共查询到19条相似文献,搜索用时 140 毫秒
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建立了考虑线性热漏的不可逆双谐振通道能量选择性电子(energy selective election,ESE)制冷机模型,导出了制冷机制冷率和制冷系数的表达式,应用有限时间热力学理论研究了系统制冷率与制冷系数最优性能,通过数值计算,详细分析了热漏、能量宽度、能量间距等设计参数对ESE制冷机最优性能的影响。研究发现,系统的制冷率和制冷系数都会随热漏的增加而减小;给定能量间距时,制冷率和制冷系数都会随能量宽度的增加而先增大后减小,存在最优的能量宽度使制冷率或制冷系数达到最大值;给定能量宽度时,制冷率和制冷系数会随能量间距的增加而先增加后减小,存在最优的能量间距使制冷率或制冷系数达到最大值。合理地选取能量宽度、能量间距等参数,可以使不可逆的双谐振ESE制冷机设计于最大制冷率或最大制冷系数的状态。 相似文献
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A model of a single-barrier solid-state thermionic refrigerator with external heat transfer is established in this paper. The performance of the refrigerator is analyzed and optimized by using the combination of finite-time thermodynamics and nonequilibrium thermodynamics. The general expressions for cooling load and coefficient of performance (COP) of the refrigerator are derived. The optimum regions of cooling load and COP are obtained and the effects of the heat reservoir temperature and thermal conductance of the barrier material on the performance of the refrigerator are analyzed by detailed numerical examples. The results obtained are compared with those obtained by using traditional analysis without considering external heat transfer. For the fixed total heat transfer surface area of two heat exchangers, the ratios of the heat transfer surface area of the hot-side heat exchanger to the total heat transfer surface area of the heat exchangers are optimized for maximizing the cooling load and COP of the refrigerator, respectively. The effects of the total heat transfer surface area and the applied voltage on the optimum performance of the refrigerator are analyzed. The results obtained herein may provide some theoretical guidelines for the design and application of practical solid-state thermionic refrigerators. 相似文献
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Optimum allocation of heat transfer surface area for cooling load and COP optimization of a thermoelectric refrigerator 总被引:4,自引:0,他引:4
The theory of finite time thermodynamics is applied to analyze and optimize the performance of a thermoelectric refrigerator, which is composed of multi-elements. For the fixed total heat transfer surface area of two heat exchangers, the ratio of the heat transfer surface area of the high temperature side heat exchanger to the total heat transfer surface area of the heat exchangers is optimized for maximizing the cooling load and the coefficient of performance of the thermoelectric refrigerator. The effects of various parameters on the optimum performance are analyzed. The results may provide guides for the analysis and optimization of practical thermoelectric refrigerators. 相似文献
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Irreversible four-temperature-level absorption refrigerator 总被引:2,自引:0,他引:2
A refrigeration cycle is modeled as a demonstration of an irreversible absorption refrigeration cycle. This four-temperature-level model takes into account the heat resistance, heat leakage, and irreversibilities due to internal dissipation of the working fluid. The fundamental optimal relationships between: (1) the coefficient of performance (COP) and the cooling load; (2) the maximum COP and the corresponding cooling load; and (3) the maximum cooling load and the corresponding COP of the cycle, all coupled to constant-temperature heat reservoirs, are derived by using finite-time thermodynamics. The optimal distribution relationships of the heat-transfer surface areas are also presented. Moreover, the effects of the cycle parameters on the COP and the cooling load of the cycle are studied by detailed numerical examples. The results obtained herein are useful for optimal design and performance improvement of absorption refrigeration cycles. 相似文献
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Tong Zheng Lingen Chen Fengrui Sun Chih Wu 《International Journal of Thermal Sciences》2004,43(12):4343-1195
On the basis of an endoreversible absorption refrigeration cycle model with Newton's heat transfer law, an irreversible four-heat-reservoir cycle model with another linear heat transfer law of Q∝Δ(T−1) is built by taking account the heat leak and heat resistance losses. The fundamental optimal relation between the coefficient of performance (COP) and the cooling load, the maximum COP and the corresponding cooling load, as well as the maximum cooling load and the corresponding COP of the cycle with another linear heat transfer law coupled to constant-temperature heat reservoirs are derived by using finite-time thermodynamics. The optimal distribution relation of the heat-transfer surface areas is also obtained. Moreover, the effects of the cycle parameters on the COP and the cooling load of the cycle are studied by detailed numerical examples. The results obtained herein are of importance to the optimal design and performance improvement of a four-heat-reservoir absorption refrigeration cycle. 相似文献
