The relations among enthalpy, temperature and quality of nonazeotropic refrigerant mixtures (NARMs) in the phase change region (temperature gliding region) are investigated to seek a possibility for linear approximations. Using REFPROP, a refrigerant property calculation package developed by MST, temperature-enthalpy, temperature-quality, quality-enthalpy relations are investigated for 4 binary and 15 ternary NARMs. Those 19 NARMs tested are the most promising alternative refrigerants for conventional CFC and HCFC refrigerants. A normalized enthalpy, which is a pseudo-quality in a sense, is defined based on the dew and bubble point enthalpies to compare with the conventional quality. The results show that the pseudo-quality and the conventional quality are almost identical independent of system pressure for all the NARMs tested while enthalpy-temperature and quality-temperature relations are diverse and highly pressure dependent depending on mixture combinations. The significance of the near-identical relation between the two qualities is that the easy-to-calculate pseudo-quality can replace quality in convective heat transfer coefficient representations.