0#1
Refrigeration is the process of MAINTAINING a lower temperature as compared to the surroundings. Be it continuous generation of work from heat or maintaining a lower temp, we have to conduct these operations in cycles. Every continuous operation runs on cycle. The cycles on which refrigeration processes function are known as refrigeration cycles. General direction of heat flow in from a higher temperature to a lower one. Obviously to make the heat flow in opposite direction, we would have to do some external work.
#2
Cycles discussed in Power Cycles (work producing cycles) were running on different working fluids. It was sometimes water, sometimes vapour, sometimes air. In refrigeration cycles too, the cycles need some fluid which is to be circulated. That fluid is known as refrigerant. There are many refrigerants being used, for example, ammonia, water, air, R-134, etc
#4
Refrigeration effect: It is the amount of heat which is to be extracted from storage space in order to maintain a lower temperature. Its unit is kJ/kg.
CAUTION: In some questions, you might be asked to calculate refrigeration effect but unit might be in kW, so be flexible in dealing with this term!!!
#5
Unit of Refrigeration: Tonne of Refrigeration (TR)
It is the amount of heat that is to be removed from one tone water at 0°C in order to covert it into ice at 0°C in one day (=24 hours).
The amount of heat require to change water into ice is nothing but latent heat.
Calculating the latent heat to be removed from 1 ton (=1000 kg) in 24 hours, we get: 1 TR = 3.5 kW = 211 kJ/min
Basically 1 TR would mean the amt of heat removed = 211KJ/min from storage space. Latent heat for solid to liquid does not vary significantly with change in pressure.
#6
On P-v and T-s diagrams, all work producing cycles are clockwise and all work consuming (refrigeration cycles) are counter-clockwise.
#7
Ideal Refrigeration Cycle: As I stated earlier that reversing a power cycle will give refrigeration cycle, reversing a work producing Carnot cycle will give a Carnot Refrigeration Cycle.
