refrigeration cycle fused for vapor compression.pptx

vcrs cycle

1. Basic Refrigeration Cycle

2. Contents Introduction Purpose of Refrigeration How Does VCRS Work Four basic processes Coefficient of performance (COP) Understanding COP

3. Introduction Refrigeration involves the  process of removing heat from a product and cooling it to a lower  temperature than the actual. Refrigeration is a cyclic process that uses a refrigerant and a few components to perform the operation. The most frequently used refrigeration cycle is the vapour compression refrigeration system (VCRS) , in which the refrigerant is vaporized and condensed alternately. What is Refrigeration, and how does it work?

4. Purpose of Refrigeration Preserve food and perishable goods by slowing down bacterial growth. Provide comfort cooling in residential and commercial buildings. Support industrial processes that require specific temperature conditions.

5. How Does VCRS Work Source of Figure- https://makeagif.com/gif/vapour-compression-cycle-BbbwyO Fig. 1 . Vapour Compression Refrigeration Cycle.

6. Four basic processes 1-2 Isentropic Compression (in the compressor) 2-3 constant pressure heat rejection ( in a condenser ) 3-4 isentropic expansion ( in the throttling valve) 4-1 constant pressure heat addition ( in the evaporator)

7. Ideal VCRS Assumptions The refrigerant at the entry of the compressor and exit of the evaporator should be saturated vapour . Refrigerant at the exit of the condenser or entry of the expansion device should be a saturated liquid.

8. Coefficient of performance (COP) Where: Qcold – the amount of heat removed from the cooling space (refrigeration effect). W - work input to the refrigeration system (usually the work done by the compressor).

9. Understanding COP COP > 1 : Indicates that the system is efficient, as it provides more cooling than the work input. COP < 1 : Indicates that the system is inefficient, as it requires more work input than the cooling provided.

10. Effect of Evaporator pressure on COP Decrease in refrigeration effect Increase in work input Decrease in COP

11. Effect of condenser pressure on COP Decrease in refrigeration effect Increase in work input Decrease in COP

12. Effect of superheating in the Evaporator Increase in refrigeration effect Increase in work input May increase or decrease in COP depending upon the refrigerant.

13. Effect of subcooling in the condenser Increase in refrigeration effect Compressor work remains constant. Increase in the COP.

14. Properties of Refrigerant The critical temperature of refrigerant should be high. Enthalpy of vaporization should be high. Thermal conductivity of refrigerant should be high. The freezing point should be low. Non-toxic and non-flammable.

15. Numerical Problem Suppose a refrigeration system removes 2KJ of heat from a refrigerated space (Qcold) and the work input to the compressor is 0.5 KJ. Calculate the COP of the System . COP = Qcold/W = 2000 J/500 J = 4 This means that for every joule of work input, the system removes 4 joules of heat from the refrigerated space.