In comparison to R134a systems, the new refrigerant is at a disadvantage as R1234yf absorbs slightly less energy per unit of flow in a refrigerant cycle. In order to increase the performance level to that of R134a it is advised to use an Internal Heat exchanger (IHX). An Internal Heat exchanger (IHX) is used to transfer heat between the low side pressure and the high pressure flow circuits. Its function is to improve system performance by further sub-cooling the refrigerant being supplied to the evaporator through the refrigerant control device. In fact a tube in a tube.