg/m3
The density of the liquid ρ of the fluid passing through the pipe is 1440kg/m3
Frequently Asked Questions(FAQs)
Q1: Write the differences between Mass Flow Rate and Volume Flow Rate.
In the article we will discuss about the topic of “High Discharge Pressure” and their related facts with types, causes, and how the high discharge pressure is related with the other parameters with several facts.
High discharge pressure can be defined as the pressure of the gas compressor’s which carrying by the suction line into the air conditioning system is facing leakage from the discharge valve is present in the compressor’s output side and combined with an indicator’s lower suction pressure.
The phenomenon named high discharge pressure of an air conditioning system can be easily fixed without facing any problem.
When the dirt is present in the compressor and if it is continuously flow by the coil in the refrigeration system then the flow of the air could not get sufficient place to flow properly in the coils and increases unwanted temperature and pressure. So, if at beginning we focus on cleaning of the dirt then high discharge pressure easily can avoided.
The problem is mainly arising from the compressor. If at the beginning of the process we go through over the compressor then this unwanted high discharge pressure can be easily avoided. If the condition of the air conditioning system is not handling immediately then the compressor it needs to repair.
In the next step we need to observe the condition of the evaporator coil. The refrigerant of the compressor passes through the outlet of the evaporator due to high temperature. In this situation the expansion valve need to open immediately to move the refrigerant.
Or the other process to control the high discharge pressure in the air conditioning system is to observe the expansion valve for the temperature and the pressure.
The phenomenon measured by the measuring instrument which is Bourdon tube pressure gauge, Manometer.
The main reason behind the high discharge pressure is excess amount of pressurized gas is present in the refrigeration system which is flowing from the compressor’s suction line to evaporator coil.
The high discharge pressure is excess amount of vaporised gas is present in the compressor’s suction line in the fixed area of the air conditioning system which is increases unwanted temperature and pressure because of the heat transfer is not happed properly.
The main reason behind this situation is the refrigerant present in the compressor of the air conditioning system is not able to transfer into heat which is carrying by the evaporator coil.
The coils are usually made with metal such as copper, tungsten which is used in the high discharge pressure in the air conditioning system. The evaporator coil and condenser unit connected with the help of suction line.
In the suction line present refrigerant is pressurized about 60 – 72 pound per square. When this amount of pressurized refrigerant is crosses the compressor the pressure is arise and thus the inside temperature is also increases. This condition can slow the whole process even can damage the air conditioning system.
The high discharge pressure is an unwanted situation which is occurs by the present of insufficient compressor of the refrigeration system in the cooling medium which may be water or gas.
The term of insufficient compressor means the leakage should be contained by the discharge valve of the compressor which is situated outside of the compressor. In the refrigeration system the refrigerant is present in the suction line of the compressor which obviously not enough for the cooling medium that could be liquid gas or water.
When the refrigerant of the compressor is not totally transfer into heat then the low head pressure is continuously increases and the pressurized range of the cooling medium became too high near about 72 PSI which is not required to the system. At the high discharge pressure the temperature of the refrigeration system is also became high than the normal temperature because of the present oil could not able to lubricate properly when the cylinders and compressor are too hot.
The chillers are works in the basic law of vapour absorption or in the law of vapour absorption.
A device by which heat can be remove with the help of the vapour compressor from a coolant which should be stayed in a liquid form in the refrigeration system is called high discharge pressure in chillers.
If we go through the refrigeration cycle then we could find t first the liquid which is present in refrigeration system is circulated in the heat exchanger for coiling the liquid. The excess amount of heat which is produced in refrigeration system during the refrigeration cycle that would be discharge in the atmosphere to balanced the whole process.
The chillers can be classified in some categories in basic of technology used in the compressor. The classification chillers name given in below,
Reciprocating chillers
Centrifugal chillers
Scroll chillers
Screw chillers
The chillers classified in the basis of system names are given below
Water chillers
Air chillers
Evaporative condensed chillers
High discharge pressure cause:
The reason of high discharge pressure is briefly summarize in below,
1. When the compressor of the air conditioning system carry the cooling medium.
The cooling medium can be water or liquid gas.
