Heat Energy To Mechanical Energy: How To Convert, FAQs And Facts

Heat engines are the most common devices that convert heat energy to mechanical energy. The major discussion in this article is about how to convert heat energy to mechanical energy.

In a heat engine, the thermal properties of gases like expansion or compression, or the properties associated during phase transitions of substances are exploited to promote energy conversion. The energy released during high temperature to low temperature transition is transformed to mechanical energy.

How to convert heat energy to mechanical energy?

In our day-to-day life, we encounter several machineries that convert heat energy to mechanical energy, like pressure cooker, power plants, internal combustion engine, steam engine, etc. We shall discuss on how energy conversion takes place in these contexts.

Internal combustion engines

Engines in automobiles are internal combustion engines.

heat energy to mechanical energy — **Internal Combustion Engine**
Image Credits: Flickr

An internal combustion engine works mainly by the ignition and combustion of the fuel present in the engine. It consists of a moving piston in addition to a fixed cylinder. Once the fuel is subjected to ignition and then combustion, gases expand which moves the piston. Moving piston now rotates the crankshaft, which ultimately drives the vehicle’s wheels through the system of gears.

Accordingly heat energy from the fuel combustion is transformed to mechanical energy.

Steam Engine

Steam engines are a kind of external combustion engines where fuel is burned externally.

In a steam engine, water is initially converted to steam. The heat energy of the superheated steam moves a piston back and forth in a cylinder. This motion, in turn, rotates the crankshaft which facilitates the rotatory motion for the driving machinery. Thus energy transformation from heat energy to mechanical energy is obtained.

At present, steam engines have been replaced by more economical and efficient devices like internal combustion engines, electric motors, etc.

Power plants

The main objective of a power plant is to generate electricity from the combustion of fuel like natural gas or coal. While the overall energy conversion in power plant is chemical energy to electrical energy, an intermediate process converts heat energy to mechanical energy.

As the fuel undergoes combustion, chemical energy is converted to heat energy. The hot gases generated from the combustion converts water to steam. This steam travels through high pressure and high temperature, which then expands through a turbine, rotating it and hence mechanical energy is generated.

Pressure cooker

Pressure cooker is one of the common example in our daily life for the conversion of heat energy to mechanical energy.

In a pressure cooker, the heat from the external agent (like stove), converts water to steam. The steam possesses enough heat energy to move the cooker whistle. The motion of the cooker whistle is due to the mechanical energy.

Propulsion of rockets

A part of energy conversion in rocket engines is from heat to mechanical energy.

A rocket engine contains a combustion chamber within which heat energy is generated by the hot pressurized gas. This energy of the gas is often referred to as its enthalpy. When this hot gas is released, the rocket motor converts enthalpy into kinetic energy (a form of mechanical energy). This kinetic energy powers the rocket for its propulsion.

images — **Rocket Propulsion**
Image Credits: Pixabay

Energy transformations from one kind to another follow the principle of conservation of energy.

Heat Energy To Mechanical Energy: Frequently Asked Questions

Describe the two kinds of mechanical energy with examples.

An object’s position and motion determines its mechanical energy. Mechanical energy is generally classified into:

Kinetic Energy

Potential Energy

The combination of both the potential energy and the kinetic energy of a body gives its net mechanical energy.

Kinetic energy of a body is the energy possessed due to its motion. For example, the energy we exert when we run, play, jump, dance, etc is kinetic energy. The motion of a car is due to the kinetic energy (mechanical energy) generated from the engine.

download — **Children playing football – Kinetic Energy**
Image Credits: Pixabay

Potential energy of a body is due to its position or configuration. An object raised to a certain height contains gravitational potential energy. A rock present at the edge of a cliff possesses potential energy. Rubber band pulled to its extremes possess elastic potential energy. Hydroelectric power is obtained from the water stored in dams because, the potential energy of the water stored in the dam is converted to the kinetic energy of the rotating turbines and then finally electrical energy.

download 1 — **Elastic Potential Energy** **– Rubber Band**
Image Credits: Wikimedia Commons

What is meant by an external combustion engine? Give examples.

Unlike an internal combustion engine which burns fuel within the engine, an external combustion engine works by the combustion of fuel outside the engine.

Examples for an external combustion engine are:

Boiling water heater

Steam engine

The working efficiency of an external combustion engine is only about 15-25 % in contrast to that of internal combustion engines which is 35-45% efficient.

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Deeksha Dinesh

Hello, I am Deeksha Dinesh, currently pursuing post-graduation in Physics with a specialization in the field of Astrophysics. I like to deliver concepts in a simpler way for the readers.