流体机械
流體機械
류체궤계
FLUID MACHINERY
2013年
11期
56-60,36
,共6页
自然工质R290%珠状凝结%分形维数%传热量%热流密度
自然工質R290%珠狀凝結%分形維數%傳熱量%熱流密度
자연공질R290%주상응결%분형유수%전열량%열류밀도
natural refrigerant R290%dropwise condensation%fractal dimension%heat transfer capacity%heat flux
通过对自然工质R290蒸气珠状凝结传热过程的微尺度特性分析得出，在一定的过冷度、液珠半径和分形维数下，液珠的导热热阻随接触角的增大而增大，促进层的热阻在接触角为90°时最小，气液界面的热阻随着接触角的增大而减小，单个液珠的总传热热阻随着接触角的增大呈现出先减小后增大的变化规律，即存在最佳接触角，在此最佳接触角下，单个液珠的总传热热阻最小，单个液珠的传热量最大，换热表面的热流密度最高。随着液珠半径的增大，最佳接触角减小。随着过冷度的增加和分形维数的增大，换热表面液珠成核中心密度增大，表面的热流密度增加。在一定的过冷度下，液珠半径增大，液珠分布密度减少，分形维数增大，液珠的分布密度增加。在一定的分形维数和过冷度下，随着液珠半径的减小，换热表面的热流密度增大。
通過對自然工質R290蒸氣珠狀凝結傳熱過程的微呎度特性分析得齣，在一定的過冷度、液珠半徑和分形維數下，液珠的導熱熱阻隨接觸角的增大而增大，促進層的熱阻在接觸角為90°時最小，氣液界麵的熱阻隨著接觸角的增大而減小，單箇液珠的總傳熱熱阻隨著接觸角的增大呈現齣先減小後增大的變化規律，即存在最佳接觸角，在此最佳接觸角下，單箇液珠的總傳熱熱阻最小，單箇液珠的傳熱量最大，換熱錶麵的熱流密度最高。隨著液珠半徑的增大，最佳接觸角減小。隨著過冷度的增加和分形維數的增大，換熱錶麵液珠成覈中心密度增大，錶麵的熱流密度增加。在一定的過冷度下，液珠半徑增大，液珠分佈密度減少，分形維數增大，液珠的分佈密度增加。在一定的分形維數和過冷度下，隨著液珠半徑的減小，換熱錶麵的熱流密度增大。
통과대자연공질R290증기주상응결전열과정적미척도특성분석득출，재일정적과랭도、액주반경화분형유수하，액주적도열열조수접촉각적증대이증대，촉진층적열조재접촉각위90°시최소，기액계면적열조수착접촉각적증대이감소，단개액주적총전열열조수착접촉각적증대정현출선감소후증대적변화규률，즉존재최가접촉각，재차최가접촉각하，단개액주적총전열열조최소，단개액주적전열량최대，환열표면적열류밀도최고。수착액주반경적증대，최가접촉각감소。수착과랭도적증가화분형유수적증대，환열표면액주성핵중심밀도증대，표면적열류밀도증가。재일정적과랭도하，액주반경증대，액주분포밀도감소，분형유수증대，액주적분포밀도증가。재일정적분형유수화과랭도하，수착액주반경적감소，환열표면적열류밀도증대。
By analyzing the microscale characteristics of natural refrigerant R 290 vapor dropwise condensation heat transfer , the following conclusions are obtained .At a certain subcooling degree , droplet radius and fractal dimension , the thermal resistance of single droplet conductivity increases with the increase of contact angle , the thermal resistance of promoting layer has the smallest value at the contact angle of 90°, the thermal resistance of vapor-liquid interface decreases with the increase of contact angle , the total thermal resistance of single droplet decreases first and then increases with the increase of contact angle , namely has proved the existence of the optimum contact angle , and at this optimum contact angle , the total thermal resistance of single droplet has a smallest value, the heat transfer capacity of single droplet and the heat flux of heat transfer surface have the largest value .Also, with the increase of droplet radius , the optimum contact angle decreases .Moreover , with the increase of subcooling degree and fractal dimension , the nucleation density of dropwise condensation increases on the heat transfer surface , so the heat flux en-hances .At certain subcooling degree , with the increase of droplet radius , the distribution density of condensation droplet re-duces, however, with the increase of fractal dimension , the distribution density of condensation droplet increases .At a certain fractal dimension and subcooling degree , with the reduceing of droplet radius , the heat flux of heat transfer surface increases .
