新型微小型平板CPL蒸发器流动与传热分析

Analysis of Flow and Heat Transfer in Novel Evaporator of Miniature Flat Plate Capillary Pumped Loop

提出一种新型微小型平板毛细抽吸两相流体回路(Capillary pumped loop,CPL)的蒸发器结构,使其能够适应高热流密度散热的要求。分析蒸发器由于微型化后侧壁导热对系统传热能力的影响。建立新型蒸发器毛细多孔芯内的传热传质数学模型和液体补偿腔的流动与传热模型以及蒸汽槽道和金属外壁区域的导热模型,并用SIMPLE算法对蒸发器进行整场耦合求解。数值结果表明,工质蒸发发生在多孔芯上表面以及侧壁附近,采用热导率较大的铝外壁时,蒸发器加热表面的温度水平较低且温度均匀性较好,但侧壁导热的影响导致CPL的传热能力不高。外壁采用热导率较小的不锈钢可以明显提高CPL的传热极限能力,但同时却较大地增加了加热表面的温度水平以及不均匀性。采用组合结构的蒸发器一方面可以提高系统的传热能力,同时降低了加热表面的温度水平和温度梯度。

A novel evaporator of miniature flat plate capillary pumped loop（CPL） is presented for application of dissipating high heat flux.Based on the structure characteristics of miniature flat plate CPL evaporator,the effect of metal side wall conduction of evaporator on the CPL work limit is analyzed.An overall numerical model for the miniature flat plate CPL evaporator is presented,which includes heat and mass transfer in the porous wick structure,liquid flow and heat transfer in the compensation cavity and heat transfer in the vapor grooves and metallic wall.The entire evaporator is solved with SIMPLE algorithm as a conjugate problem.The numerical results show that liquid evaporation takes place near the upper and left surfaces of wick structure in the evaporator.The flat plate evaporator with single aluminum wall results in lower heat transfer limit,but leads to low temperature level and good isothermal behavior of the heated surface.On the other hand,the evaporator with single stainless steel wall leads to higher heat transport capacity,but to higher temperature level of the heated surface.The evaporator with combined wall（upper wall with aluminum,side and bottom wall with stainless steel） increases heat transfer limit,and decreases temperature level and temperature gradient on the heated surface,which implies that the CPL can operate safely and cooled apparatus also can work effectively under high heat fluxes.