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ELECTRO-THERMAL MODELING AND EXPERIMENTAL DESIGN OF CAPILLARY DRIVEN MICROCHANNEL HEAT EXCHANGER

TEAM: CHIMES PROFESSOR: Dr. Suresh Sitaraman Georgia Institute of Technology

PROJECT OVERVIEW

In response to the need for compact, high-performance thermal management systems, this project focused on the design and simulation of CHIMES (Compact High-Performance Microchannel Evaporator System)—a capillary-driven cooling solution for ultra-dense electronics. The objective was twofold:

  • Numerically simulate phase-change dynamics and capillary behavior under various initial states.
  • Redesign and validate an experimental prototype incorporating PDMS sealing for reliability and manufacturability.

METHODS & APPROACH

SIMULATION PHASE

  • Developed a detailed 3D CFD model using polyhedral meshing (~487k elements) with 1 µm resolution.
  • Implemented boundary conditions for capillary-driven flow (1 atm pressure inlet/outlet, symmetry).
  • Used a VOF (Volume of Fluid) multiphase model to simulate interface evolution from:
    • Flooded channel
    • Meniscus-formed channel
    • Dried-out channel
  • Introduced an energy jump model at the liquid-vapor interface to simulate evaporation as a thermal discontinuity, enabling robust yet efficient handling of phase change.
  • Compared wall temperature results: Flooded (~380 K) vs. Meniscus (~375 K), validating HTC behavior.

EXPERIMENTAL PHASE:

  • Addressed leakage and support issues by redesigning the bottom plate to integrate PDMS sealing.

    • Change From

    Change To

  • Built LabVIEW-controlled setups with thermocouples to monitor real-time TIM interface temperatures under dynamic conditions. Integrated DAQ hardware with calibrated CJC to log temperature differentials, identify thermal failure paths, and validate cooling strategies.

RESULT AND IMPACTS

  • Simulation Findings::
    • The meniscus configuration resulted in more favorable boiling conditions and better heat dissipation.
    • Confirmed that energy jump modeling effectively captures interface evaporation phenomena with minimal computational complexity.
  • Experimental Advancements:
    • Experimentally measured and calculated maximum and average dissipated powers at each studied flow rate, extrapolated from experimental thermal resistance for a set surface temperature of 105 °C

TOOLS & TECHNOLOGIES

  • Software: ANSYS Fluent, CAD (Creo), MATLAB
  • Simulation Methods: VOF multiphase modeling, energy jump condition, polyhedral meshing
  • Materials: Silicon, PDMS, glass, PC, TIM
  • Measurement Goals (Future): Thermal resistance, boiling onset, channel flooding

FUTURE SCOPE

  • Simulate pumping-driven flow and validate flooding vs. dry-out at higher heat fluxes.
  • Fabricate and test the redesigned CHIMES prototype using the new PDMS-enabled structure.
  • Integrate heat source instrumentation and conduct thermal performance benchmarking under transient loads.