Abstract:

Concentration difference nondestructive energy storage can convert heat energy into the chemical potential energy of the solution. It can be used in solar lithium bromide absorption refrigeration system to improve the working stability of the system effectively. However, when the concentration of the solution is too high or the operating temperature is too low, it s easy to precipitate and crystallize, which will cause difficulty in putting energy. The membrane energy accumulator can solve the problem that it is difficult to release energy when crystallization occurs in the lithium bromide concentration difference accumulator. In order to analyze the internal heat and mass transfer characteristics of the membrane energy accumulator, the experimental test system of heat and mass transfer in the energy release process of the membrane energy accumulator is set up. And the mathematical model of heat and mass transfer of the membrane energy accumulator applied in the solar absorption refrigeration system is established. The CFD software is used to solve the three dimensional mathematical model. Comparing the calculated results with the experimental results, the mass transfer deviation of the water vapor molecule is less than 6%, and the solution temperature deviation is less than 15%, the reliability of the unsteady mathematical model is verified and the model is used as an analytical tool for heat and mass transfer in the energy release process of the membrane energy accumulator. According to the experimental and simulation results, the average mass transfer efficiency of 70% MS (mass fraction lithium) bromide solution is improved by 44.03% compared with 60% MS solution. When the evaporation temperature increases from 4.5℃ to 12.3℃, the average mass transfer efficiency will increase by 108.34%. And the mass transfer efficiency is improved by 40.77% with the decrease of effective length from 80 mm to 30 mm. The average mass transfer efficiency of water vapor can be improved by increasing the initial concentration, evaporation temperature, or reducing the effective length of the membrane channel.

Key words: membrane energy accumulator, heat transfer, mass transfer, membranes, experiment and simulation

摘要：

膜构架蓄能器是以中空纤维膜为基本结构，不仅能够实现蓄能，同时能够解决溴化锂溶液浓度差蓄能器中结晶后的放能困难的问题。搭建了膜蓄能器放能过程传热传质实验测试系统，建立了应用于太阳能吸收式制冷系统中的膜架构蓄能器传热传质的三维数学模型，并利用 CFD 软件进行了求解。将计算结果与实验结果相比较，验证了该三维非稳态数学模型的可靠性。实验和仿真结果表明，质量分数为70% 的溴化锂溶液的水蒸气分子平均传质速率比质量分数为60%的溶液高44.03%；当蒸发温度从4.5℃提高到12.3℃时，水蒸气分子的平均传质速率将提高108.34%；当膜通道的有效长度从80 mm减少到30 mm时，水蒸气分子的传质速率会提高40.77%。

关键词: 膜蓄能器, 传热, 传质, 膜, 实验与仿真