【摘要】：蒸發(fā)制冷循環(huán)系統(tǒng)作為機(jī)載環(huán)控系統(tǒng)的重要組成部分,對(duì)其冷凝換熱機(jī)理的研究具有十分重要的意義。本文以垂直旋轉(zhuǎn)狀態(tài)下板式換熱器為研究對(duì)象,利用實(shí)驗(yàn)和數(shù)值模擬相結(jié)合的方法,研究了旋轉(zhuǎn)狀態(tài)下板式換熱器的冷凝換熱特性。選取R22作為制冷劑,設(shè)計(jì)單級(jí)壓縮制冷劑循環(huán)系統(tǒng),并搭建旋轉(zhuǎn)換熱實(shí)驗(yàn)臺(tái)。通過改變換熱器的放置角度、R22進(jìn)口流量、冷卻水進(jìn)口流量、轉(zhuǎn)速等條件,對(duì)不同工況下R22的冷凝換熱過程進(jìn)行研究。運(yùn)用數(shù)值模擬方法,分析不同轉(zhuǎn)速下板片流道內(nèi)R22冷凝換熱過程。當(dāng)換熱器處于靜止?fàn)顟B(tài)時(shí),R22進(jìn)口流量從18 m3/h增加到28 m3/h,R22側(cè)換熱系數(shù)、冷卻水側(cè)換熱系數(shù)以及總傳熱系數(shù)都呈增長(zhǎng)趨勢(shì)。為研究重力對(duì)換熱的影響,對(duì)0~180°放置的板式換熱器內(nèi)流體的換熱特性進(jìn)行實(shí)驗(yàn)分析,得到R22側(cè)出口壓力、溫度及換熱系數(shù)受重力影響的變化范圍均在4%以內(nèi),冷卻水側(cè)換熱系數(shù)幾乎不受影響。由于旋轉(zhuǎn)過程中板式換熱器向周圍環(huán)境的散熱方式為強(qiáng)化對(duì)流換熱,旋轉(zhuǎn)導(dǎo)致的熱量損失不可忽略。本文提出了兩種熱損失量計(jì)算公式,由兩種公式計(jì)算得出:熱損失量變化值為0.20~2.29 kW,二者差值的變化范圍為-0.57~2.75 kW,最大偏差約為總換熱量的5%。當(dāng)板式換熱器處于垂直旋轉(zhuǎn)狀態(tài)時(shí),R22和冷卻水的換熱性能會(huì)受到R22進(jìn)口流量、冷卻水進(jìn)口流量以及轉(zhuǎn)速等因素的影響。轉(zhuǎn)速為0~60 rpm,旋轉(zhuǎn)對(duì)R22進(jìn)出口壓差變化范圍為0.2~0.6 MPa。轉(zhuǎn)速的增加對(duì)冷卻水進(jìn)口流量影響較小,轉(zhuǎn)速從0 rpm增加到60 rpm,冷卻水進(jìn)口流量從13 m3/h下降到12.97 m3/h。R22進(jìn)口參數(shù)以及冷卻水進(jìn)口參數(shù)確定的情況下,轉(zhuǎn)速由0 rpm增加到60 rpm過程中,R22側(cè)換熱系數(shù)增加了83.98~129.49 W/(m2·K),增長(zhǎng)率為4.42~8.26%;冷卻水側(cè)換熱系數(shù)增加了433.17~435.73 W/(m2·K),增長(zhǎng)率為5.00~6.99%。根據(jù)R22出口冷凝液的雷諾數(shù)、普朗特?cái)?shù)與努塞爾數(shù)之間的關(guān)系,對(duì)適用于本文實(shí)驗(yàn)條件的R22冷凝換熱實(shí)驗(yàn)關(guān)聯(lián)式進(jìn)行擬合。在靜止?fàn)顟B(tài)下實(shí)驗(yàn)關(guān)聯(lián)式的基礎(chǔ)上,引入旋轉(zhuǎn)數(shù)Ro,擬合垂直旋轉(zhuǎn)狀態(tài)下R22冷凝換熱的實(shí)驗(yàn)關(guān)聯(lián)式,該實(shí)驗(yàn)關(guān)聯(lián)式擬合精度較高,偏差在±5%以內(nèi)。利用CFX模擬計(jì)算了板式換熱器單元流道模型在0~350 rpm的轉(zhuǎn)速范圍內(nèi)的冷凝換熱過程。在低轉(zhuǎn)速(0~60 rpm)數(shù)值模型與實(shí)驗(yàn)結(jié)果驗(yàn)證的基礎(chǔ)上,得出高轉(zhuǎn)速(120~350 rpm)對(duì)R22在板式換熱器通到內(nèi)的冷凝換熱過程產(chǎn)生了更大的影響,尤其是對(duì)R22沿程壓降的影響顯著。
[Abstract]:Evaporative refrigeration system, as an important part of airborne environmental control system, is of great significance to the study of condensation heat transfer mechanism. In this paper, the condensation heat transfer characteristics of plate heat exchangers in rotating state are studied by means of experiment and numerical simulation, taking the plate heat exchanger under vertical rotation as the research object. R22 was selected as refrigerant to design a single stage compression refrigerant circulation system and set up a rotating heat transfer test bed. The condensation heat transfer process of R22 under different working conditions was studied by changing the setting angle of the heat exchanger, the inlet flow rate of R22, the inlet flow rate of cooling water, the rotational speed and so on. The condensation heat transfer process of R22 in plate channel at different speeds was analyzed by numerical simulation. When the heat exchanger is in static state, the inlet flow rate of R22 increases from 18 m3 / h to 28 m3 / h, and the heat transfer coefficient of R22 side, cooling water side and total heat transfer coefficient all show an increasing trend. In