Investigation of effects of heater tube angle on the pool boiling heat transfer coefficient

In this experimental study, the effects of slope changes on the heat transfer coefficient in the pool boiling in deionized water have been investigated. The experiments were carried out in the average surface roughness of 0.21 µm on a copper cylinder by changing in the surface slope including 0°, 5°, 10°, 15°, 20°, 25°, and 30°. The range of heat flux was from 21 to 77 kW.m-2 in the atmospheric conditions. The results indicated that by increasing the heater slope, the departure frequency and bubble departure diameter on the heater surface were increased which lead to an increase in the mixing, turbulence, and the heat transfer coefficient. Finally, the slope of 15° has reached the highest heat transfer coefficient with an increase of 20.09% compared to other slopes. Besides the optimized model was mostly overlapped with the experimental results in which Stephan Abdelsalam model with an average error of 13.9% and McNelly model by an average error of 24% had the minimum and maximum amount of error among the other models, respectively.