Explain the effect of superheating and subcooling on the performance of vapour compression cycle
Effect of superheating: As shown in the figure a & b the effect of superheating is to increase the refrigerating effect, but this increase in the refrigerating effect is at the cost of increase in amount of work spent to attain upper pressure limit. Since the increase in work is more as compared to increase in refrigerating effect, therefore overall effect of superheating is to give a low value of C.O.P.
ii) Effect of sub-cooling: sub-cooling is the process of cooling the liquid refrigerant below the condensing temperature for a given pressure. In figure the process of sub-cooling is shown by 2’-3’. As is evident from the figure the effect of sub-cooling is to increase the refrigerating effect. Thus sub-cooling results in increase of C.O.P provided that no further energy has to be spent to obtain the extra cold coolant required.