本文選題：變流量 + 復疊式制冷�。� 參考：《天津商業(yè)大學》2017年碩士論文

【摘要】：在制冷系統(tǒng)設(shè)計過程中,考慮到壓縮比和系統(tǒng)運行效率,單級蒸氣壓縮制冷循環(huán)一般用到蒸發(fā)溫度-30℃以上的系統(tǒng),如果壓縮比繼續(xù)升高,單級壓縮制冷系統(tǒng)中壓縮機的相對余隙容積增加,輸氣系數(shù)會急劇下降,造成系統(tǒng)能效比的顯著降低。解決大壓縮比工況下的制冷系統(tǒng)運行問題,研究人員給出了兩套技術(shù)可行的方案,其一是采用雙級壓縮制冷系統(tǒng),其二是采用復疊式制冷系統(tǒng)。上述兩種方案均可有效解決大壓縮比帶來的效率下降問題。從目前的研究情況來看,雙級壓縮制冷系統(tǒng)仍存在其技術(shù)應(yīng)用的缺點,其不能解決單機雙級壓縮制冷系統(tǒng)的容量問題和配組式雙級壓縮機的回油問題。復疊式制冷系統(tǒng)由兩個單機壓縮制冷系統(tǒng)組成,壓縮機獨立運行,有效解決了雙級壓縮制冷系統(tǒng)的兩個問題。本文以冷庫制冷系統(tǒng)用復疊式制冷系統(tǒng)為研究對象,開展級間匹配問題的相關(guān)研究。目前國內(nèi)外制冷系統(tǒng)中,復疊系統(tǒng)大多采用的是定頻壓縮機,高低溫級系統(tǒng)流量比固定,一般根據(jù)工況和制冷劑特性選擇最佳流量比,在實際環(huán)境當中,工況隨時處于變換中,蒸發(fā)溫度根據(jù)不同需要也會發(fā)生改變,甚至在一些特殊情況下制冷劑也會更換,要保持系統(tǒng)最佳運行狀態(tài)就需要改變系統(tǒng)流量比;此外,定頻壓縮制冷系統(tǒng)通常通過開停機來實現(xiàn)溫度恒定,造成壓縮機頻繁啟停,耗電量增加,也會降低制冷系統(tǒng)的壽命,另一方面啟停式制冷也會造成冷庫溫度波動較大,會造成食品干耗嚴重。針對目前冷庫儲存問題上的不足,本課題提出一種變流量復疊式制冷系統(tǒng),高低溫級均采用轉(zhuǎn)子式變頻壓縮機,在相同工況條件下,通過調(diào)節(jié)節(jié)流閥開度和壓縮機頻率,改變高低溫級吸氣壓力,從而找到最佳冷凝蒸發(fā)器的壓力,減小冷凝蒸發(fā)器的換熱溫差,減小冷庫溫度波動。最終達到制冷系統(tǒng)高效運行和降低食品干耗的作用。在理論方面,課題以復疊式制冷系統(tǒng)的優(yōu)化為目標,理論分析R410A單工質(zhì)復疊式制冷循環(huán)在最佳中間溫度下高低溫級流量比和制冷系數(shù)COP的關(guān)系。理論分析結(jié)果表明:當?shù)蜏丶壛髁勘仍龃髸r中間溫度增加,COP先增大后減小,存在一個使COP值最大的最佳流量比;工況溫度對COP的影響會大于流量比變化的影響,當環(huán)境溫度上升或需要降低庫溫時,需要減小低溫級流量,當庫溫需要迅速降溫時,則需要增大低溫級流量,同時還要調(diào)節(jié)高溫級流量以確保復疊式制冷系統(tǒng)處于最佳的高低溫級流量比。在理論分析的基礎(chǔ)上,設(shè)計和搭建了復疊式制冷實驗系統(tǒng),系統(tǒng)由直流變頻轉(zhuǎn)子式R410A壓縮機、風冷式冷凝器、釬焊式板式換熱器,電子膨脹閥組成,采用熱平衡法測試復疊式制冷系統(tǒng)的制冷量。搭建了既能進行單機壓縮制冷循環(huán)又能切換為復疊壓縮制冷循環(huán)的變制冷劑流量制冷系統(tǒng),以滿足不同系統(tǒng)的運行測試。本文通過理論建模和實驗驗證,總結(jié)出系統(tǒng)隨負荷及工況變化時,高、低溫系統(tǒng)制冷劑流量值和冷凝蒸發(fā)器最佳溫度關(guān)系以及不同工況對系統(tǒng)能效的影響。研究表明:蒸發(fā)溫度越高,冷凝溫度越低,復疊換熱溫差越小,壓縮機吸氣過熱度越小,冷凝過冷度越大系統(tǒng)的COP越大。影響系統(tǒng)性能的主要因素是蒸發(fā)溫度和低溫級系統(tǒng)冷凝過冷度。在提供-30℃以下低溫時,R410A復疊式制冷循環(huán)系統(tǒng)比R410A雙級壓縮系統(tǒng)在安全使用,環(huán)境保護和能源節(jié)約方面更加具有優(yōu)勢。通過實驗測量的數(shù)據(jù)驗證了蒸發(fā)溫度與冷凝溫度對復疊制冷系統(tǒng)的影響,R410A的蒸發(fā)過熱度控制在4~6℃之間,有利于系統(tǒng)性能的提高。
[Abstract]:In the process of the design of the refrigeration system, considering the compression ratio and the operating efficiency of the system, the single stage steam compression refrigeration cycle usually uses the system above the evaporation temperature of -30 centigrade. If the compression ratio continues to rise, the relative clearance volume of the compressor in the single stage compression refrigeration system increases and the gas transmission coefficient will drop sharply, resulting in the significant energy efficiency ratio of the system. To solve the problem of refrigeration system operation under the condition of large compression ratio, the researchers have given two sets of technically feasible schemes, one is using a double stage compression refrigeration system, and the other is a cascade refrigeration system. The above two schemes can effectively solve the problem of reducing the efficiency caused by the large compression ratio. The compression refrigeration system still has its shortcomings. It can not solve the problem of the capacity of the single machine and double stage compression refrigeration system and the problem of oil recovery of the matching double stage compressor. The cascade refrigeration system consists of two single compressor refrigeration systems, and the compressor operates independently, and the two problems of the double stage compression refrigeration system are effectively solved. In this paper, a cascade refrigeration system used in cold storage refrigeration system is taken as the research object, and the related research on the problem of interstage matching is carried out. At present, most of the refrigeration systems in the refrigeration system are fixed frequency compressor, the flow ratio of the high and low temperature level system is fixed, and the optimum flow ratio is chosen according to the working condition and the refrigerant characteristics. When the condition is changing at any time, the evaporation temperature will change according to the different needs, and even in some