Metal fiber network materials for compact heat exchangers

Abstract

Compact convective heat exchangers are becoming increasingly important in various areas of applications dealing with micro-devices. Metallic fibre networks are highly porous materials having certain thermal and mechanical characteristics which offer several advantages for heat exchangers. However, optimisation of the material and the structure is subject to several conflicting requirements. A high internal surface area favours rapid heat exchange with the fluid, but may be associated with a relatively low permeability, inhibiting fluid flow. This introduces uncertainty about the optimal scale of the porosity. There are relatively complex interplays between performance, exchanger size and pore (fibre network) architecture. It is difficult to just use experimental data as a guide, and modelling approaches should be explored.
Finding the optimal heat exchanger structure is also complex and challenging due to various constrains. Numerical model is used in the paper to find the dependence of heat exchange performance on fibre network architecture and operating conditions. The paper discusses how the performance of a heat exchanger is affected by its dimensions, heat exchange at fibre surfaces, thermal properties of fibre core, operating temperatures, phenomena on exchanger walls, the core permeability and pumping system characteristics. A simplified analytical model is presented as well, which allows qualitative examinations. The validity of both models is assessed by comparison with experimental data.

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