Optimization of X-shaped louvered fin and tube heat exchangers while maintaining the physical meaning of the performance evaluation criterion

•We discuss the optimization of heat exchangers with respect to a PEC.•Performing this optimization at constant Reynolds number gives misleading results.•It is shown how to account for the influence of the Reynolds number on the PEC.•The X-shaped louvered fin heat exchanger is optimized using the VG-1 criterion.

The optimization of heat exchangers requires a goal function. A very common choice for this goal function is a performance evaluation criterion (PEC). However, most commonly used PECs are not only a function of the heat exchanger geometry, but also of the Reynolds number. For such optimizations, the Reynolds number should not be kept fixed as shown in this paper. Furthermore, the current work demonstrates how to account for the influence of the Reynolds number correctly, to maintain the physical meaning of the PEC. This method is applied to the optimization of the X-shaped louvered fin and round tube heat exchanger. The variable geometry VG-1 criterion is used as the PEC. A surrogate model is used to enhance the performance of the optimization routine.