Abstract: In the low-temperature heating capacity experiment of the production verification test (PVT) phase of a certain household air-conditioning outdoor unit project, the frequency reduction phenomenon because of high exhaust temperature caused by the expansion valve flux deviation at the same opening value occurred. Combing linear regression analysis with air conditioner experiments, when the expansion valve with the current flow control level was tested on the whole machine, the lower limit of the initial opening without exhaust frequency reduction was 150 B. However, because the system parameters were set at 140 B, the exhaust temperature was too high during the open-loop stage and frequency reduction occurred. The flow deviation of the expansion valve is the main reason for the occurrence of frequency reduction. To solve this problem, an optimization plan was proposed for the manufacturer to screen the lower limit of flow rate and increase the system expansion valve opening setting to 160 B. The peak exhaust temperature dropped by 17.3%, and there was a margin of more than 3℃ from the frequency reduction temperature. It has been fully verified by experiments that this solution can effectively solve the problem of exhaust frequency reduction under low-temperature heating conditions.

Key words: Flow deviation, Miniaturized air conditioning, Air conditioning defrosting, Initial opening, Exhaust frequency reduction