本文選題：R245fa + 水平圓管�。� 參考：《天津商業(yè)大學(xué)》2016年碩士論文

【摘要】：科學(xué)技術(shù)的發(fā)展,在給人類帶來益處的同時(shí),也嚴(yán)重污染著環(huán)境,其中臭氧層破壞與溫室效應(yīng)尤為突出。能源的浪費(fèi)與不環(huán)保制冷劑的應(yīng)用造成大量碳氧化物與氟氯烴物質(zhì)的排放。隨著R245fa(五氟丙烷)的性質(zhì)被發(fā)現(xiàn)以來,越來越多的學(xué)者對(duì)其蒸發(fā)及凝結(jié)換熱進(jìn)行研究與關(guān)注。R245fa具有零臭氧消耗潛能值(ODP)和較低的全球變暖潛勢(shì)(GWP),已經(jīng)被提出替代R11,R114和R141b等中高溫制冷劑。并且R245fa在低壓冷水機(jī)組、高溫?zé)岜煤途郯滨ヅ菽袠I(yè)的應(yīng)用具有良好前景,實(shí)驗(yàn)證明該制冷劑不可燃并具有良好的毒理學(xué)特性。本文研究純工質(zhì)R245fa在水平圓管內(nèi)凝結(jié)換熱的實(shí)驗(yàn)特性并對(duì)工況進(jìn)行優(yōu)化分析。本文研究了R245fa在內(nèi)徑為4.38mm水平銅管內(nèi)凝結(jié)換熱過程,實(shí)驗(yàn)工況為:工質(zhì)冷凝溫度30℃-55℃,工質(zhì)質(zhì)量流速92(kg/m2s)-276(kg/m2s),換熱溫差20℃,冷卻水質(zhì)量流速1056(kg/m2s)-1752(kg/m2s)。得出不同質(zhì)量流速下?lián)Q熱系數(shù)隨干度的變化規(guī)律與不同冷凝溫度下?lián)Q熱系數(shù)隨干度的變化規(guī)律。以工質(zhì)進(jìn)口溫度與冷卻水溫度作為邊界條件,質(zhì)量流速、冷凝溫度以及干度作為相關(guān)變量,對(duì)目標(biāo)函數(shù)h尋找區(qū)域最大值,并引入熵分析法對(duì)流動(dòng)性能與傳熱性能進(jìn)行評(píng)價(jià)。得出以下相關(guān)結(jié)論:(1)驗(yàn)證了純工質(zhì)R245fa在單管凝結(jié)換熱過程中換熱系數(shù)由冷凝溫度、工質(zhì)質(zhì)量流速以及干度共同影響。(2)干度在0.7-0.9之間R245fa單管凝結(jié)換熱系數(shù)達(dá)到最大值,并且兩相流型均為環(huán)狀流。(3)通過熵分析法分析得出,在冷凝溫度30℃-45℃,工質(zhì)流量184(kg/m2s)-276(kg/m2s)工況下,其ΔQ/ΔP最大,在此范圍內(nèi),既保持了較高的換熱系數(shù)并有優(yōu)良的流動(dòng)性能,同時(shí)最大換熱系數(shù)出現(xiàn)在冷凝溫度30℃-40℃。R245fa在4.38mm單管凝結(jié)換熱實(shí)驗(yàn)中冷凝溫度對(duì)換熱性能的影響大于對(duì)流動(dòng)性能的影響。(4)R245fa冷凝換熱系數(shù)在干度為0.1-0.7,變化率基本相同,在質(zhì)量流速較大情況下,干度達(dá)到0.7-0.8時(shí),變化率變小。在工質(zhì)質(zhì)量流速較小時(shí),換熱系數(shù)隨干度近似線性增加。(5)實(shí)驗(yàn)數(shù)據(jù)對(duì)比Kim關(guān)聯(lián)式,R245fa冷凝換熱實(shí)驗(yàn)值與Kim關(guān)聯(lián)式誤差在15%以內(nèi)。本文針對(duì)純工質(zhì)R245fa水平圓管內(nèi)凝結(jié)換熱的特性開展研究,研究不同工況下的分段以及整體換熱系數(shù),并分析換熱規(guī)律,這對(duì)R245fa高效冷凝器的設(shè)計(jì)提供了理論依據(jù)并有一定的實(shí)踐指導(dǎo)意義。
[Abstract]:The development of science and technology not only brings benefits to human beings, but also pollutes the environment seriously, especially ozone layer destruction and Greenhouse Effect. The waste of energy and the application of non-environmental refrigerants cause a large amount of carbon oxides and HCFCs emissions. Since the discovery of the properties of R245fa (pentafluoropropane), More and more scholars have studied the evaporation and condensation heat transfer. R245fa has zero ozone depletion potential (ODP) and low global warming potential (GWP) and has been proposed to replace the R11R114 and R141b refrigerants. The application of R245fa in low pressure chiller, high temperature heat pump and polyurethane foam industry has a good prospect. The experiment shows that the refrigerant is not combustible and has good toxicological properties. In this paper, the experimental characteristics of condensation heat transfer of pure working fluid R245fa in a horizontal circular tube are studied and the working conditions are optimized. The condensation heat transfer process of R245fa in 4.38mm horizontal copper tube is studied in this paper. The experimental conditions are as follows: refrigerant condensation temperature 30 鈩，

本文編號(hào)：2114784