Convective boiling heat transfer coefficient,

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Next: Nucleate boiling heat transfer Up: Saturated boiling heat transfer Previous: Saturated boiling heat transfer Contents Index

Convective boiling heat transfer coefficient, $h_{\mbox{\protect\scriptsize c}}$

The convective boiling heat transfer coefficient, $h_{\mbox{\protect\scriptsize c}}$ is defined by

$\begin{displaymath} h_{\mbox{\protect\scriptsize c}} \;\hbox{$=$\kern-0.68em\raise1.1ex \hbox{$\scriptscriptstyle\triangle$}}\;h_{1\phi} F \end{displaymath}$

(11.44)

where

single-phase liquid heat transfer coefficient given by a slightly modified version of (11.37),

$\begin{displaymath} h_c = C \left[ \frac{\mbox{$<\!{G}\!>$}(1-\mbox{$<\!{x}\!>... ...k_\ell} \right]_m^{0.33} \left( \frac{k_\ell}{D_H} \right)_m \end{displaymath}$

(11.45)

where C [--] is defined by (11.34) and $<\!{x}\!>$ is the flow quality [--]. Note that the author has exchanged the Dittus-Boelter correlation originally in the Chen correlation with the correlation by El-Genk et al (11.37) since it is appropriate in the rod bundle geometry.

l

the so-called Reynolds number factor [--] which is a hydrodynamic dimensionless parameter to be discussed in the subsequent.

The F-factor is defined by

$\begin{displaymath} F \;\hbox{$=$\kern-0.68em\raise1.1ex \hbox{$\scriptscripts... ... }{\mbox{\bf Re}_{\mbox{\protect\scriptsize f}}} \right]^{0.8} \end{displaymath}$

(11.46)

where $Re_{\mbox{\protect\scriptsize TP}}$ is an effective Reynolds number for the two-phase flow [--] and $\mbox{\bf Re}_f$ is the Reynolds number based on the liquid fraction of the flow [--], ie defined by

$\begin{displaymath} \mbox{\bf Re}_f \;\hbox{$=$\kern-0.68em\raise1.1ex \hbox{$... ...;\frac{\mbox{$<\!{G}\!>$}(1-\mbox{$<\!{x}\!>$}) D_e}{\mu_\ell} \end{displaymath}$

(11.47)

The F-factor being a flow parameter depends only on the turbulent Martinelli parameter, $X_{\mbox{\protect\scriptsize tt}}$ [--], defined by

$\begin{displaymath} \frac{1}{X_{\mbox{\protect\scriptsize tt}}} \;\hbox{$=$\ker... ..._g} \right]^{0.5} \left[ \frac{\mu_g}{\mu_\ell} \right]^{0.1} \end{displaymath}$

(11.48)

Values for $F= F(X_{\mbox{\protect\scriptsize tt}})$ originally shown graphically by Chen at some discrete $[1/X_{\mbox{\protect\scriptsize tt}}]$ values are given in Table 11.1.

$\begin{table} % latex2html id marker 38285 \rule{\textwidth}{0.8mm} \refstepco... ...box{$64.0$\ }} & {\mbox{$73.4$\ }} & & & & &\\ \hline \end{tabular*}\end{table}$

Next: Nucleate boiling heat transfer Up: Saturated boiling heat transfer Previous: Saturated boiling heat transfer Contents Index

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