Transient Flow Boiling Model Development for Microchannel Evaporators
Abstract
High heat flux devices such as laser diode-powered directed energy weapons and the power electronics contained within power inverter, modules are a strategic technology for the U.S. Department of Defense (DoD), and integration onto existing and new platforms will i,ncrease cooling demand requirements. Embedded two-phase cooling in micro-channels offers a promising thermal management strategy wit,h high heat transfer rates, nearly isothermal device conditions, low required pumping power, and lower temperature lift from integra,ted vapor compression systems. These features result in improved Size, Weight, and Power (SWaP) of component systems, which in turn, allow for smaller and more flexible platforms. However, many of these strategic technologies operate under highly transient modes s,uch as high frequency pulses or cold start-ups. Embedded cooling strategies generally reduce the package thermal capacitance alongsi,de thermal resistance and can exacerbate the temperature excursions caused by these transient heating events. Previous Colorado Stat,e University (CSU) efforts for ONR have shown that transient heat loads on low thermal resistance microchannel evaporators spur larg,e temperature overshoots and flow instabilities at the onset of boiling which could result in undesirable shifts in performance and, premature device damage or failure. Unfortunately, a two-phase evaporator model does not exist to predict the impact of transient h,eat-loads on high heat flux devices. Furthermore, the impact of integrating additional thermal energy storage as a thermal buffer di,rectly into the evaporator with a solid-liquid phase change material (PCM) is not well understood. In the proposed effort, CSU plans, to develop an experimentally-validated predictive model for two-phase microchannel evaporators with low thermal resistances under t,ransient heating. The model will encompass a range of operating conditions to be as general as possible and that can be inserted int,o PCKAs transient system-level simulation tool ATTMO NavyHHF for SWaP design tradeoff studies. In addition, PCM will be integrated, into the evaporator packaging to understand the performance trade-offs of including thermal energy storage into a low thermal resis,tance evaporator experiencing transient heat loads. CSU hypothesizes that embedded PCM will buffer the transient thermal response of, the evaporator and reduce temperature overshoots and flow instabilities which could inhibit practical usage of embedded two-phase c,ooling strategies.The proposed effort is intended to support ongoing efforts by ONR and ARL to investigate thermally enabling archit,ectures for high heat flux devices. CSU will first focus on validating the modeling framework with existing tools developed in the T,EAPPSprogram, while working closely with ARL to develop and design new test sections and test facility which can accommodate transie,nt heating and PCM integration. A large dataset comprising a wide range of testing conditions will be collected while continuing to, workwith ARL on PCM integration into the evaporators using advanced packaging techniques. Further data will be collected here, and, a semi-empirical predictive model will be developed in ATTMO NavyHHF for use as a SWaP design trade-offs tool for future DoD strate,gic platforms.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 08, 2022
- Source ID
- N000142212149
Entities
People
- Todd Bandhauer
Organizations
- Colorado State University
- Office of Naval Research
- United States Navy