In the present experimental study, boiling and condensation heat transfer coefficients between R404A and R152a flow in a horizontal smooth tube were compared. The outer and inner diameters of the tube were 9.52 mm and 7.55 mm, respectively, and the heated length was 1045 mm.
In case of flow boiling, the mass flux ranged from 150 to 350 kg/$m^2$ and the test section were uniformly heated from 6 to 14 kW/$m^2$. The quality range was from 0.1 to 0.9 at the saturation temperature from 12 to 17 $^\circ$ . For the present experimental range, the experimental data best fits the Gungor and Winterton(1986) flow boiling correlation within the mean deviation of 6 % for R404A and Kandlikar(1990) flow boiling correlation within the mean deviation of 10 % for R152a among the correlations tested.
In case of flow condensation, the mass flux ranged from 150 to 400 kg/$m^2$ and the test section were uniformly heated from 8 to 12.5 kW/$m^2$. The quality range was from 0.2 to 0.8 at the saturation temperature from 27.3 to 34 $^\circ$. A modified correlation for the flow condensation, based on the Dobson and Chato correlations, was proposed. The modified correlation reduced the average deviations of 16 % for R404A and 7 % for R152a compared to the original Dobson and Chato(1998) correlations.
