Interaction effects between parameters in a vortex generator and louvered fin compact heat exchanger

Heat exchangers for air conditioning applications are often of the fin and tube type. By choosing special fin geometries, the thermal performance of the heat exchanger can be enhanced. One of the recently proposed fin geometries for round tubes is the combination of louvers with a delta winglet vortex generator (VG). Several parameters impact the performance of this design, such as the louver angle and the angle of attack of the vortex generator. The fin geometry can be optimised by performing numerical simulations for different values of these parameters. Many authors use design of experiments techniques to reduce the number of simulations, such as the Taguchi method. However, this often implies the assumption that interaction effects between the parameters are negligible. In this work, a full factorial analysis is done to resolve all interaction effects. It is shown that there are important interactions between the height of the VG, the aspect ratio of the VG and the louver angle. These interactions are of the same order of magnitude as the main effect of the parameters and are therefore not negligible. Taking these interactions into account, the impact of the parameters on the heat transfer coefficient, the friction factor and the VG-1 performance evaluation criterion (PEC) are mapped. It is shown that the fin pitch is by far the most important parameter. Varying the louver angle, VG aspect ratio, the VG height ratio or the VG angle of attack results in a change of the VG-1 PEC of between 0% and 3.5%, depending on the interaction with other parameters.