Aerodynamic optimization of axial fans mounted on outdoor air conditioning units

In order to improve the efficiency of axial fans used in outdoor air conditioning units, this study proposes a method to optimize blade shapes even amid conditions where axial fans are susceptible to the flow field generated by their surrounding components. A multi-objective optimization problem is formulated and solved using a combined numerical simulation and a genetic algorithm. A system of incompressible Navier-Stokes equations involving the turbulence model and a multiple reference frame approach is performed in steady state using the finite volume method. As a result, the Pareto frontier is obtained for the objective functions defined as the minimization of the shaft power coefficient and the maximization of the flow coefficient. Compared to the conventional optimization method which assumes that the fan is isolated from surrounding components, the fan obtained in this study demonstrates remarkable features, especially around the blade tip. In addition, experimental results show that the optimized fan, which is mounted on the outdoor unit, is more efficient than the baseline fan. The proposed method is capable of simulating the wake generated by the components situated in the upstream area of the fan, which has not been taken into account when it comes to the conventional method.