Abstract:
Increasingly, military and civilian applications of electronics require extremely high-heat
fluxes on the order of 1000 W/cm2. Thermal management solutions for these severe
operating conditions are subject to a number of constraints, including energy consumption,
controllability, and the volume or size of the package. Calculations indicate that the
only possible approach to meeting this heat flux condition, while maintaining the chip
temperature below 65°C, is to utilize refrigeration. Here, we report an initial thermodynamic
optimization of the refrigeration system design. In order to hold the outlet quality
of the fluid leaving the evaporator to less than approximately 20%, in order to avoid
reaching critical heat flux, the refrigeration system design is dramatically different from
typical configurations for household applications. In short, a simple vapor-compression
cycle will require excessive energy consumption, largely because of the additional heat
required to return the refrigerant to its vapor state before the compressor inlet. A better
design is determined to be a “two-loop” cycle, in which the vapor-compression loop is
coupled thermally to a pumped loop that directly cools the high-heat-flux chip.
