Exergy Analysis, Entropy Generation Minimization, and Constructal Theory

2006 ◽  
pp. 117-143 ◽  
Author(s):  
Adrian Bejan
Keyword(s):  
Entropy Generation ◽  
Exergy Analysis ◽  
Constructal Theory ◽  
Entropy Generation Minimization

Exergy Analysis and Entropy Generation Minimization of Thermoelectric Waste Heat Recovery for Electronics

2011 ◽  
Author(s):  
Kazuaki Yazawa ◽  
Ali Shakouri
Keyword(s):  
Entropy Generation ◽  
Energy Recovery ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Exergy Analysis ◽  
Waste Heat ◽  
Electronic Systems ◽  
Maximum Output ◽  
Entropy Generation Minimization ◽  
Energy Payback

Energy recovery from waste heat is attracting more and more attention. All electronic systems consume electricity but only a fraction of it is used for information processing and for human interfaces, such as displays. Lots of energy is dissipated as heat. There are some discussions on waste heat recovery from the electronic systems such as laptop computers. However the efficiency of energy conversion for such utilization is not very attractive due to the maximum allowable temperature of the heat source devices. This leads to very low limits of Carnot efficiency. In contrast to thermodynamic heat engines, Brayton cycle, free piston Stirling engines, etc., authors previously reported that thermoelectric (TE) can be a cost-effective device if the TE and the heat sink are co-optimized, and if some parasitic effects could be reduced. Since the heat already exists and it is free, the additional cost and energy payback time are the key measures to evaluate the value of the energy recovery system. In this report, we will start with the optimum model of the TE power generation system. Then, theoretical maximum output, cost impact and energy payback are evaluated in the examples of electronics system. Entropy Generation Minimization (EGM) is a method already familiar in thermal management of electronics. The optimum thermoelectric waste heat recovery design is compared with the EGM approach. Exergy analysis evaluates the useful energy flow in the optimum TE system. This comprehensive analysis is used to predict the potential future impact of the TE material development, as the dimensionless figure-of-merit (ZT) is improved.

scholarly journals Exergy Analysis of a Domestic Refrigerator

2018 ◽  
Vol 24 (9) ◽  
pp. 1 ◽  
Author(s):  
Loauy Abd Al-Azez Mahdi ◽  
Wahid S. Mohammad ◽  
Samir Akram Mahmood
Keyword(s):  
Entropy Generation ◽  
Exergy Analysis ◽  
Thermal Conductance ◽  
Internal Surface ◽  
Exergy Efficiency ◽  
System Component ◽  
Minimum Entropy ◽  
Internal Surface Area ◽  
Domestic Refrigerator ◽  
Entropy Generation Minimization

An energy and exergy thermodynamic analysis using EES program was done for a domestic refrigerator working with R-134a using vapor compression refrigeration cycle. The analysis deals with the system component, i.e. compressor, condenser, evaporator and the expansion device. The analysis depends on the entropy generation minimization approach to improve the refrigerator performance by exploring the optimum design points. These design points were derived from three different theories governing the entropy generation minimization using exergy analyzing method. These theories were first applied to find the optimum balance between the hot inner condenser area and the cold inner evaporator area of the refrigerator and between its hot and cold thermal conductances. Nine types of condensers were used according to its internal surface area and thermal conductance, in order to reach the minimum entropy generation in the refrigerator. The results showed that the compressor has the lowest exergy efficiency of 25%. The expansion device was the second component after the compressor with exergy efficiency of 92%, followed by the condenser with an efficiency of 93%. The evaporator was found to have an exergy efficiency of 98 %. The experimental tests were repeated for the nine condensers sizes with three different ambient temperatures 25℃, 30℃ and 35℃.  The exergy analysis showed that the design of the refrigerator mainly depends on thermal conductance calculations rather than the surface inner area estimation.  

Design Methodology for Branching Fluid Network Heat Sinks

2006 ◽  
Author(s):  
R. M. Moreno ◽  
Y.-X. Tao
Keyword(s):  
Entropy Generation ◽  
Design Methodology ◽  
Heat Sinks ◽  
Constructal Theory ◽  
Pumping Power ◽  
Thermal Systems ◽  
Entropy Generation Minimization ◽  
Fluid Network ◽  
Fluid Networks

In this paper recent works from the areas of entropy generation minimization and constructal theory are extended and combined with previous works from the area of physiological transport geometry prediction. From this a design methodology is developed which can be applied to branching fluid networks having the objective of maximizing the removal of heat from a given volume while minimizing the pumping power required. The methods are essentially a set of equations that serve as a resource for designers incorporating branching fluid networks as components within fluid-thermal systems that have the goal of transferring and remove heat while minimizing the entropy generation or destruction of available work.

Sign in / Sign up

Export Citation Format

Share Document