竖壁自储水式蒸馏器空腔自然对流换热及产水特性

Natural convection heat transfer and fresh water yield in vertical plate cavity with film evaporation and raw water reservoir

引言 利用太阳能进行海水淡化是解决淡水短缺的重要途径之一。世界范围内对此课题展开了多方面的研究,最具代表意义的是太阳能多效蒸馏技术以及露点蒸馏技术。太阳能多效蒸馏技术由于具有结构简单、易维护和安装以及运动部件少等优点，引起了许多学者的重视。由于该类装置充分利用了蒸馏过程中蒸汽的凝结潜热，产水效率普遍较高。

A triple-effect regeneration solar distiller with raw water reservoir is designed and its operation principle is introduced.Experiments with different heating power were carried out with chrome steel strip heater for 6.5 h.In each stage,the temperature and fresh water yield of distiller were measured.The total fresh water yield of each stage in one day and the relation between evaporation rate per unit area and temperature in the vertical distiller were obtained.The experimental results with constant heating power shows that the performance ratio of the evaporation can reach 1.81 with 600 W heating power and its optimal heating energy per day is about 14 MJ.Therefore,it is suggested the area of matched solar collector is 1.5 m2 when the equipment is operated in general weather.A theoretical model is proposed in this study,which can be used for natural convection heat and mass transfer with film evaporation and raw water reservoir inside the vertical cavity.An empirical formula between Nusselt number and Rayleigh number is obtained,which is suitable for calculation of vertical plate cavity with film evaporation and raw water reservoir.