In-tube heat transfer and pressure drop of R-134a and ester lubricant mixtures in a smooth tube and a micro-fin tube. Part 1: Evaporation
- Kansas State Univ., Manhattan, KS (United States). Dept. of Mechanical Engineering
- Iowa State Univ., Ames, IA (United States). Dept. of Mechanical Engineering
In-tube heat transfer coefficients and pressure drops during evaporation are reported for mixtures of refrigerant R-134a and a penta erythritol ester mixed-acid lubricant. The ester lubricant was tested at viscosities of 169 SUS and 369 SUS over a lubricant concentration range of 0% to 5% in both a smooth tube and a micro-fine tube. The average saturation temperature used was 1 C (33.8 F). Measurements were taken for the refrigerant-lubricant mixture over a mass flux range of 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) in test tubes with an outer diameter of 9.52 mm (3/8 in.). Heat transfer coefficients during evaporation increased at low concentrations of the 169-SUS ester lubricant and then dropped off at high lubricant concentrations in both the smooth tube and the micro-fin tube. The higher viscosity 369-SUS lubricant decreased the heat transfer coefficients in both tubes over the range of lubricant concentrations tested. Pressure drops during evaporation increased in both the smooth tube and the micro-fin tube with the addition of ester lubricant of either viscosity. The heat transfer coefficients for the micro-fin tube were 100% to 50% higher than those for the smooth tube, with the higher values occurring at low mass fluxes. Pressure drops in the micro-fin tube were 10% to 20% higher than those in the smooth tube.
- OSTI ID:
- 33253
- Report Number(s):
- CONF-9406105-; TRN: IM9518%%74
- 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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