In the present study the optimum heat exchanger inventory allocation to maximize the thermal performance of a two-stage vapor compression system with two evaporators has been investigated. Both the cooling (A/C) and heating (H/P) Carnot and non-Carnot non-isentropic cycles have been considered. The optimum operating ranges of cycle parameters that maximize both the coefficient of performance (COP) and exergetic efficiency (η2) of the cycles for both cooling and heating purposes are discussed. The research upon which this paper partly reports covered all possible ranges of cycle parameters using the Monte-Carlo method. For the Carnot cycle, maximum values of the cooling coefficient of performance (COPC), cooling exergetic efficiency (ηIIC), heating coefficient of performance (COPH), and heating exergetic efficiency (ηIIH) were found to be 9.6, 0.47, 10.7 and 0.87, respectively. The low-pressure (LP) thermal load and temperature difference in the condenser were found to critically affect both the A/C and H/P performance, while the heat conductance ratio and the mass flow rate ratio were found to have a pronounced effect on only the H/P performance. The best A/C and H/P cycle performance may be achieved by having the two evaporators with both the thermal load and mass flow rate in the high-pressure loop to be 20% less than that in the low-pressure loop. The analysis performed on the non-Carnot two-compressor, two-evaporator A/C and H/P non-isentropic cycles determined both the feasible and optimal ranges of variations of the controlling parameters. The combined maximum values of the low- and high-pressure evaporator thermal loads was found to be 10–15% lower than the maximum value of the condenser heat rejection rate, thus reflecting the relative sizes of these units as heat exchangers. Other factors that may help provide guidance for utilizing the system for cooling and heating purposes include the values of the COPC and COPH, the relative amounts of the mass flow rates in the low-pressure and high-pressure loops of the cycle, and the values of the low-pressure and high-pressure compressor powers.
- Heat Transfer Division
Optimal Allocation of Heat Exchanger Inventory for Maximum COP and Exergetic Performance of a Two-Stage Vapor Compression Cycle
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Abdel-Rahim, YM, & Sherif, SA. "Optimal Allocation of Heat Exchanger Inventory for Maximum COP and Exergetic Performance of a Two-Stage Vapor Compression Cycle." Proceedings of the ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. Volume 1: Heat Transfer in Energy Systems; Thermophysical Properties; Theory and Fundamental Research in Heat Transfer. Minneapolis, Minnesota, USA. July 14–19, 2013. V001T01A022. ASME. https://doi.org/10.1115/HT2013-17804
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