溶液热回收型太阳能集热/再生器的再生性能分析

该文使用溶液热回收的方法提高太阳能集热/再生器(collector/regenerator)的再生效率。通过数值模拟的方法分析玻璃盖板高度、溶液参数、空气参数、太阳辐射强度等因素对溶液侧有热回收的太阳能集热/再生器再生效率的影响。结果显示,在模拟条件下,使用热回收器使装置的溶液再生段由1 m升高为1.5 m,再生效率增加约93.6%,相当于C/R板长近似增加0.8 m,且热回收器效率越高装置再生性能越好;流量参数存在最佳值使得再生效率最高,且空气流量(溶液流量)的最佳值随着溶液流量(空气流量)的提高而增加。空气流量的较佳范围为100~150 kg/h,溶液流量的较佳范围为8~15 kg/h;在流量参数的较佳范围内,分析玻璃盖板高度对系统性能的影响,发现玻璃盖板高度的较佳范围为0.08~0.1 m;加热溶液比加热空气更能有效的提高再生效率;减小溶液的浓度或减小再生用空气的相对湿度,均会提高再生效率;在全年太阳能辐射强度较强地区宜采用带热回收器的C/R装置。这些结果为太阳能集热/再生器的设计和性能分析提供了一定的理论依据。

Regeneration performance analysis of solar collector/regenerator with solution heat recovery

Abstract: Solar liquid desiccant air-conditioning system has attracted many attentions owing to the advantages of utilizing low grade thermal energy such as solar energy, in which the solar collector and regenerator can be designed respectively. In addition, solar collector and solution regenerator can be combined together to construct solar collector/regenerators (C/Rs) that have better performance of regeneration. Solar C/Rs are the key component of system, because the cooling capacity of system is determined mainly by the regeneration efficiency. Moreover, in order to reduce top heat losses and eliminate contamination of the solution by dust, the C/Rs can be covered with the glazing plate. An experimental study on the effect of glazing plate height of solar C/Rs indicated that the optimum glazing plate height is 0.07 m, and the performance of the optimally glazed C/R is better than an unglazed C/R for hot humid climates. Analysis based on experimental data and numerical simulation was presented, and the results show a higher inlet solution temperature can increase the performance of regeneration. So the method of preheating the inlet solution was adopted to increase the efficiency of solar C/R, and solution heat recovery device was used to preheat the inlet solution by recovering the heat from the outlet solution. However, there have not been sufficient studies on the effect of various parameters on C/R performance with solution heat recovery. In this paper, the solution heat recovery device, by recovering heat from the outlet solution to preheat the inlet solution, was adopted to increase the efficiency of solar C/R. The numerical simulation method was adopted for analyzing the effects of the glazing plate height, solution parameters, air parameters, solar radiation intensity and other factors on the regeneration efficiency of solar C/R with solution heat recovery. Several physical assumptions were made, followed by modeling of counter-flow regeneration. And the previous experimental data were used for the comparison with the numerical results to validate numerical model. In the simulation conditions, the results show: Using a heat recovery device can improve the regeneration efficiency by 93.6% equivalent to adding 0.8 m length of C/R; the higher efficiency of heat recovery device causes the higher regeneration performance; the flow rates have an optimum value, which yields a maximum rate of water evaporation and regeneration efficiency. The optimum values of flow rates of solution (or air) increased with the increase in air flow rate (or solution flow rate), and the optimum ranges of flow rates of solution and air are 8-15 and 100-150 kg/h, respectively. The optimum range of glazing plate height is 0.08-0.1 m when flow rates are in the optimum ranges; higher inlet temperature of solution or air both can increase regeneration efficiency, but the method of heating solution is much more effective than heating air; the decrease of inlet concentration of solution or relative humidity of air both can be in favor of solution regeneration; the higher solar radiation intensity yields better performance of regeneration for the solar CR with heat recovery. All these results can provide guidance for the design and performance analysis of the solar CR.