Design and experiment study of membrane based isothermal dehumidifier in HVAC system

Abstract

As passive building systems improve, sensible loads decrease and the air conditioning system takes on a greater role in dehumidification. Isothermal dehumidifier with membrane, which utilizes a vacuum pump to create a partial vapor gradient between membranes, has the potential to save significant energy by operating just for latent cooling as a thermally decoupled system. Although research has concentrated on analyzing the dehumidification and energy performance of isothermal dehumidifiers via simulation studies, their design and experimental analysis for dehumidification systems in HVAC systems remain rare. In this study, we constructed a prototype of an isothermal dehumidifier using hollow fiber membrane modules and vacuum pumps for an air conditioning system. Under different air conditions, the constructed prototype was evaluated for dehumidification characteristics (i.e., isothermal process, moisture removal rate, and dehumidification efficacy). Three factors were used to choose the air conditions for testing the dehumidification performance: air temperature, air humidity, and air velocity. The experiment results indicated that the isothermal dehumidifier dried the air without changing the temperature, and the overall dehumidification performance of the prototype system indicated that the humidity ratio difference was between 3.8 and 14 g/kg, the moisture removal rate was between 0.12 and 1.0 kg/h, and the dehumidification effectiveness was between 36% and 81%.