Performance evaluation of a membrane-based flat-plate heat and mass exchanger used for liquid desiccant regeneration
Performance evaluation of a membrane-based flat-plate heat and mass exchanger used for liquid desiccant regeneration
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DOI：
10.1016/j.applthermaleng.2018.05.011
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发表时间：
2018-07
影响因子：
6.4
通讯作者：
H. Bai;Jie Zhu;Ziwei Chen;Junze Chu;Yiwen Liu
中科院分区：
文献类型：
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作者：
H. Bai;Jie Zhu;Ziwei Chen;Junze Chu;Yiwen Liu
液体除湿空调系统因其不需要冷凝水而具有巨大的节能潜力，近年来得到了很大的发展。在系统中，再生非常重要，因为干燥剂溶液在干燥后需要重新浓缩。本研究主要探讨一种用于液体除湿再生之膜式平板式热质交换器之操作特性。液体干燥剂和空气呈交叉流布置，并通过半透膜分离以避免携带问题。通过数值模拟和实验测试，研究了再生性能。采用溶液侧效率、温度下降速率（TDR）和湿通量速率（MFR）对蓄热室的传热传质性能进行了评价。主要操作参数的影响进行了评估，其中包括无量纲参数（即传热单元数NTU和溶液与空气的质量流率比NTU），溶液入口特性（即温度Tsol，in和浓度Csol，in）和空气入口条件（即温度Tair，in和湿度比Wair，in）。结果表明，m_（max）和NTU是两个最重要的参数，它们对再生性能的影响是相互影响的。在低NTU下增加NTU或在低NTU下增加NTU对性能的改善几乎没有好处。虽然增大再生效率和NTU可以提高再生性能，但当再生效率和NTU分别大于2和4时，其提高幅度有限。提高溶液入口温度是提高再生性能的有效途径，而空气入口温度和空气湿度对再生性能的影响不大。
Liquid desiccant dehumidification system has gained much progress recently for its considerable energy saving potential without liquid water condensation. Within the system, regeneration is of great importance since diluted desiccant solution after dehumidification needs to be re-concentrated. The operational characteristics of a membrane-based flat-plate heat and mass exchanger used for liquid desiccant regeneration are investigated in this study. The liquid desiccant and air are in a cross-flow arrangement, and separated by semi-permeable membranes to avoid carry-over problem. The regeneration performance is examined by numerical simulation and experimental test. Solution side effectiveness, temperature decrease rate (TDR) and moisture flux rate (MFR) are applied to evaluate heat and mass transfer in the regenerator. Effects of main operating parameters are assessed, which include dimensionless parameters (i.e. number of heat transfer unitsNTUand solution to air mass flow rate ratiom∗), solution inlet properties (i.e. temperatureTsol,inand concentrationCsol,in) and air inlet conditions (i.e. temperatureTair,inand humidity ratioWair,in). It is found thatm∗andNTUare two of the most important parameters and their effects on the regeneration performance are interacted with each other. There is hardly benefit to the performance improvement by increasingNTUat lowm∗or increasingm∗at lowNTU. Even though the regeneration performance can be improved by increasingm∗andNTU, its improvement gradient is limited whenm∗andNTUexceed 2 and 4 respectively. It is also found that increasing solution inlet temperature is an effective approach to enhance the regeneration performance, while air inlet temperature and humidity ratio have negligible effects on it.