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This paper analyses the performance of a real heat pump plant via methods of entropy generation minimization or finite‐time thermodynamics. The analytical relations between heating load and pressure ratio, and between coefficient of performance (COP) and pressure ratio of real closed regenerated Brayton heat pump cycles coupled to constant‐ and variable‐temperature heat reservoirs are derived. In the analysis, the irreversibilities include heat transfer‐irreversible losses in the hot‐ and cold‐side heat exchangers and the regenerator, the non‐isentropic expansion and compression losses in the compressor and expander, and the pressure drop loss in the pipe and system. The optimal performance characteristics of the cycle may be obtained by optimizing the distribution of heat conductances or heat transfer surface areas among the two heat exchangers and the regenerator, and the matching between working fluid and the heat reservoirs. The influence of the effectiveness of regenerator, the effectiveness of hot‐ and cold‐side heat exchangers, the efficiencies of the expander and compressor, the pressure recovery coefficient and the temperature of the heat reservoirs on the heating load and COP of the cycle are illustrated by numerical examples. Published in 1999 by John Wiley & Sons, Ltd. 相似文献
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The ecological optimization and parametric study of an irreversible Ericsson cryogenic refrigerator cycle with finite heat capacities of external reservoirs is studied. The ecological function is defined as the cooling load minus the loss of the cooling load (the irreversibility) due to the entropy generation rate. The ecological function is optimized with respect to working fluid temperatures and the values of the cooling load, power input, the loss rate of the cooling load and COP are calculated for a typical set of operating parameters. The effects of different operating parameters on the ecological function, cooling load, the loss rate of the cooling load and COP are studied. The loss rate of the cooling load and the power input are found to be increasing functions of the cycle temperature ratio and decreasing functions of COP while the COP is found to be a decreasing function of the cycle temperature ratio. On the other hand, there exist the optimal values of the cycle temperature ratio and COP at which the ecological function and cooling load attain their maximum values. Also the ecological function and the cooling load are found to be increasing functions of the sink‐side heat capacitance rate and the effectiveness on the source‐, sink‐, and regenerative‐side heat exchangers while the decreasing functions of the source‐side heat capacitance rate. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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Based on a simple irreversible variable-temperature heat reservoir air (Brayton) refrigeration cycle model, a performance analysis and optimization of a real air refrigerator is carried out using finite-time thermodynamics. To maximize the cooling load and the coefficient of performance (COP) of the cycle, the allocation of a fixed total heat-exchanger inventory and thermal-capacity rate matching between the working fluid and heat reservoirs are optimized, respectively. The influences of pressure ratio, the total heat-exchanger inventory, the efficiencies of the compressor and expander, the thermal capacity rate of the working fluid and the ratio of the thermal-capacity rates of the heat reservoirs on the performance of the cycle are shown by numerical examples. The results obtained provide guidances for the design of practical air-refrigeration plants. 相似文献
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《Exergy》2002,2(3):167-172
On the basis of endoreversible absorption refrigeration cycle model with the sole irreversibility of heat transfer between the working fluid and the heat reservoirs, an irreversible model of absorption refrigeration cycle with heat transfer law of q∝Δ(T−1), which includes the heat leak from the heat sink to the cooled space and irreversibilities due to the internal dissipation of the working fluid besides the finite-rate heat transfer between the working fluid and the external heat reservoirs, is established and used to derive the relation between the optimal coefficient of performance and the cooling load and the optimal distribution of the heat-transfer surface areas of the heat exchangers. The practical optimal regions of the cycle are determined and new bounds of the primary performance parameters are given. A numerical example is provided to illustrate the performance characteristic of endoreversible and irreversible cycles. 相似文献