14.4.6 Initializing the Auxiliary Fluid Temperature

When the heat exchanger group is connected to an upstream heat exchanger group, ANSYS FLUENT will automatically set the initial guess for the auxiliary fluid inlet temperature, $T_{\rm in}$, to be equal to the $T_{\rm in}$ of the upstream heat exchanger group. Thus the boundary condition $T_{\rm in}$ for the first heat exchanger group in a connected series will automatically propagate as an initial guess for every other heat exchanger group in the series. However, when it is necessary to further improve convergence properties, you will be allowed to override $T_{\rm in}$ for any connected heat exchanger group by providing a value in the Initial Temperature field. Whenever such an override is supplied, ANSYS FLUENT will automatically propagate the new $T_{\rm in}$ to any heat exchanger groups further downstream in the series. Similarly, every time the $T_{\rm in}$ boundary condition for the first heat exchanger group is modified, ANSYS FLUENT will correspondingly update every downstream heat exchanger group.

If you want to impose a non-uniform initialization on the auxiliary fluid temperature field, first connect the heat exchanger groups and then set $T_{\rm in}$ for each heat exchanger group in streamwise order.

All heat exchangers included in a group must use the fixed $T_{\rm in}$ option. All heat exchangers within a heat exchanger group must have the same $T_{\rm in}$. In other words, no local override of this setting is possible through the Ungrouped Macro Heat Exchanger dialog box.