Generally, vh/vT$dT term is larger than 0 because refrigerant mass flow rate decreases and gas-cooler effectiveness increase as expansion valve is closed. This is presented in Fig. 8. The case which is presented in Fig. 8 is the same as the case of Table 2. Dh/DP represents the ratio of increased enthalpy to the increase of pressure according to the expansion valve opening change ((hiþ1 hi)/ (Piþ1 Pi)) and it can be regarded as a corresponding term of vh/vP.