Forced convective boiling in vertical tubes for saturated pure components and binary mixtures

Abstract

Kner is an effective Knudsen number, defined byThe flux density on the wall is given by and a is the probability that a particle-particle collision does not significant for very small particles possessing sufficient thermal energy to escape the attractive London-van der Walls force where S t p k is defined as C, ( A l l ) result in agglomeration. The probability a may be quite zap UkPp Stpk = 9P (Dahneke, 1976)' Here we sufficiently large for a to be nil. that the particles are Manuscript receioedjune 28,1979; reoisionOver 1 000 sets of data for forccd convective hailing of distilled water, ethylene glycol and aqueous mixtures of ethylene glycol are reported. Most of these data were taken in the annular flow regime. These data indicate a previously unrecognized Prandtl number effect on the hoiling heat transfer for hoth pure components and mixtures. A significant reduction in thc heat transfer coefficient is observed for mixtures attrihutablc to mass transfer effects. An expression is developed which accounts for hoth of these effects and correlates the experimental data to within a mean deviation of 14.9%. This correlation reduces to the standard Chen correlation for pure fluids with Prandtl numbers close to unity.

A composite heat transfer correlation for saturated flow boiling in small channels

“…Past formulations of the Chen correlation [38][39][40][41] corrected the nucleate boiling term with a suppression factor S ( 1) to account for the suppression of nucleate boiling with an increase in vapor quality which inhibits bubble growth and leads to dryout at high vapor qualities.…”

“…Figure 3 shows semi-logarithmic plots of this ratio for representative correlations chosen for being the most commonly used or for their best agreement with the database. The Bennett and Chen [39] correlation, which was developed for conventional channels and is valid for x < 0.7, works best for moderate vapor qualities but tends to overestimate the heat transfer coefficient in small channels. The Kandlikar and Balasubramanian [47] correlation, which was proposed for minichannels and microchannels, shows a far wider spread over the whole vapor quality range.…”

“…The Chen correlation is based on a physical superposition approach and is valid for vapor qualities below 0.7. The original equation and most later modifications [39][40][41][42] were designed for conventional tubes, but nonetheless extrapolate favorably to small channels. Due to its sound physical basis and its independence from specific flow patterns, this approach has been chosen as the basis for the new correlation presented here, and it has been modified to account for the effects of small channel size.…”

“…Figure 3. Ratio of calculated to measured heat transfer coefficient Ф as a function of thermodynamic quality using correlations proposed by Bennett and Chen [39], Liu and Winterton [46], Thome et al [21,22], Kandlikar and Balasubramanian [47], Cooper [12], and the proposed correlation.…”

Numerical investigation of diameter effect on heat transfer of supercritical water flows in horizontal round tubes

“…The big specific heat capacity (c p ) will allow SCW to absorb lots of heat without the evident temperature increase. This phenomenon is quite like the boiling heat transfer that the heat is absorbed by the liquid to generate the vapor rather than to increase the temperature in [22]. Therefore the tube wall temperature does not increase evidently.…”