This Small Business Innovation Research (SBIR) Phase II project will develop an advanced heat sink and a two-phase pumped loop for cooling high power laser diodes and other high heat flux devices. An advanced coating will be applied to the heat sink to enhance the boiling process, suppress flow instabilities and improve overall heat sink performance. The objectives of this Phase II project are to: (1) develop and validate a two-phase heat sink model, (2) develop a system-level model for a two-phase pumped loop, (3) design and fabricate the heat sink and pumped loop system and (4) test the prototype loop in the laboratory and on an actual system. The key benefits of the technology include high heat flux capability and isothermal cooling. The system will be compact and designed such that it can be integrated with high heat flux components.
The broader impact/ commercial potential of this project will be to provide a new cooling solution for dissipating high heat fluxes in products used in the electronics and optoelectronics industries including compact high-power lasers. The technology developed will be capable of handling higher heat fluxes than those that can be managed with state-of-the-art, commercially available single-phase coolers. Moreover, the technology will not use refrigerants that have high Global Warming Potential. This program will also be performed in close collaboration with researchers at an academic institution and aide in the technical training of students in basic and applied research and new product development. The results of this study will be disseminated in the heat transfer community through conference presentations and journal publications.
Intellectual Merit: An advanced pumped two-phase cooling system for removing the excess heat from high power electronics and lasers was developed in this Small Business Innovation Research project. The initial focus of the project was on the development of the evaporator (heat sink), which is a key component in the system. The evaporator directly interfaces to the electronic component(s) or laser and transfers the heat from the device to a refrigerant that flows through the evaporator. The refrigerant enters as a liquid, absorbs heat as it partially vaporizes and exits from the evaporator as a mixture of liquid and vapor. In essence, the refrigerant boils as it absorbs heat from the device. In addition, a new coating was developed and applied to the evaporator surface to enhance the boiling process. This coating enables the evaporator to dissipate more heat than can otherwise be removed from an identical uncoated heat sink while maintaining a very uniform temperature over the heated surface. Isothermality is important in laser cooling, for example, where emission wavelengths are sensitive to temperature. In addition to the development of the evaporator, a complete cooling system was then developed and tested. Results showed that devices that high heat flux devices can efficiently be cooled with minimal power needed to pump the refrigerant through the cooling loop. Advanced Cooling Technologies, Inc. is now working with several commercial and military customers to tailor the technology to meet their requirements and commercialize the technology. Broader Impact: Efficient cooling solutions for next-generation electronics and high power lasers are needed. Applications are in the automotive, aerospace, medical, alternative energy and military sectors, which are at the core strength of our high-tech industries. Lasers, for example, are used for surgery, machining, telecommunications. High power electronics are used in hybrid electric systems and wind power generators. Our cooling system provides an effective way to cool these devices and has distinct advantages over current cooling techniques; specifically, pumped two-phase cooling can handle high heat fluxes with low pumping power and provide a nearly isothermal heated surface in a lightweight, compact system. The technology will enable the use of next-generation lasers and electronics. Results from this work have been disseminated in journal publications, conference proceedings and presentations, and a free online publically-available NASA Tech Brief webinar. Also, a portion of the work served to help train students through our industry-academic partnership on this program.
