Two-Phase Electronic Cooling Using Mini-Channel and Micro-Channel Heat Sinks: Part 1—Design Criteria and Heat Diffusion Constraints

Mini-channel (D = 2.54 mm) and micro-channel (D = 510 μm) heat sinks with a 1-cm² heated surface were tested for their high heat flux performance with flow boiling of R-113. Experimental results yielded CHF values in excess of 200 W cm⁻² for flow rates less than 95 ml min⁻¹ (0.025 gpm) over a range of inlet subcooling from 10 to 32°C. Heat diffusion within the heat sink was analyzed to ascertain the optimum heat sink geometry in terms of channel spacing and overall thickness. A heat sink thickness to channel diameter ratio of 1.2 provided a good compromise between minimizing overall thermal resistance and structural integrity. A ratio of channel pitch to diameter of less than two produced negligible surface temperature gradients even with a surface heat flux of 200 W cm⁻². To further aid in determining channel diameter for a specific cooling application, a pressure drop model was developed, which is presented in the second part of the study.