AT-19-C048 — Sensitivity Study of Crystallization Fouling in a Liquid-to-Air Membrane Energy Exchanger using Three Desiccant Solutions

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Liquid-to-air membrane energy exchangers (LAMEEs) can serve as alternatives to conventional heat exchangers in heating, ventilating and air-conditioning systems. This is possible because LAMEEs use semi-permeable membranes to simultaneously transfer heat and moisture between air and liquid desiccant streams. However, research has shown that LAMEEs are susceptible to crystallization fouling if ions precipitate from desiccant solutions and accumulate in membranes. The main objective of this paper is to perform a sensitivity study of crystallization fouling in a LAMEE using three desiccant solutions. Experimental tests are performed by using dry air to dehydrate three desiccant solutions, namely LiCl(aq), MgCl2(aq), and NaCl(aq), at room temperature conditions. An indirect method is used to determine the impact of crystallization fouling on the LAMEE by analyzing the changes in moisture flux through the membrane during a test. In addition, a direct method (scanning electron microscopy – SEM) is used to examine the presence of deposits on membranes after a test. The results show that crystallization fouling negatively impacts the LAMEE by reducing the moisture flux through the membrane, and resulting in a fouling rate of 0.4 – 29 g/(m2·h2). A desiccant solution with a higher equilibrium relative humidity (ERH) is found to produce a higher fouling rate compared to a solution with lower ERH, i.e. NaCl(aq) > MgCl2(aq) > LiCl(aq). SEM micrographs confirm the presence of crystal deposits on the membranes tested using the three desiccant solutions. Furthermore, a cake layer which consists of large cubic crystals is observed on the surface of the membrane tested using the desiccant with the highest ERH (i.e., NaCl(aq)). The findings of the paper have significant practical value with regards to the selection of suitable desiccant solutions that can minimize the risk of crystallization fouling in LAMEEs.

Citation: 2019 Winter Conference, Atlanta, GA, Conference Papers

Product Details

Published:

2019

Number of Pages:

9

Units of Measure:

Dual

File Size:

1 file , 2.5 MB

Product Code(s):

D-AT-19-C048