Pool boiling data and prediction method for enhanced boiling tubes with R-134a, R-236fa and R-1234ze(E)

The phase-change process of enhanced surface pool boiling is an effective mode of heat transfer requiring on-going investigation with new refrigerants. Two of the latest generation Wolverine Tube Inc. (Turbo-B5) and Wieland Werke (Gewa-B5) enhanced boiling tubes have been studied under pool boiling conditions with refrigerants R-134a, R-236fa and R-1234ze(E). A 1.027 m length of tube with semi-local heat flux and heat transfer coefficient measurements was tested in each case. The Wilson plot method was validated and used to characterise the inside heat transfer coefficient of the heating water. Pool boiling tests were carried out for saturation temperatures of 5–25 °C and heat fluxes from 15 to 70 kW m−2, based on the outer tube diameter. It was found that heat flux and refrigerant type had the dominant effect on heat transfer. A new enhanced tube pool boiling correlation was proposed, based on a boiling heat transfer mechanism in the near-wall region.