The primary focus of this paper is to study the film cooling performance for a row of cylindrical holes each supplemented with two symmetrical anti vortex holes which branch out from the main holes. The anti-vortex design was originally developed at NASA-Glenn Research Center by Dr. James Heidmann, co-author of this paper. This “anti-vortex” design is unique in that it requires only easily machinable round holes, unlike shaped film cooling holes and other advanced concepts. The hole design is intended to counteract the detrimental vorticity associated with standard circular cross-section film cooling holes. The geometry and orientation of the anti vortex holes greatly affect the cooling performance downstream, which is thoroughly investigated. By performing experiments at a single mainstream Reynolds number of 9683 based on the free stream velocity and film hole diameter at four different coolant-to-mainstream blowing ratio of 0.5, 1, 1.5, 2 and using the transient IR thermography technique, detailed film cooling effectiveness and heat transfer coefficients are obtained simultaneously from a single test. When the anti vortex holes are nearer to the primary film cooling holes and are developing from the base of the primary holes, better film cooling is accomplished as compared to other anti vortex hole orientations. When the anti vortex holes are laid back in the upstream region, film cooling diminishes considerably. Although an enhancement in heat transfer coefficient is seen in cases with high film cooling effectiveness, the overall heat flux ratio as compared to standard cylindrical holes is much lower. Thus cases with anti vortex holes placed near the main holes certainly show promising results.

The primary focus of this paper is to study the film cooling performance for a row of cylindrical holes each supplemented with two symmetrical antivortex holes, which branch out from the main holes. The antivortex design was originally developed at NASA-Glenn Research Center by James Heidmann, coauthor of this paper. This “antivortex” design is unique in that it requires only easily machinable round holes, unlike shaped film cooling holes and other advanced concepts. The hole design is intended to counteract the detrimental vorticity associated with standard circular cross-section film cooling holes. The geometry and orientation of the antivortex holes greatly affect the cooling performance downstream, which is thoroughly investigated. By performing experiments at a single mainstream Reynolds number of 9683 based on the freestream velocity and film hole diameter at four different coolant-to-mainstream blowing ratios of 0.5, 1, 1.5, and 2 and using the transient IR thermography technique, detailed film cooling effectiveness and heat transfer coefficients are obtained simultaneously from a single test. When the antivortex holes are nearer the primary film cooling holes and are developing from the base of the primary holes, better film cooling is accomplished as compared to other antivortex hole orientations. When the antivortex holes are laid back in the upstream region, film cooling diminishes considerably. Although an enhancement in heat transfer coefficient is seen in cases with high film cooling effectiveness, the overall heat flux ratio as compared to standard cylindrical holes is much lower. Thus cases with antivortex holes placed near the main holes certainly show promising results.

Metal-based microchannel heat exchangers (MHEs) offer potential solutions to high heat flux removal applications, such as cooling of high-performance microelectronic and energy-efficient lighting modules. Efficient fabrication of metal-based MHEs and quantitative flow and heat transfer measurements on them are critical for establishing the economic and technical feasibility of such devices. In this paper, all-Cu MHE prototypes were fabricated. Results of flow and heat transfer testing made on these Cu-based MHE prototypes are reported. Efficient fabrication of Cu-based high-aspect-ratio microscale structures (HARMSs) was achieved through direct molding replication using surface-engineered metallic mold inserts. Replicated Cu HARMSs were assembled through solid-state bonding to form all-Cu MHE prototypes. Flow and heat transfer testing of the Cu MHE prototypes was conducted to determine the average rate of heat transfer from the solid Cu body to water flowing within the enclosed microchannel array. Experimentally observed flow and heat transfer data are analyzed and shown to agree with known macroscale correlations once surface roughness and entrance length effects are taken into account.

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