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烧结多孔表面分布式阵列射流沸腾 被引量:4
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作者 崔付龙 洪芳军 +1 位作者 林涛 李文韬 《科学通报》 EI CAS CSCD 北大核心 2020年第17期1760-1769,共10页
使用50,100和200μm粒径的铜粉,分别烧结制作了厚度为2倍粒径的多孔结构表面,以新型环保电子冷却液HFE7000为工质,进行了分布式阵列射流沸腾的换热性能实验,并将实验结果与光滑表面进行了对比.结果表明,烧结多孔表面增加了对流换热面积... 使用50,100和200μm粒径的铜粉,分别烧结制作了厚度为2倍粒径的多孔结构表面,以新型环保电子冷却液HFE7000为工质,进行了分布式阵列射流沸腾的换热性能实验,并将实验结果与光滑表面进行了对比.结果表明,烧结多孔表面增加了对流换热面积,增强了流体扰动,大大强化了单相段换热性能,且流量越高,强化效果越显著;100和200μm颗粒烧结表面的强化效果接近,且明显好于50μm颗粒烧结表面,表明粒径和厚度对传热性能具有重要影响.在射流沸腾换热过程中,多孔烧结表面提供了更多的气化核心和更大的换热面积,但同时也增加了蒸汽逸出阻力,100μm颗粒烧结表面强化效果最佳,其最大沸腾换热系数比光滑表面提高了61%.分布式射流是沸腾表面补液的主要途径,由于HFE7000本身表面张力小、亲水性好,多孔表面吸液能力对于临界热流密度(critical heat flux,CHF)的影响较小,100μm颗粒烧结表面的CHF和光滑表面相比仅提高了17%.尽管如此,烧结多孔表面的核态沸腾偏离点(departure from nucleate boiling,DNB)与CHF之间的热流密度区间显著变大,对实际应用过程有利. 展开更多
关键词 烧结多孔表面 分布式阵列射流 沸腾强化 临界热流密度
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A building unit decomposition model for energy leakage by infrared thermography image analysis
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作者 Yan SU fangjun hong Lianjie SHU 《Frontiers in Energy》 SCIE CSCD 2020年第4期901-921,共21页
A quantitative energy leakage model was developed based on the thermography image data measured for both external and internal building surfaces.The infrared thermography images of both surfaces of doors,windows,and w... A quantitative energy leakage model was developed based on the thermography image data measured for both external and internal building surfaces.The infrared thermography images of both surfaces of doors,windows,and walls of an office building in the Hengqin Campus of University of Macao were taken at various times in a day for four seasons.The transient heat flux for sample units were obtained based on measurements of the seasonal transient local temperature differences and calculations of the effective thermal conductivity from the multiple-layer porous medium conduction model.Effects of construction unit types,orientations,and seasons were quantitatively investigated with unit transient orientation index factors.The corresponding electric energy consumption was calculated based on the air conditioning system coefficient of performance of heat pump and refrigerator cycles for different seasons.The model was validated by comparing to the electric meter records of energy consumption of the air conditioning system.The uncertainties of the predicted total building energy leakage are about 14.7%,12.8%,12.4%,and 15.8%for the four seasons,respectively.The differences between the predicted electric consumption and meter values are less than 13.4%and 5.4%for summer and winter,respectively.The typical daily thermal energy leakage value in winter is the highest among the four seasons.However,the daily electric energy consumption by the air conditioning system in summer and autumn is higher than that in winter.The present decomposition model for energy leakage is expected to provide a practical tool for quantitative analysis of energy leakage of buildings. 展开更多
关键词 heat conductivity heat coefficient heat flux infrared thermography thermal image
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