Is Boiler Closed System Or Machine? 5 Facts You Should Know

In this article we will try to answer the question “is Boiler Closed System or Machine?”

Before starting the discussion we should have proper knowledge of the three terms Boiler, Closed System and Machine.

What is a Boiler?

A boiler is a closed vessel in which generally water is heated and the vaporized fuel is used for various applications like water heating, cleaning,  cooling,  sanitization, power generation, cooking etc.

Steam is produced from the interaction of water passing through pipes and hot flue gases generated from combustion of fuel.

What is a Closed System?

It is a type of thermodynamic system where mass is conserved within the boundaries of the system, but energy is allowed to freely enter or exit the system. In simple words in a closed system exchange of energy in the form of heat or work is allowed but exchange of matter is not allowed.

What is a Machine?

A physical system consisting of moving parts is designed to perform a definite job using electricity, gas or steam. A machine consists of certain moving elements.

How is Boiler Closed System?

A boiler which is mainly used to produce hot water or steam, can be resembled with a closed system.

A boiler along with the connected pipes can be considered as a closed system. The heat energy supplied from the combustion of fuel( mainly coal) causes the stored water inside the bolier be heated up and if it continues further then water is converted into steam.

Steam generated or boiled water is piped from the boiler for different applications. Without considering the attached pipes, a boiler does not represent a closed system as continuous exit of steam and entry of condensate has taken place.

is boiler closed system
Schematic diagram of a marine-type water tube boiler; Image Credit: Wikipedia

Is a Combi Boiler a Closed System?

A combi boiler can provide instant heating as well as hot water supply in one unit. 

Absence of a tank in a combi boiler makes it different from the other boilers, the innermost heating part of a combi boiler is on a pressurized closed loop system. It is heated by the boiler as per the requirement. In case of a domestic hot water supply requirement, the mains supply is directly connected with the boiler.

No need to refill hot tank and with the help of mains pressure a regular flow of hot water is possible. Within a sealed system combination boiler pump the water around the heating system.

Due to the absence of an external feed and expansion tank this type of boilers require very less space.

Is A Boiler A Closed Loop System?

Ideally a Boiler is a closed loop system as water is heated to produce steam and the steam is passed through the pipes to the heat exchanger where the steam get condensed, the condensate is returned back to the boiler again.

Most of the boilers are not perfectly sealed due to this reason a little bit leakage is always associated.

The method of conversion of water into steam inside a boiler is not complex, more attention should be paid to continuous steam production. For that a measure and control of the water level inside the steam drum is required.

Is Boiler a Machine?

A boiler can not be considered as a machine since it has no any movable element.

Generally machines contain certain components that allow movements, a physical system using power to apply forces and control movement to perform an action. On the contrary a boiler is a device used to generate steam by heating water.

is Boiler a Ventilation System?

A boiler itself does not require ventilation, but waste gases generated during the operation need to be escaped.

Ventilation refers to the air required to burn the fuel of a boiler. Air vents or any additional ventilation are not required to attach in a  boiler cupboard but sufficient amount of oxygen is necessary to burn the gas and keep certain parts cool.

Modern condensing boilers consist of a balanced flue pipe The gas boilers which are installed from April 2005 onwards can be considered as modern condensing boilers. The best feature of these boilers are their flue pipe.

Balanced flue pipe consists of two tubes, one of which carry the waste gases out from the boiler to the surrounding and through the other one fresh air comes inside the boiler.This method provides the necessary ventilation of a condensing boiler.

Before 2005, the old boilers are not room sealed and have open flue, this indicates waste gases produced are released to the atmosphere but no any provision to bring oxygen inside the boiler.So they need to be well ventilated. Making mistakes with boiler ventilation system may cause serious problem.

Is boiler a power producing device?

A boiler is a power producing device once it is coupled with a steam turbine and generator along with some auxiliaries.

The main components of steam power plants are boilers, steam turbines, generators and some other associated parts. Here the function of a boiler is to produce steam at quite high pressure. The heat energy of steam is then converted into mechanical energy with the help of steam turbine. Finally this mechanical energy is converted into electric power by the generators.

Boilers have broad application in different industries such as power sectors, thermal power plants, food industries, sugar plants, textiles etc. Steam produced by the steam boilers are essential to rotate the turbine blades for power generation as well as certain other applications in factories.

An industrial boiler, originally used for supplying steam to a steam engine; Image Credit: Wikipedia


In this article we discuss” is boiler a closed system or machine?”. To wrap up the article we can say a boiler generates steam following the criteria of a closed system. A boiler act as a power-producing device coupling with a steam turbine. But due to the absence of any movable components, we can not compare it with a machine.

Sangeeta Das

I am Sangeeta Das. I have completed my Masters in Mechanical Engineering with specialization in I.C Engine and Automobiles. I have around ten years of experience encompassing industry and academia. My area of interest includes I.C. Engines, Aerodynamics and Fluid Mechanics. You can reach me at

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