Patent ID: 11927379
Assignee: XI'AN JIAOTONG UNIVERSITY
Field: Thermal processes and apparatus (Mechanical engineering)
Classification: CPC F  Y | IPC F

Claim 5:
6. The control method of claim 4, comprising:
accurately assessing a degree of frosting of the CO2 heat pump system based on measurement values of an ambient temperature sensor and an evaporation fin temperature sensor; determining that the CO2 evaporator of the CO2 heat pump system has been sufficiently frosted as long as following three conditions are all met, and entering a defrosting mode to defrost, wherein the following three conditions lie in that: a frosting time of a unit is greater than a setting time; a measured ambient temperature is lower than a defrosting ambient temperature setting value; and a temperature difference between the measured ambient temperature and a measured temperature of evaporation fins is greater than a defrosting temperature difference setting value; and
when defrost starts, setting the opening degree of the electronic expansion valve (13) to be the maximum, opening the defrosting solenoid valve (14), closing the waterway two-way regulating valve (4), stopping a fan of the CO2 evaporator (15), such that high-temperature and high-pressure gas of the outlet of the CO2 compressor (11) flows through the CO2 gas cooler, the two parallel electronic expansion valves (13) and the defrosting solenoid valve (14) for throttling and pressure reduction, and then enters the CO2 evaporator, and fully exchanges heat with a frost layer in the CO2 evaporator, so as to achieve defrosting as soon as possible.