Experimental study of vacuum-based membrane dehumidifier for HVAC system: Parametric analysis and dehumidification performance

Abstract

Vacuum-based membrane dehumidifiers (VMDs), an emerging air dehumidification technology, use selective membranes to remove moisture from humid air; these dehumidifiers have the potential to save energy and enhance thermodynamic efficiency through decoupled latent and sensible cooling. In this study, a prototype of a vacuum-based membrane dehumidifier at the scale of an air-conditioning system was developed, and its dehumidification characteristics were experimentally evaluated under various test conditions (i.e., air temper-ature, air humidity, air velocity, and pressure on the permeate side). Four indices were selected to examine the dehumidification performance of the system: the humidity ratio difference, moisture removal rate, dehumidi-fication efficacy, and performance coefficient. The results revealed that the humidity ratio difference ranged 3.38-14.76 g/kg, moisture removal rate 0.16-1.09 kg/h, dehumidification effectiveness 35.4 %-82.7 %, and COP 0.16-0.86. In the parametric analysis of the prototype, the airflow rate and humidity ratio are identified as essential parameters for the dehumidification performance. Moreover, the thermodynamic perspective in the Psychrometric chart and transient operation were utilized to evaluate the operational characteristics of the prototype unit. All experimental results showed that the difference in temperature between the inlet and outlet air was less than 1.5 degrees C, and the saturation time is shown to be within 5 min.