Energy efficiency measurement and analysis of magnetically levitated direct-expansion air conditioning units in subway stations

Performance research on magnetically levitated direct-expansion air conditioning units in subway stations used to stay in the laboratory or engineering prototype stages, and due to the influence of the factors such as on-site construction, installation and commissioning of the units, the actual operation performance of the units may be different from the prototype. Therefore, this paper selects four magnetically levitated direct-expansion air conditioning units that have been put into operation in Luoyang Metro to test and analyse their actual operating performance. The actual measurement results show that the field-measured performance under 100% and 75% load conditions is consistent with the laboratory test performance, but the measured performance of half of the units under 50% load condition is lower than the laboratory test performance by 21% to 38%. Attention should be paid to the commissioning of operating parameters under low-load conditions. The cooling capacity can be flexibly adjusted through the parameters such as air supply volume and air supply temperature setting values. In Luoyang subway station, the measured refrigeration coefficient of performance of the units in the range of 40% to 80% of the long-term operating load reaches 7.4 to 12.0. The part load performance of the unit is excellent, and it can be well adapted to the subway station with the characteristics of low passenger flow and low air conditioning load due to operation in early and recent periods for a long time.