Abstract:

The existence of lithium bromide can significantly improve the process of generation and reduce energy consumption of rectification. But it has negative effect on the absorption process of ammonia. Therefore, the new cycle of NH₃-H₂O-LiBr absorption refrigeration system based on membrane separator was proposed to separate lithium bromide from the solution stream entering absorber and improve absorption performance. And the experiment for separating lithium bromide in the membrane separator was carried out. The results showed that the separation efficiency of lithium bromide can reach 98% after twice solution cycle in membrane separator. Based on the separation efficiency of experiments, the Aspen Plus monitor process was used for further simulating and analyzing the NH₃-H₂O-LiBr absorption refrigeration system with membrane separator. Simulation results indicated that due to the application of membrane separator, the energy consumption of new cycle based on membrane separator was lower than the normal absorption system and the COP can be improved nearly 10%. When generator temperature increased from 60℃ to 120℃, the generator heat load decreased and the COP of absorption cycle increased with the highest value of 0.5869 at the mass fraction of lithium bromide ranging from 0—30%.

Key words: absorption refrigeration, simulation, COP, Aspen Plus, membrane separator

摘要：

氨-水-溴化锂（NH₃-H₂O-LiBr）三元吸收式制冷系统中溴化锂的存在有利于发生过程的进行，降低循环精馏热，但阻碍了吸收氨的传质过程，对吸收性能不利。对此本文提出基于膜分离器的氨-水-溴化锂吸收式制冷循环，可将溴化锂从进入吸收器的溶液中分离出来，进而改善吸收性能。并进行了在膜分离器中分离溴化锂的实验，实验结果表明NH₃-H₂O-LiBr三元溶液在膜分离器中两次循环后分离效率达98%。基于实验中的分离效率，利用Aspen Plus模拟器，进一步模拟分析了基于膜分离器的氨-水-溴化锂吸收式制冷系统，并计算其性能系数（COP）。结果表明，与普通三元循环相比，基于膜分离器的新型循环的能耗较低，性能系数可提高近10%。当发生温度从60℃升高到120℃时，循环的发生器热负荷逐渐降低，COP逐渐增大，最大达0.5869，较普通循环高6%，此时溴化锂质量分数变化范围为0~30%。

关键词: 吸收式制冷, 模拟, 性能系数, Aspen Plus, 膜分离器