how is the step by step procedure of hot gas defrosting inrefrigeration plants using AMMONIA gas ?

Question

Dear sirs,
Please answer my question with some elaboration so as to carry out the hot gas defrosting in a blast freezer used for freezing tuna fish to a temperatue of mius 45 degree Celcius. Let me know whether the defrosting is done while the compressor is kept running to provide hot gas supply to the evaporator and to clear the liquified hotgas from the evaporator. With regards.JOSEPH.

Answer 1

You should be able to do this by installing valves to reverse the flows of the ammonia gas. This should be similar to how a heat pump operates. You'll have to figure out the control strategy as far as how long the reversed flow should be applied to defrost the unit. And yes, your compressor will have to still be running to produce the heat and keep circulation going.

Answer 2

hot gas bypass valves dump the discharge right back into the low side bringing up your suction pressure high enough to defrost.while the compressor is running. generally the defrost cycle is controlled by a probe inserted between the fins of the evap.when the ice builds up enough to complete the circuit it energizes the hot gas solenoid.