Showing papers by "Avram Bar-Cohen published in 2021"

The ICECool Fundamentals Effort on Evaporative Cooling of Microelectronics

Abstract: The Intrachip Enhanced Cooling Fundamentals (ICECool Fun) effort was launched by the Defense Advanced Research Projects Agency (DARPA) under the leadership of Dr. Avram Bar-Cohen during 2012–2015 to target an order of magnitude improvement in chip level and hot spot heat fluxes, compared to the then state-of-the-art (SOA). Evaporative cooling technologies to achieve potential targets of 1 kW/cm2 at the chip level and 5 kW/cm2 at the hot spot level were targeted. A key goal was to improve fundamental understanding of the evaporative cooling physics at the relevant scales, and a numerical modeling capability to enable the co-design of such solutions in emerging computing and communications systems. A summary of the five projects pursued under this effort is provided, including the key accomplishments and developed capabilities.

Thermal and optical performance of cryogenically cooled laser diode bars mounted on pin-finned microcoolers

Abstract: This study investigates the thermal performance of cryogenic micro-pin fin coolers for high-power laser diode (LD) bars. An open-loop liquid nitrogen cooling system, used to operate LD bars at cryogenic temperatures, is developed and characterized. The comparison study demonstrates that the total thermal resistance value of the micro-pin fin cooler, ranging from 0.03 to 0.04 °C/W, is only 1/3 of that of the micro-gap cooler and, thus, contributes significantly to reducing the LD operating temperature and enhancing its efficiency. In this study, the peak optical power of 68.8 W was observed at an LD bar package base temperature of − 100 °C, providing a 20% increase relative to the optical power of 57.3 W for a nominal operating condition with an LD bar package base temperature of 41 °C. This result clearly illustrates the enhancement in optical performance made possible by cryogenic cooling with a pin fin microcooler.

Thermal Performance of Cryogenic Micro-Pin Fin Coolers with Two-Phase Liquid Nitrogen Flows

Abstract: This study experimentally explores the thermofluidic performance of a cryogenic micro-pin fin cooler with two-phase liquid nitrogen flows. The liquid nitrogen cooling system is introduced to investigate the performance of the micro-pin cooler in a cryogenic condition. The result reveals that the nominal value of the base heat transfer coefficients of the micro-pin fin cooler with liquid nitrogen flows, 240 kW/m2-K at a mass flow rate of 2.23 g/s, is an order of magnitude greater than that with FC-72 flows. The result also demonstrates that the base heat transfer coefficient of the micro-pin fin cooler is nearly three times greater than that of the micro-gap cooler, not containing any fins. This study shows the feasibility of the cryogenic micro-pin fin cooler for thermally controlling very high heat density devices such as high-power laser diode bars, of which the heat density can reach 2000 kW/m2.

Selectively-pliable chemical vapor deposition (cvd) diamond or other heat spreader

Abstract: A system includes at least one component configured to generate thermal energy, a heat spreader configured to remove thermal energy from the at least one component, and at least one substrate configured to remove thermal energy from the heat spreader. The heat spreader includes a first portion and a second portion. The first portion of the heat spreader is coupled to the substrate, and the second portion of the heat spreader is coupled to the at least one component. The first portion of the heat spreader includes high aspect-ratio structures that are separated from one another. The high aspect-ratio structures cause the first portion of the heat spreader to be pliable and able to accommodate a mismatch in coefficients of thermal expansion between a material in the heat spreader and a material in the substrate.