INVESTIGATION OF THERMAL DISPERSION FOR STEADY AND PULSATING WATER FLOW IN METAL FOAM

The dispersion coefficient in metal foam is critical for analysis and design using the volume-averaged equations. This coefficient is hardly investigated for steady flow, and has not been reported for nonsteady flows in metal foam. This paper presents experimental and numerical investigations on the thermal dispersion coefficient in a metal-foam rectangular channel for steady and pulsating water flow. The foam channel was asymmetrically heated from one side representing a heat sink. The heating was accomplished by applying a constant heat flux. For the steady-state investigation, Reynolds number based on the hydraulic diameter of the channel ranged from 365 to 1164. For this range, the experimental thermal dispersion was obtained and given in the form of a correlation. For the pulsating flow investigation, the flow frequency ranged from 0.07 to 0.17 Hz with a maximum velocity amplitude of 0.07 m/s. The thermal dispersion coefficient was obtained experimentally for the pulsating flow in metal foam, most likely for the first time. Results have shown that the velocity amplitude has a significant effect on the thermal dispersion coefficient, whereas the frequency has a limited effect. The dispersion coefficient for pulsating flow was significantly higher than that for steady-state flow, and the difference between the two increased with Reynolds number. This increase in dispersion for pulsating flow is responsible in part for the increased heat transfer.