Enhancement of R123 Pool Boiling by the Addition of N-Hexane.
Enhancement of R123 Pool Boiling by the Addition of
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.
1-800-553-6847 or 703-605-6000;
Order number: PB96-165956
building technology; additives; enhanced heat transfer;
fluid heating; GEWA-T; pool boiling; R123; thermal
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.