Investigation of geometrical-based thermo-fluidic characteristics of micro flow boiling coolers for automated-constant-temperature conditions

Abstract

Keeping temperature at desired level is a prioritized issue for electronics. In practice, micro-processors operate at different speeds due to variable workloads; therefore, micro flow boiling coolers should successfully manage variable thermal loads to provide stable surface temperature. Present paper, as first in literature, for automated-constant-temperature conditions, thermo-fluidic characteristics of micro flow boiling coolers having micro pin-fins, micro cavities, and enlarging cross section were investigated. A structured heat sink (SHS) was compared to an ordinary one (OHS). Under transient conditions, variable heat loads were applied (145 – 205 W; corresponding to 216 to 312 kWm−2), and depending on target surface temperature (104 ± 0.5 °C), the micro-pump automatically provided the required flow rate. Thermal reaction, thermo-fluidic characteristics, mass flux trend, and pumping-power-ratio (PPR) were compared for both heat sinks, and results were discussed based on flow physics. For cooling under same conditions, SHS decreases pumping power requirement between 0.37 and 0.47 times compared to OHS. Higher mass flux doesn't mean lower temperature at every condition in micro flow boiling. SHS requires lesser mass flux (as average, by up to 66 %) to provide the same target temperature compared to OHS. When first exposed to heating power, SHS offers a 118.7 % higher heat transfer coefficient compared to OHS.