基于竖管降膜的多效太阳能苦咸水蒸馏器设计及性能分析

工业化太阳能苦咸水淡化系统对基础设施要求高,无法满足当前缺水地区小型分布式淡水制备的需求。针对上述问题,该研究提出一种新型基于竖管降膜的多效太阳能苦咸水蒸馏器,其具有液膜蒸发、多效运行、传热热阻小、热能利用效率高等特点。基于封闭小空间内蒸发冷凝机理,分析装置内水蒸气传热传质过程,基于此,分别测试定输入功率运行工况下,一效、二效、三效和四效蒸馏器的产水速率、蒸发温度和冷凝温度的变化规律,研究不同效数对装置单位能耗产水率l和性能系数(Gain Output Ratio,GOR)等的影响,分析多效太阳能苦咸水蒸馏器的投资回收周期等经济评估参数。结果表明,装置单位能耗产水率、产水速率和性能系数均随运行效数的增加而增大,当输入电功率为200 W时,四效苦咸水蒸馏器达到稳态运行时单位能耗产水率和产水速率分别为1.45 g/kJ、1.039 kg/h,分别比三效蒸馏器增加36.80%、35.88%,四效苦咸水蒸馏器运行温度为83.76℃,蒸发冷凝总温差为19.07℃,性能系数达到3.36,投资成本回收周期约为5.69 a,具有较好的分布式制水应用前景。

Design and performance analysis of multi-effect solar brackish water distillation devices based on vertical tube falling film

Freshwater and energy are indispensable resources for human survival and social developments.However,fresh water scarcity is expanding and intensifying around the world because of rapid population growth,industry development,abnormal climate and urbanization.Especially,the shortage of useful water has become more obviously for isolated or arid regions.Great amount of groundwater in these regions found in wells usually remains brackish water.To obtain safe and pure drinking water,various brackish water distillation technologies have been increasingly recommended as a viable alternative.However,conventional distillation processes have indicated highly energy consumption,and potential environmental impacts due to the utilization of fossil fuels.It is necessary to utilize solar energy for the brackish water distillation,in order to meet the high requirement of potable water and agriculture in the remote and arid regions blessed with ample amount of solar energy.This paper therefore designed a novel multi-effect solar brackish water distillation device based on vertical tube falling film,which allows testing of four operational modes,i.e.,single-effect,double-effect,triple-effect and four-effect.Compared with conventional solar brackish water distillation device,some advantages can be achieved,such as falling film evaporation,multi-effect operation,smaller thermal resistance,and higher efficiency of thermal utilization.The working principle was introduced for the four-effect device and structure.A theoretical analysis of heat and mass transfer process of the device was carried out.The water yield,evaporation temperature and condensation temperature of the device for four operation modes were tested under the fixed heating power operation.The effects of the different operation effects on the water yield per energy and GOR(Gain Output Ratio)were investigated,together with the economic analysis of the multi-effect devices.The results demonstrated that when the heating power was 200W,the water yield per energy and the total water production of the four-effect device were 1.45 g/kJ and 1.039 kg/h,indicating an increase by 36.80%and 35.88%than that of the triple-effect device,respectively.The steady-state operation temperature was 83.76℃,while the total temperature difference of evaporation and condensation was 19.07 oC in the four-effect device.The GOR of four-effect device can reach 3.36.The payback period of four-effect device was 5.69 years.Performance and economic analyses of the devices indicated a wide applicability of the system,especially for remote and arid regions.