Abstract
The use of direct expansion (DX) air conditioning (A/C) systems is widely seen in residential buildings in tropics and sub-tropics. However, most DX A/C systems are equipped with single-speed compressor and supply fan, relying on On—Off cycling as a low-cost approach to maintain only indoor dry-bulb temperature, whereas the indoor air humidity is not controlled directly. This also leads to potential inefficient energy use due to space over-cooling. This paper suggests a novel control strategy (termed Hi—Lo strategy) of using two-speed compressors in DX A/C systems for better indoor thermal environment control and higher energy efficiency. Experimental work has been carried out to test the Hi—Lo control strategy. Experimental results suggested that the novel control strategy can help improve the indoor humidity control without sacrificing energy efficiency.
Practical application: The use of ON/OFF control at part load conditions in conventional DX A/C systems will lead to undesirable relative humidity levels. The problem is more prominent when the latent load is dominant. In order to have a better dehumidification effect, a lower indoor dry bulb temperature has been often set. On the other hand, the use of variable speed compressors in DX A/C systems can be a solution to the problem of humidity control, but its cost is comparatively high. The suggested novel control strategy is a low cost approach, which can save energy and provide a better indoor humidity control using DX A/C systems.
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