Enhanced Flow Boiling Using Radial Open Microchannels With Manifold and Offset Strip Fins

Abstract

The increasing demand for designing effective cooling solutions in high power density electronic components has resulted in exploring advanced thermal management strategies. Over the past decade, phase-change cooling has received widespread recognition due to its ability to dissipate large heat fluxes while maintaining low temperature differences. In this paper, a radial flow boiling configuration through a central inlet was studied. This configuration is particularly suited for chip cooling application. Two heat transfer surfaces with (a) radial microchannels, and (b) offset strip fins were fabricated and their flow boiling performance with distilled water was obtained. Furthermore, the effect of the liquid flow rate on the boiling performance and enhancement mechanisms was also investigated in this study. At a flow rate of 240 mL/min, a maximum heat flux of 369 W/cm2 at a wall superheat of 49 °C and a pressure drop of 59 kPa was achieved with the radial microchannels, while the offset strip fins achieved a maximum heat flux of 618 W/cm2 at a wall superheat of 20 °C. Increasing the flow rate to 320 mL/min resulted in a heat flux of 897 W/cm2 demonstrating the potential of using a radial configuration for enhancing the boiling performance. The increase in flow cross-sectional area was shown to be responsible for the reduced pressure drop when compared to straight microchannel configurations. The high-speed imaging incorporated in each test provided valuable insight and understanding into the flow patterns and underlying mechanism in these geometries. With the ease of implementation, highly stable flow, and further optimization possibilities with different microchannel and taper configurations, the radial geometry is expected to provide significant performance enhancement well beyond a critical heat flux (CHF) of 1 kW/cm2.

Heat transfer augmentation in a radial curved microchannel

“…Further, high-speed visualization was performed to better understand bubble dynamics for the radial geometry. Further extending the work, Alyssa et al 19 fabricated an offset strip fin radial microchannel to compare its thermal performance with a radial straight microchannel (RSMC). Their study demonstrated the potential of removing heat fluxes as high as 618 W/cm 2 at the wall superheating of 20 °C using offset strip fins when compared to a heat flux of 396 W/cm 2 that is removed by radial straight channels for the same mass flow rate of 240 ml/min.…”

Wettability effect on flow boiling characteristics within micro-passages

“…Conventional cooling methods, such as air cooling through fans or pumped liquid cooling, cannot cope with such high heat dissipation demands. Flow boiling heat transfer within microchannels has been recognised experimentally as one of the most efficient thermal management solutions for such high-power density electronic components, dissipating heat fluxes in the order of MW/m 2 [2], [3]. However, cooling of micro-electronics utilising flow boiling within micro-passages is not yet commercially available and it is still limited to laboratory applications.…”

Evaluation of forced convective boiling heat transfer with layered parallel microchannels

“…In recent studies, heat sinks have exhibited high heat transfer performance. Recinella and Kandlikar (2018) achieved a heat flux of 6.18×10 6 W/m 2 at a wall superheat of 20.1 K and a pressure drop of 13.8 kPa with distilled water using radial open microchannels with a manifold and offset strip fins. Shultz et al (2015) achieved a heat flux of approximately 3.5×10 6 W/m 2 with a flow rate of 4.2×10 -3 kg/s and a stable pressure drop of 320 kPa with a radial array of channels using the dielectric coolant R1234ze(E).…”