Effect of desiccant adsorption isotherm on dehumidification performance of desiccant coated heat exchanger

doi:10.11949/0438-1157.20221248

Abstract

Abstract:

Compared with the traditional air compression air conditioning system, the adsorption dehumidification air conditioning system based on desiccant coated heat exchanger uses solid desiccant to deal with the latent heat load in the air, which effectively improves the evaporation temperature and greatly improves the energy efficiency of the air conditioning system. The choice of desiccant coating is very important to the performance of desiccant coated heat exchanger system. It is difficult to effectively select desiccant materials suitable for dehumidification heat exchanger system by using existing experimental and simulation methods. Based on the adsorption isotherm of desiccant, the applicability of desiccant material for dehumidification heat exchanger is discussed in this paper. Starting from the adsorption isotherm curve of desiccant， this paper discusses the dehumidification performance of desiccant with different types of adsorption isotherm curves firstly， and concludes that the desiccant with“S”type adsorption isotherm curve has the best dehumidification ability. The step pressure of“S”type adsorption isotherm is also analyzed and discussed, and the calculation method of the optimal step pressure under specific working conditions is determined. The above conclusions are consistent with the simulation results. The feasibility of obtaining desiccant with ideal adsorption isotherm by compounding hygroscopic salts and synthesizing materials with specific pore structure was also discussed.

Key words: dehumidification, desiccants, adsorption, isotherm, air conditioning

摘要：

基于除湿换热器的吸附式除湿空调系统采用固体干燥剂处理空气中的潜热负荷，可以有效地提高蒸发温度，大大提高空调系统的能效。其中，干燥剂涂层的选择对除湿换热器系统的性能至关重要，而采用现有的实验和模拟方式难以高效筛选适合除湿换热器系统的干燥剂材料。本文从干燥剂的吸附等温曲线出发，讨论了不同类型吸附曲线的干燥剂除湿性能，得出“S”型吸附等温曲线的干燥剂有最佳的除湿能力；对“S”型吸附曲线的阶跃压力进行了分析和讨论，确定了在特定工作条件下最佳阶跃压力的计算方法；讨论了通过复合吸湿盐、合成特定孔系结构材料等方式获得具有理想吸附曲线的干燥剂的可行性。

关键词: 除湿, 干燥剂, 吸附, 等温曲线, 空调

CLC Number:

TB 64

Tianyu YANG, Tianshu GE. Effect of desiccant adsorption isotherm on dehumidification performance of desiccant coated heat exchanger[J]. CIESC Journal, 2022, 73(12): 5367-5375.

杨田雨, 葛天舒. 干燥剂吸附等温曲线对除湿换热器除湿性能的影响[J]. 化工学报, 2022, 73(12): 5367-5375.

Figures/Tables 9

Fig.1 Diagram of desiccant coated heat exchanger and desiccant coating

Fig.2 Different types of adsorption isotherms classified by IUPAC[21]

Fig.3 Schematic diagram of the experimental set up

Fig.4 Isotherms of the 3 desiccant layers used in experiment (25℃)

Fig.5 Dynamic adsorption curves of the 3 desiccant layers and comparison with calculated results

Fig.6 Adsorption isotherms and simulation result of MIL-101 and silica gel-LiCl composite

Fig.7 Characteristic adsorption curves and simulation result of MIL-101, forward curve and backward curve

Fig.8 Adsorption isotherms of binary salts comprised adsorption[24]

Fig.9 Adsorption isotherms of different MOFs[29-32]

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