Comparative performance analysis of metal foam and spiral fin-and-tube heat exchangers

• MFHXs with all pore densities exhibit 6.2-14.4% lower heat transfer rates than SFHXs. • Higher pore densities result in greater heat transfer rates due to the larger surface area. • The pressure drop across MFHXs at all pore densities is 100-190% higher than that of SFHXs. • MFHXs with a pore density of 40 PPI deliver the highest GHTD values. • GHTD of MFHXs is 3.2-17.8% higher than that of SFHXs. Metal foam, owing to its excellent thermal management capability and superior mechanical properties, has been extensively employed in various engineering applications. This research investigates the application of open-cell metal foam in tubular heat exchangers to enhance their heat transfer performance. Metal foam heat exchangers (MFHXs) were designed and fabricated by wrapping metal foam around tubes typically used in fin-and-tube heat exchangers. The experimental results were compared with those obtained from spiral fin-and-tube heat exchangers (SFHXs), which are among the most widely used types today. Under identical testing conditions, the average heat transfer rate of the MFHX was approximately 6.2-14.4% lower t han that of the SFHX, whereas the pressure drop across the MFHX was about 100-190% higher. This discrepancy arises because the three-dimensional open-cell pores of the metal foam are extremely small and randomly oriented, impeding the air from flowing smoothly through the porous structure and thereby complicating the internal flow field. Consequently, only a portion of the air is able to interact effectively with the internal surface of the metal foam, resulting in incomplete heat exchange and a significant pressure drop. Nevertheless, due to its inherently porous structure, the MFHX exhibits a higher gravimetric heat transfer density than the SFHX by approximately 3.2-17.8% .