Experimental Study of Nucleate Pool Boiling of R-134a and R-410a on a Porous Surface

Boiling heat transfer enhancement is influenced by the surface distinctiveness of the boiling region. Porous surface is being widely used to enhance boiling heat transfer in the industry. An experimental study is carried out to investigate the characteristics of the pool boiling heat transfer for different fluid, namely, pure refrigerant (R-134a) and quasi-azeotropic mixture (R-410A). The test is performed on a thin porous layer over a copper tube placed horizontal at saturation temperature of 7 degrees C and also to determine its potential application to flooded refrigerant evaporators. The diameter of the coated tube was 25.4 mm, a length of 116 mm. A coated tube had a porous layer thickness of 42.2 mu m. In the experimental range (5 to 50 kWm(-2)) the boiling heat transfer coefficients are 1.25 to 2 times higher than those of the uncoated surface. For boiling within the porous surface, simplified predicted equations of various investigators are analyzed.