special circumstances, the refrigerant will be replaced. To keep the optimal operating state of the system, the system flow ratio needs to be changed. In addition, the constant frequency compression refrigeration system usually realizes the constant temperature by opening the machine, causing the compressor to start and stop frequently and consume electricity. As the quantity increases, the life of the refrigeration system will be reduced. On the other hand, the starting and stopping refrigeration will also cause the high fluctuation of the temperature of the cold storage. In view of the shortage of the cold storage problem at present, a variable flow cascade refrigeration system is put forward in this paper, and the rotor type frequency conversion compressor is used in the high and low temperature levels, and the conditions are in the same working condition. By adjusting the opening of the throttle valve and the frequency of the compressor to change the high and low temperature suction pressure, the pressure of the best evaporator is found, the heat transfer temperature difference of the evaporator is reduced and the temperature fluctuation of the cold storage is reduced. Finally, the effect of the efficient operation of the refrigeration system and the reduction of the food consumption is achieved. In theory, the subject is a cascade refrigeration system. The relationship between the high and low temperature level flow ratio and the cooling coefficient COP under the optimum intermediate temperature is theoretically analyzed. The theoretical analysis shows that when the rate of low temperature flow increases, the intermediate temperature increases, and the COP increases first and then decreases, and there is a maximum ratio of the maximum flow rate to the COP value; the temperature of the working condition is COP to COP. The influence of the flow ratio will be greater than the change of the flow ratio. When the temperature of the environment rises or needs to be reduced, the low temperature level flow should be reduced. When the temperature needs to be cooled quickly, the low temperature level flow should be increased. At the same time, the high temperature level flow should be adjusted to ensure the optimal flow ratio of the high and low temperature level at the cascade refrigeration system. On the basis of this, a cascade refrigeration experiment system is designed and built. The system consists of a DC variable frequency rotor R410A compressor, a air-cooled condenser, a brazing plate heat exchanger and an electronic expansion valve. The refrigeration capacity of the cascade refrigeration system is tested by the heat balance method. The variable refrigerant flow refrigeration system of the refrigeration cycle is used to meet the operating test of different systems. Through theoretical modeling and experimental verification, the relationship between the flow value of the refrigerant and the optimum temperature of the condensing evaporator and the effect on the system energy efficiency in different conditions are summarized by theoretical modeling and experimental verification. The higher the temperature, the lower the condensing temperature, the smaller the overlap heat transfer temperature, the smaller the superheat of the compressor, the greater the COP of the system. The main factors that affect the performance of the system are the evaporation temperature and the cryogenic degree of cryogenic system condensation. The R410A cascade refrigeration cycle system is compared with the R410A double stage compression system when providing low temperature below the temperature. The effects of the evaporation temperature and the condensation temperature on the cascade refrigeration system are verified by the experimental data. The evaporation overheat of R410A is controlled at 4~6 C, which is beneficial to the improvement of the system performance.
【學位授予單位】：天津商業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TB657