2. Temperature of the cooling medium is more than the normal temperature for the refrigeration cycle in air conditioning system.
3. Size of the evaporator is too high: If the size of the evaporator is excess than the normal size then the unbalanced situation is occurred.
4. Get not enough space to floe the refrigerant in the air conditioning system.
5. Leakage from the valve of the compressor:
In the air conditioning system one of the common problems for the phenomenon of high discharge pressure is the leakage from the compressor valve of the compressor. This is very difficult to detect but when this condition occur the gasses are emitted from the holes and the air flow is not flow properly .Thus discharge gas is moves into the compressor cylinder by the down stroke of the crankshaft.
When the sealing of the discharge valve is not done properly thus the causes low head pressure and increases the temperature .The discharge temperature became more than the usual temperature of the refrigeration cycle.
Sometimes the gases which are discharge from the compressor cylinder is run through short cycle, in this situation the flow of the present refrigerants became low. As a result the pressure and temperature became less for the heat load which is present in the condenser.
When the low refrigerant go through the condenser, the rate of the heat is reduced, means the sub cooling of condenser causes high suction pressure.
6. Damage of the piston ring of the compressor:
When the emit gasses facing leakage due to the piston ring of the compressor the pressure is developed than the normal pressure and the high suction pressure is happened. During the compressor stroke the piston ring of the compressor is produce low head pressure.
7. Leakage of the return line of the oil separator:
The purpose of the oil separator is to differentiate and control the level of the high and low sides of the air conditioning system. In the refrigeration system the oil separator is place in the higher side of the level and the compressor crankcase is situated in the lower side of the air condition system. The oil is flow by high level means the oil separator to low side of the level means in the crankcase.
If the size of the electronic expansion valve is large than the usual size then the evaporator is overfeed and causes the high suction pressure.
9. Excessive temperature:
When the flow of discharge gasses is not go properly through the suction line the temperature increases and high suction pressure is appear.
High discharge pressure type:
High discharge pressure is the inside condition of the air conditioning system. When some unnecessary situation or object is present in the refrigeration system the temperature is increases and causes a lot of problem.
The high discharge pressure is a phenomenon in the air conditioning system which is appears in present of insufficient compressor. So, the classification of high discharge pressure cannot be done only the reading of the air-conditioning system can be done.
The air conditioning system works in the between the range of 155 PSI to 30 PSI.
The reading ranges of the air conditioning system is given below,
1.100 PSI / 100PSI – In this range reading we could understand that the generated power of the refrigeration system is can not reach to the compressor thus the compressor of the air conditioning system is not properly engaged.
2.50 PSI / 50 PSI – In this reading of the range the clutch of the refrigeration system is not engaged.
3.150 PSI / 30 PSI – If the water is present in the refrigeration cycle as the cooling medium then the range is belong to the refrigeration system.
4.150 PSI / > 10 PSI – The range of the conditioning system can help to recognize us that, there should some leakage definitely present in the refrigeration system. If at this situation the technician tried to find the leakage then the condition of the refrigeration system could not go so bad but the detection of the leakage is not too easy work.
5.125 PSI / 30 PSI – The range tells us that the refrigeration system may be oil is present in the compressor of the return line from the oil separator. The alternative reason behind the range can be the charge of the refrigeration system is not enough.
In the article we will discuss about the topic of “High Suction Pressure” and their related facts with types, causes, and how the high suction pressure is related with the other parameters with several facts.
High suction pressure is the present of refrigerant to the compressor which is carrying by the suction line into the air conditioning system is facing leakage from the discharge valve which is increasing the temperature and pressure without any necessity to the system of the evaporator at its outlet.
The phenomenon high suction pressure for the air conditioning system can be easily fixed. When the dirt is contains by the coil by this situation the air flow could not flow properly by the coils and increases unwanted temperature and pressure.
The problem is mainly arising from the compressor. If at the beginning of the process we go through over the compressor then this unwanted situation can be easily avoided. If the condition of the air conditioning system is not handle by the compressor then it need to repair.
