Heat transfer coefficients and pressure drops for R-134a and an ester lubricant mixture in a smooth tube and a micro-fin tube
- Kansas State Univ., Manhattan, KS (United States)
- Iowa State Univ., Ames, IA (United States). Mechanical Engineering Dept.
This paper reports average heat transfer coefficients and pressure drops during the evaporation and condensation of mixtures of R-134a and a 150 SUS penta erythritol ester branched-acid lubricant. The smooth tube and micro-fin tube tested in this study had outer diameters of 9.52 mm (3/8 in.). The micro-fin tube had 60 fins, a fin height of 0.2 mm (0.008 in), and a spiral angle of 18{degree}. The objective of this study is to evaluate the effectiveness of the micro-fin tube with R-134a and to determine the effect of circulating lubricant. The experimental results show that the micro-fin tube has distinct performance advantages over the smooth tube. For example, the average heat transfer coefficients during evaporation and condensation in the micro-fin tube were 50--200% higher than those for the smooth tube, while the average pressure drops were on average only 10--50% higher. The experimental results indicate that the presence of a lubricant degrades the average heat transfer coefficients during both evaporation and condensation at high lubricant concentrations. Pressure drops during evaporation increased with the addition of a lubricant in both tubes. For condensation, pressure drops were unaffected by the addition of a lubricant.
- Sponsoring Organization:
- American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., Atlanta, GA (United States)
- OSTI ID:
- 653206
- Report Number(s):
- CONF-980123-; TRN: IM9827%%99
- Resource Relation:
- Conference: 1998 ASHRAE winter meeting, San Francisco, CA (United States), 17-21 Jan 1998; Other Information: PBD: 1998; Related Information: Is Part Of ASHRAE transactions 1998. Volume 104, Part 1A: Technical papers; PB: 834 p.
- Country of Publication:
- United States
- Language:
- English
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