跨临界CO_2制热系统最优排气压力的模拟研究
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摘要
为了更加方便快速地研究跨临界CO_2制热系统的系统性能变化情况,以及找到系统的最优排气压力,在Modelica/Dymola软件平台中进行了跨临界CO_2制热系统的建模和仿真,并提出了相应的最优排气压力关联式。通过对环境温度为-20~30℃、热水出口温度为60~85℃、水入口温度为5~50℃大范围工况下系统性能的仿真,结果表明:在相同的工况下,随着排气压力上升,跨临界CO_2制热系统存在一个最优COP,对应该COP的压力为最优排气压力。最优排气压力随环境温度和热水出口温度的升高而升高,随水入口温度的升高而下降。在此基础上,提出了在热水出口温度为70℃下最优排气压力与环境温度和水入口温度的拟合关联式。该结果可为水入口温度为5~50℃、环境温度为-20~30℃的跨临界CO_2制热系统性能测试提供理论依据。
The modeling and simulation for trans-critical CO_2 heat pump system was built in Modelica/Dymola to seek out the optimum discharge pressure and research the variable of the system performance quickly and conveniently, and correlation of the optimum discharge pressure was given. To simulate a large range of operating conditions of the system performance by environment temperature of-20~30℃, hot water outlet temperature of 60 ~85℃, water inlet temperature of 5 ~50℃, showed that there was an optimum COP in the trans-critical CO_2 heat pump system, and the pressure of the COP should be the optimum discharge pressure. The optimum discharge pressure increased with the increase of the ambient temperature and the temperature of the outlet hot water, and decreased with the increase of the temperature of the inlet water. Then, the correlation of optimum discharge pressure with ambient temperature and inlet water temperature was given under the condition of the outlet temperature of hot water was 70 ℃. The results can provide a theoretical basis for the performance test of the inlet water temperature of 5 ~50℃, and the ambient temperature of-20~30℃ for the trans-critical CO_2 heat pump system.
The modeling and simulation for trans-critical CO_2 heat pump system was built in Modelica/Dymola to seek out the optimum discharge pressure and research the variable of the system performance quickly and conveniently, and correlation of the optimum discharge pressure was given. To simulate a large range of operating conditions of the system performance by environment temperature of-20~30℃, hot water outlet temperature of 60 ~85℃, water inlet temperature of 5 ~50℃, showed that there was an optimum COP in the trans-critical CO_2 heat pump system, and the pressure of the COP should be the optimum discharge pressure. The optimum discharge pressure increased with the increase of the ambient temperature and the temperature of the outlet hot water, and decreased with the increase of the temperature of the inlet water. Then, the correlation of optimum discharge pressure with ambient temperature and inlet water temperature was given under the condition of the outlet temperature of hot water was 70 ℃. The results can provide a theoretical basis for the performance test of the inlet water temperature of 5 ~50℃, and the ambient temperature of-20~30℃ for the trans-critical CO_2 heat pump system.
引文
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[2]Neks覽P,Reksta H.CO2-heat Pump Water Heater:Characteristics,System Design and Experimental Results[J].International Journal of Refrigeration,1998,21(98):172-179.
[3]Wang SG,Tuo HF,Cao F,et al.Experimental Investigation on Air-source Transcritical CO2Heat Pump Water Heater System at a Fixed Water Inlet Temperature[J].International Journal of Refrigeration,2013,36(3):701-716.
[4]Wang SG,He YN,Tuo HF,et al.Effect of Heat Transfer area and Refrigerant Mass Flux in a gas Cooler on Heating Performance of Air-source Transcritical CO2Heat Pump Water Heater System[J].Energy&Buildings,2013,67(4):1-10.
[5]刘业凤,朱洪亮,张峰,等.CO2热泵热水器充注量确定及系统实验研究[J].上海理工大学学报,2015,(1).
[6]Calabrese N,Mastrullo R,Mauro AW,et al.Performance Analysis of a Rooftop,Air-to-air Heat Pump Working with CO2[J].Applied Thermal Engineering,2015,75:1046-1054.
[7]Chamoun M,Rulliere R,Haberschill P,et al.Modelicabased Modeling and Simulation of a Twin Screw Compressor for Heat Pump Applications[J].Applied Thermal Engineering,2013,58:479-489.
[8]Assaf K,Zoughaib A,Clodic D.Modelica-based Modelling and Simulation of Dry-expansion Shell-and-tube Evaporators Working with Alternative Refrigerant Mixtures[J].International Journal of Refrigeration,2011,34:1471-1482.
[9]Pfafferott T,Schmitz G.Modelling and Transient Simulation of CO2-refrigeration Systems with Modelica[J].International Journal of Refrigeration,2004,27(1):42-52.