The evaporation of HCFC141b, HFC152a and HFC23, and non-azeotropic refrigerant mixture used at the very low temperature refrigeration system is experimentally studied in a horizontal spirally grooved tube with corrugation.<br>The experiments were conducted at 0.03 to 0.47MPa of boiling pressure, 100 kg/(m²s) of mass flux, 1 to 15 kW/ m² of heat flux, -26 to 21 &deg;C of refrigerant temperature and 11.4 mm of average inner diameter.<br>It is concluded that boiling heat transfer coefficients of single-refrigerant are higher than these of non-azeotropic refrigerant mixture. And dimensionless correlation of the heat transfer coefficirnts, i.e. Lockhart-Martinelli parameters agreed with equation (10) within the limit of &plusmn;40 percent. Pressure drops of these refrigerant mixture depend on its liquid density and flow pattern.