Performance Study Of A Continuous Two-bed Refrigeration System Based On Mass Recovery

Adsorption refrigeration does not use chlorofluorocarbon refrigerants and is known as an environmentally and friendly refrigeration method.The research on single-bed adsorption refrigeration systems has become mature,but the intermittence and low performance of single-bed refrigeration systems make it unable to compete with the traditional compression refrigeration.In recent years,more and more scholars have transferred their research focus to the more efficient two-bed continuous adsorption refrigeration systems.The current mainstream two-bed continuous refrigeration system adopts two identical water-bath adsorbers,and improves the cooling capacity and refrigeration performance of the system by heat recovery,mass recovery or the combination of both.However,the high thermal load and low recycling efficiency of the system limit the improvement of the performance and market promotion of the continuous adsorption refrigeration system.In view of the above problems,this paper carried out the following research work:（1）A new two-bed continuous refrigeration system was constructed.The two adsorbers were direct-heating adsorber and water-bath adsorber respectively.Direct-heating adsorber could share the heat load of the system and reduced the area of solar collector and the cost of the system.Hot water could store energy that ensured the stability of the system operation.In order to improve the refrigeration performance of the system,mass recovery process was adopted.The results showed that the COPs of the system with and without mass recovery were 0.122 and 0.107 respectively.The former was 14.02% higher than the latter.The optimal mass recovery time was 180 seconds.The COP of the system were increased by 2.52%and 6.09% respectively,compared with the mass recovery time of 160 seconds and200 seconds.（2）In the two-bed continuous refrigeration system,the refrigeration capacity and desorption temperature of two adsorbers were different,and the cycle refrigeration capacity of the system was often limited by the adsorber with poor refrigeration capacity,resulting in the adsorber with high refrigeration capacity could not fully play its advantages.In order to match the refrigeration capacity of the two-bed system and improve the refrigeration performance,the method of mass recovery after enhancing desorption was adopted.Two systems were designed which could be called mode 1 and mode 2.Mass recovery after enhancing desorption was only applied to water-bath adsorber in mode 1.However,mass recovery after enhancing desorption was applied to two adsorbers in mode 2.The results showed that the cooling capacity of the water-bath adsorber was increased from 0.133 MJ to0.145 MJ due to the enhanced desorption effect of the vacuum pump,and the matching effect of the refrigeration capacity of the two beds was realized.For mode2,the matching effect of two bed was not as good as that of mode 1,because the pressure drop effect of the vacuum pump could not make the pressure of the adsorber close to 0 k Pa.The matching effect of the two beds was greatly affected by desorption temperature,but the refrigeration performance of the system was higher than that of mode 1.（3）This paper further studied the influence of enhancing mass recovery on system performance.The influences of different speed and connection mode of mass transfer pump on mass recovery depth,system pressure,temperature and performance of two-bed refrigeration system were studied experimentally.The results showed that the higher the speed of mass transfer pump,the better the pressure drop effect,the higher the COP of the system.When the speeds were 2333r/min,2833 r/min and 3333 r/min,the COPs of the system were 0.118,0.119 and0.122,respectively.Compared with the natural mass recovery,the COP of the system did not improve,mainly because time of enhance mass recovery was too long,resulting in too much energy consumption.When the dual-pump parallel mode was adopted,the COP of the system was greatly improved,reaching 0.125.Finally,the effect of different enhancing recovery time on the refrigeration performance of the system was discussed,and the results showed that the best enhancing recovery time was 20 min.