为评估多温区制冷系统性能,探究其在农产品冷库贮藏中应用的可行性,设计了低碳环保型多温区复叠制冷系统。该研究以CO_(2)双温区与三温区复叠制冷系统为研究对象,通过设置压力调节阀(简称节流系统)和增压压缩机(简称增压系统)解决不同...为评估多温区制冷系统性能,探究其在农产品冷库贮藏中应用的可行性,设计了低碳环保型多温区复叠制冷系统。该研究以CO_(2)双温区与三温区复叠制冷系统为研究对象,通过设置压力调节阀(简称节流系统)和增压压缩机(简称增压系统)解决不同并联温区间的压差问题,建立两类制冷系统的热力学模型,分析了双温区和三温区复叠制冷系统运行参数对其性能系数(coefficient of performance,COP)与?效率的影响,并在参考工况下对双温区和三温区复叠制冷系统的两种运行模式进行了对比。结果表明:增压系统性能系数与?效率均高于节流系统,参考工况下双温区与三温区增压系统相对于节流系统性能系数分别提升30.4%和23.4%;双温区与三温区复叠制冷系统各部件中,冷凝器具有最大的?损,采用压力调节阀给节流系统带来了更大的能量损失;同工况下,该研究所设计的双温区和三温区增压系统性能系数是CO_(2)/R134a单温区复叠系统的1.5和2.3倍;经济性对比发现,双温区与三温区复叠制冷循环增压系统年度总成本比节流系统分别节省6554和8156美元。因此,多温区增压系统在热力性能与经济性上均优于节流系统,研究结果可为CO_(2)多温区复叠制冷系统的开发与应用提供理论基础。展开更多
Falling film configurations play an important role in characterizing the heat transfer due to changes in hydrodynamic behavior.The purpose of this study is to establish a novel film distributor to investigate the hydr...Falling film configurations play an important role in characterizing the heat transfer due to changes in hydrodynamic behavior.The purpose of this study is to establish a novel film distributor to investigate the hydrodynamic behavior of the falling film on the vertical tube.The falling film thickness and flow patterns on the vertical tube were analyzed at a feed water temperature of 30℃ for film Re ranged from 53 to 4544 and the heat fluxes ranged from 1.33 to 49.45 kW/m^(2).The correlation between the average falling film thickness and the film Re was fitted;the maximum deviation between the experimental data and the predicted values was 7.58%.Additionally,the film thickness changed sharply when the heat flux increased to a certain value.With the further increase of the heat flux,dry patches appeared on the surface of the experimental tube.There was Marangoni effect on vertical tube and the falling film thickness and flow patterns were significantly affected by heating.The interval value of the critical heat flux with film Re was obtained.Compared with the porous film distributor reported in the literature,the critical heat flux of the new film distributor increased by 3.72%-56.95%.展开更多
文摘为评估多温区制冷系统性能,探究其在农产品冷库贮藏中应用的可行性,设计了低碳环保型多温区复叠制冷系统。该研究以CO_(2)双温区与三温区复叠制冷系统为研究对象,通过设置压力调节阀(简称节流系统)和增压压缩机(简称增压系统)解决不同并联温区间的压差问题,建立两类制冷系统的热力学模型,分析了双温区和三温区复叠制冷系统运行参数对其性能系数(coefficient of performance,COP)与?效率的影响,并在参考工况下对双温区和三温区复叠制冷系统的两种运行模式进行了对比。结果表明:增压系统性能系数与?效率均高于节流系统,参考工况下双温区与三温区增压系统相对于节流系统性能系数分别提升30.4%和23.4%;双温区与三温区复叠制冷系统各部件中,冷凝器具有最大的?损,采用压力调节阀给节流系统带来了更大的能量损失;同工况下,该研究所设计的双温区和三温区增压系统性能系数是CO_(2)/R134a单温区复叠系统的1.5和2.3倍;经济性对比发现,双温区与三温区复叠制冷循环增压系统年度总成本比节流系统分别节省6554和8156美元。因此,多温区增压系统在热力性能与经济性上均优于节流系统,研究结果可为CO_(2)多温区复叠制冷系统的开发与应用提供理论基础。
基金This work was supported by National Key Research and Development Program of China(No.2020YFF0303902)the National Natural Science Foundation of China(No.51876216 and No.21978308)Special Fund for Central Guiding Local Science and Technology Development(ZYYD2022B11,2022ZY0048).
文摘Falling film configurations play an important role in characterizing the heat transfer due to changes in hydrodynamic behavior.The purpose of this study is to establish a novel film distributor to investigate the hydrodynamic behavior of the falling film on the vertical tube.The falling film thickness and flow patterns on the vertical tube were analyzed at a feed water temperature of 30℃ for film Re ranged from 53 to 4544 and the heat fluxes ranged from 1.33 to 49.45 kW/m^(2).The correlation between the average falling film thickness and the film Re was fitted;the maximum deviation between the experimental data and the predicted values was 7.58%.Additionally,the film thickness changed sharply when the heat flux increased to a certain value.With the further increase of the heat flux,dry patches appeared on the surface of the experimental tube.There was Marangoni effect on vertical tube and the falling film thickness and flow patterns were significantly affected by heating.The interval value of the critical heat flux with film Re was obtained.Compared with the porous film distributor reported in the literature,the critical heat flux of the new film distributor increased by 3.72%-56.95%.