In the next step we need to observe the condition of the evaporator. The refrigerant is passes through the outlet of the evaporator due to high temperature. In this situation the expansion valve need to open to move the refrigerant.
Or the other process to control the high pressure suction in the air conditioning system is to observe the expansion valve for the temperature and the pressure.
The phenomenon measured by the measuring instrument which is, Manometer.
The main reason behind the high suction pressure is excess amount of temperature and pressure is present in the system which is flowing from the compressor of the air conditioning system.
The high suction pressure is excess amount of refrigerant is present in the evaporator’s suction line with in the fixed area of the air conditioning system which is increases unwanted temperature and pressure.
The main reason behind this situation is the refrigerant present in the evaporator of the air conditioning system is not able to transfer into heat which is carrying by the evaporator coil.
The coils are usually made with metal such as copper, tungsten which is used in the high section pressure in the air conditioning system. The evaporator coil and condenser unit connected with the help of suction line. Mainly the refrigerants present in the evaporator carrying by the suction line which could not move the heat properly.
In the suction line present refrigerant is pressurized about 60 – 72 pound per square. When this amount of pressurized refrigerant is crosses the compressor the pressure is arise and thus the inside temperature is also increases. This condition can slow the whole process even can damage the air conditioning system.
High suction pressure causes:
In this portion we will discuss the causes behind the reason of the high suction pressure. The reasons are discuss in given below briefly,
Leakage from the valve of the compressor:
In the air conditioning system one of the common problems for the phenomenon of high suction pressure is leakage of the compressor valve. This is very difficult to detect but when this condition occur the gasses are emitted from the holes and the air flow is not flow perfectly .The discharge gas is moves into the compressor cylinder by the down stroke of the crankshaft.
When the sealing of the discharge valve is not done properly thus the causes low head pressure and increases the temperature thus the discharge temperature is more than the usual temperature.
Sometimes the gases which are discharge from the compressor cylinder is run through short cycle, in this situation the flow of the present refrigerants became low. As a result the pressure and temperature became less for the heat load which is present in the condenser.
When the low refrigerant go through the condenser, the rate of the heat is reduced, means the subcooling of condenser causes high suction pressure.
Damage of the piston ring of the compressor:
When the emit gasses facing leakage due to the piston ring of the compressor the pressure is developed than the normal pressure and the high suction pressure is happened. During the compressor stroke the piston ring of the compressor is produce low head pressure.
Leakage of the return line of the oil separator:
The purpose of the oil separator is to differentiate and control the level of the high and low sides of the air conditioning system. In the refrigeration system the oil separator is place in the higher side of the level and the compressor crankcase is situated in the lower side of the air condition system. The oil is flow by high level means the oil separator to low side of the level means in the crankcase.
If the oil is could not flow properly in the air conditioning system then high pressure is occur and high suction pressure is appear.
When the refrigerant is overcharged:
If the size of the electronic expansion valve is large than the usual size then the evaporator is overfeed and causes the high suction pressure.
Excessive temperature:
When the flow of discharge gasses is not go properly through the suction line the temperature increases and high suction pressure is appear.
High suction pressure types:
High suction pressure is the inside condition of the air conditioning system. When some unnecessary situation or object is present in the refrigeration system the temperature is increases and causes a lot of problem.
High suction pressure cannot be classified the pressure reading inside the air conditioning system can be classified. The reading of the pressure measuring instrument is, Pressure Gauge.
In the air conditioning system if the suction side the pressure is increasing continuously then the low head pressure will be increasing inside the system. When the refrigeration system continuously faces the less temperature the amount of capacity will be also decreases.
When the discharge gasses facing the leakage of the piston ring of the compressor the high head pressure is appears.
The pressure is developed inside the refrigeration system more than the normal pressure. When the pressure is sudden increases the temperature is also increases. Thus, the unwanted unbalanced condition of high suction pressure is happened. During the compressor stroke the piston ring of the compressor is produce low head pressure than the normal pressure.
High suction pressure in refrigeration system:
The condition of high suction pressure in the refrigeration system is occurs just because of the absence of the insufficient compressor.
