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Enhancement of R123 Pool Boiling by the Addition of N-Hexane.


pdf icon Enhancement of R123 Pool Boiling by the Addition of N-Hexane. (1529 K)
Kedzierski, M. A.

NISTIR 5780; March 1996.

Sponsor:

Department of Energy, Washington, DC

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: PB96-165956

Keywords:

building technology; additives; enhanced heat transfer; fluid heating; GEWA-T; pool boiling; R123; thermal conductivity

Abstract:

This paper presents the heat transfer data used to file international patent WO 94/18282. The data consisted of pool boiling performance of a GEWA-TTM surface for three fluids: (1) pure R123, (2) R123/n-hexane (99/1), and (3) R123/n-hexane (98/2). The heat flux and the wall superheat were measured for each fluid at 277.6 K. A (47 + 7)% increase over the pure R123 heat flux was achieved with the addition of 1% mass hexane to R123. Similarly, the R123/hexane (99/2) mixture gave a maximum percent heat flux enhancement over pure R123 of (29 + 7)%. The boiling was filmed with a 16 mm high-speed camera. The observations were used to describe various boiling modes on the GEWA-TTM surface. The addition of hexane to pure R123 caused a simultaneous reduction in the bubble diameter and increase in the site density. The increase in site density enhanced the boiling despite the reduction in bubble size. Presumably, the site density enhancement was caused by a layer enriched in hexane at the heat transfer surface. The addition of hexane to R123 also improved natural convection. The natural convection was influenced by the greater thermal conductivity of the excess layer which may have contained 55% mass hexane.