The Study on a Dual Evaporating Temperatures-Based Chilled Water System Applied in Small-to-Medium Residential Buildings

In small-to-medium-scaled residential buildings, direct expansion air-conditioning (DX A/C) systems were commonly used in indoor environment control only indoor air temperature. The uncontrolled humidity would cause indoor health and comfort issue. In this study, a dual evaporating temperatures-based chilled water system was proposed and designed for the application in small-to-medium-scaled residential buildings. An experimental prototype was established and tested in an existing psychrometric chamber. With two suction inlets of the compressor and the cooperation of two different electronic expansion valves, two evaporating temperatures were achieved. The lower one was used to generate the low-temperature chilled water, say 4–6 °C, to handle the outdoor air, which could be used to deal with the indoor latent load. On the other hand, the higher one was used to generate high-temperature chilled water of 16–18 °C, to deal with the indoor sensible heat, so as to achieve temperature and humidity independent control. Experiments were carried out under typical operation conditions in Shanghai. The results showed that the proposed system was able to operate stably under different conditions, and the chilled water temperatures could be maintained at required level. Therefore, the system proposed is feasible and would provide a novel solution for the issue of temperature and humidity independent control in small-to-medium-scaled residential buildings.