scholarly journals A critique of some modern applications of the Carnot heat engine concept: the dissipative heat engine cannot exist

2010 ◽  
Vol 466 (2119) ◽  
pp. 1893-1902 ◽  
Author(s):  
Anastassia M. Makarieva ◽  
Victor G. Gorshkov ◽  
Bai-Lian Li ◽  
Antonio Donato Nobre
Keyword(s):  
Heat Input ◽  
Heat Engine ◽  
External Heat ◽  
Mechanical Work ◽  
Physical Models ◽  
Carnot Cycle ◽  
Engine Model ◽  
Dissipative Heat ◽  
Internal Dissipation ◽  
Engine Concept

In several recent studies, a heat engine operating on the basis of the Carnot cycle is considered, where the mechanical work performed by the engine is dissipated within the engine at the temperature of the warmer isotherm and the resulting heat is added to the engine together with an external heat input. This internal dissipation is supposed to increase the total heat input to the engine and elevate the amount of mechanical work produced by the engine per cycle. Here it is argued that such a dissipative heat engine violates the laws of thermodynamics. The existing physical models employing the dissipative heat engine concept, in particular the heat engine model of hurricane development, need to be revised.

Comment on Makarieva et al . ‘A critique of some modern applications of the Carnot heat engine concept: the dissipative heat engine cannot exist’

2010 ◽  
Vol 467 (2125) ◽  
pp. 1-6 ◽  
Author(s):  
Marja Bister ◽  
Nilton Renno ◽  
Olivier Pauluis ◽  
Kerry Emanuel
Keyword(s):  
Wind Speed ◽  
Heat Engine ◽  
Dissipative Heating ◽  
Dissipative Heat ◽  
External Objects ◽  
Laws Of Thermodynamics ◽  
Physical Laws ◽  
Work Done ◽  
Fundamental Physical ◽  
Engine Concept

Makarieva et al . (2010) assert that a dissipative heat engine is impossible and criticize earlier published work that they claim violates the laws of thermodynamics. Here we show that the earlier work does not violate fundamental physical laws and suggest that Makarieva et al . (2010) were misinterpreting expressions for wind speed as ones for work done on external objects. Moreover, we dispute their assertion that dissipative heating is necessarily compensated by a reduction of external heating.

scholarly journals Can Quantum Correlations Lead to Violation of the Second Law of Thermodynamics?

Entropy ◽  
2021 ◽  
Vol 23 (5) ◽  
pp. 573
Author(s):  
Alexey V. Melkikh
Keyword(s):  
Quantum Entanglement ◽  
Local Equilibrium ◽  
Heat Engine ◽  
Thermodynamic Quantity ◽  
Second Law Of Thermodynamics ◽  
Quantum Correlations ◽  
Von Neumann Entropy ◽  
Second Law ◽  
Carnot Cycle ◽  
Technical Discussion

Quantum entanglement can cause the efficiency of a heat engine to be greater than the efficiency of the Carnot cycle. However, this does not mean a violation of the second law of thermodynamics, since there is no local equilibrium for pure quantum states, and, in the absence of local equilibrium, thermodynamics cannot be formulated correctly. Von Neumann entropy is not a thermodynamic quantity, although it can characterize the ordering of a system. In the case of the entanglement of the particles of the system with the environment, the concept of an isolated system should be refined. In any case, quantum correlations cannot lead to a violation of the second law of thermodynamics in any of its formulations. This article is devoted to a technical discussion of the expected results on the role of quantum entanglement in thermodynamics.

scholarly journals Action and Entropy in Heat Engines: An Action Revision of the Carnot Cycle

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 860
Author(s):  
Ivan R. Kennedy ◽  
Migdat Hodzic
Keyword(s):  
Heat Engine ◽  
Working Fluid ◽  
Field Energy ◽  
Carnot Cycle ◽  
Gibbs Potential ◽  
Atmospheric Gases ◽  
Temperature Dependent ◽  
Expansion Phase ◽  
Heat Engines ◽  
The Difference

