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Description
Spray cooling is a high-performance thermal management technique capable of dissipating extremely high heat fluxes while enabling compact system designs. It is regarded as a key enabling technology in applications where conventional air or single-phase liquid cooling is no longer sufficient, including power electronics and high-performance computing, aerospace and defense systems, high-power laser and optoelectronic devices, as well as industrial and automotive thermal management.
Its exceptional performance derives from the exploitation of the latent heat of evaporation, allowing heat flux dissipation exceeding 1000 W/cm² with water and over 100 W/cm² with dielectric fluids, while ensuring uniform cooling of localized hot spots.
However, spray cooling effectiveness is strongly influenced by surface–liquid interactions, and smooth surfaces often suffer from dry spot formation or excessively thick liquid films, which degrade heat transfer and promote premature critical heat flux (CHF) conditions.
To mitigate these limitations, surface engineering at the millimetric, micrometric, and nanometric scales has been extensively investigated.
At the millimetric scale, macro-structures such as straight fins, pin fins, and pyramidal geometries have demonstrated significant enhancements in heat transfer coefficient (HTC) and CHF compared to flat surfaces, mainly due to increased wetted area and improved liquid management.
Among these configurations, straight fins generally provide superior performance owing to efficient drainage, channeling effects, and stable operation under inclined spray conditions. Nevertheless, despite the extensive literature on conventional millimetric structures, the potential of offset strip fins with millimetric hydraulic diameters in spray cooling applications remains largely unexplored.
Offset strip fins are widely adopted in compact heat exchangers due to their ability to significantly increase heat transfer area and promote flow disruption, thereby enhancing convective heat transfer. Their interaction with impinging sprays, and their influence on liquid redistribution, film thinning, and evaporation mechanisms, have not yet been systematically investigated.
This work aims to address this gap by experimentally studying spray cooling on offset strip fin surfaces, with emphasis on quantitative surface temperature mapping.
The primary objective of the study is to assess whether offset strip fins can enhance spray cooling performance compared to conventional millimetric fin geometries, and quantify the influence of surface orientation. Experiments are conducted for both horizontal and vertical surface orientations using water as the working fluid, to evaluate the role of gravity on liquid drainage and fluid management. Surface temperature measurements are obtained using infrared thermography and thermochromic liquid crystals, enabling a quantitative comparison between the two measurement techniques. The combined IR–TLC approach is used to validate temperature mapping and to establish an uncertainty framework for thermographic measurements during spray impingement and evaporation.
The experimental approach is designed to characterize heat transfer phenomena including cooling efficiency and thermal non-uniformity, through metrics such as spatial temperature non-uniformity and hotspot statistics, and to provide insight into the coupled effects of surface geometry, orientation, and spray–surface interaction mechanisms for high heat flux thermal management applications.
