Experimental study of the split-type air conditioner with the variable-speed compressor, variable-speed supply fan, and electronic expansion valve

Abstract

Buildings often use air conditioning systems to regulate the indoor thermal environment in terms of temperature and humidity. These parameters are hard to control within the desired limits by only using traditional constant-speed compressors and constant-speed supply fans. The constant-speed devices with on-off control methods consume a high rate of energy and provide unsatisfactory control, especially for indoor humidity. Therefore, variable speed compressor (VSC) technology was developed to overcome the problems of control and energy consumption. In this study tested a split-type air conditioning system with a capacity of 1 ton (12,000 BTU/hr, 3.5 KW) of refrigeration was tested using R410A as the working fluid under different operating conditions. The system consists of a VSC, an air-cooled condenser, an electronic expansion valve (EEV), and a direct expansion evaporator (DX) with a variable-speed fan. The effect of compressor speed, degree of superheating, EEV opening, and supply fan speed on system performance was considered. Through experiments, concluded several points. First of all, the highest superheat was 20 ℃ at constant compressor speed. On the other hand, the smallest superheat was 10 ℃ at constant compressor speed. The performance coefficient increases when the compressor speed decreases. The highest value of the COP is 4.71, which can be obtained at the compressor speed of 3000 rpm and DS is  20 ℃, while the lowest value of the COP is 1.74 at the compressor speed of 5000 rpm and DS is 10 ℃ because of the increasing the compressor speed leads to an increase in energy consumption and a decrease in the COP, increasing the closing of the expansion valve opening leads to an increase in DS because of a decrease in the flow rate of the refrigerant to the evaporator. Finally, refrigeration capacity and COP increase linearly with evaporator temperature and airflow velocity due to the heat exchange process.