Heat Engine Questions

Heat is a type of energy that can be quickly transferred from one object to another. One of the most exciting concepts is a heat engine that works based on this principle. A heat engine transforms the energy closed in fuels, such as natural gas, coal, gasoline, wood, and peat, into force and motion. As fuel burns in an engine, it releases energy to fuel factory machinery and locomotives. Therefore, heat engines are engines that burn fuel to release heat. So, a heat engine is an engine that transfers the chemical energy of fuel into thermal energy, which is used for application purposes.

In general, heat engines can be classified into two types. They are:

• Internal combustion engines
• External combustion engines

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Important Questions with Answers

1. What are the advantages of external combustion engines?

Here are some of the benefits of external combustion engines.

• The external combustion engine is compatible with most types of fuels.
• The external combustion engine is economical.
• It can operate at high altitudes and emits minimal pollution.

2. Describe the types of heat engines with examples.

In general, heat engines can be categorised into two main types:

1. Internal Combustion Engines

Internal combustion engines, commonly used in vessels, ships, motorcars, aircraft, and trains, are the most well-known type of heat engine. They are called so because the fuel is ignited to accomplish work inside the engine. The equivalent combination of air and gasoline is later expelled as exhaust. In this form, fuel burning occurs inside the system. Pistons are primarily used in internal combustion heat engines. In heat engines, pistons move up and down inside the cylinders. When a single movement of a piston moves in the upward and downward direction inside the cylinder, it is also called the stroke.

Here are some examples of internal combustion engines.

• Piston engine
• Gas turbine
• Jet engine
2. External Combustion Engines

External heat engines are nothing but steam engines that are different from internal heat engines; the heat source is distinct from the working gas. Because the combustion carries out outside the engine, these heat engines are usually known as external combustion engines. A heat engine contains a functional fluid heated by combustion in an outer source through the heat exchanger. In these heat engines, fuel is burned outside the engine, or in another way, we can say it is burned outside the combustion chamber. External combustion, for example, would include utilising a flame to convert water into steam and then using the steam to control a turbine. Internal combustion, like in a car engine, occurs when fuel ignites inside a piston, performs work, and is released.

Here are some examples of external combustion engines.

• Nuclear reactors
• Coal-fired power plant
• Natural gas power plant

3. What is the principle of a heat engine?

The first and second laws of thermodynamics restrict the operation of a heat engine. An external combustion engine produces force and motion by burning fuel outside and away from the main engine. In terms of external combustion engines, steam engines are one of the best examples.

4. What makes a heat engine impossible?

A perfect heat engine is hard to achieve since heat engines always produce waste heat. To be more specific, heat is a low-grade kind of energy. This energy can be lost by various methods, including conduction, radiation, and convection.

5. What is the maximum efficiency of a heat engine?

Due to practical limitations, heat engines often operate at around 30% to 50% efficiency. Heat engines cannot achieve 100% thermal efficiency, that is η=1, according to the second law of thermodynamics.

6. What is the purpose of a temperature difference in a heat engine?

Increasing the temperature of the fluid inside the cylinder makes the cycle more efficient initially, as does lowering the temperature at the opposite end of the process. In other words, an efficient heat engine operates between the most crucial temperature difference possible.

7. What is a heat engine?

A heat engine is an engine that turns the chemical energy of the fuel into thermal energy, which is then used to perform practical work.

8. Why is a heat engine important?

The ability to put heat to work, for us, is one of the essential things. A heat engine performs this by converting heat into work using thermodynamic principles. Examples of heat engines include jet engines and diesel engines, gasoline and steam turbines that produce electricity.

9. A heat engine functions specifically on a high-temperature heat reservoir.

a. True

b. False

Answer: b. False

Explanation: A heat engine cannot function on a very high-temperature heat reservoir because the cycle cannot complete without the cooling in the condenser. A heat engine always wastes some energy by transmitting it to a low-temperature reservoir to end the process.

10. What creates thermal energy?

When an increasing temperature causes atoms and molecules to move quickly and collide, they produce thermal energy, which is also named heat energy.

Practice Questions

1. Describe the advantages of external combustion engines.
2. What is the difference between a heat pump and a heat engine?
3. How can we find the efficiency of a heat engine?
4. What are the major components of a heat engine?
5. How does a heat engine power a machine?

Watch the video below to learn more about Thermodynamics Devices.

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