2. Experiment
The experimental model was essentially an aluminum alloy
(6061-T6) pipe with open-cell aluminum foam brazed to the inside
surface of it, as shown in Fig. 1. Brazing minimized thermal contact
resistance. The pipe had inner diameter 50.80 mm, wall thickness
of 6.35 mm and length of 305.00 mm. The foam was commercially
obtained (ERG Materials and Aerospace), and it had 20 pores per
inch (ppi) and 87.6% porosity.
One-mm diameter 4-mm deep holes were drilled along the wall
of the tube. The holes were spaced 10 mm from each other. The
first hole was 1 mmaway from the inlet of the foam pipe. Each hole
housed a type-K thermocouple and was filled with thermal epoxy,
which prevented air pockets. A surface heater was wrapped around
the outer surface of the foam pipe. The rating of the heater was
1780W at 60 V. During experimental runs, the heater was