Graphic general solutions for desiccant coated heat exchangers based on dimensional analysis

Abstract

Solid desiccant, featuring thermally-driven mass transfer, is nowadays a hotspot in the field of mass adsorption/separation, energy allocation and water harvesting. Former studies indicate that the efficiency in such systems is dominated by the adsorption dynamics of the desiccant-based components. Accordingly, enormous efforts have been attempted on it to derive comprehensive parametric analysis or even theoretical solutions. Given the complexity in adsorption nature and the diversity in sorbent-sorbate interaction, however, the results obtained are either biased for incomplete research or lack of precision due to oversimplification. Here, we propose that dimensional analysis can fill this niche by its potential in freedom reduction and feature generalization. Specifically, desiccant coated heat exchangers (DCHEs) are chosen to demonstrate the method. Our work reveals, 4 dimensionless indexes (Ψa, K0, K1, K2), extracting from 13 original parameters, are sufficient to identify the adsorption performance in DCHEs, hence making the derivation of graphic general solutions possible. Meanwhile, stepwise elongation method is outlined to overcome the common difficulties aroused by nonlinear isotherms. It is for the first time that the dehumidification performance of DCHEs can be universally represented in a concise form, regardless of the disparities in operating temperature, inlet flow conditions, device configuration and desiccant properties. Afterwards, the application range of the proposed graphic solutions is specified. In view of the compatible nature of dimensional analysis, this method can be expediently extended to other sorption-related devices, and thus propels the theoretical development and technological innovation in the corresponding field.