Effect of Non-Convective Zone Thickness on Thermal Efficiency of Salt Gradient Solar Ponds

An improved radiation transmission and thermal efficiency model for solar ponds has been proposed based on both the Hull Model and Wang/Seyed-Yagoobi Model in this paper.The new model is more accurate to actual measured conditions because multiple reflections and turbidity effects are included.Absorption penetration,thermal conductivity loss and thermal efficiency under different Non-Convective Zone thicknesses are numerically analyzed and thoroughly discussed.The results show thatΔT/I0 plays a critical role for the thermal efficiency of solar pond.Furthermore,it is found through calculation that there is an optimum thickness of the Non-Convective Zone.When the Non-Convective Zone thickness is less than this critical threshold,both temperature and thermal efficiency are decreased with increasing turbidity.However,when the Non-Convective Zone thickness is greater than this critical threshold,the increasing turbidity within a certain range will be beneficial to improve the thermal efficiency of solar pond.In addition,optimum Non-Convective Zone thickness is also related to the temperature,turbidity,salinity variation and bottom reflectivity.

太阳池非对流层最佳厚度及最大效率数值模拟

本文对现有的太阳池辐射透射模型及稳态热效率模型进行了改进,改进的模型既考虑了池水浊度的影响又考虑了池内多重反射的影响,更接近实际情况。在改进的稳态热效率模型基础上,通过数值模拟的方法,对太阳池非对流层最佳厚度及其最大效率的相关影响因素作了较为详细的分析和讨论。认为太阳池非对流层最佳厚度及其最大效率取决于太阳池尺寸和结构、太阳辐射强度、储热层和上对流层的温差、太阳辐射在水中的透射率、池底反射率、水浊度、池水的物理特性以及池深度等综合因素,其中,△T/I0(储热层和上对流层的温差与水面太阳辐射强度的比值)是影响太阳池非对流层最佳厚度的主要因素,这为太阳池高效运行提供了理论指导。

基于一/二次能源采暖最优保温厚度分析

对3个气候区域4个城市住宅建筑计算采用XPS保温最优保温厚度,20年生命周期节省经济成本和保温回收期。分析现值因子和采暖度日数对保温效果的影响。结果表明,供暖热源种类和气候因素对最优保温厚度影响作用较大。基于采暖度日数法计算得到4种能源的最优保温厚度,由薄到厚依次为:天然气,煤炭,电,液化石油气。随着能源种类和气候区域的变化,最优保温厚度3.3~17.4 cm,生命周期节省经济成本244.1~517.9元/m2,保温投资回收期2.7~1.3年。最优保温厚度与生命周期节省经济成本方面,二次能源要高于一次能源。

夏热冬冷地区的墙体节能研究

墙体表面的颜色、墙壁的朝向、绝缘隔热材料的选择是影响建筑节能的主要因素。因此,在考虑太阳能辐射影响的同时,分析墙体表面颜色、墙壁朝向以及绝缘隔热材料(包括膨胀珍珠岩、聚氨酯泡沫塑料、挤塑聚苯乙烯泡沫塑料、岩棉毡、膨胀蛭石等5种绝缘隔热材料)对建筑能耗的影响。选择上海、长沙、韶关和成都4个典型城市代表夏热冬冷地区的4个分区,用这4个城市的气象年数据进行经济性分析。结合墙体表面的颜色、墙壁的朝向、绝缘隔热材料等三方面的影响,计算出墙体的最佳保温层厚度。在此基础上,计算出在20年的生命周期内所节约的最大成本及投资回收期。