Heat transfer of pulsating water flow through aluminum-foam channel under asymmetric constant heat flux boundary condition

In the present study, the effect of pulsating inlet velocity condition on heat transfer in metal foam was investigated experimentally. Square wave shaped water velocity profiles with different amplitudes and frequencies were applied to the inlet of a rectangular channel filled with aluminum foam having 20 pores per inch and a porosity of 91.8%. A constant heat flux (12787 W/m²) was applied to one side of the porous channel. The non-heated surfaces were insulated. The surface temperatures, water inlet and outlet temperatures and volumetric flow rates were measured and recorded. The dimensionless flow frequency parameter (M) and dimensionless flow amplitude (Re_m) parameter were changed in the ranges 4.8–7.3 and 492–1388, respectively. The results showed that there was a strong relationship between average Nusselt number and flow velocity amplitude. Generally, average Nusselt number was seen to increase with increasing frequency parameter and/or amplitude parameter. Correlations for the local time-averaged and surface-averaged Nusselt numbers are proposed. A meaningful comparison between steady-state and pulsating heat transfer is provided. It showed that heat transfer advantages of pulsating flow were only present for a certain low range of Reynolds number, beyond which pulsating flow heat transfer approached that of steady state.