FEM for the 3-D analysis of conjugate conduction-convection heat transfer in cross-flow micro heat exchangers

Purpose - The purpose of this paper is to develop a simplified but accurate finite element procedure for the analysis of the conjugate conduction-convection heat transfer in cross-flow micro heat exchangers. Design/methodology/approach - The velocity fields in single microchannels are calculated by solving the parabolised form of the momentum equations and later mapped onto the three-dimensional grid, corresponding to an appropriate portion of the micro heat exchanger, which is used for the solution of the energy equation in its elliptic form. To allow the use of finite elements elongated in the flow direction, layers of perpendicular microchannels can be meshed independently with grids that do not match at the common interface (domain decomposition). Findings - An original and easy-to-implement method has been developed to deal with non-matching grids. Computed results show that increasing the number of microchannels per layer yields relative pressure drop increments that are larger than those displayed by the relative heat flow rates. Research limitations/implications - The simplified procedure requires the assumption of constant thermophysical properties. The adopted domain decomposition technique yields non-symmetric system matrices. Practical implications - The procedure can be very useful in the design of cross-flow micro heat exchangers. Originality/value - The finite element procedure described in the paper requires only limited computational resources for the analysis of the conjugate conduction-convection heat transfer in cross-flow micro heat exchangers with a large number of microchannels per layer.