ISSN Online: 2377-424X
ISBN Print: 0-85295-345-3
International Heat Transfer Conference 10
POOL BOILING FROM ENHANCED SURFACES IN PURE AND BINARY MIXTURES OF R-113 AND R-11
Resumo
Pool boiling from horizontal tubes with smooth and
enhanced surfaces has been experimentally investigated in pure
refrigerant R-113, pure R-ll, and mixtures of R-ll and R-113
of approximately 25, 50, and 75% R-113 by mass.
Instrumented tubes were electrically heated and mounted
horizontally in a pool of a saturated refrigerant at near
atmospheric pressure. The enhanced surfaces were a knurled
surface (Wolverine's Turbo-B) and a porous surface (Linde's
High Flux). Values of the heat flux for a given wall superheat
in pure fluids generally were 2 to 10 times larger for the
enhanced surfaces than for the smooth surface. The heat
transfer performance for each of the enhanced surfaces was
affected differently by changes in the porosity, wall superheat, and fluids, which was considered to be the result of different heat transfer mechanisms: nucleate boiling and thin film vaporization. The performance of all three surfaces decreased in fluid mixtures, with the largest degradation occurring in a mixture of 25% R-ll/75% R-113. The enhanced surfaces consistently performed better in the fluid mixtures than the smooth tubes. The degradation in the smooth tube heat transfer coefficients obtained in fluid mixtures depends on the difference between the liquid and vapor molar concentration.