Despite the remarkable success of Carnot’s heat engine cycle in founding the discipline of thermodynamics two centuries ago, false viewpoints of his use of the caloric theory in the cycle linger, limiting his legacy. An action revision of the Carnot cycle can correct this, showing that the heat flow powering external mechanical work is compensated internally with configurational changes in the thermodynamic or Gibbs potential of the working fluid, differing in each stage of the cycle quantified by Carnot as caloric. Action (@) is a property of state having the same physical dimensions as angular momentum (mrv = mr2ω). However, this property is scalar rather than vectorial, including a dimensionless phase angle (@ = mr2ωδφ). We have recently confirmed with atmospheric gases that their entropy is a logarithmic function of the relative vibrational, rotational, and translational action ratios with Planck’s quantum of action ħ. The Carnot principle shows that the maximum rate of work (puissance motrice) possible from the reversible cycle is controlled by the difference in temperature of the hot source and the cold sink: the colder the better. This temperature difference between the source and the sink also controls the isothermal variations of the Gibbs potential of the working fluid, which Carnot identified as reversible temperature-dependent but unequal caloric exchanges. Importantly, the engine’s inertia ensures that heat from work performed adiabatically in the expansion phase is all restored to the working fluid during the adiabatic recompression, less the net work performed. This allows both the energy and the thermodynamic potential to return to the same values at the beginning of each cycle, which is a point strongly emphasized by Carnot. Our action revision equates Carnot’s calorique, or the non-sensible heat later described by Clausius as ‘work-heat’, exclusively to negative Gibbs energy (−G) or quantum field energy. This action field complements the sensible energy or vis-viva heat as molecular kinetic motion, and its recognition should have significance for designing more efficient heat engines or better understanding of the heat engine powering the Earth’s climates.

The Role of Internal Irreversibilities in the Performance and Stability of Power Plant Models Working at Maximum ϵ-Ecological Function

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Gabriel Valencia-Ortega ◽  
Sergio Levario-Medina ◽  
Marco Antonio Barranco-Jiménez
Keyword(s):  
Power Plants ◽  
Heat Engine ◽  
Combined Cycle ◽  
Ecological Function ◽  
Operating Conditions ◽  
Maximum Efficiency ◽  
Working Fluid ◽  
Engine Model ◽  
Improved Stability ◽  
The Stability

Abstract The proposal of models that account for the irreversibilities within the core engine has been the topic of interest to quantify the useful energy available during its conversion. In this work, we analyze the energetic optimization and stability (local and global) of three power plants, nuclear, combined-cycle, and simple-cycle ones, by means of the Curzon–Ahlborn heat engine model which considers a linear heat transfer law. The internal irreversibilities of the working fluid measured through the r-parameter are associated with the so-called “uncompensated Clausius heat.” In addition, the generalization of the ecological function is used to find operating conditions in three different zones, which allows to carry out a numerical analysis focused on the stability of power plants in each operation zone. We noted that not all power plants reveal stability in all the operation zones when irreversibilities are considered through the r-parameter on real-world power plants. However, an improved stability is shown in the zone limited by the maximum power output and maximum efficiency regimes.

Thermodynamic Processes

2019 ◽  
pp. 132-147
Author(s):  
Robert H. Swendsen
Keyword(s):  
Real World ◽  
Heat Engine ◽  
Second Law Of Thermodynamics ◽  
Heat Pumps ◽  
Second Law ◽  
Carnot Cycle ◽  
Heat Engines ◽  
Negative Temperatures ◽  
Special Case ◽  
Thermodynamic Processes

This chapter begins by defining terms critical to understanding thermodynamics: reversible, irreversible, and quasi-static. Because heat engines are central to thermodynamic principles, they are described in detail, along with their operation as refrigerators and heat pumps. Various expressions of efficiency for such engines lead to alternative expressions of the second law of thermodynamics. A Carnot cycle is discussed in detail as an example of an idealized heat engine with optimum efficiency. A special case, called negative temperatures, where temperatures actually exceed infinity, provides further insights. In this chapter we will discuss thermodynamic processes, which concern the consequences of thermodynamics for things that happen in the real world.

scholarly journals Optimal Power and Efficiency of Multi-Stage Endoreversible Quantum Carnot Heat Engine with Harmonic Oscillators at the Classical Limit

Entropy ◽  
2020 ◽  
Vol 22 (4) ◽  
pp. 457 ◽  
Author(s):  
Zewei Meng ◽  
Lingen Chen ◽  
Feng Wu
Keyword(s):  
Classical Limit ◽  
Heat Engine ◽  
Combined Cycle ◽  
Harmonic Oscillators ◽  
Total Power ◽  
Cycle Period ◽  
Carnot Cycle ◽  
Heat Current ◽  
Operating Modes ◽  
Multi Stage

