化工进展
化工進展
화공진전
Chemical Industry and Engineering Progress
2015年
11期
3846-3851
,共6页
脉动热管%数值模拟%长度比值%启动时间%热阻
脈動熱管%數值模擬%長度比值%啟動時間%熱阻
맥동열관%수치모의%장도비치%계동시간%열조
pulsating heat pipe%numerical simulation%length ratio%start-up time%thermal resistance
脉动热管是一种结构简单、传热性能突出的新型传热元件，由于运行过程涉及沸腾与冷凝及两相流动，传热及流动机理复杂，因此目前对其运行过程的相关数值模拟尚不成熟。本文采用VOF（volume of fluid）模型，考虑表面张力和壁面接触角的影响，采用数值模拟软件对单环路脉动热管的流动及传热特性进行了研究。数值模拟中，单环路脉动热管的充液率为40%～60%，热端加热功率为10～40W，探讨了热管蒸发段与冷凝段长度比对热管启动及换热性能的影响，并分析了脉动热管运行时流型特征。结果表明：随蒸发段和冷凝段长度比值增大，脉动热管启动时间缩短，且换热性能有一定提高；但在低充液率时，容易出现“干烧”现象。在低加热功率时，脉动热管的启动方式为温度突变式；而在高加热功率时，其启动方式为温度渐变式。此外，通过蒸发段的温度振荡特征可以确定脉动热管的启动时间。
脈動熱管是一種結構簡單、傳熱性能突齣的新型傳熱元件，由于運行過程涉及沸騰與冷凝及兩相流動，傳熱及流動機理複雜，因此目前對其運行過程的相關數值模擬尚不成熟。本文採用VOF（volume of fluid）模型，攷慮錶麵張力和壁麵接觸角的影響，採用數值模擬軟件對單環路脈動熱管的流動及傳熱特性進行瞭研究。數值模擬中，單環路脈動熱管的充液率為40%～60%，熱耑加熱功率為10～40W，探討瞭熱管蒸髮段與冷凝段長度比對熱管啟動及換熱性能的影響，併分析瞭脈動熱管運行時流型特徵。結果錶明：隨蒸髮段和冷凝段長度比值增大，脈動熱管啟動時間縮短，且換熱性能有一定提高；但在低充液率時，容易齣現“榦燒”現象。在低加熱功率時，脈動熱管的啟動方式為溫度突變式；而在高加熱功率時，其啟動方式為溫度漸變式。此外，通過蒸髮段的溫度振盪特徵可以確定脈動熱管的啟動時間。
맥동열관시일충결구간단、전열성능돌출적신형전열원건，유우운행과정섭급비등여냉응급량상류동，전열급류동궤리복잡，인차목전대기운행과정적상관수치모의상불성숙。본문채용VOF（volume of fluid）모형，고필표면장력화벽면접촉각적영향，채용수치모의연건대단배로맥동열관적류동급전열특성진행료연구。수치모의중，단배로맥동열관적충액솔위40%～60%，열단가열공솔위10～40W，탐토료열관증발단여냉응단장도비대열관계동급환열성능적영향，병분석료맥동열관운행시류형특정。결과표명：수증발단화냉응단장도비치증대，맥동열관계동시간축단，차환열성능유일정제고；단재저충액솔시，용역출현“간소”현상。재저가열공솔시，맥동열관적계동방식위온도돌변식；이재고가열공솔시，기계동방식위온도점변식。차외，통과증발단적온도진탕특정가이학정맥동열관적계동시간。
Pulsating heat pipe(PHP)is a high-efficiency heat transfer device with simple structure and excellent thermal performances. With phenomena such as boiling,condensation and two-phase flow, the mechanism of heat transfer and flow is quite complex and the relevant numerical investigation still needs to improve. A two-dimensional single loop closed-loop pulsating heat pipe(CLPHP)was numerically investigated by CFD software in this research. The start-up characteristics and thermal performances of CLPHP with different length ratios of the evaporation section to the condensation one were studied by volume of fluid(VOF)approach. Considering the effects of surface tension and wall contact angle,the continuum surface force model was adopted. The input power(ranged from 10 W to 40 W) and filling ratio(40%,50%,and 60%)were applied in present numerical investigation. The motions of creation and oscillation of bubbles and vapor/liquid plugs were discussed. The numerical results were compared with experimental data of available literature. The results showed that the start-up time and the thermal resistance of CLPHP could be reduced when the input power was increased on the evaporation section. For the same filling ratio and input power,reducing the length of condensation section within a suitable range was helpful to accelerate the start-up of CLPHP and decrease the thermal resistance,while the “dry-out” occurred easily at low filling ratio. Two types of start-up,the temperature abrupt change at lower input power and the temperature gradual change at higher input power,were observed as well. The temperature oscillation feature at evaporation section can be used to determine the start-up time of CLPHP.
