Suggestion of new correlations for the exergy efficiency and coefficient of exergy performance of annulus section of conically coiled tube-in-tube heat exchangers

2019 ◽  
Vol 152 ◽  
pp. 309-319 ◽  
Author(s):  
Khaled Al-Salem ◽  
Ebrahim Hosseini ◽  
Alireza Nohesara ◽  
Mohsen Mehri ◽  
Mohamed Ali ◽  
...  
Keyword(s):  
Heat Exchangers ◽  
Exergy Efficiency ◽  
Coiled Tube ◽  
Exergy Performance

Modelling, Analyses and Optimization for Exergy Performance of an Irreversible Intercooled Regenerated Brayton CHP Plant: Part 1 — Thermodynamic Modelling and Parametric Analyses

2017 ◽  
Author(s):  
Lingen Chen ◽  
Bo Yang ◽  
Huijun Feng ◽  
Zemin Ding
Keyword(s):  
Heat Exchangers ◽  
Variable Temperature ◽  
Pressure Ratio ◽  
Exergy Efficiency ◽  
Heat Reservoir ◽  
Output Rate ◽  
Rate Versus ◽  
Optimum Heat ◽  
Set Up ◽  
Parametric Analyses

A variable-temperature heat reservoir irreversible intercooling regenerated Brayton combined heat and power (CHP) plant model is set up in this paper. The model considers the heat transfer losses in all the heat exchangers, the working substance pressure drop loss in the piping, and the expansion and compression losses in turbine and compressor. Exergy output rate and exergy efficiency are considered as the research targets, and their analytical formulae are obtained. The optimal performances are gotten by optimizing the intercooled pressure ratio and total pressure ratio. The influences of some important parameters on the performances are studied in detail. Besides, the relation of exergy output rate versus exergy efficiency is investigated, and the curve is loop-shaped one. The results indicate that optimum heat capacity rate matching between the heat reservoir and working substance, and optimum heat consumer required temperature exist respectively, which generate double-maximal exergy output rate and double-maximal exergy efficiency, respectively. The heat conductance allocation optimization of all the heat exchangers will be carried out in Part 2 of this paper.

scholarly journals Numerical Analysis on the Performance of High Concentration Photovoltaic Systems Under the Nonuniform Energy Flow Density

2021 ◽  
Vol 9 ◽  
Author(s):  
Haifei Chen ◽  
Yunjie Wang ◽  
Yuwei Ding ◽  
Baorui Cai ◽  
Jie Yang
Keyword(s):  
Heat Exchangers ◽  
Energy Flow ◽  
Single Channel ◽  
Exergy Efficiency ◽  
Flow Density ◽  
High Concentration ◽  
Cell Temperature ◽  
Single Jet ◽  
Jet Nozzle

Photovoltaic panels can directly convert solar energy into electricity, but temperature will have a certain impact on the efficiency of photovoltaic cells. Especially under the condition of nonuniform energy flow density of high-power concentration, it is of great significance to maintain the temperature uniformity of cells. Therefore, based on the radiation under nonuniform heat flux density, four heat exchangers were proposed: single-channel serpentine flow, multi-channel flat plate, full jet, and single-jet nozzle. Taking into account the uniformity of the cell temperature, the single-jet nozzle and single-channel serpentine flow can better maintain the uniformity of the temperature field compared with other heat exchangers. Especially under high-concentration energy flow density, considering the quality of heat and electricity, the performance of the four-jet nozzles is the best from the perspective of exergy efficiency. Under the condition of four-jet nozzles, the electrical efficiency and thermal efficiency of the cell can be maintained at about 29 and 62.5%, respectively, and the exergy efficiency of the system can reach 31%.

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