From the term for the insufficient compressor means the leakage should be present in the discharge valve of the compressor. In the refrigeration system the refrigerant present in the compressor is not enough for the cooling medium. When the refrigerant of the compressor is not totally transfer into heat this low head pressure is increases and temperature increases.
High suction pressure in heat mode:
The high suction pressure is a phenomenon where the pressurized gas is reaching about 60 -72 pounds per square and crated an imbalance situation inside the refrigeration system.
When the discharge gasses are passes through the condenser the dirt can be present in it. Mixing the dirt with discharge gasses the motion of the flow cannot be stay as same as a result the quantity of the vaporized gas is increases and the heat properly does not transfer thus the temperature is also increases and causes extreme high head pressure to the air conditioning system.
High suction pressure in heating:
When the refrigeration system is go through the condition of the high suction pressure the inside temperature and pressure is also increases.
This condition of high suction pressure in heating occurs for the insufficient compressor. From the term of insufficient compressor we easily could say that, definitely a leakage should be present in the discharge valve. In the refrigeration system the refrigerant present in the compressor is not enough for the cooling medium.
High suction pressure in heat pump:
Heat pump can be defined as, by the help of the refrigeration cycle without taking any external power the device by which hot or cool medium is flowing in a closed or domestic medium by transferring the thermal energy from a less temperature space to more temperature area.
If in the heat pump of the refrigeration cycle without taking any external power the flowing liquid could not flow in normal manner then the pressure and temperature will be increases in the refrigeration system and high suction pressure is appear.
What causes high suction pressure and high discharge pressure?
The high suction pressure is an unwanted phenomenon of the air conditioning system. The sudden increasing of the temperature and pressure not only damage the equipment but also can damage the whole system. In below the causes of this phenomenon briefly described.
Causes of the high suction pressure:
1.Heavy load of the system:
From the compressor the discharge gas is flow in a motion to the evaporator. When the gas is flow if the gaps are present in the compressor due to less uses the discharge gas could not transfer properly to the heat thus the air conditioning system became very high due to heavy load.
2.The capacity of the expansion valve of the air conditioning system is too high.
3. Leakage of the compressor’s valve
4. The capacity of the regulation is higher than the normal
5.Dirt present in the suction line and the evaporator coil
6.Unbalance of the oil flow in the oil separator
7. Subcooling of the condenser
8.Heavy size of the equipments
High discharge pressure can be described as, the pressure of the compressor in the refrigeration system is produced by the discharge gases is usually more than the normal pressure generated in the outside of the compressor.
Causes of the high discharge pressure:
1. When the compressor of the air conditioning system carry the cooling medium.
2. Temperature of the cooling medium is more than the normal temperature for the refrigeration or air conditioning system.
In this article we will discuss about the relationship between the Volume Flow Rate and Density.
In a process industry the measurement of Flow Rate(both Mass and Volumetric Flow Rates) of a fluid is very important .If we know the density of the particular fluid then we can convert Volume Flow Rate into Mass Flow Rate of a particular pipe line and vice versa.
In some cases it is preferable to measure volumetric flow rate in comparison to mass flow rate since volume flow measuring devices are less expensive than mass flow measuring devices.
But if we know the density of the fluid we can easily convert the measured volume flow rate in terms mass flow rate as per requirement.
Volume Flow Rate is the measure of amount of any fluid passing through a flow measuring instrument per unit time. Units are litre/minute, cubic centimetres per minute etc. It is denoted by Q.
Density is the physical property of a matter which refers to the mass contained in a unit volume. Units are kilogram/cubic meter, gram/cubic meter etc. It is denoted by ρ.
Volume Flow Rate and Density relation
Density, ρ=Mass/Volume=m/V
Volume Flow Rate, Q=V/t
Volume Flow Rate
Where,
Q= Volume flow rate m3/s or L/s .
V=Volume of fluid in litre or cubic metre
=Average velocity of flow in m/s
( Average value is considered because at every part velocity of the fluid is not same)
A=Cross sectional area occupied by the moving fluid m2.
If we multiply density of the fluid and its volume flow rate we will get mass flow rate of the fluid. In simple words mass flow rate is density times its volume flow rate.