order to study the effect of gravity on heat transfer, the heat transfer characteristics of fluid in plate heat exchanger placed at 0 擄were analyzed experimentally. The variation range of outlet pressure, temperature and heat transfer coefficient of R22 side affected by gravity was less than 4%. The heat transfer coefficient on the side of cooling water is almost unaffected. The heat loss caused by rotation can not be ignored because the heat dissipation from plate heat exchanger to the surrounding environment is enhanced convective heat transfer. In this paper, two formulas for calculating the heat loss are presented. The results show that the maximum deviation of the difference between the heat loss and the heat loss is about 5% of the total heat transfer in the range of-0.57? 2.75 kW,. The variation of the difference between the two is 0.20? 2.29?. When the plate heat exchanger is in a vertical rotating state, the heat transfer performance of R22 and cooling water will be affected by the inlet flow rate of R22, the inlet flow rate of cooling water and the rotational speed. The range of pressure difference between R22 and R22 is 0.2 渭 0.6 MPa. when rotating speed is 0 / 60 rpm,. The increase of rotating speed has little effect on the inlet flow rate of cooling water. When the rotating speed increases from 0 rpm to 60 rpm, the inlet flow rate of cooling water decreases from 13 m3 / h to 12.97 m3/h.R22 / h and the inlet parameters of cooling water are determined. In the process of increasing rotation speed from 0 rpm to 60 rpm, the heat transfer coefficient of R22 side increased by 83.98? 129.49 W / (m2 路K),) to 4.42? 8.26%. The heat transfer coefficient of cooling water increased 433.17 / 435.73 W / (m2 路K),) to 5.00 渭 6.99%. According to the relationship between Reynolds number, Plantt number and Nussel number of R22 outlet condensate, the experimental correlation of R22 condensation heat transfer suitable for the experimental conditions in this paper is fitted. Based on the experimental correlation in static state, the rotation number Ro, is introduced to fit the condensation heat transfer of R22 in vertical rotation state. The fitting precision of the experimental correlation is higher and the deviation is less than 鹵5%. The condensation heat transfer process of the flow channel model of plate heat exchanger unit in the speed range of 0 ~ 350 rpm was simulated by CFX. Based on the verification of the numerical model of low speed (0? 60 rpm) and the experimental results, it is concluded that the high speed (120? 350 rpm) has a greater effect on the condensation heat transfer process of R22 in the plate heat exchanger, especially on the pressure drop along the path of R22. The experimental results show that the high speed (120? 350 rpm) has a greater effect on the condensation heat transfer process of R22 in the plate heat exchanger.
【學(xué)位授予單位】：南京航空航天大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2016
【分類號(hào)】：V245.3

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