结构参数对全玻璃真空管太阳热水器夜间热损失的影响研究

文章建立了三维非稳态的全玻璃真空管太阳热水器的数值模型,分析了夜间散热时,该热水器内的流动和传热特征,并且在夜间同一工况下,模拟研究了贮热水箱保温材料的导热系数、保温厚度,以及真空管涂层的发射率对贮热水箱温度、真空管温度和该热水器夜间热损失的影响。分析结果表明:随着散热过程的持续进行,全玻璃真空管太阳热水器内温度分层情况越来越明显,内部流体的流速越来越小,真空管内静滞区域自下往上逐渐扩大;当贮热水箱保温材料的导热系数由0.035 W/(m·℃)减小至0.020 W/(m·℃)时,该热水器的夜间热损失减少了8.5%;当贮热水箱保温厚度由50 mm增加至60 mm时,该热水器的夜间热损失减少了5.0%;当真空管涂层的发射率由0.06减小至0.05时,该热水器的夜间热损失减少了4.0%。

Effects of structural parameters on heat loss of all-glass vacuum tube solar water heater at night

In this paper,a three-dimensional unsteady numerical model of all-glass vacuum tube solar water heater was established.The flow and heat transfer characteristics of the water heater during heat dissipation at night were analyzed.Under the same condition,the effects of thermal conductivity and thickness of insulation material of the heat storage tank,and the coating emissivity of the vacuum tube on temperature in the tank and tube and heat loss of the water heater at night were also simulated.The analytical result showed that the temperature stratification in the water heater became more and more obvious,the flow rate of internal fluid was getting smaller and smaller,and the static stagnation area in the vacuum tube expanded gradually from bottom to top.In addition,when the thermal conductivity of insulation material of the heat storage tank was reduced from 0.035 W/(m·℃)to 0.020 W/(m·℃),the night heat loss of the water heater was reduced by 8.5%;When the insulation thickness of the heat storage tank was increased from 50 mm to 60 mm,the night heat loss of the water heater was reduced by 5.0%;when the coating emissivity of the vacuum tube was reduced from 0.06 to 0.05,the night heat loss of the water heater was reduced by 4.0%.