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Related Concept Videos

Heat Engines01:10

Heat Engines

3.1K
A heat engine is a device used to extract heat from a source and then convert it into mechanical work used for various applications. For example, a steam engine on an old-style train can produce the work needed for driving the train.
Whenever we consider heat engines (and associated devices such as refrigerators and heat pumps), we do not use the standard sign convention for heat and work. For convenience, we assume that the symbols Qh, Qc, and W represent only the amounts of heat transferred...
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The Carnot Cycle01:30

The Carnot Cycle

3.2K
Converting work to heat is an irreversible process, and the purpose of a heat engine is to reverse the effect partially. Heat engines aim to increase the efficiency of the reversal, that is, maximize the work retrieved from heat. If the efficiency of a heat engine were 100%, it would imply reversing the process completely without introducing any other effect. Thus, it would violate the second law of thermodynamics.
What could be the theoretical limit to the efficiency of a heat engine? The...
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Refrigerators and Heat Pumps01:07

Refrigerators and Heat Pumps

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Refrigerators or heat pumps are heat engines operating in a reverse direction. For a refrigerator, the focus is on removing heat from a specific area, whereas, for a heat pump, the focus is on dumping heat into one particular area. A refrigerator (or heat pump) absorbs heat Qc from the cold reservoir at Kelvin temperature Tc and discards heat Qh to the hot reservoir at Kelvin temperature Th, while work W is done on the engine’s working substance.
A household refrigerator removes heat from...
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The Carnot Cycle and the Second Law of Thermodynamics01:20

The Carnot Cycle and the Second Law of Thermodynamics

2.9K
The Carnot engine works between two heat reservoirs of fixed temperatures. The Carnot cycle begs the following question: Is it possible to devise a heat engine that is more efficient than a Carnot engine between two fixed temperatures? The answer lies in designing a Carnot refrigerator.
Since the individual steps in a Carnot cycle can be reversed, the entire cycle is, thus, reversible. If a Carnot cycle is reversed, it becomes a Carnot refrigerator. It extracts heat Qc from a cold reservoir at...
2.9K
Efficiency of The Carnot Cycle01:16

Efficiency of The Carnot Cycle

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The hypothetical Carnot cycle consists of an ideal gas subjected to two isothermal and two adiabatic processes. Since the internal energy of an ideal gas depends only on its temperature, which is the same before and after the completion of the Carnot cycle, there is no change in its internal energy. Hence, using the first law of thermodynamics, the total heat exchanged by the ideal gas equals the total work done. Thus, we can quantify the efficiency of the Carnot cycle via the heat exchanged...
2.9K
Mechanisms of Heat Transfer01:14

Mechanisms of Heat Transfer

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Heat transfer between the human body and its environment occurs through four main mechanisms: conduction, convection, radiation, and evaporation.
Conduction, accounting for approximately 3% of body heat loss at rest, is the process of exchanging heat between molecules of two materials in direct contact. This can result in both heat loss and gain. For instance, when the body is submerged in water, which conducts heat 20 times more effectively than air, it can either lose or gain significant...
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Related Experiment Video

Updated: Sep 30, 2025

Asymmetric Thermoelectrochemical Cell for Harvesting Low-grade Heat under Isothermal Operation
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Adaptive Heat Engine.

A E Allahverdyan1, S G Babajanyan1, N H Martirosyan1

  • 1Yerevan Physics Institute, Alikhanian Brothers Street 2, Yerevan 375036, Armenia.

Physical Review Letters
|July 30, 2016
PubMed
Summary

This study introduces an adaptive heat engine that adjusts its structure to thermal baths without external control. This innovation allows engines to utilize unknown resources and adapt to their operational environment.

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Area of Science:

  • Thermodynamics
  • Engineering
  • Artificial Intelligence

Background:

  • Traditional heat engines require complex on-line control or external fitting to match environmental parameters.
  • This limitation hinders their efficiency and adaptability in diverse operational settings.

Purpose of the Study:

  • To investigate a novel model of an adaptive heat engine.
  • To explore an engine design that autonomously adjusts its structure based on environmental feedback.

Main Methods:

  • Developing a theoretical model for an adaptive heat engine.
  • Analyzing the feedback mechanisms enabling structural adaptation.
  • Investigating the engine's ability to utilize unknown resources.

Main Results:

  • The adaptive heat engine eliminates the need for on-line control and external fitting.
  • The engine demonstrates self-adaptation to varying thermal bath conditions.
  • Adaptation resources are identified and linked to available prior environmental information.

Conclusions:

  • Adaptive heat engines offer a more autonomous and flexible approach to thermal energy conversion.
  • This model paves the way for engines that can operate efficiently in unpredictable environments.
  • Understanding adaptation resources is key to designing robust and intelligent heat engines.