本文選題：二氧化碳　切入點(diǎn)：雙級(jí)壓縮　出處：《西安建筑科技大學(xué)》2013年碩士論文

【摘要】：在民用建筑中實(shí)現(xiàn)空調(diào)系統(tǒng)同時(shí)供冷、制熱和供應(yīng)生活熱水是當(dāng)今社會(huì)的普遍需求，熱回收式熱泵空調(diào)的出現(xiàn)不僅滿足了這種需求，而且也適應(yīng)了社會(huì)對(duì)于節(jié)能和環(huán)保的要求。但目前熱回收系統(tǒng)普遍存在著冷熱量互相制約、功能單一、效率較低等問題。本文提出了一種串聯(lián)式CO_2雙級(jí)壓縮制冷熱泵系統(tǒng)，該系統(tǒng)不僅能夠回收利用冷凝熱，而且可以根據(jù)用戶的需要同時(shí)制冷和生產(chǎn)生活熱水，解決了現(xiàn)有熱回收式系統(tǒng)所存在的冷熱量互相制約問題。 本文以系統(tǒng)性能系數(shù)為目標(biāo)分別計(jì)算分析了熱水換熱器出口CO_2溫度、蒸發(fā)溫度、壓縮機(jī)排氣壓力，中間壓力、過熱度、過冷度以及流量系數(shù)對(duì)串聯(lián)式二氧化碳雙級(jí)壓縮制冷熱泵系統(tǒng)循環(huán)性能的影響。研究表明：在全熱回收工況下，蒸發(fā)溫度、熱水換熱器出口CO_2溫度對(duì)循環(huán)的COP有顯著的影響，而蒸發(fā)器出口過熱度、氣液分離器中制冷劑過冷度對(duì)COP的影響較��；熱水換熱器出口CO_2溫度決定了隨著高壓壓縮機(jī)排氣壓力的升高，COP是否會(huì)出現(xiàn)峰值；也決定了中間排氣壓力是否存在最優(yōu)值。 當(dāng)熱水換熱器出口CO_2溫度降到特征溫度以下，按用戶需要改變系統(tǒng)補(bǔ)氣量時(shí)，系統(tǒng)循環(huán)會(huì)出現(xiàn)特征高壓排氣壓力點(diǎn)，當(dāng)系統(tǒng)高壓排氣壓力低于特征排氣壓力時(shí)，提高補(bǔ)氣量，系統(tǒng)的循環(huán)性能大于全熱回收工況；當(dāng)高壓排氣壓力大于特征排氣壓力時(shí)，提高補(bǔ)氣量，，系統(tǒng)的循環(huán)性能將小于全熱回收工況。類似地，當(dāng)熱水換熱器出口CO_2溫度低于特征溫度時(shí)，同樣也存在特征中間壓力點(diǎn)。特征中間壓力受蒸發(fā)溫度、熱水換熱器出口CO_2溫度以及高壓排氣壓力的影響。系統(tǒng)循環(huán)參數(shù)的選擇需綜合考慮以上因素，才能保證系統(tǒng)高效運(yùn)行。
[Abstract]:The realization of air conditioning system in civil buildings at the same time to supply cooling, heating and supply of domestic hot water is a common demand in today's society, the emergence of heat recovery heat pump air conditioning not only to meet this demand, It also meets the requirements of the society for energy saving and environmental protection. But at present, the heat recovery system generally has the problems of mutual restriction of cold and heat, single function, low efficiency, etc. In this paper, a series CO_2 two-stage compression refrigeration heat pump system is proposed. The system can not only recover and utilize condensate heat, but also refrigerate and produce domestic hot water simultaneously according to the needs of users, thus solving the problem of mutual restriction of cold and heat in the existing heat recovery system. In this paper, the outlet CO_2 temperature, evaporation temperature, compressor exhaust pressure, intermediate pressure, superheat degree of the hot water heat exchanger are calculated and analyzed respectively with the system performance coefficient as the target. The effects of undercooling degree and flow coefficient on the cycle performance of a series CO2 two-stage compression refrigeration heat pump system are studied. The results show that the evaporation temperature and the CO_2 temperature at the outlet of the hot water exchanger have significant effects on the circulating COP under the condition of total heat recovery. However, the superheat at the outlet of evaporator and the refrigerant undercooling in the gas-liquid separator have little effect on COP, and the CO_2 temperature at the outlet of the hot water exchanger determines whether the cop will peak with the increase of the exhaust pressure of the high pressure compressor. It also determines whether there is an optimum value for the intermediate exhaust pressure. When the CO_2 temperature at the outlet of the hot water exchanger drops below the characteristic temperature and changes the system air supply according to the user's requirement, the system cycle will appear the characteristic high pressure exhaust pressure point, when the system high pressure exhaust pressure is lower than the characteristic exhaust pressure, the supply gas quantity will be increased. The cycle performance of the system is greater than that of total heat recovery. When the high pressure exhaust pressure is greater than the characteristic exhaust pressure, the circulation performance of the system will be smaller than that of the total heat recovery. When the outlet CO_2 temperature of the hot water exchanger is lower than the characteristic temperature, there are also the characteristic intermediate pressure points. The influence of CO_2 temperature and high pressure exhaust pressure on the outlet of hot water heat exchanger. The selection of system cycle parameters needs to consider the above factors comprehensively in order to ensure the efficient operation of the system.
【學(xué)位授予單位】：西安建筑科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2013
【分類號(hào)】：TU83

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