Experimental investigations have been performed to determine the detailed module-by-module pressure drop and heat transfer coefficient of turbulent flow inside a circular finned tube. The tubes are provided with longi...Experimental investigations have been performed to determine the detailed module-by-module pressure drop and heat transfer coefficient of turbulent flow inside a circular finned tube. The tubes are provided with longitudinal fins continuous or interrupted in the stream wise direction by arranging them both in a staggered and in-line manner. Experiments are carried out for two different fin geometries, with two numbers of fins (N = 6 and 12). All tested finned tubes have 16 modules each with length equal to the tube diameter (L = D = 30 mm). The thermal boundary condition considered here, is a uniform heat flux. The module-by-module heat transfer coefficient is found to vary only in the first modules, and then attained a constant thermally periodic fully developed value after eight to twelve modules. The results also showed that in the periodic hydrodynamic fully developed region, the value of the pressure drop along the tube with continuous fins is greater than that of the in-line arrangement, and lower than that of the staggered arrangement. Furthermore, the results showed that in the periodic fully developed region, the tube with continuous fins produces a greater value of the heat transfer coefficients than that the tube with interrupted fins, especially through a high range of Reynolds number (5 × 104 > Re > 2 × 104). The tube with Staggered arrangement of fins produces a greater value of the heat transfer coefficient than the tube with continuous fins and the in-line arrangement finned tube at low Reynolds number (Re < 1.2 × 104).). It was found that the fins efficiency is greater than 90 percent;in the worst case (maximum Reynolds number with continuous fins tube).展开更多
To study the congestion of interrupted flow on urban roads, a comprehensive evaluation method is proposed. First, based on the results of correlation analysis between different parameters of interrupted flow, the traf...To study the congestion of interrupted flow on urban roads, a comprehensive evaluation method is proposed. First, based on the results of correlation analysis between different parameters of interrupted flow, the traffic parameters of interrupted traffic flow are divided into two categories： the basic parameters and the operation parameters. Polynomial regression is used to formulize the nonlinear relationships between the basic parameters and the operation parameters. Then, the congestion model incorporating both operational and volume characteristics of traffic flow is proposed. The inputs of the model are the basic parameters, while the output is a dimensionless index value between 0 and 1. Finally, the proposed methods are compared with existing evaluation measures of congestion. Results show that the proposed indices can capture the variation of both the basic parameters and the operation parameters, which is more balanced compared with the existing evaluation measures.展开更多
Background:The long-term outcomes of patients treated with a Kawashima procedure and keeping the antegrade pulmonary blood flow(AnPBF)in single-ventricle(SV)and interrupted inferior vena cava(IVC)heart disease is stil...Background:The long-term outcomes of patients treated with a Kawashima procedure and keeping the antegrade pulmonary blood flow(AnPBF)in single-ventricle(SV)and interrupted inferior vena cava(IVC)heart disease is still uncertain as yet.Methods:We investigated 18 patients who underwent the Kawashima procedure with SV physiology and an interrupted IVC between January 2009 and June 2018,perioperative,operative and postoperative characteristics were recorded.Results:A total of 18 patients underwent the Kawashima procedure at a median age of 2.7 years(range 0.5–24.7 years),of which 12(66.7%)were male and 6(33.3%)were female.The mean saturation was 76.2±8.5%in preoperative period and 94.2±2.2%in postoperative period.All patients had kept AnPBF.The median duration of mechanical ventilation was 12 h(range 2.5–22.5 h)and the median duration of pleural drainage was 5 days(range 2–27 days).The median hospital stay was 9 days(range 6–70 days).There was no operative death and no mortality was seen in early postoperative period.Follow-up was 100%completed,with an average follow-up period of 6.1±2.7 years(range 1–11 years).4 patients died during the follow-up.The overall 5 and 10 years’survival rates estimated by Kaplan-Meier method were 88%and 68%,respectively.Although there were no