Session: 04-11-01 Posters

Paper Number: 195117

195117 - Heat Transfer Characteristics of Impinging Jets 

Abstract: 

Jet flows are widely used in aerospace propulsion, turbine blade cooling, manufacturing, and thermal management of high-power electronics. Increasing heat fluxes in modern electronic systems, driven by continued miniaturization and rising power densities, present a significant challenge for conventional cooling methods. Air cooling remains the most widely used approach due to its low cost and simplicity; however, its relatively low thermal conductivity limits achievable heat transfer coefficients at elevated heat loads. While liquid-based cooling techniques can achieve significantly higher heat transfer rates, they introduce additional system complexity and cost. As a result, there is growing interest in enhancing single-phase convective cooling methods to bridge the gap between simplicity and performance.

In impinging jet flows, heat transfer performance is commonly characterized by the Nusselt number, which reflects the strength of convective heat transfer at the target surface. Previous studies on subsonic impinging jets have shown that both local and surface-averaged Nusselt number distributions depend strongly on Reynolds number, jet-to-surface spacing, and inlet turbulence characteristics. In these flows, turbulence, shear-layer instabilities, and coherent vortical structures in the stagnation and wall-jet regions play a major role in determining the heat transfer distribution and can produce secondary Nusselt number peaks. For supersonic impinging jets, the problem becomes more complex due to compressibility effects, shock structures, strong pressure gradients, and temperature variations, all of which interact with turbulence and near-wall flow development. Shock-induced heating, stand-off shocks, and underexpanded jet structures can generate secondary heat-transfer peaks. These effects also alter wall-jet development, making heat transfer prediction more sensitive to Mach number, nozzle pressure ratio, and jet-to-surface spacing.

To investigate the flow structures and heat transfer characteristics over a wide range of pressure and temperature ratios in detail, a computational fluid dynamics (CFD) approach is employed with different turbulence fidelities, including Reynolds-averaged Navier–Stokes (RANS), Detached Eddy Simulation (DES), and Large Eddy Simulation (LES), for both axisymmetric and fully three-dimensional comparisons. The flow and heat transfer characteristics are examined over a wide range of pressures and temperatures. Close comparison with the literature data not only helps validate the approach, but also provides an opportunity to draw conclusions for high-density flows. The analysis further quantifies the impact of expansion-induced flow structures on temperature distributions, velocity fields, and effective convective heat transfer coefficients. Particular attention is given to how reduced-pressure conditions alter the coupling between flow acceleration, turbulence, and heat transfer. The low-pressure configuration consists of a high-speed jet impinging on a heated surface under reduced ambient pressure, allowing the jet to expand over a larger surface area. This configuration is expected to mitigate strong shock formation, which can otherwise locally increase temperatures and degrade cooling effectiveness.

The results of this work evaluate whether reduced-pressure jet expansion can serve as a viable intermediate cooling strategy between conventional air cooling and more complex high-performance systems. This has important implications for next-generation thermal management in electronics, where achieving higher heat transfer rates without significantly increasing system complexity is critical. The findings also provide insight into flow structures relevant to jet-assisted landing, positioning, and space manufacturing applications.

Presenting Author: Marie Borca-Tasciuc Rensselaer Polytechnic Institute

Presenting Author Biography: 

Authors:

Marie Borca-Tasciuc Rensselaer Polytechnic Institute
Ozgur Tumuklu Rensselaer Polytechnic Institute