發(fā)布時(shí)間：2018-08-07 22:01

【摘要】：在當(dāng)前嚴(yán)峻的環(huán)境壓力下，制冷劑的替代和新型制冷劑的開(kāi)發(fā)已經(jīng)刻不容緩，而減量延續(xù)技術(shù)可以作為當(dāng)前形式下對(duì)制冷劑替代工質(zhì)的補(bǔ)充與過(guò)渡。通過(guò)統(tǒng)計(jì)和調(diào)查發(fā)現(xiàn)，在相同制冷量前提下，降膜蒸發(fā)所消耗的制冷工質(zhì)要低于滿液式蒸發(fā)器的四分之一。 本文以制冷劑的減量替代作為研究背景，針對(duì)水平管降膜蒸發(fā)的流動(dòng)機(jī)理、傳熱特性、強(qiáng)化方式進(jìn)行了深入的分析和總結(jié)，并對(duì)制冷系統(tǒng)中降膜蒸發(fā)技術(shù)的應(yīng)用以及系統(tǒng)含油對(duì)傳熱系數(shù)的影響等幾個(gè)方面逐一進(jìn)行總結(jié)和說(shuō)明。在不同的運(yùn)行工況下，降膜蒸發(fā)的傳熱特征具有不同的變化規(guī)律，同時(shí)系統(tǒng)所含潤(rùn)滑油會(huì)對(duì)其傳熱特性產(chǎn)生一定影響，發(fā)現(xiàn)潤(rùn)滑油的存在會(huì)明顯降低了換熱系數(shù)。通過(guò)搭建R134a的制冷循環(huán)系統(tǒng)，將水平管降膜蒸發(fā)器應(yīng)用于系統(tǒng)的蒸發(fā)器中，從而進(jìn)行水平管降膜蒸發(fā)的實(shí)驗(yàn)研究，以制冷劑的噴淋量、熱流密度、蒸發(fā)溫度作為研究變量進(jìn)行實(shí)驗(yàn)對(duì)比分析，總結(jié)實(shí)驗(yàn)規(guī)律。 此外，根據(jù)水平管降膜蒸發(fā)的傳熱機(jī)理，改變管外表面結(jié)構(gòu)可以不同程度提高管外對(duì)流換熱系數(shù)，因此在實(shí)驗(yàn)過(guò)程中加入了機(jī)械加工的TJX管、EX管、測(cè)試1管、測(cè)試2管進(jìn)行實(shí)驗(yàn)研究。分析表明，強(qiáng)化管的降膜蒸發(fā)傳熱特性主要與熱流密度、工質(zhì)噴淋量以及管型的不同強(qiáng)化特征有關(guān)，而隨著熱流密度的增加，管外傳熱系數(shù)均出現(xiàn)升高趨勢(shì)，但經(jīng)過(guò)臨界熱流密度后，強(qiáng)化管的傳熱系數(shù)均呈現(xiàn)出不同程度的下降趨勢(shì)，同時(shí)強(qiáng)化表面的傳熱系數(shù)要明顯優(yōu)于光滑管，不同強(qiáng)化管的傳熱系數(shù)也不盡相同，說(shuō)明強(qiáng)化表面結(jié)構(gòu)對(duì)實(shí)驗(yàn)結(jié)果也具有一定影響。 最后，利用光滑管變工質(zhì)噴淋量的實(shí)驗(yàn)數(shù)據(jù)與Ribatski和Thome預(yù)測(cè)的傳熱模型進(jìn)行對(duì)比計(jì)算，并在此基礎(chǔ)上進(jìn)行公式擬合，擬合結(jié)果與實(shí)驗(yàn)數(shù)據(jù)之間的誤差在±20%以內(nèi)，并在此基礎(chǔ)上提出了適用于強(qiáng)化管的強(qiáng)化系數(shù)，，為強(qiáng)化管的傳熱特性研究提供參考。
[Abstract]:Under the severe environmental pressure, the replacement of refrigerant and the development of new refrigerant are urgent, and the technology of deweighting continuation can be used as the supplement and transition of refrigerant substitute in the current situation. Through statistics and investigation, it is found that the refrigerant consumption of falling film evaporation is lower than 1/4 of the full liquid evaporator under the same refrigerating capacity. Based on the research background of refrigerant reduction substitution, the flow mechanism, heat transfer characteristics and strengthening methods of falling film evaporation in horizontal tube are analyzed and summarized in this paper. The application of falling film evaporation technology in refrigeration system and the influence of oil content on heat transfer coefficient are summarized and explained one by one. Under different operating conditions, the heat transfer characteristics of falling film evaporation have different laws, and the lubricating oil contained in the system will have a certain influence on its heat transfer characteristics. It is found that the existence of lubricating oil will obviously reduce the heat transfer coefficient. By setting up the refrigeration cycle system of R134a, the horizontal tube falling film evaporator is applied to the evaporator of the system, and the experimental study of the horizontal tube falling film evaporation is carried out. The evaporation temperature is used as the research variable to carry on the experiment contrast analysis, summarizes the experimental rule. In addition, according to the heat transfer mechanism of falling film evaporation in horizontal tube, the convection heat transfer coefficient can be improved in varying degrees by changing the outer surface structure of the tube. Therefore, the machined TJX tube ex tube is added in the experiment, and the 1 tube is tested. Test 2 tubes for experimental study. The analysis shows that the heat transfer characteristics of falling film evaporation of the enhanced tube are mainly related to the heat flux density, the amount of liquid spray and the different strengthening characteristics of the tube type, but the heat transfer coefficient outside the tube increases with the increase of the heat flux density. However, after the critical heat flux, the heat transfer coefficient of the strengthened tube is decreased in different degrees, and the heat transfer coefficient of the strengthened surface is obviously better than that of the smooth tube, and the heat transfer coefficient of the different strengthened tubes is also different. It shows that the strengthened surface structure also has a certain influence on the experimental results. Finally, the experimental data of variable working fluid spray quantity in smooth tube are compared with the heat transfer model predicted by Ribatski and Thome, and the formula fitting is carried out on the basis of which, the error between the fitting result and the experimental data is less than 鹵20%. On this basis, the enhancement coefficient suitable for the enhanced tube is put forward, which provides a reference for the study of the heat transfer characteristics of the enhanced tube.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TB657;TB611

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