Modeling of boiling- and tow-phase flow in offset-strip-fin heat-exchanger geometries
The two-phase heat-transfer and pressure-drop characteristics of offset-strip-fin heat-exchanger geometries are examined using both experimental and analytical modeling techniques. Newly-obtained boiling-flow heat-transfer data are presented for two large-scale offset fin geometries at low-to-moderate wall-superheat conditions. Data for which nucleate boiling appeared to be completely suppressed were analyzed together with similar results for other offset fin surfaces to study the effects of channel dimensions on the convective evaporation component of the local heat transfer coefficient. Although these data were found to be well correlated in terms of modified forms of the F and Martinelli parameters used in previous studies of round-tube flows, a single F-factor correlation valid for all combinations of fin and channel dimensions did not appear to exist. The two-phase pressure-drop characteristics of offset-fin surfaces were found to be much different than those of round tubes. Measured values of the frictional component of the two-phase pressure-drop in these geometries were observed to be 20-50% higher than those for round tubes at the same flow conditions. A detailed computational model of annular two-phase flow in channels with offset strip fins was developed in the second part of this study.
- Research Organization:
- California Univ., Berkeley, CA (USA)
- OSTI ID:
- 6107369
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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