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Convective Boiling and Condensation Heat Transfer With a Twisted-Tape Insert for R12, R22, R152a, R134a, R290, R32/R134a, R32/R152a, R290/R134a, R134a/R600a.


pdf icon Convective Boiling and Condensation Heat Transfer With a Twisted-Tape Insert for R12, R22, R152a, R134a, R290, R32/R134a, R32/R152a, R290/R134a, R134a/R600a. (1019 K)
Kedzierski, M. A.; Kim, M. S.

NISTIR 5905; 95 p. January 1997.

New Approach Toward Low-Temperature Thermal Engineering Without Fluorocarbon Refrigerants, 45th. Oji International Seminar. Proceedings. September 16-19, 1997, Tomakomai City, Japan, 223-232 pp, 1998.

Thermal Science and Engineering, Vol. 6, No. 1, 113-1201, 1998.

Available from:

National Technical Information Service (NTIS), Technology Administration, U.S. Department of Commerce, Springfield, VA 22161.
Telephone: 1-800-553-6847 or 703-605-6000;
Fax: 703-605-6900.
Website: http://www.ntis.gov
Order number: PB97-140594

Keywords:

azeotropes; flow boiling; in-tube condensation; twisted tapes; enhanced heat transfer; refrigernant mixtures; refrigerants

Abstract:

Measured, local-average Nusselt numbers (Nu) for in-tube, convective boiling and condensation with a twisted-tape insert are presented for: R12, R22, R152a, R134a, R290, R32/R134a, R32/R152a, R290/R134a, and R134a/R600a. The heat transfer data were obtained from a fluid heated/fluid cooled, 9.7 m long condenser and evaporator of a breadboard refrigeration cycle. Convective-boiling, heat-transfer data were taken for transition and turbulent all-liquid Reynolds numbers. Convective-condensation, heat-transfer data were taken for laminar and turbulent all-liquid Reynolds numbers. The measured convective boiling and condensation Nusselt numbers for the single component and the azeotropic mixtures were each correlated to a single expression consisting of a product of dimensionless properties. The single component convective-boiling correlation was modified to predict the zeotropic mixture data. The predictions obtained from the modified flow-boiling correlations found in the literature were significantly different from the present Nusselt number measurements. Presumably, the correlations from the literature could account for neither the partial dryout induced by the tape nor the bubbly-mist flow introduced by an expansion valve.