硅胶粒径对太阳能吸附制冷系统性能的影响

针对以硅胶-水为工质对的太阳能吸附式制冷系统，实验研究了不同粒径的硅胶材料对吸附床传热传质特性及系统制冷能力的影响。三组对比实验的硅胶材料平均粒径分别为1mm、3mm和5mm，在太阳辐射接近的条件下完成实验测试，结果表明粒径中等的硅胶材料表现最优，其制冷系数COP和按照循环周期定义的比制冷功率SCP₂均最高。小粒径材料虽然使吸附剂填充量有所增加，但是会导致吸附床轴向传质阻力增加，影响其末端吸附能力的发挥。而材料的粒径过大，则会降低吸附床的吸附剂填充量及其传热性能，从而导致预热脱附和冷却过程的时间延长，不利于系统的制冷性能改善。实验结果表明，吸附剂粒径是影响太阳能吸附式制冷系统工作性能的一个重要因素，在系统设计中需要给予重视。

Effect of particulate diameter of silica gel on performance of solar adsorption refrigeration system

The effect of silica gel adsorbent with different particle sizes on the heat and mass transfer and the cooling capacity of the solar adsorption refrigeration system was experimentally investigated. The system adopted the silica gel-water as the work pair for refrigeration. Under close solar radiation conditions, contrast experiments were conducted in three groups of silica gel particle of 1mm, 3mm and 5mm in average diameter. The results revealed that the silica gel particle of the medium size performed the best with both the highest COP and tspecific cooling power SCP₂, which was defined by the whole cycle time. Although the small particle size increased the filling mass of the adsorbent, it also caused the increment of the mass transfer resistance along the adsorption bed axis. This increment of the mass transfer resistance frustrated the adsorbent near the bed end to fully play the role. On the other hand, the silica gel particle of the big size would deteriorate the heat transfer of the bed, leading to longer time in process of the preheat and the cooling to the bed. In general, it was demonstrated that the particulate diameter of the adsorbent material was a significant factor to impact the performance of the solar adsorption refrigeration system and should be paid full attention in engineering design.