In-tube heat transfer and pressure drop of R-134a and ester lubricant mixtures in a smooth tube and a micro-fin tube: part II - condensation

Average in-tube heat transfer coefficients and pressure drops during condensation are reported for condensation of refrigerant R-134a/lubricant mixtures in a smooth tube and a micro-fin tube of 9.52-mm (3/8-in.) outer diameter. The lubricants tested were 169-SUS and 369-SUS penta erythritol ester mixed acids. Heat transfer coefficients decreased with the addition of lubricants in all cases. Condensation pressure drops increased with the addition of the 169-SUS ester lubricant in both the smooth tube and the micro-fin tube. The addition of the 369-SUS lubricant did not affect pressure drops in the smooth tube, but it decreased the pressure drops in the micro-fin tube.

In-tube heat transfer and pressure drop of R-134a and ester lubricant mixtures in a smooth tube and a micro-fin tube: part II - condensation Conference Paper