| Lithium bromide absorption refrigeration unit with heat as the driving force,can use the waste heat in industrial production and solar energy,environmentally friendly water as the refrigerant,these advantages make it in the field of HVAC has a wide application prospect.However,the performance of the single-effect lithium bromide absorption refrigeration system is low,and it decreases with the decrease of the temperature of the driving heat source.In this regard,relevant scholars found that the membrane heat exchanger replaced the solution heat exchanger of the lithium bromide absorption refrigeration unit,which can reduce the driving heat source temperature,improve the COP of the system and reduce the cycle rate.However,there are few studies on heat and mass transfer characteristics of lithium bromide solution in membrane heat exchanger and the effect of membrane heat exchanger on thermal load and performance of lithium bromide absorption refrigeration system.Therefore,this article set the film heat exchanger performance test-bed,analyzes the hot side of the entrance to the solution of temperature and flow rate and concentration on the heat transfer and mass transfer characteristics,the influence of lithium bromide system thermodynamic calculation model is established,analyzed the different external factors affect the performance of lithium bromide absorption refrigeration system,and discusses the membrane alternative solution heat exchanger caused by the difference of the heat exchanger.The specific research results are as follows:（1）analysis of the lithium bromide solution inlet temperature on membrane hot side heat exchanger heat and mass transfer performance of the influence law of the hot side of the lithium bromide solution temperature increased by 40 ° C to 45 ° C,membrane increases heat exchanger heat transfer temperature difference,latent heat of vaporization of water vapor rises,the circulating heat and water vapor mass transfer process are affected,to spread heat increase 7%,increase the membrane flux was 4%,The mass and heat transfer coefficient increased by 52.8%,the pressure drop inside the membrane tube increased by 22.6%,and the pressure drop across the shell was basically unchanged.（2）When the flow rate of lithium bromide solution on the hot side changes,the flow rate of solution in the membrane changes,which has a great influence on convective heat transfer.When the flow rate of lithium bromide solution on the hot side increases from 5.4m3/h to 5.9m3/h,the heat transfer increases by 12.5%,but the mass transfer process is not affected.The increase of membrane flux is only 1%,the mass transfer heat is not affected,and the membrane heat transfer coefficient increases by 26.7%.The pressure drop inside the membrane tube increased by17.9%,and the pressure drop across the shell tended to be stable.（3）chose high concentration of sodium chloride solution as working medium,on both sides of membrane concentration difference about 5%（1-2%）lithium bromide solution concentration,membrane flux increase of 24.6%,to spread heat by19%,its increasing of hot side inlet temperature and flow rate changing law is similar to the lithium bromide solution,through the film heat exchanger smuggled qualitative mechanism analysis and experimental contrast found,The molecular-Knudsen diffusion model is more suitable for the mass transfer process in membrane heat exchangers,and the relative error between the empirical formula and the experimental value is within 4%.（4）With the increase of the temperature of the driving heat source,the heat load of evaporator,condenser and generator increases,the heat load of the absorber is stable,the circulation rate of the system decreases,and the COP of the system increases,and the rising rate of COP decreases continuously.New refrigeration system compared with the traditional refrigeration system,heat source temperature rise along with the driver,evaporator,condenser and absorber heat load difference is small and stable,generator heat load difference gradually rise,new refrigeration system performance is superior to the traditional refrigeration system,and the COP of the initial growth and circulating rate of initial decline rate is higher.（5）As the inlet temperature of cooling water increases,the heat loads of evaporator,condenser,generator and absorber all decrease,and the COP of the system decreases,while the circulation rate increases,and the COP decrease increases after 30°C.Compared with the traditional refrigeration system,the heat load difference of evaporator,condenser and absorber in the new refrigeration system is also very small and stable,the heat load difference of generator decreases gradually,and the COP changes in the same trend.（6）With the increase of the inlet temperature of refrigerant water,the heat load of evaporator and absorber increases,the heat load of condenser basically stays the same,the heat load of generator decreases,but the decrease is very small,COP shows a stable upward trend,and the cycle rate shows a stable downward trend;Compared with the traditional refrigeration system,the new refrigeration system has the same thermal load and systematic change rule,and the difference is stable. |
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