| As populations,cooling demands and environmental pressures have grown,developing and utilizing green cooling technologies is considered one of the most effective ways,at present,to fit the cooling demands and to relieve the environmental stress.Solar-powered adsorption refrigeration with the advantages of non-corrosiveness,no moving parts and employing environmentally friendly working pairs has been become one of the best choices to refrigerate.However,some defects,low temperature of the heat resource and long time for the basis cooling cycle have heavily affected the performance of system.Around the above two affects,this paper carries out the following research work:(1)In this paper,the adsorber of solar adsorption refrigeration system is composed of four groups of adsorber units of compound parabolic concentrator(CPC)combined with finned-tube.The adsorber units of compound parabolic concentrator combined with finned-tube can not only enhance the heat source from the outside,but also improve the internal heat transfer performance.In order to analyse the effect of the inner fins of adsorber unit on the temperature distribution of the filled adsorbents,the heat transfer performance of adsorption tube with or without inner fins was compared by using simulation software of computational fluid dynamics(CFD),and an experimental model was built to verify the simulation results.the results show that in the isosteric heating,the maximum temperature gradient of activated carbon in the finned-tube and the finless-tube is 4.1 and 28.1 °C,respectively,and the temperature distribution of the activated carbon in the finned-tube is more uniform,which greatly reduces the possibility of the desorbed methanol from the outer activated carbon being desorbed by low temperature activated carbon during the diffusion to the central mass transfer channel.(2)After studying of the heat transfer performance of the CPC finned-tube units by using CFD software,this paper will further study the best enhanced mass transfer way to combine the micro-vacuum pump with the CPC adsorption refrigeration system.Based on the existing CPC adsorption refrigeration system,the desorption performance of the systems under three different enhanced mass transfer and a natural mass transfer modes is compared under the heat source environment of the indoor solar simulator and the outdoor sunny conditions,and the parameters of the system under four mass transfer modes are analyzed and compared.It is concluded that the desorption performance of the CPC adsorption refrigeration system under the mode 2(one pump with two condensers)is the best,and the volume of desorbed methanol is at least 19% higher than that of the natural mass transfer mode.(3)There is no polyurethane thermal insulation cotton wrapping on the surface of the adsorbers with CPC concentrator,the temperature of the adsorber is more easily fluctuated by the fluctuation of solar radiation intensity under the cloudy conditions,and the temperature fluctuation of activated carbon will affect the desorption capacity of methanol in the adsorber.The enhanced mass transfer mode 2(one pump with two condensers)is applied in the CPC adsorption refrigeration system,and the performance of the CPC adsorption refrigeration system is compared with that of the natural mass transfer mode under the same weather conditions.Under the condition of cloudless and cloudy weather,the performance of the enhanced mass transfer mode 2 is increased by 39.0% and 52.8%,respectively,than that of in natural mass transfer mode.The effective utilization of refrigerant can be increased by 51.2% and 61.2% compared to the adsorption refrigeration system without CPC concentrators.The results show that the advantages of enhanced mass transfer mode is more obvious than that of natural mass transfer under sunny day with a partly cloudy sky. |
