Experimental studies of boiling heat transfer of R417A on three single horizontal doubly-enhanced tubes have been conducted at the saturation temperature of 8 ℃. A modified Wilson plot technique was used to obtain the boiling heat transfer coefficients

and the thermal resistance analysis was conducted. The results indicate that the intube heat transfer coefficients of the three enhanced tubes are within 2.524-2.658 times as those of smooth tube

which were rolled 0.32-0.34 mm high spiral channel. For the same type of enhanced heat transfer surface

the trends of boiling heat transfer coefficient with the wall temperature difference are similar. Boiling heat transfer coefficients of tube E30 (42 fin per inch) are 4.5 percent higher than those of tube E32(50 fpi) at the same temperature difference. It is indicated that the boiling heat transfer coefficient and its trend were closely related with fin density (pore diameter) and tube type. Boiling heat transfer of R417A on doubly- enhanced tubes

the outer thermal resistance was about 70% of the total thermal resistance

further enhancement was useful for improving the overall heat transfer performance. Boiling heat transfer coefficient of R417A is only one third of R134a at approximate conditions

R134a is the main component of R417A

indicating that the boiling heat transfer of mixed refrigerants are quite different with pure refrigerants.