At the classical limit, a multi-stage, endoreversible Carnot cycle model of quantum heat engine (QHE) working with non-interacting harmonic oscillators systems is established in this paper. A simplified combined cycle, where all sub-cycles work at maximum power output (MPO), is analyzed under two types of combined form: constraint of cycle period or constraint of interstage heat current. The expressions of power and the corresponding efficiency under two types of combined constrains are derived. A general combined cycle, in which all sub-cycles run at arbitrary state, is further investigated under two types of combined constrains. By introducing the Lagrangian function, the MPO of two-stage combined QHE with different intermediate temperatures is obtained, utilizing numerical calculation. The results show that, for the simplified combined cycle, the total power decreases and heat exchange from hot reservoir increases under two types of constrains with the increasing number (N) of stages. The efficiency of the combined cycle decreases under the constraints of the cycle period, but keeps constant under the constraint of interstage heat current. For the general combined cycle, three operating modes, including single heat engine mode at low “temperature” (SM1), double heat engine mode (DM) and single heat engine mode at high “temperature” (SM2), appear as intermediate temperature varies. For the constraint of cycle period, the MPO is obtained at the junction of DM mode and SM2 mode. For the constraint of interstage heat current, the MPO keeps constant during DM mode, in which the two sub-cycles compensate each other.

Testing of a CR5 Solar Thermochemical Heat Engine Prototype

2010 ◽  
Author(s):  
Richard B. Diver ◽  
James E. Miller ◽  
Nathan P. Siegel ◽  
Timothy A. Moss
Keyword(s):  
Heat Engine ◽  
Chemical Conversion ◽  
Liquid Hydrocarbon ◽  
Lessons Learned ◽  
Solar Furnace ◽  
Liquid Fuels ◽  
Test Facility ◽  
Efficient Production ◽  
Solar Thermochemical ◽  
Engine Concept

Sandia National Laboratories (SNL) is investigating thermochemical approaches for reenergizing CO2 and H2O feed stocks for input to synthetic liquid hydrocarbon fuels production. Key to the approach is the Counter-Rotating-Ring Receiver/Reactor/Recuperator (CR5), a novel solar-driven thermochemical heat engine concept for high-temperature carbon dioxide and water splitting based on two-step, nonvolatile metal oxide thermochemical cycles. The CR5 integrates two reactors, recuperators, and solar receiver and intrinsically separates the product gases. The CR5 thermochemical heat engine concept and the underlying thermodynamics and kinetics have many uncertainties. While results from laboratory scale material tests are promising, they are different than what occurs in a CR5. To evaluate the potential of the CR5 we have designed and built a CR5 prototype. The overall objective of the SNL Sunshine to Petrol (S2P) project is to show a solar thermochemical pathway for the efficient production of liquid fuels from CO2 and H2O feed stocks. To achieve the overall long-term goal of 10% efficient conversion of sunlight to petroleum, the thermochemical solar conversion of sunlight to CO needs to be 20% efficient. The short-term goal for the CR5 prototype is to demonstrate a solar to chemical conversion efficiency of at least 2%. In this paper, we present initial test results for the CR5 prototype in the 16 kWt National Solar Thermal Test Facility (NSTTF) solar furnace in Albuquerque, NM. Lessons learned from the initial tests and approaches for improving performance to achieve our goals are also presented.

Effect of External Heat Input on Fluid Sloshing Dynamic Performance in a Liquid Oxygen Tank

2020 ◽  
Vol 21 (4) ◽  
pp. 879-888
Author(s):  
Zhan Liu ◽  
Yuyang Feng ◽  
Yuanliang Liu ◽  
Jia Yan ◽  
Yanzhong Li
Keyword(s):  
Heat Input ◽  
Dynamic Performance ◽  
External Heat ◽  
Liquid Oxygen ◽  
Fluid Sloshing

Modeling of a New Crank-Less Rotary Heat Engine Concept for Solar Power Utilization

2018 ◽  
Author(s):  
Muhammad I. Rashad ◽  
Hend A. Faiad ◽  
Mahmoud Elzouka
Keyword(s):  
Degrees Of Freedom ◽  
Unit Cost ◽  
Heat Engine ◽  
Structure Design ◽  
Operating Conditions ◽  
Design Parameters ◽  
Working Fluid ◽  
Heat Engines ◽  
And Performance ◽  
Engine Concept

This paper presents the operating principle of a novel solar rotary crank-less heat engine. The proposed engine concept uses air as working fluid. The reciprocating motion is converted to a rotary motion by the mean of unbalanced mass and Coriolis effect, instead of a crank shaft. This facilitates the engine scaling and provides several degrees of freedom in terms of structure design and configuration. Unlike classical heat engines (i.e. Stirling), the proposed engine can be fixed to the ground which significantly reduce the generation unit cost. Firstly, the engine’s configuration is illustrated. Then, order analysis for the engine is carried out. The combined dynamics and thermal model is developed using ordinary differential equations which are then numerically solved by Simulink™. The resulting engine thermodynamics cycle is described. It incorporates the common thermodynamics processes (isobaric, isothermal, isochoric processes). Finally, the system behavior and performance are analyzed along with studying the effect of various design parameters on operating conditions such as engine speed, output power and efficiency.

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