Numerical investigation on the performance of cross-flow micro heat exchangers

The purpose of this paper is twofold: to describe a relevant improvement to an in-house FEM procedure for the heat transfer analysis of cross-flow micro heat exchangers and to study the influence of microchannel cross-sectional geometry and solid wall thermal conductivity on the thermal performance of these microdevices.

The velocity field in each microchannel is calculated separately. Then the energy equation is solved in the whole computational domain. Domain decomposition and grids that do not match at the common interface are employed to make meshing more effective. Some flow maldistribution effects are taken into account.

The results show that larger thermal conductivities of the solid walls and rectangular cross-sectional geometries with higher aspect ratios allow the maximization of the total heat flow rate in the device. However, on the basis of the heat transfer per unit pumping power, the square cross-section could be the best option.

The value of the average viscosity is assumed to be different in different microchannels, but constant within each of the microchannels.

The procedure can represent a valuable tool for the design of cross-flow micro heat exchangers.

In spite of requiring limited computational resources, the improved procedure can take into account flow maldistribution effects stemming from non-uniform microchannel temperatures.