Heat transfer enhancement and pressure drop performance for R417A flow boiling in internally grooved tubes

• Enhancement factors for R417A focus on a range of 1.26–2.0 and 1.5–2.8 respectively.
• Penalty factors for R417A focus on a range of 1.8–2.6 and 1.67–2.3 respectively.
• Enhancement parameter was treated as a synthetical evaluation of micro-fin tube.
• Tube III possesses a better heat transfer enhancement efficiency than Tube II.
• The narrower fin root distance and the gentle slope of grooved wall are more favorable.

The experimental study on heat transfer and pressure drop for R417A flow boiling in horizontal smooth and internally grooved tubes was conducted. Based on the experimental results, heat transfer and pressure drop performance for R417A in different tubes were compared, and the influences of vapor quality and mass flux on heat transfer enhancement and pressure drop performance were analyzed and discussed. The result indicates: enhancement factors of R417A in Tube II and Tube III focus on a range of 1.26–2.0 and 1.5–2.8 respectively, and enhancement factors vary with vapor qualities and mass fluxes. The total pressure drops for R417A in Tube II and Tube III are 1.8–2.6 times and 1.67–2.3 times of R417A in smooth tube respectively. Both enhancement factor and penalty factor increase with increasing mass flux, while enhancement parameters show different situations in different internally grooved tubes. Compared with Tube II, Tube III possesses a better heat transfer enhancement efficiency.