Experimental optimization study of direct expansion evaporative condensation air conditioning systems in South China subway stations

Taking a subway station operating in the hot summer and warm winter zone as an example, this paper conducts experimental research on the direct expansion evaporative condensation air conditioning system, and the main factors affecting the COP of the system are analysed. The optimized study is carried out on the system, including adopting the frequency conversion operation strategy for the terminal fans and descaling the evaporative condensers. The comparison is made with a conventional station using cooling towers and chillers as cold sources on the same line. The results show that the refrigeration system COP of the direct expansion evaporative condensation air conditioning system is 4.55, which is lower than 5.24 of the conventional cold source station on the same line. After adopting the frequency conversion operation strategy for the terminal fans, the energy-saving effect is significant, the temperature and the CO2volume fraction in the public area of the station are basically maintained at the design conditions, the energy consumption of the refrigeration system compressor is reduced by 9.6%, the energy consumption of the terminal fans is reduced by 21.0%, and the COP of the single-end refrigeration system of the station is increased from 2.88 to 3.47 with an increase of 20.5%. After descaling the evaporative condensers, the COP of the single-end refrigeration system of the station is increased from 3.49 to 4.24 with an increase of 21.4%.