Saturated boiling heat transfer

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Next: Convective boiling heat transfer Up: Flow boiling heat transfer Previous: Onset of nucleate boiling Contents Index

Saturated boiling heat transfer

Saturated boiling heat transfer exist per definition when the following inequality is fulfilled

$\begin{displaymath} \mbox{$<\!{x_e}\!>$} > 0 \end{displaymath}$

(11.40)

where $\mbox{$<\!{x_e}\!>$}$ is the equilibrium quality defined by (6.95) (see p.

). Note that since we have subcooled boiling, saturated boiling heat transfer also occurs in a case where the bulk liquid temperature is below saturation!

The requirement (11.40) can by utilizing (6.95) be stated as

$\begin{displaymath} \mbox{$<\!{h}\!>$}- h_f > 0 \end{displaymath}$

(11.41)

Saturated boiling heat transfer in forced convection flow has been investigated by many researchers over the years. One of the most widely used correlations is that of Chen, which is recommended by Lahey and Moody [18] and Hsu [38, p. 262].

Chen [48] defines

$\begin{displaymath} h_{2\phi} = h_{\mbox{\protect\scriptsize NcB}} + h_{\mbox{\protect\scriptsize c}} \end{displaymath}$

(11.42)

where $h_{2\phi}$ is the effective flow boiling heat transfer coefficient [W/( ${\mbox{m}}^2\cdot$ K)] and $h_{\mbox{\protect\scriptsize NcB}}$ and $h_{\mbox{\protect\scriptsize c}}$ describe heat transfer due to nucleate and convective boiling respectively. The effective flow boiling heat transfer coefficient, $h_{2\phi}$ , is defined as

$\begin{displaymath} h_{2\phi} \;\hbox{$=$\kern-0.68em\raise1.1ex \hbox{$\scrip... ...$}}\;\frac{ q_w''}{ T_w - T_{\mbox{\protect\scriptsize sat}} } \end{displaymath}$

(11.43)

Next: Convective boiling heat transfer Up: Flow boiling heat transfer Previous: Onset of nucleate boiling Contents Index

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