电力建设
電力建設
전력건설
ELECTRIC POWER CONSTRUCTION
2015年
8期
15-21
,共7页
直接空冷凝汽器%跨尺度模拟%传热%冻结
直接空冷凝汽器%跨呎度模擬%傳熱%凍結
직접공냉응기기%과척도모의%전열%동결
direct air￣cooling condenser%cross￣scale simulation%heat transfer%freezing
针对冬季直接空冷凝汽器的防冻工业需求，将翅片管和空冷单元这2个尺度的模型耦合起来，既考察翅片管束的整体流动换热性能，又考察直接冷却翅片管内凝结水的冲击换热特性，为确定冬季低温运行条件下空冷凝汽器管内凝结换热甚至结冰计算提供第3类热边界条件。建立了空冷单元模型和翅片管模型，然后，将三维进口风条件下的翅片管级数值模拟结果简化成输入-输出代理模型；从空冷单元系统级数值模拟中获得系统级边界-迎风面的速度分布；进而将翅片管数值模拟代理模型应用到系统边界上，得到了系统边界上翅片管冲击换热特性以及翅片管平均对流换热特性的空间分布。数值计算结果表明，冲击换热系数比平均对流换热系数大一个数量级；在迎风面上冲击换热系数和平均对流换热系数均呈现出上低下高、左右不对称的特点；冲击换热系数随着转速的下降而下降。
針對鼕季直接空冷凝汽器的防凍工業需求，將翅片管和空冷單元這2箇呎度的模型耦閤起來，既攷察翅片管束的整體流動換熱性能，又攷察直接冷卻翅片管內凝結水的遲擊換熱特性，為確定鼕季低溫運行條件下空冷凝汽器管內凝結換熱甚至結冰計算提供第3類熱邊界條件。建立瞭空冷單元模型和翅片管模型，然後，將三維進口風條件下的翅片管級數值模擬結果簡化成輸入-輸齣代理模型；從空冷單元繫統級數值模擬中穫得繫統級邊界-迎風麵的速度分佈；進而將翅片管數值模擬代理模型應用到繫統邊界上，得到瞭繫統邊界上翅片管遲擊換熱特性以及翅片管平均對流換熱特性的空間分佈。數值計算結果錶明，遲擊換熱繫數比平均對流換熱繫數大一箇數量級；在迎風麵上遲擊換熱繫數和平均對流換熱繫數均呈現齣上低下高、左右不對稱的特點；遲擊換熱繫數隨著轉速的下降而下降。
침대동계직접공냉응기기적방동공업수구，장시편관화공랭단원저2개척도적모형우합기래，기고찰시편관속적정체류동환열성능，우고찰직접냉각시편관내응결수적충격환열특성，위학정동계저온운행조건하공냉응기기관내응결환열심지결빙계산제공제3류열변계조건。건립료공랭단원모형화시편관모형，연후，장삼유진구풍조건하적시편관급수치모의결과간화성수입-수출대리모형；종공랭단원계통급수치모의중획득계통급변계-영풍면적속도분포；진이장시편관수치모의대리모형응용도계통변계상，득도료계통변계상시편관충격환열특성이급시편관평균대류환열특성적공간분포。수치계산결과표명，충격환열계수비평균대류환열계수대일개수량급；재영풍면상충격환열계수화평균대류환열계수균정현출상저하고、좌우불대칭적특점；충격환열계수수착전속적하강이하강。
For the antifreezing industrial demand of direct air￣cooling condenser in winter, the model on finned tube scale was coupled with that on air￣cooling unit scale, both the whole heat transfer characteristics in finned tube bundle and the impingement heat transfer characteristic of condensate water in air￣cooling finned tube were studied, which could provide the third thermal boundary condition for the calculation of the in￣tube condensation heat transfer and freezing in direct air￣cooling condenser under the condition of low temperature operation in winter. The air￣cooling condenser cell model and finned tube model were constructed. Then, the simulation results of finned tube under 3D inlet wind velocity boundary condition was simplified as input￣output type agent model. The velocity distribution at the windward surface and symmetric boundary was obtained from air￣cooling condenser cell numerical simulation. Then the finned tube agent model was applied in the symmetric boundary to obtain the spatial distribution of the impingement heat transfer characteristics and average convective heat transfer characteristics of finned tube at symmetric boundary. The numerical calculation results show that, the impinging heat transfer coefficient has a larger magnitude than the average convective heat transfer coefficient; at the windward surface, the distributions of those two coefficients are both up￣down asymmetrical and left￣right asymmetrical;and the impinging heat transfer coefficient decreases with the decrease of the rotational speed.
