Hotspot cooling with flow boiling of dielectric fluid thermasolv IM6 in a minichannel having elliptical pin fin arrays

Pin fin structures integrated within small channels have been utilized to enhance heat transfer, improve flow distribution, and facilitate the formation and movement of vapor bubbles in flow boiling. These features make them ideal for high-heat flux cooling applications and achieving a high cooling performance. On the other hand, dielectric fluids offer a combination of electrical insulation, low saturation temperature, effective thermal performance, and stability, making them a preferred choice in advanced heat management systems where water may not be practical or safe to use. The implementation of a pin fin array along a minichannel to flow boiling can serve in effectively cooling localized hotspot regions. In this regard, we investigated the thermal performance of a dielectric fluid, THERMASOLV IM6, in flow boiling in a minichannel heat sink having eight segmented hotspots and featuring staggered elliptical pin fins under various heat fluxes (7.8 to 29.3 W/cm²) and two different mass fluxes (212 and 286 kg/m²s). In the configuration, the primary minichannel was subdivided into smaller minichannels (4 × 3 mm², W × H), each passing through regions with elliptical pin fins (0.5 × 1 mm [minor × major axis]) to exploit boiling heat transfer enhancements. Depending on the heating conditions, single-phase, subcooled, and saturated flow regimes were identified within the minichannels. The corresponding heat transfer coefficients for each hotspot were obtained. Additionally, associated flow patterns as a function of heat flux were observed through flow visualization. The results showed that upon transitioning to the saturation zone, a significant increase in the heat transfer coefficient was observed, while local heat transfer coefficient decreased as the heat flux was increased for saturated flow, similar to the single-phase and subcooled flows.