We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What is a Heat Engine?

By Parker Brown
Updated May 17, 2024
Our promise to you
About Mechanics is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At About Mechanics, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject-matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

A heat engine is a device used to convert thermal energy, or heat, into mechanical work. This is done when heat, originating from a hot source, goes through the engine itself and into a cold sink. The cold sink is the lower-temperature part of a thermodynamic cycle, such as the condensing unit found in the Rankine, or steam, cycle. There are many different types of heat engines, each of which has its own specific cycle. Some examples of heat engines would include steam and internal combustion engines, along with Stirling engines and gas turbines.

Commonly, a heat engine will be confused with the thermodynamic cycle taking place within the engine itself. This is mainly because heat engines are often classified by their specific thermodynamic cycles. The device itself that converts thermal energy to work is known as the "engine," while the thermodynamic model being applied to the engine is the "cycle." Due to this, steam engines are not referred to as Rankine engines.

An efficient heat engine will try and mimic its respective cycle as well as possible. The higher the temperature difference between the hot source and the cold sink within the cycle, the more efficient the engine is. For example, an efficient steam engine requires both a high-temperature heat source and a low-temperature cold sink. In the Rankine cycle, a boiler makes use of a high-temperature burner to convert water into the steam. This steam goes through the engine and is then condensed back into water through a low-temperature condenser.

The colder the condenser is, the more steam will be condensed back into water. This is because condensers are made to effectively reverse the saturation process carried out by the boiler. Doing so will help achieve higher condensing rates; the higher the rate is, the more water will be returned. This helps to increase the overall efficiency of the steam cycle.

While heat engine efficiency can be highly optimized through a large difference in temperatures between the hot source and cold sink, it is still limited. This is because the temperature of the cold sink is dependent on the temperature surrounding it, which in some situations, cannot be cooled to ideal conditions. Due to this, the efficiency of a heat engine is limited to the temperature limits of the cold sink. A common solution to this is to increase the temperature of the hot source; yet even this is limited to a lack of material strength under high temperatures.

Heat engine efficiency varies depending upon the specific engine and cycle. Thermal efficiency ranges anywhere from 3% to around 70%, with car engines achieving a thermal efficiency somewhere around 25%. The more efficient heat engines are found in large power plants, where both gas and steam turbines are used to generate electricity.

About Mechanics is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
About Mechanics, in your inbox

Our latest articles, guides, and more, delivered daily.

About Mechanics, in your inbox

Our latest articles, guides, and more, delivered daily.