太阳能热水器内部流动性能正交模拟

研究全玻璃真空管式太阳能热水装置内部的流动性能,分别针对有无反光板和具有不同长径比、倾斜角度以及集热管插管深的直流全玻璃真空管式太阳能热水器进行仿真模拟,以不同进口温度、质量流量以及输入热流模拟热水器的各种试验工况。采用正交试验效应计算方法,定量分析对集热管内循环流速、停滞区比值、漩涡数等流场指标起主要影响作用的因素。结果表明:对集热管内循环流速影响最大的是集热管下表面热流(约占绝对效应总和的26%)以及水箱入口温度(24%)。对集热管内停滞区比值影响最大的是集热管下表面热流,占25%,其次为集热管偏离垂直方向的角度,占15%。水箱入口初温和集热管长径比是对集热管内漩涡数影响最大的2个因素,分别占绝对总效应的36%和29%。因此等权重衡量各因素对集热器3个流场指标的影响差异,未来热水器结构改进的方向渐次为:增加反光板,减小长径比,降低入口温度,增加入口质量流速,增大倾斜角度,增加选择性吸收涂层吸收比,进而增加上表面热流,最后减小集热管插入深度。

Inner flow simulation of all glass evacuated tube solar water heater based on orthogonal simulation

A simulation of the all glass evacuated tube solar water heater was performed,which includes consisting of different structures with different aspect ratios,tilt angle,with or without reflector and the depth of the collector tube in tank.A variety of test conditions of water heater was simulated at different inlet temperatures,mass flows and input heats.To improve the design of water heaters,some influential flow indexes,including the loop flow rate,the stagnant region ratio,and the vortex number were analyzed based on the orthogonal test method.Results showed that the circulation flow rate of the collector tube was affected by the heat under the collector tube,with 26% of the sum of absolute effect,and by the initial inlet temperature of the water tank,with 24%.Stagnation ratio of the collector tube was affected by the heat under the collector tube,with 25%,and the incline angle of collector,with 15%.The aspect ratio of the collector and the initial inlet temperature of the water tank were the two factors for determining the number of vortex in the collector,with 36% and 29% of the same of absolute effect,respectively.An advice to improve the solar heater in the future was given based on a hypothesis that the effects were evaluated equally.The order was to increase reflector,to reduce the aspect ratio,to lower inlet temperature,to increase inlet mass flow rate,to increase tilt angle,to improve the selective absorbing coating selection,thus,to increase the top surface heat of collector,and to reduce the depth of the collector tube in tank finally.