Related Experiment Video
Updated: Jul 4, 2026
04:35
Comparative Study of Simulation of Temperature Rise in Ring Main Unit
Published on: July 5, 2024
Coupled heat devices in linear irreversible thermodynamics
B Jiménez de Cisneros1, A Calvo Hernández
1Departamento de Física Aplicada, Universidad de Salamanca, 37008 Salamanca, Spain.
Summary
This study models heat engines and refrigerators using coupled devices, revealing that individual device performance doesn't need to match for optimal overall system efficiency in finite-time thermodynamics.
Area of Science:
- Thermodynamics
- Energy Conversion
- Irreversible Processes
Background:
- Linear irreversible thermodynamics provides models for heat engines and refrigerators.
- Finite-time thermodynamics explores efficiency limits and operational strategies.
- Coupled heat devices can represent complex thermodynamic systems.
Purpose of the Study:
- To develop analytical models for heat engines and refrigerators using coupled irreversible heat devices.
- To explore the relationship between individual device performance and overall system behavior.
- To derive results and techniques from finite-time thermodynamics.
Main Methods:
- Modeling heat engines and refrigerators as a chain of coupled heat devices.
- Applying linear irreversible thermodynamics principles.
- Deriving endoreversible efficiencies and irreversible heat device models.
Main Results:
- Analytical models for heat engines and refrigerators were defined using coupled devices.
- Techniques from finite-time thermodynamics were derived.
- A counterintuitive finding: individual device operation regimes do not need to be uniform for desired overall performance.
Conclusions:
- Coupled heat device chains offer a framework for analyzing irreversible thermodynamics.
- Optimal overall performance does not necessitate identical individual device operation.
- This approach provides insights into efficient energy conversion under irreversible conditions.
Related Concept Videos
01:30The Carnot Cycle
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...
What could be the theoretical limit to the efficiency of a heat engine? The...
01:20The Carnot Cycle and the Second Law of Thermodynamics
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...
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...
01:18Entropy
The first law of thermodynamics is quantitatively formulated via an equation relating the internal energy of a system, the heat exchanged by it, and the work done on it. A quantitative formulation of the second law of thermodynamics leads to defining a state function, the entropy.
When an ideal gas expands isothermally, the disorder in the gas increases. From the molecular perspective, the gas molecules have more volume to move around in.
Consider an infinitesimal step in the expansion, which...
When an ideal gas expands isothermally, the disorder in the gas increases. From the molecular perspective, the gas molecules have more volume to move around in.
Consider an infinitesimal step in the expansion, which...
01:15Statements of the Second Law of Thermodynamics
The second law of thermodynamics can be stated in several different ways, and all of them can be shown to imply the others. The Clausius’ statement of the second law of thermodynamics is based on the irreversibility of spontaneous heat flow. It states that heat will not flow from the colder body to the hotter body unless some other process is involved. Additionally, as per the Kelvin’s statement, it is impossible to convert the heat from a single source into work without any other effect. This...
01:10Heat Engines
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...
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...
01:20Mechanisms of Heat Transfer II
In convection, thermal energy is carried by the large-scale flow of matter. Ocean currents and large-scale atmospheric circulation, which result from the buoyancy of warm air and water, transfer hot air from the tropics toward the poles and cold air from the poles toward the tropics. The Earth’s rotation interacts with those flows, causing the observed eastward flow of air in the temperate zones. Convection dominates heat transfer by air, and the amount of available space for the airflow...