Impact of Particulate Deposition on the Thermohydraulic Performance of Metal Foam Heat Exchangers: A Simplified Theoretical Model

Abstract

Assuming uniform particulate deposit layer, with deposition layer thickness in the range of 10–400 μm, on the ligaments of a metal foam heat sink, the effects of airborne particle deposition on the steady-state thermohydraulic performance of a metal foam heat sink are examined theoretically. Using a cubic cell model, changes in the foam internal structure, due to deposition, have been theoretically related to the increased pressure drop due to partial blockage of the pores. Our results suggest that the fouled to clean pressure drop ratio is only a function of the ligament to pore diameter ratio. Another interesting observation is that, compared to clean foams, the pressure drop can increase by orders of magnitude depending on the extent to which the pores are blocked. To examine the fouling effects on heat transfer from the foams, a thermal resistance network has been used. Moreover, the heat transfer from metal foams is more affected by fouling at higher fluid velocities. For example, when air is pushed through foams which their ligaments are uniformly covered by particles at 3 m/s, up to 15% decrease in the total heat transfer from the heated surface is predicted.