Improved Design and Experimental Investigation of a Unitary Dehumidification Unit with Hot Gas Reheat

To deliver comfortable conditioned air by reducing humidity levels while enhancing comfort levels in an air space under varied load conditions, an improved design for fully modulating dehumidification with a hot gas reheat system was developed. By managing the charge balance between the cooling and reheat modes, the modulation operating map for the reheat opening was expanded. Different microchannel heat exchanger (MCHE) reheat coil patterns and solutions were analyzed. The test results showed that an air-resourced unitary unit equipped with this novel MCHE reheat system solution improved the balance between the refrigerant charge requirements and the cooling and reheat modes. Under rating conditions, the energy efficiency ratio (EER) in the reheat mode increased by 17%, and water condensate removal through dehumidification was enhanced by 6%. The modulating valve reheat port opening range could be increased from a baseline of 20%-70% to 15%-85%. For the rated reheat dehumidification condition, the reheat temperature rise modulating range increased from 8.3-14.4 ℃ to 6.1-19.4 ℃. This innovative solution was proven to achieve a wider adjustable operating map that improved dehumidification capacity and power conservation.