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Next: Thermal design code input/output Up: Thermal design model implementation Previous: Thermal design model implementation Contents Index

Flow charts of main procedures

The thermal design calculations are closely connected to the hydraulics calculations since the flow boiling heat transfer calculations imply knowledge of the flow variables. As a consequence, part of the implementation directly accesses the results from the hydraulics calculation. Furthermore, the z-coordinates which are selected for the thermal design calculations are a subset of the z-coordinates in the computational grid used for the core hydraulics computations. This is to simplify the interface between the thermal design calculations and the hydraulics calculations. If we choose a general set of z-coordinates in the thermal design code we would have to interpolate in the hydraulics results--a very cumbersome task. However, choosing a subset of the hydraulics grid is, in practice, adequate.

As we mentioned in the chapter which describe the thermal design model we are forced to calculate the wall temperature T_w in the subcooled and saturated regions iteratively, ie by utilizing a numerical non-linear solver. In both cases we use a secant method to obtain the solution and practical calculations show that this method is quite fast--using a reasonable accuracy criterion of $\varepsilon = 0.1 {\mbox{ \mbox{${}^\circ\mbox{C}$}}}$ a solution is obtained in typically 3 iterations.

For completeness we include flow charts which show the major steps in the thermal design code (Figure 12.1) and the calculational steps in the calculation of the wall temperature (Figure 12.2).

All the functions in the thermal design code have been tested but these test results are due to time and space constraints not reproduced here. Excluding the implementation of the Chen correlation all functions are of rather simple type and have therefore been tested against hand calculations. The implementation of the Chen correlation^12.1 is a bit more involved and the author has therefore tested this part of the code against an example calculation found in [40, p. 258-262].

$\begin{figure} % latex2html id marker 40720\rule{\textwidth}{0.2mm} \rule{0cm}... ...re}\hspace{1em}The most important steps in the thermal design code.}\end{figure}$

$\begin{figure} % latex2html id marker 40782\rule{\textwidth}{0.2mm} \rule{0cm}... ...space{1em}Procedure for calculation of the wall temperature, $T_w$.}\end{figure}$

Next: Thermal design code input/output Up: Thermal design model implementation Previous: Thermal design model implementation Contents Index

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