波纹角对波纹竖板冷凝换热特性的影响
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摘要
为了提高板式换热器的换热性能,探究换热板片的波纹角对波纹竖板冷凝侧换热特性的影响,优化其结构参数,采用建模计算的方法定量分析了波纹角对板片换热面积、液膜下落时间、流体努塞尔数、摩擦系数等参数的影响,并用可视化实验观察了不同波纹角下液膜流动路径的特点。分析结果表明,波纹角的变化对板片换热面积影响很小,可以忽略。波纹角越小,液膜下落时间越短,排液速度越快,液膜厚度越小,越有利于冷凝传热。波纹角越大,冷凝液的流动路径越接近波纹状流型,扰动越剧烈,增大了流体的雷诺数和努塞尔数,且雷诺数值越大,努塞尔数对波纹角的变化越敏感。流体与波纹板的摩擦系数也会随着波纹角的增大而增大,蒸气冷凝时产生的摩擦压降也越大。
In order to improve the heat transfer performance of plate heat exchanger and optimize its structural parameters, the influence of chevron angle on condensation heat transfer characteristics of corrugated vertical plates is investigated. The effects of chevron angle on heat transfer area, falling time of liquid film, Nusselt number of fluid and friction coefficient of plate heat exchanger were analized quantitatively. The liquid film flow paths on corrugated vertical plates with different chevron angles were observed by visual experiment. The results indicated that the change of chevron angle has little effect on the heat transfer area of corrugated vertical plates. With the decrease of chevron angle, for the liquid film, the falling time decrease, the discharging speed improve, the thickness reduce, and the condensation heat transfer is enhanced. With the increase of chevron angle, the flow path of condensate is closer to ripple flow pattern, which intensifies the disturbance of condensate and increases the Reynolds number and Nusselt number of flow. The larger the Reynolds number is, the more sensitive the Nusselt number is to the change of chevron angle. The friction coefficient between fluid and corrugated plate will also increase with the increase of chevron angle, and the friction pressure drop of vapor will also increase.
In order to improve the heat transfer performance of plate heat exchanger and optimize its structural parameters, the influence of chevron angle on condensation heat transfer characteristics of corrugated vertical plates is investigated. The effects of chevron angle on heat transfer area, falling time of liquid film, Nusselt number of fluid and friction coefficient of plate heat exchanger were analized quantitatively. The liquid film flow paths on corrugated vertical plates with different chevron angles were observed by visual experiment. The results indicated that the change of chevron angle has little effect on the heat transfer area of corrugated vertical plates. With the decrease of chevron angle, for the liquid film, the falling time decrease, the discharging speed improve, the thickness reduce, and the condensation heat transfer is enhanced. With the increase of chevron angle, the flow path of condensate is closer to ripple flow pattern, which intensifies the disturbance of condensate and increases the Reynolds number and Nusselt number of flow. The larger the Reynolds number is, the more sensitive the Nusselt number is to the change of chevron angle. The friction coefficient between fluid and corrugated plate will also increase with the increase of chevron angle, and the friction pressure drop of vapor will also increase.
引文
1 赵林林,丁玉栋,朱恂,等.不同壁面特性下液膜铺展性能数值模拟[J].原子能科学技术,2017,51(5):865-871.Zhao Linlin,Ding Yudong,Zhu Xun,et al.Numerical simulation of liquid film spreading performance with different wall features [J].Atomic Energy Science and Technology,2017,51(5):865-871.
2 李相鹏,陈冰冰,高增梁.规整填料表面液膜流动特性的数值模拟[J].化工学报,2013,64(6):1925-1933.Li Xiangpeng,Chen Bingbing,Gao Zengliang. Numerical Simulation on hydraulic characteristics of liquid film on structured packing surface[J].CIESC Journal,2013,64(6):1925-1933.
3 王华金,谢宛妮,孙永利,等.新型正交波纹板流体力学性能CFD模拟[J].化工学报,2015,66(12):4743-4750.Wang Huajin, Xie Wanni,Sun Yongli.CFD simulation of hydrodynamics of orthogonal wave type tray [J].CIESC Journal,2015,66(12):4743-4750.
4 Hoffmann A,Ausner I,Repke J,et al.Fluid dynamics in multiphase distillation processes in packed towers[J].Computers & Chemical Engineering, 2005,29(6),1433-1437.
5 Hoffmann A,Ausner I,Repke J,et al.Detailed investigation of multiphase (gas-liquid and gas-liquid-liquid) flow behaviour on inclined plates [J].Chemical Engineering Research and Design,2006,84(2),147-154.
6 谷芳,刘春江,袁希钢,等.倾斜波纹板上液膜流动的CFD研究[J].化工学报,2005,56(3):462-467.Gu Fang,Liu Chunjiang,Yuan Xigang,et al.CFD simulation of liquid film flow on inclined wavy plates surface [J].CIESC Journal,2005,56(3):462-467.
7 孙树瑜,王树楹,余国琮.金属波纹板规整填料塔中液体有效流速[J].化工学报,1997,48 (6):736-739.Sun Shuyu,Wang Shuying,Yu Guocong,et al.Liquid effective velocity in a column containing corrugated metal sheet packing [J].CIESC Journal,1997,48 (6):736-739.
