Effect of altitude on heat transfer performance of full-scale metal foam heat exchangers produced by additive manufacturing

Abstract

Increasing altitude negatively impacts heat exchangers efficiency, limiting vehicle power and system performance. To address this, enhancing heat exchangers performance and compactness is crucial. Metal foam, with its high porosity and large specific surface area, is ideal for cooling fins in automotive heat exchangers. This study used laser additive manufacturing with 6061 aluminum powder to fabricate two Kelvin open-cell metal foam heat exchangers: a double-layer (DKHE) and a three-layer (TKHE) structure, both measuring 80 mm × 270 mm × 210 mm. Performance was assessed in a plateau simulation chamber across altitudes from 0 m to 4500 m. Results showed that at a gas flow rate of 1500m³/h at 0 m, the overall heat transfer coefficients for TKHE and DKHE were 1625 W/m²·K and 1301.7 W/m²·K, respectively. At 4500 m, these values dropped by 47.7% and 37.2%, respectively. Pressure drops also decreased by 40% and 39.2%, respectively. The area goodness factor indicated TKHE's superior performance. Additionally, permeability K and inertia coefficient f_i, both increasing with altitude, were 36% and 104% higher for TKHE than DKHE. This research applies additive manufacturing for heat exchangers manufacturing which avoids the degradation of heat exchangers performance due to contact thermal resistance. Addressing the performance data gap for metal foam heat exchangers in plateau regions and laying the foundation for future design improvements.