In-tube heat transfer and pressure drop of R-134a and ester lubricant mixtures in a smooth tube and a micro-fin tube. Part 2: Condensation
- Kansas State Univ., Manhattan, KS (United States). Dept. of Mechanical Engineering
- Iowa State Univ., Ames, IA (United States). Dept. of Mechanical Engineering
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. Lubricant concentrations ranged from 0% to 5%. The average saturation temperature in the test tube was approximately 40 C (104 F). The mass flux of the refrigerant-lubricant mixtures was varied from 85 kg/m{sup 2}{center_dot}s (62,700 lb/ft{sup 2}{center_dot}h) to 375 kg/m{sup 2}{center_dot}s (276,640 lb/ft{sup 2}{center_dot}h). Heat transfer coefficients during condensation 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. Pure R-134a heat transfer coefficients in the micro-fin tube were 100% to 200% higher than those in the smooth tube, with the higher values occurring at the lower mass fluxes. Pressure drops in the micro-fin tube were 20% to 50% higher than those in the smooth tube. Design equations are presented that aid in predicting the heat transfer coefficients and pressure drops of R-134a/lubricant mixtures in the smooth and micro-fin tubes.
- OSTI ID:
- 33254
- Report Number(s):
- CONF-9406105-; TRN: IM9518%%75
- Resource Relation:
- Conference: 1994 American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) annual meeting, Orlando, FL (United States), 25-29 Jun 1994; Other Information: PBD: 1994; Related Information: Is Part Of ASHRAE transactions 1994: Technical and symposium papers. Volume 100, Part 2; PB: 1372 p.
- Country of Publication:
- United States
- Language:
- English
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