Mathematical model of Heat Transfer Coefficient in the annulus without Natural Thermal Convection is given as:
| (1) | U = \epsilon_a \cdot \frac{ 2\, \lambda_a}{d_t \cdot \ln (d_{ci}/d_t) } |
where
\epsilon_a | Natural Convection Heat Transfer Multiplier |
The most popular empirical correlations for Natural Convection Heat Transfer Multiplier are:
(2)
\epsilon = \begin{cases}
1, & \mbox{if } \ {\rm Ra} < 10^3
\\
0.18 \cdot {\rm Ra}^{0.25}, & \mbox{if } \ {\rm Ra} > 10^3
\end{cases}
(3)
\epsilon = \begin{cases}
1, & \mbox{if } \ {\rm Ra} < 10^3
\\
0.105 \cdot {\rm Ra}^{0.3}, & \mbox{if } \ 10^3 < {\rm Ra} < 10^6
\\
0.4 \cdot {\rm Ra}^{0.2}, & \mbox{if } \ {\rm Ra} > 10^6
\end{cases}
See also
Physics / Thermodynamics / Heat Transfer / Heat Transfer Coefficient (HTC) / Heat Transfer Coefficient (HTC) @model
[ Rayleigh number ]