Abstract:

An absorption refrigeration cycle using two working pairs was presented, taking LiBr solution with low saturated vapor pressure as the working pair for the low-pressure stage and LiCl solution with higher saturated vapor pressure for the high-pressure stage. The thermodynamic performance of the cycle was investigated and evaluated with variable operation conditions. It shows that the single stage absorption chiller with LiCl solution as the working fluid has a higher COP than LiBr solution when the driven heat temperature is low. The low grade solar energy driving the absorption chiller can be extended to 55—75℃ and the maximal COP can reach up to 0.47 owning to two working fluids. Consequently, the available operation time is increased and the efficiency of solar collector is improved. In particular, the intermediate pressure has a significant influence on the COP of the system, and there is an optimal intermediate pressure making the COP of the system maximum. The theoretical analyses reveal that the optimal intermediate pressure for the system lies from 2.5 kPa to 4.0 kPa.

Key words: absorption, solar energy, two working pairs, thermodynamic analysis

摘要：

提出一种基于双工质对的吸收式制冷循环,该循环分别采用饱和蒸气压较高的LiCl水溶液作为高压级工质对,饱和蒸气压较低的LiBr水溶液作为低压级工质对。对不同运行工况下循环的热力性能进行了理论计算与分析。结果表明,当驱动热源温度较低时,LiCl水溶液比LiBr水溶液表现出更好的热力性能。而且,基于双工质对的吸收式制冷循环可以将低位太阳能的利用温区扩宽到55～75℃,循环热力系数最高达0.47。还可以增加白天低温太阳能的利用时间,提高太阳能集热效率。另外,中间压力对循环热力性能影响显著,存在最佳的中间压力使循环热力性能达到最大,热力分析结果表明中间压力范围为2.5～4.0 kPa。

关键词: 吸收式制冷, 太阳能, 双工质对, 热力分析