Heat Transfer and Two-Phase Flow Regimes in Manifolded Microgaps - R245fa Empirical Results

Two-phase embedded cooling has great potential for meeting the increasing thermal management needs of high-heat flux electronics. Use of manifold microgap channels further enhances the effectiveness of embedded cooling while maintaining low pressure drop and pumping power and has demonstrated average channel wall heat transfer coefficients exceeding 45,000 W/m
²
K, with the dielectric refrigerant R245fa as the working fluid. The current R245fa study uses simultaneous high-speed imaging and infrared thermography to provide phenomenological insights into the flow behavior and its associated local heat transfer occurring on the manifolded microgap channel wall. The thermofluid behavior was found to display a strong dependence on the flow thermodynamic quality, with peak heat transfer coefficients occurring at approximately 30% quality and decreasing by a factor of 2-3 with further increases in quality.