Investigation of Control Process in Liquid Refrigerant Defrosting System

Year 2018, Volume: 21 Issue: 4, 214 - 219, 04.12.2018

Meng Wang , Runqing Zang Yanhe Li Wenqing Li

https://doi.org/10.5541/ijot.435774

Abstract

The liquid refrigerant defrosting system (LRDS) has the
advantages that the refrigeration process is continuous, the temperature
fluctuation of the cold storage is small, and the cooling energy of the frost
can be recovered effectively. However, the system is too complex to apply and
promote in the modern cold storage. In order to solve the problem of operation
difficulty, the control experiments were carried out, including the beginning
of the defrosting (BD), the end of the defrosting (ED), the draining time (DT)
and the time difference between the two air coolers start-up (TDTACS). The
results showed that the LRDS started to defrost when the air pressure
difference was higher than 0.5mbar. The outlet should be located at the middle
part of the lower 1/3 part of the evaporation surface. The measuring pressure
tube inserted the fin 20mm, and the nozzle was perpendicular to the evaporation
pipe. The experimental ambient temperature was 30℃, and the frost mass
was 3kg. The gas return temperature at the ED was 3.0℃, 4.0℃, 5.0℃, 6.4℃ and 7.4℃ respectively when
the cold storage temperature was 0℃, 5℃, 10℃, 15℃ and 20℃ respectively. The DT
was controlled between 140s and 180s, which could prevent the wet compression.
In order to get the TDTACS, the manual control could be adopted for the first
defrosting. Then the air pressure difference control could be used. The two air
coolers could refrigerate and defrost alternately.

Keywords

Cold storage; defrosting; automatic control; air cooler.

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