Manifold optimization of gas-to-gas micro heat exchangers

In this paper a numerical investigation of the fluid-dynamic performance of a micro heat exchanger based on a large number of parallel straight microchannels connected to an inlet and outlet manifold is presented. Two numerical models are built by means of a commercial CFD code (ANSYS FLUENT) in order to simulate the full device adopting a 2D and a 3D geometry. The distribution of the mass flow among the parallel microchannels is studied as a function of the manifold shape, of the position of the feeding and venting ports and of the imposed feeding pressure for a fixed exit pressure equal to ambient conditions. The numerical results have evidenced that the CFD analysis can be considered a useful tool for the optimisation of the micro heat exchanger geometry in order to improve the level of uniformity of the mass flow and pressure distribution among the channels. By comparing the results obtained for the same heat exchanger with a 3D and a 2D numerical model it has been demonstrated how the 2D simulations tends to overestimate the mal-distribution of the mass flow among the channels.