A three-dimensional analysis of the flow through the outdoor unit of a gas-engine heat pump system has been carried out. The computational domain that includes an axial-flow fan, and finned-tube heat exchangers is calculated with a general purpose numerical analysis code, FLUENT. The Navier-Stokes equations with the standard k-ε turbulence model are solved by the SIMPLE algorithm using second-order upwind scheme. The fan is modeled as a thin actuator disk using the measured fan data and the heat exchanger module is approximated by a porous medium whose permeability and inertia drag factor are also obtained by the experimental means. The calculated total flow rate is compared favorably with the measured data.
The total flow rate and the flow uniformity have been studied parameterically for various configurations. Among major parameters are the fan RPM, the heat exchanger arrangement and the fan location. The optimal configurations that make the partial flow rate uniform is suggested.