How to calculate Density from Volumetric Flow Rate?
Density is one of the important physical property and has influence on flow rates.
Density varies as per the type of fluid and atmospheric conditions. For example, density of cold water and hotwater are different. Though oil and water both are liquid, they have vast difference in density.
Volume Flow Rate is given by
Q=V/t Eq(1)
Where, V=Volume
t=Time
Volume, V=Mass/Density
Or V=m/ρ
Substituting value of V in eq (1)
Q=m/ρ. t
ρ=m/Q . t Eq(2)
ρ=mass flow rate/volume flow rate
Density and Flow Rate
Flow Rate of a process line is the rate at which a fluid is passing through it.
Generally flow rate is expressed in terms of Mass Flow Rate(kg/min) and Volume Flow Rate(l/min). Density is the ratio of mass to volume(kg/ m3).
The relation between Density and Flow rate is given as follows:
Density,ρ=mass flow rate/volume flow rate
Density (ρ)is the mass per unit volume of a material. Fluid with high density means more number of molecules per unit volume that means more viscous or heavier and more energy is required to move the fluid resulting low velocity.
Density varies directly with pressure and inversely with temperature. Since liquids are generally incompressible in nature, therefore there is no influence of pressure on density measurement of liquid. Only change in temperature have to be considered.
Gases are compressible in nature and density of gases change with variation of temperature and pressure.
How is Density related to Flow Rate?
To control processes in an industry and to get maximum output from a process specific value of a fluid flow rate is always required.
Density is one of the physical properties of a substance which is influenced by temperature change. As the temperature increases, the kinetic energy of the molecules of the substance also increases resulting a change in density of the substance.
Different flow measuring devices are used in an industry to get accurate measurements.To get the idea of a flow rate of a fluid we should also have a knowledge of fluid density.
Density of a fluid varies with temperature, now in industrial process if the temperature changes, it leads to decrease in density of the fluid, resulting in increase in the volume. Similarly, when the temperature decreases the volumetric flow decreases due to higher fluid density.
This variation in the volumetric flow because of variation in temperature leads to inaccurate accounting and mass balance of the process. To counter the same industrial processes normally carry out a procedure called temperature compensation of flow.
In case of compressible fluids(gases), along with temperature pressure also plays a significant impact on density of the fluid. Hence for gases the compensative flow takes into account the density change with both temperature and pressure.
PV=nRT Eq(1)
Where, n=m/Mw
ρ=m/V
From Eq 1,
ρ=PMw/RT Eq(2)
P = Pressure
T = Temperature
V = Volume
Mw = Molecular Weight
n = Number of moles
R = Gas constant
ρ = steam or gas density
Depending upon the various conditions we will get different outputs for design and real situations.
Using the ρRealand ρDesign formulas, we can derive the formula for real density of the process considering pressure and temperature compensation.
The ratio of volume of a substance and its mass is known as Density ρ.
Whenever we apply heat to a liquid or gas the kinetic energy of the molecules increases due to which they cover a larger space resulting in higher volume. This implies that density is inversely proportional to the temperature.
On the other hand if pressure is applied to a body it gets compressed resulting lesser volume and higher density.
Example1: The density of the liquid is A liquid is flowing through a pipe of inner radius 6 cm with a velocity of 12m/s and the density 940 kg/m3.Determine the mass flow rate of the flow.
Solution:
Here velocity, v=12m/s, Radius of the pipe, r=6 cm, Density of liquid, ρ=940 kg/m3=
Area of the pipe=π. r2=π. 62 cm2=113.04 cm2=0.011304 m2
Volume Flow Rate= Q= v. A=12 . 0.011304=0.1356 m3/s
Example2: Determine the velocity of flowing water through a circular pipe. Here the inner radius of the pipe is 2cm and flow rate if water is 0. 056m3/s. Consider the density of water as ρ=998kg/m3.
Solution:
Here Radius of the pipe, r=2 cm, Flow Rate, Q=0.056m3/s, Density, ρ=998 kg/m3
Area of the pipe= π . r2 = π . 22 cm2=12.56 cm2=0.00125 m2
