Cooling of Large Area for Flow Boiling in Narrow Channels by Improved Liquid Supply

Abstract

Heat generation density from semiconductor devices increases with the rapid development of electronic technology. The cooling system using boiling two-phase phenomena attracts much attention because of its high heat removal potential. Experiments on the increase of CHF for flow boiling in narrow channels by improved liquid supply were conducted for the development of high-performance space cold plates. A large surface of 150mm in heated length and 30mm in width with grooves of an apex angle of 90 deg, 0.5mm in depth and 1mm in pitch was employed. A structure of narrow heated channel between parallel plates with an unheated auxiliary channel was devised and tested by using water for different combinations of gap sizes and volumetric flow rates, where inlet of the main heated channel and the outlet of auxiliary unheated channel were closed in order to prevent the flow instability observed frequently at low flow rate for parallel two channels. The data were compared with those for the two parallel channels. CHF values of 2×106W/m2 were obtained for the improved configuration. For gap sizes of 2mm and 5mm at high volumetric flow rate larger than 3.60l/min, the extension of dry-patches were observed at the upstream location of the main heated channel resulting burnout not at the downstream but at the upstream. The values of pressure drop for gap size of 2mm were higher than that for gap size of 5mm. When the performance of cooling system was evaluated by the pump power ignoring its variation of efficiency with volumetric flow rate, i.e., the power defined as the product of the pressure drop and the total volumetric flow rate, higher values of CHF were obtained for gap size of 5mm as far as the same pump power was concerned.