scholarly journals Improving Heat-Engine Performance by Employing Multiple Heat Reservoirs

2020 ◽  
Author(s):  
Jack Denur
Keyword(s):  
Heat Engine ◽  
Engine Performance

Micro Thermal Engines: Is There Any Room at the Bottom?

1999 ◽  
Author(s):  
Richard B. Peterson
Keyword(s):  
Heat Transfer ◽  
Scaling Laws ◽  
Critical Role ◽  
Heat Engine ◽  
Engine Performance ◽  
Characteristic Size ◽  
Operating Efficiency ◽  
Simple Scaling ◽  
Small Structure ◽  
Micro Heat Engine

Abstract Richard P. Feynman introduced the field of microscale and nanoscale engineering in 1959 by giving a talk on how to make things very small. Feynman’s premise was that no fundamental physical laws limit the size of a machine down to the microscopic level. Is this true for all types of machines? Are micro thermal devices fundamentally different than mechanically-based machines with respect to their scaling laws? This paper demonstrates that micro thermal engines do indeed suffer serious performance degradation as their characteristic size is reduced. A micro thermal engine, and more generally, any thermally-based micro device, depends on establishing a temperature difference between two regions within a small structure. In this paper, the performance of a micro thermal engine is explored as a function of the characteristic length parameter, L. In the development, the important features of thermal engines are discussed in the context of developing simple scaling laws predicting the dependency of the operating efficiency on L. After this is accomplished, a general model is derived for a heat engine operating between two temperature reservoirs and having both intrinsic and extrinsic sources of irreversibility, i.e. thermal conductances and heat leakage paths for the heat flow. With this model and typical numerical values for the conductances, micro heat engine performance is predicted as the characteristic size is reduced. This paper demonstrates that under at least one particular formulation of the problem, there may indeed be some room at the bottom. However, heat transfer does play a critical role in determining micro engine performance and depending on how the heat transfer through the engine is modeled, vanishingly small efficiencies can result as the characteristic engine size goes to zero.

scholarly journals CHANGE OF HEAT ENGINE PERFORMANCE BY ELECTRO-PHYSICAL INFLUENCE ON FUEL

2016 ◽  
Vol 2016 (2) ◽  
pp. 45-49
Author(s):  
Irina Morozova ◽  
◽  
Sergey Maksymov ◽  
Yuriy Tereschenko
Keyword(s):  
Heat Engine ◽  
Engine Performance

scholarly journals INVALIDITY OF ISOTHERMAL ANALYSIS IN ESTIMATING THE THERMAL PERFORMANCE OF STIRLING ENGINE AND CRYOCOOLER

2021 ◽  
Vol 21 (4) ◽  
pp. 274-288
Author(s):  
Hailaa Jabbar Kareem ◽  
Ali A. F. Al-Hamadani ◽  
Ali Noaman Ibrahim
Keyword(s):  
Heat Exchangers ◽  
Heat Engine ◽  
Engine Performance ◽  
Thermodynamic Cycle ◽  
Low Noise ◽  
Stirling Engine ◽  
Isothermal Model ◽  
Working Space ◽  
Isothermal Analysis ◽  
Noise Vibration

The Stirling engine is an external heat engine, which is considered as the best option for extracting work from concentrated solar power applications. The most prominent characteristics of the engine are low noise, vibration, and emissions besides reflexivity of usage with any kind of heat source such as solar, biomass, industrial heat, etc. In the present paper, the STE-1008 gamma-type Stirling engine had been analyzed by using an isothermal model to demonstrate the failure of the model in analyzing the STE-1008 considering it firstly as an engine and secondly as a cryocooler. The energy equation had been used to demonstrate the disability of the isothermal model in achieving a successful thermal analysis for engine performance. In addition, a MATLAB code had been developed to check the credibility of the isothermal model in the estimation of the engine thermal parameters. The findings of the isothermal analysis revealed that the heat exchangers are unnecessary. But, in reality; all the necessary heat transfer occur within the heat exchangers rather than in the working space boundaries. Therefore, that is invalid conclusion. However, Schmidt's theory is capable of capturing the essential engine features superbly. In particular, it is capable of capturing the fundamental interplay between the mechanically restricted movement of the engine components as well as the thermodynamic cycle which is obtained from this theory.

scholarly journals Optimal engine performance using inference for non-identical finite source and sink

2015 ◽  
Vol 29 (33) ◽  
pp. 1550217 ◽  
Author(s):  
Preety Aneja ◽  
Harsh Katyayan ◽  
Ramandeep S. Johal
Keyword(s):  
Prior Distribution ◽  
Prior Information ◽  
Heat Engine ◽  
Engine Performance ◽  
The Other ◽  
Thermodynamic Process ◽  
Finite Systems ◽  
Maximum Work ◽  
Source And Sink ◽  
Good Agreement

We quantify the prior information to infer the optimal characteristics for a constrained thermodynamic process of maximum work extraction for a pair of non-identical finite systems. The total entropy of the whole system remains conserved. The ignorance is assumed about the final temperatures of the finite systems and then a prior distribution is assigned to the unknown temperatures. We derive the estimates of efficiency for this reversible model of heat engine with incomplete information. The estimates show good agreement with efficiency at optimal work for arbitrary sizes of systems, however the estimates become exact when one of the reservoir becomes very large in comparison to the other.