【參考文獻】

相關(guān)期刊論文 前10條

1 劉圣春;陳勇;寧靜紅;;R404A雙級壓縮載冷循環(huán)和復疊式制冷循環(huán)系統(tǒng)對比分析[J];低溫與超導;2016年03期

2 張銘;張曉迪;宋德躍;李添龍;周明杰;;制冷系統(tǒng)氣液分離器有效容積的設(shè)計分析[J];制冷與空調(diào)(四川);2015年04期

3 郭耀君;謝晶;朱世新;王金鋒;;雙級壓縮與復疊式壓縮制冷系統(tǒng)的技術(shù)經(jīng)濟分析[J];化工進展;2015年08期

4 金旭;蔣爽;王樹剛;;雙級壓縮中間壓力與變工況參數(shù)關(guān)系的理論分析[J];流體機械;2014年12期

5 寧靜紅;曾凡星;;回熱器對復疊式制冷系統(tǒng)性能的影響[J];低溫工程;2014年02期

6 梁幸福;楊衛(wèi)波;金甌;周必安;陳世坤;;雙級復疊式蓄冷系統(tǒng)性能的試驗研究[J];流體機械;2014年02期

7 吳敏;;制冷設(shè)備中載冷劑的選擇分析[J];潔凈與空調(diào)技術(shù);2013年03期

8 臧潤清;劉琦;李星;;直接供液與重力供液制冷系統(tǒng)的對比研究[J];低溫與超導;2012年02期

9 金旭;王樹剛;張騰飛;李照義;祖豐;;變工況雙級壓縮中間壓力及其對系統(tǒng)性能的影響[J];化工學報;2012年01期

10 李軍;;復疊制冷系統(tǒng):理論分析篇[J];制冷與空調(diào);2010年05期

相關(guān)碩士學位論文 前2條

1 曾凡星;冷凝蒸發(fā)器對復疊式制冷系統(tǒng)性能影響的研究[D];天津商業(yè)大學;2015年

2 閆t熋，

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