Research On Defrosting Control Methods Of Constant Temperature And Humidity System

In order to maintain the temperature under the confine of fruits and vegetables storage when defrosting, and at the same time defrost as least as possible in a period of time, the optimum beginning time and end time of defrost of this cold storage system must be found.For this purpose, the impact on parameters of air temperature, humidity and fan speed when frost is analyzed. And the influences on the rise of temperature inside the cold storage of different beginning time and end time of defrost are also studied. Based on the analysis of the frost and defrost experiment results, the time that the system stable operate, the fin temperature, the pressure margin of the air through the evaporator, the margin of bank temperature and evaporation temperature, the rate of the margin change of bank temperature and evaporation temperature are taken as the control parameters of the defrost beginning time, and the pressure margin of the air through the evaporator and the fin temperature are taken as the main control parameters of the defrost end time. The values of the parameters are also confirmed.On account of the characteristics of frequency-conversion of this system,"low-frequency defrosting"is proposed this paper. And the pros and cons of"low-frequency defrosting"and"shutdown defrosting"are analysised. The defrost interface and the defrost control process are completed finally.