Valved Heat Engine Working on Modified Atkinson Cycle

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
C. V. Ramesh
Keyword(s):  
Thermal Efficiency ◽  
Heat Engine ◽  
Engine Performance ◽  
Inertial Force ◽  
Expansion Ratio ◽  
Stirling Engine ◽  
Performance Criteria ◽  
Stirling Cycle ◽  
Heat Engines ◽  
Atkinson Cycle

There is immense scope for the development of heat engines that can directly convert solar and biochemical renewable sources of thermal energy to high-grade energy. Regenerative Stirling cycle heat engine with its performance criteria of highest thermal efficiency and high mean effective pressure is theoretically the best engine for small capacity reciprocating heat engine. However, the practical Stirling engine performance is far from the ideal. As an alternative, practical heat engines based on thermodynamic cycles (without regeneration) other than the Stirling cycle have been suggested. This paper deals with a new concept in the design of reciprocating heat engine working on modified Atkinson cycle. In the Atkinson cycle, expansion ratio being higher than compression ratio, the thermal efficiency is better than that of the standard Otto cycle. Heat engine design based on the suggested modified Atkinson cycle can be an alternative to the practical Stirling engine. In the conceptual mechanical design of the engine suggested here, apart from utilizing the principle of Atkinson cycle for achieving higher thermal efficiency, the mechanical configuration of the reciprocating engine ensures a high degree of inertial force balancing. This can result in reduced vibrations in the mountings of the power units.

Renewable Energy from the Ocean

1994 ◽  
Author(s):  
William H. Avery ◽  
Chih Wu
Keyword(s):  
Undergraduate Students ◽  
Heat Engine ◽  
Engine Performance ◽  
Production Methods ◽  
Thermal Energy Conversion ◽  
Wide Range ◽  
The Status ◽  
Upper Level ◽  
Ocean Thermal Energy ◽  
Power And Mechanical Engineering

Scientists and engineers around the world are striving to develop new sources of energy. One source, ocean thermal energy conversion, has virtually unlimited potential. It is based on techniques that exploit heat produced by solar energy that may, in turn, be used to produce fuel and electricity. This book reviews the status and background of this promising technology. William H. Avery is the leading expert in this field, and his co-author Chih Wu is an authority on heat engine performance. Together they describe the workings of an OTEC power plant and how such a system might be implemented as part of a futuristic national energy strategy. The book is the only detailed presentation of basic OTEC technology, its testing and improvement. It is based on extensive development initiatives undertaken internationally during the period from 1974 through 1985. The book offers a thorough assessment of the economics of OTEC in comparison with other energy production methods. It will be of interest to a wide range of professionals in energy research, power and mechanical engineering, and to upper-level undergraduate students taking courses in these fields.

scholarly journals Numerical Investigation of Working Fluid Effect on Stirling Engine Performance

2015 ◽  
Vol 10 (1) ◽  
Keyword(s):  
Distributed Generation ◽  
Heat Engine ◽  
Engine Performance ◽  
Volume Ratio ◽  
Stirling Engine ◽  
Working Fluid ◽  
Prime Mover ◽  
Thermal Generation ◽  
Swept Volume ◽  
Engine Power

The Stirling engine is achieving great concern in the actual energy area since it has many advantages such as its cleanness and quietness. It is also considered a flexible prime mover for useful for several applications such as micro- cogeneration, solar thermal generation and other micro-distributed generation conditions. Theoretically, the Stirling cycle engine can efficiently convert heat into the mechanical work at the Carnot efficiency. The importance of the choice of working fluid is also demonstrated in the literature. In fact, the Stirling engine power can be increased ten times by changing the working fluid from air to hydrogen for example. This paper represents an evaluation of the on working fluid of a solar-dish Stirling heat engine. Thermal efficiency, exergetic efficiency and the rate of entropy generation corresponding to the optimum value of the output power are also evaluated. Numerical results demonstrate that the swept volume ratio is independent of the choice of working fluid.

Sign in / Sign up

Export Citation Format

Share Document