Combining Liquid-Desiccant Dehumidification with a Dew-Point Evaporative Cooler: A Design Analysis

This article uses a numerical model to analyze a concept combining a liquid desiccant dehumidifier with a dew-point indirect evaporative cooler. Each of these components, or stages, consists of an array of channel pairs, where a channel pair is two air channels separated by a thin plastic plate. In the first stage, a liquid desiccant film lining one side of the plates removes moisture from the process (supply-side) air through a membrane. An evaporatively cooled exhaust airstream on the other side of the plastic plate cools the desiccant. The second stage sensibly cools the dried process air with a dew-point evaporative cooler. This article uses a parametric analysis to illustrate the key design tradeoff for this concept: device size (a surrogate for cost) versus energy efficiency. The analysis finds the design parameters with the largest effect on this tradeoff and finds the combinations of design parameters giving near-optimal designs, which are designs with the highest efficiency for a given device size. The results indicate that there are two key parameters contributing to this tradeoff: the supply-side air channel thickness and the exhaust-air flow rate in the evaporative cooler.