8 刘梅,宋朝匣,吴正人,等.非平整倾斜表面上流动液膜的影响因素分析[J].化工进展,2015,34(1):75-79.Liu Mei,Song Zhaoxia,Wu Zhengren,et al.Analysis on flow film over uneven and inclined wall [J].Chemaical Industry And Engineering ProgresS,2015,34(1):75-79.
9 Longo G A,Mancin,Righetti,et al.HFC404A condensation inside a small brazed plate heat exchanger: Comparison with the low GWP substitutes propane and propylene[J].Journal of Refrigeration,2017,81:41-49.
10 Sarraf,Launay,TAdrist.Analysis of enhanced vapor desuperheating during condensation inside a plate heat exchanger[J].International Journal of Thermal Sciences,2016,106:96-108.
11 Mancin S,Del C D, Rossetto L.Condensation of superheated vapour of R410A and R407C inside plate heat exchangers: experimental results and simulation procedure[J].Journal of Refrigeration,2012,35(7):2003-2013.
12 Longo G A,Mancin,Righetti,et al.A new model for refrigeration condensation inside a brazed plate heat exchanger (BPHE)[C].Proceedings of the 15th International Heat Transfer Conference,2014.
13 Jokar A,Hosni M H,Eckels S J.Dimensional analysis on the evaporation and condensation of refrigerant R-134a in minichannel plate heat exchangers[J].Applied Thermal Engineering,2006,26(17/18):2287-2300.
14 Grabenstein V,Kabelac S.Experimental and theoretical analysis of the local condensation heat transfer in a plate heat exchanger[C].6th European Thermal Sciences Conference,2012.
15 Han D H,Lee K J,Kim Y H.The characteristics of condensation in brazed plate heat exchangers with different chevron angles[J].Applied Thermal Engineering,2013,23(10):1209-1225.
2 李相鹏,陈冰冰,高增梁.规整填料表面液膜流动特性的数值模拟[J].化工学报,2013,64(6):1925-1933.Li Xiangpeng,Chen Bingbing,Gao Zengliang. Numerical Simulation on hydraulic characteristics of liquid film on structured packing surface[J].CIESC Journal,2013,64(6):1925-1933.
3 王华金,谢宛妮,孙永利,等.新型正交波纹板流体力学性能CFD模拟[J].化工学报,2015,66(12):4743-4750.Wang Huajin, Xie Wanni,Sun Yongli.CFD simulation of hydrodynamics of orthogonal wave type tray [J].CIESC Journal,2015,66(12):4743-4750.
4 Hoffmann A,Ausner I,Repke J,et al.Fluid dynamics in multiphase distillation processes in packed towers[J].Computers & Chemical Engineering, 2005,29(6),1433-1437.
5 Hoffmann A,Ausner I,Repke J,et al.Detailed investigation of multiphase (gas-liquid and gas-liquid-liquid) flow behaviour on inclined plates [J].Chemical Engineering Research and Design,2006,84(2),147-154.
6 谷芳,刘春江,袁希钢,等.倾斜波纹板上液膜流动的CFD研究[J].化工学报,2005,56(3):462-467.Gu Fang,Liu Chunjiang,Yuan Xigang,et al.CFD simulation of liquid film flow on inclined wavy plates surface [J].CIESC Journal,2005,56(3):462-467.
7 孙树瑜,王树楹,余国琮.金属波纹板规整填料塔中液体有效流速[J].化工学报,1997,48 (6):736-739.Sun Shuyu,Wang Shuying,Yu Guocong,et al.Liquid effective velocity in a column containing corrugated metal sheet packing [J].CIESC Journal,1997,48 (6):736-739.
8 刘梅,宋朝匣,吴正人,等.非平整倾斜表面上流动液膜的影响因素分析[J].化工进展,2015,34(1):75-79.Liu Mei,Song Zhaoxia,Wu Zhengren,et al.Analysis on flow film over uneven and inclined wall [J].Chemaical Industry And Engineering ProgresS,2015,34(1):75-79.
9 Longo G A,Mancin,Righetti,et al.HFC404A condensation inside a small brazed plate heat exchanger: Comparison with the low GWP substitutes propane and propylene[J].Journal of Refrigeration,2017,81:41-49.
10 Sarraf,Launay,TAdrist.Analysis of enhanced vapor desuperheating during condensation inside a plate heat exchanger[J].International Journal of Thermal Sciences,2016,106:96-108.
11 Mancin S,Del C D, Rossetto L.Condensation of superheated vapour of R410A and R407C inside plate heat exchangers: experimental results and simulation procedure[J].Journal of Refrigeration,2012,35(7):2003-2013.
12 Longo G A,Mancin,Righetti,et al.A new model for refrigeration condensation inside a brazed plate heat exchanger (BPHE)[C].Proceedings of the 15th International Heat Transfer Conference,2014.
13 Jokar A,Hosni M H,Eckels S J.Dimensional analysis on the evaporation and condensation of refrigerant R-134a in minichannel plate heat exchangers[J].Applied Thermal Engineering,2006,26(17/18):2287-2300.
14 Grabenstein V,Kabelac S.Experimental and theoretical analysis of the local condensation heat transfer in a plate heat exchanger[C].6th European Thermal Sciences Conference,2012.
15 Han D H,Lee K J,Kim Y H.The characteristics of condensation in brazed plate heat exchangers with different chevron angles[J].Applied Thermal Engineering,2013,23(10):1209-1225.