Critical heat flux enhancement using composite porous structure produced by selective laser melting

Abstract

• Uniform porous structures (with single pore size) and Composite porous structures（with two different pore sizes) are fabricated by selective laser melting. • Composite porous structure has the best heat transfer performance. • Critical heat flux enhancement of up to 3.2 times is achieved. • Gas-liquid flow characteristics of the composite porous structure is analyzed. Cross scale composite porous structures have been proved to have a better effect on enhanced boiling heat transfer. Accurate control of composite pore size and porous structure thickness is important for the study of enhanced boiling heat transfer. In this study, composite porous structures were manufactured with selective laser melting (SLM) technique from aluminum alloy (AlSi10Mg) powder. The heat transfer characteristics of a composite porous structure with composite pores (0.6 mm small pores and 2 mm large pores) for pool boiling under atmospheric pressure were investigated. A comparative analysis was performed with the uniform porous structure (0.6 mm pores) and the composite porous structure. The results shown that the composite porous structure can significantly increase the critical heat flux (CHF) compared to the plain copper surface. The CHF of the composite porous structure was higher than that of the uniform porous structure with the same height. As the height increases, the nucleate boiling heat transfer performance with composite porous structures will decrease, due to the larger gas–liquid resistance as a result of the height increment. In the range of 1.5–4.5 mm studied in this research, the 1.5 mm high composite porous structure achieves the maximum increase in CHF. The maximum CHF was 346.6 W/cm 2 , which was 3.2 times that of the plain surface. The large pores in the composite porous structure can play a role of shunting to reduce the escape resistance of the bubbles, which can further enhance CHF.