Fabrication of Open-Channel Aluminum Alloys and Its Application to Heat Exchangers

Aluminum alloys with open-channel structure are fabricated by casting the melt of aluminum alloys using wire-extraction method. Template stainless steel wires are coated with release agents such as boron nitride and alumina, which are embedded in the melt of aluminum alloys. After solidified, the wires are extracted by tensile test machine to fabricate channel holes so that open-channel aluminum alloys are produced. The microvoids are formed in alloys AC4CH and Al-7%Si, when the wires are coated with boron nitride. However, no microviods are observed in the alloys A1050 and A6063. It is found that the formation of microvoids is attributed to the addition of silicon, which may evolve nitrogen gas pores. Cross-flow type microchannel heat exchangers are fabricated, and heat exchange performance is investigated. The experimental results of heat exchange rate and pressure loss are in good agreement with the predicted results based on heat transfer calculation, which suggests that open-channel aluminum alloys are superior for heat exchangers.