Cooling load density characteristics of an endoreversible variable-temperature heat reservoir air refrigerator

Abstract

SUMMARYThe performance optimization of an endoreversible air refrigerator with variable-temperature heat reservoirs is carried out by taking the cooling load density, i.e. the ratio of cooling load density to the maximum specific volume in the cycle, as the optimization objective in this paper. The analytical relations of cooling load, cooling load density and coefficient of performance are derived with the heat resistance losses in the hot-and cold-side heat exchangers. The maximum cooling load density optimization is performed by searching the optimum pressure ratio of the compressor, the optimum distribution of heat conductance of the hot-and cold-side heat exchangers for the fixed total heat exchanger inventory, and the heat capacity rate matching between the working fluid and the heat reservoirs. The influences of some design parameters, including the heat capacitance rate of the working fluid, the inlet temperature ratio of heat reservoirs and the total heat exchanger inventory on the maximum cooling load density, the optimum heat conductance distribution, the optimum pressure ratio and the heat capacity rate matching between the working fluid and the heat reservoirs are provided by numerical examples. The refrigeration plant design with optimization leads to a smaller size including the compressor, expander and the hot-and cold-side heat exchangers.

Cooling load and coefficient of performance optimizations for real air-refrigerators

“…[13]. Zhou et al [11,12,15,16] analyzed and optimized the cooling load density of a simple endoreversible [11,12] and irreversible [15,16] constant- [11,15] and variable- [12,16] temperature heat-reservoir Brayton refrigeration-cycles. Chen and Su [17] optimized the exergetic efficiency of an irreversible Brayton refrigeration-cycle.…”

“…[10,12,14,15,17], the optimum allocation of heat-exchanger inventory and thermal-capacity rate matching between the working fluid and heat reservoirs of the simple irreversible variable-temperature heat-reservoir air-(Brayton) refrigeration cycle is studied in this paper. The optimum performance characteristic is obtained.…”

“…Recently, some progress in the research and development of air (Brayton) refrigeration cycles has been achieved [6][7][8][9]. The method of finite time thermodynamic analysis has been also applied to the performance studies of simple endoreversible [10][11][12] and irreversible [13][14][15][16][17] Brayton refrigeration cycles, as well as regenerated endoreversible [18] and irreversible [19][20][21] Brayton refrigeration cycles. For a fixed total heat-exchanger inventory of heat exchangers (i.e., the sum of heat conductances of the all heat exchangers) in the refrigeration cycle, the optimum performance of the cycle can be obtained by optimizing the distribution of the heat exchanger inventory between the hot-and cold-side heat-exchangers [10,[20][21][22][23][24][25].…”

Cooling-load density optimization for a regenerated air refrigerator

“…Some authors, including Erbay and Yavuz [12], and Yavuz and Erbay [13], have taken the cooling-load density, defined as the ratio of cooling-load to the maximum specific volume in the cycle, as the optimization objective and analyzed the optimum performance of the Stirling refrigerator as well as the Ericsson refrigerator with a realistic regenerator due to the polytropic processes applied for the heat absorption and rejection. Zhou et al analyzed and optimized the cooling-load density of endoreversible simple air refrigeration cycles coupled to constant- [14] and variable- [15] temperature heat-reservoirs, and of an irreversible simple air refrigeration cycle coupled to constant-temperature heat-reservoirs [16].…”

Exergetic efficiency optimization for an irreversible Brayton refrigeration cycle

“…Luo et al [21] optimized cooling load and COP performance of irreversible simple Brayton refrigeration cycle coupled to constant-temperature heat reservoirs. Zhou et al analyzed and optimized cooling load density of the endoreversible simple Brayton refrigeration cycles coupled to constant- [22] and variable- [23] temperature heat reservoirs, of the irreversible simple Brayton refrigeration cycle coupled to constant- [24] and variable- [25] temperature heat reservoirs, and of irreversible regenerated Brayton refrigeration cycles coupled to constant- [26] and variable- [27] temperature heat reservoirs. The cooling load density was defined as the ratio of cooling load to the maximum specific volume in the cycle.…”