ENERGY - Exergy Based Performance Analysis Of A Solid Adsorption Solar Refrigerator

ABSTRACT  

The Energy - Exergy based performance analysis of the Solid Adsorption Solar Refrigerator is presented. The system comprises the collector/generator/adsorber, the condenser and the evaporator. It utilizes activated carbon/methanol as its adsorbent/adsorbate working combination. The exergy performance analysis of this refrigerator involves detailed assessment of all the following sub-processes that make up the refrigeration cycle, which are isosteric heat-up phase, desorption phase, isosteric cool-down phase and re-adsorption phase. The exergy performance of the Condenser and the Evaporator in a quasi-static regime of operation were also reported. Exergy destruction equations were generated for each subprocess and utilized in estimating the amount of exergy destroyed with reference to varying ambient environment temperatures recorded at 30 mins interval and at constant (average) temperature of 301 K for all test days. The ranges of exergy destruction during each subprocess, for varying reference temperature analysis for test days I, II and III were determined as 0.000 – 3.362 kJ, 0.000 – 2.720 kJ and 0.000 – 5.516 kJ for the isosteric heat-up phase; 302.059 – 2874.119 kJ, 144.778 – 3249.376 kJ and 574.044 – 2999.723 kJ for the desorption phase; 0.247 – 8.357 kJ, 0.350 – 8.737 kJ and 0.007 – 5.933 kJ for the isosteric cool-down phase; 0.000 – 32.183 kJ, 0.000 – 281.807 kJ and 0.000 – 84.715 kJ for the re-adsorption phase; 1.746 – 21.485 kJ, 0.790 – 16.706 kJ and 2.809 – 17.275 kJ in the condenser and in the evaporator as 6.868 – 41.350 kJ, 1.344 63.580 kJ and 1.515 – 54.507 kJ. The ranges of exergy destruction during each sub-process, based on constant (average) reference temperature analysis for test days I, II and III were determined as 0.000 – 3.384 kJ, 0.000 – 2.720 kJ and 0.000 – 5.533 kJ for the isosteric heat-up phase; 292.510 – 2736.713 kJ, 141.392 – 3190.508 kJ and 565.081 – 2912.175 kJ for the desorption phase; 0.248 – 8.248 kJ, 0.352 – 8.651 kJ and 0.008 – 5.880 kJ for the isosteric cool-down phase; 55.327 – 128.443 kJ, 86.251 – 139.388 kJ and 0.000 – 124.244 kJ for the re-adsorption phase; 0.524 – 3.353 kJ, 0.347 – 8.975 kJ and 1.641 – 5.918 kJ in the Condenser and in the Evaporator as 16.234 – 64.322 kJ, 8.738 – 97.613 kJ and 10.514 – 77.084 kJ. The exergy efficiency values for the varying reference temperature analysis were obtained for test days I, II and III as 0.01331, 0.04380 and 0.01226 respectively and for constant (average) reference temperature as 0.02275, 0.05933 and 0.02162 for test days I, II and III respectively. The exergy analysis indicates losses of the highest magnitude during desorption and re-adsorption phases. Choices of collector/generator/adsorber with lower heat emissions during desorption and readsorption, with more efficient cooling in the condenser, will improve the overall efficiency of the system.  

KEY WORDS: ADSORPTION, DESORPTION, EXERGY, EXERGY EFFICIENCY,  EXERGETIC TEMPERATURE FACTOR, EXERGY DESTRUCTION