【摘要】：隨著全球的ODS的全面淘汰,臭氧層保護(hù)工作取得階段性的成果,全球的環(huán)境保護(hù)形勢發(fā)生了深刻的變化,溫室氣體排放、全球變暖取代臭氧層破壞上升為現(xiàn)階段世界范圍內(nèi)環(huán)境保護(hù)的首要任務(wù)與課題。為了應(yīng)對全球氣候變暖給人類經(jīng)濟(jì)和社會發(fā)展帶來的不利影響,當(dāng)前國際社會限制和削減HFCs使用和消費的呼聲日益高漲。在全球淘汰含氟溫室氣體的大環(huán)境下,二氧化碳作為傳統(tǒng)制冷劑的替代冷媒,憑借其獨特優(yōu)勢在制冷領(lǐng)域得到了越來越多的應(yīng)用,在多種復(fù)雜的場合發(fā)揮著重要的作用,其應(yīng)用系統(tǒng)型式多樣,主要包括:復(fù)疊系統(tǒng)、載冷系統(tǒng)和跨臨界系統(tǒng)。其中跨臨界制冷系統(tǒng)以CO_2作單一制冷劑,該系統(tǒng)的應(yīng)用在降低制冷系統(tǒng)對環(huán)境的不利影響方面具有獨特的優(yōu)勢,其能效表現(xiàn)的好壞直接影響其發(fā)展和推廣應(yīng)用。本文對基本的增壓系統(tǒng)、帶并行壓縮的增壓系統(tǒng)和帶機械過冷的增壓系統(tǒng)三種跨臨界二氧化碳系統(tǒng)進(jìn)行理論分析。通過了解國外相關(guān)課題的研究現(xiàn)狀以及熱力循環(huán)理論分析得出以下結(jié)論:(1)基本增壓系統(tǒng)隨氣體冷卻器出口溫度的不同,存在最優(yōu)排氣壓,使力得系統(tǒng)COP最大,且出口溫度越低,最優(yōu)排氣壓力越低;隨中間壓力的增加,基本增壓系統(tǒng)制冷量、COP呈逐漸降低的變化趨勢,但變化趨勢較為平緩;隨蒸發(fā)壓力降低,基本增壓系統(tǒng)的COP逐漸減小,且氣體冷卻器出口溫度越低,系統(tǒng)COP下降越明顯。(2)帶并行壓縮的增壓系統(tǒng)中氣體冷卻器出口溫度高于臨界溫度時,系統(tǒng)存在最優(yōu)排氣壓力和中間壓力使得系統(tǒng)COP最大。氣冷器出口溫度為32℃時,最優(yōu)排氣壓力和中間壓力分別為80bar和35bar;氣冷器出口溫度為37℃時,最優(yōu)排氣壓力和中間壓力分別為90bar和40bar。(3)機械過冷系統(tǒng)能提升增壓系統(tǒng)的COP:過冷度分別為2.5℃、5℃、7℃、10℃時,系統(tǒng)最大COP分別提升4.8%、9.3%、12.4%、14.5%。(4)通過對三種系統(tǒng)的分析對比發(fā)現(xiàn)帶有并行壓縮的系統(tǒng)和機械過冷系統(tǒng)相比基本的增壓系統(tǒng),在相同工況下COP均有所提高,而且機械過冷系統(tǒng)的COP要高于帶并行壓縮的系統(tǒng)。在計算的工況范圍內(nèi),帶并行壓縮的增壓系統(tǒng)最大COP比基本的增壓系統(tǒng)最大COP高7.8%;機械過冷度為5℃的系統(tǒng)的最大COP比基本的增壓系統(tǒng)最大COP高30.7%;機械過冷度為10℃的系統(tǒng)的最大COP比基本的增壓系統(tǒng)的最大COP高38.2%。而且相比基本的增壓系統(tǒng)帶并行壓縮的增壓系統(tǒng)和機械過冷系統(tǒng)最優(yōu)氣體冷卻器壓力要低。(5)通過理論分析和選型計算,搭建了增壓系統(tǒng)實驗臺。
[Abstract]:With the total elimination of ODS in the world, the ozone layer protection has made a phased achievement, the global environmental protection situation has undergone profound changes, greenhouse gas emissions, Global warming, instead of ozone layer destruction, is the most important task of environmental protection all over the world. In order to cope with the adverse effects of global warming on human economic and social development, the international community is increasingly clamoring to limit and reduce the use and consumption of HFCs. In the global environment of eliminating fluorine-containing greenhouse gases, carbon dioxide, as the alternative refrigerant of the traditional refrigerant, has been applied more and more in the field of refrigeration with its unique advantages, and plays an important role in many complex situations. Its application system is diverse, including: overlay system, carrier cooling system and transcritical system. CO_2 is used as a single refrigerant in the transcritical refrigeration system. The application of the system has a unique advantage in reducing the adverse impact of the refrigeration system on the environment. The performance of its energy efficiency directly affects its development and application. In this paper, three kinds of transcritical carbon dioxide systems, namely, the basic supercharging system, the supercharging system with parallel compression and the supercharging system with mechanical undercooling, are theoretically analyzed. The following conclusions are drawn by understanding the current research situation of foreign related subjects and the theoretical analysis of thermodynamic cycle: (1) the optimal exhaust pressure exists in the basic pressurized system with different outlet temperature of the gas cooler, which makes the COP of the system maximum. The lower the outlet temperature, the lower the optimal exhaust pressure. With the increase of the intermediate pressure, the refrigerating capacity of the basic supercharging system, COP decreased gradually, but the change trend was relatively gentle. With the decrease of evaporation pressure, the COP of the basic booster system decreases gradually, and the lower the outlet temperature of the gas cooler, the more obvious the decrease of the system COP. (2) when the outlet temperature of the gas cooler in the supercharged system with parallel compression is higher than the critical temperature, The optimal exhaust pressure and intermediate pressure make the system COP maximum. When the outlet temperature of the air cooler is 32 鈩，

本文編號：2294934