Experimental analysis of upward flow boiling heat transfer in a channel provided with copper metallic foam

This work deals with the flow boiling heat transfer inside a channel filled with metallic foam soldered to its lateral walls. The survey on this topic shows that the work in this field is at its beginning. The tested metallic foam samples are made from copper with 36 PPI (Pore per Inch Linear) and 97% porosity and the working fluid being used is n-pentane. In the present work the independent variables are the mass flux in the range from 10 to 100 kg/m2s and the heating power with values between 0 and 25 W/cm2. There are two dependent variables which are the temperature (for the heated wall and inside the channel) and the exit quality. The thermal results are compared to those given by Gungor–Winterton and Shah. The comparison with the Gungor–Winterton correlation shows that the metallic foam insert enhances the heat transfer coefficient by a factor in the range of 2–4 for low quality. Furthermore an inversion point is identified where the effectiveness of the channel filled with metallic foam is reversed compared to a plain channel. This point is given for a constant wall temperature superheat.

► The goal of this work is the analysis of the metallic foam insert on flow boiling.
► The analysis is carried out in terms of the wall heat transfer coefficient.
► The heat transfer coefficient is compared to results in the literature for plain tube.
► The heat transfer coefficient is enhanced by a factor from 2 to 4 for low quality.
► An operational point is identified where the heat transfer effectiveness is reversed.