NUCLEATE BOILING HEAT TRANSFER OF REFRIGERANTS R-134A AND R-404A ON POROUS AND STRUCTURED SURFACE TUBES

This manuscript provides the boiling heat transfer test results of refrigerants R-134a and R-404A at saturation temperatures of 4.4 and 26.7 °C on a porous surface tube, a structured surface tube and two plain surface tubes. A very wide range of heat flux from 0.8 to 120 kW/m² was tested in this study. The test results show that the heat transfer coefficients on plain surfaces are independent of tube material and agree reasonable well with those predicted by Cooper [1984] correlation. The porous tube contains various sizes of pores. Those caused the boiling heat transfer be enhanced at different heat flux conditions. Therefore, the slope of heat transfer coefficients of the porous tube is more gently than that of the plain and structured tubes.