Cold room freezer down temperature slow from -10C to -18C.

Type：Company News Date：2017-08-18 08:59:16

Cold room freezer down tempeareture slow from -10C to -18C. why?

Hello every body. Hope you are fine. Its still a little hot in China,+32C but much better than 2 weeks ago. finally we finish one cold room freezer of L8mxW2.5mxH2m total 40CBM space and cold room temperature is -18C, the compressor is copeland scroll ZSI15KQE, this is very different with ZB series becuase it has freon injection to cool compressor motor automatic,and the evaporating temperature can reach -30C, that means cold room can reach -25C. but ZB compressor only reach -20C evaporating temperature. the evaporator is aluminium pipe with diameter 32mm x 2.0mm with 2 swings. total long is 40x3=120m. but we make 135m. everything is finished installation, make vacuum,charge about 5kg freon. low pressure was 0.2Mpa and High pressure is 1.3Mpa. set temperature from -15C to -18C, start to temperature down. from +39C to -10C very fast,about 1 hour,but it was difficult to come down from -10C to -18C, it took 2 to 3 hours to come down 1 degree. why? any engineer who know why? was 5HP compressor is too small? but just empty cold room. we assembled 2 units of 3RT expansion valve.

Finally,we closed the expansion valve 2.5 rings. temperature come down fast. 10min for 1 degree.

Conclusion:

1)For -18C to -25C cold room, compressor need to be bigger. I think 6HP is better for 40CBM if use pipe type evaporator.

2)Its much slow to down temperature after -10C to pipe type evaporator.

3)You will find the pipe type evaporator was much cooler than air-cooler type evaporator with fan at same temperature of -18C.

4)Expansion valve need to be big when high temperature phase,but it must be small when low temperature phase.

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