significant differences in the duration of postoperative follow-up between the death group and the survival group(p>0.05),the major systemic ventricular end-diastolic diameter(SVEDD)(p=0.018)and the degree of AVVR(p=0.001)showed significant difference between the two groups.The diameters of main pulmonary artery showed significant growth in both the death group(p=0.015)and the survival group(p=0.012)over time.SVEDD had no significant increase in the survival group(p=0.665)but was significantly larger in the death group(p=0.014).Multivariable risk factors of late mortality in patients treated with Kawashima procedure were follow-up AVVR(p=0.044;HR:3.124;95%CI:1.030–9.473)and SVEDD(p=0.031;HR:9.766;95%CI:1.226–77.8).14 patients(100展开更多
文摘Experimental investigations have been performed to determine the detailed module-by-module pressure drop and heat transfer coefficient of turbulent flow inside a circular finned tube. The tubes are provided with longitudinal fins continuous or interrupted in the stream wise direction by arranging them both in a staggered and in-line manner. Experiments are carried out for two different fin geometries, with two numbers of fins (N = 6 and 12). All tested finned tubes have 16 modules each with length equal to the tube diameter (L = D = 30 mm). The thermal boundary condition considered here, is a uniform heat flux. The module-by-module heat transfer coefficient is found to vary only in the first modules, and then attained a constant thermally periodic fully developed value after eight to twelve modules. The results also showed that in the periodic hydrodynamic fully developed region, the value of the pressure drop along the tube with continuous fins is greater than that of the in-line arrangement, and lower than that of the staggered arrangement. Furthermore, the results showed that in the periodic fully developed region, the tube with continuous fins produces a greater value of the heat transfer coefficients than that the tube with interrupted fins, especially through a high range of Reynolds number (5 × 104 > Re > 2 × 104). The tube with Staggered arrangement of fins produces a greater value of the heat transfer coefficient than the tube with continuous fins and the in-line arrangement finned tube at low Reynolds number (Re < 1.2 × 104).). It was found that the fins efficiency is greater than 90 percent;in the worst case (maximum Reynolds number with continuous fins tube).
基金The National High Technology Research and Development Program of China(863 Program)(No.2011AA110302-01)
文摘To study the congestion of interrupted flow on urban roads, a comprehensive evaluation method is proposed. First, based on the results of correlation analysis between different parameters of interrupted flow, the traffic parameters of interrupted traffic flow are divided into two categories： the basic parameters and the operation parameters. Polynomial regression is used to formulize the nonlinear relationships between the basic parameters and the operation parameters. Then, the congestion model incorporating both operational and volume characteristics of traffic flow is proposed. The inputs of the model are the basic parameters, while the output is a dimensionless index value between 0 and 1. Finally, the proposed methods are compared with existing evaluation measures of congestion. Results show that the proposed indices can capture the variation of both the basic parameters and the operation parameters, which is more balanced compared with the existing evaluation measures.
基金This study was supported by the NationalKey R&D Program of China[2017YFC1308100].
文摘Background:The long-term outcomes of patients treated with a Kawashima procedure and keeping the antegrade pulmonary blood flow(AnPBF)in single-ventricle(SV)and interrupted inferior vena cava(IVC)heart disease is still uncertain as yet.Methods:We investigated 18 patients who underwent the Kawashima procedure with SV physiology and an interrupted IVC between January 2009 and June 2018,perioperative,operative and postoperative characteristics were recorded.Results:A total of 18 patients underwent the Kawashima procedure at a median age of 2.7 years(range 0.5–24.7 years),of which 12(66.7%)were male and 6(33.3%)were female.The mean saturation was 76.2±8.5%in preoperative period and 94.2±2.2%in postoperative period.All patients had kept AnPBF.The median duration of mechanical ventilation was 12 h(range 2.5–22.5 h)and the median duration of pleural drainage was 5 days(range 2–27 days).The median hospital stay was 9 days(range 6–70 days).There was no operative death and no mortality was seen in early postoperative period.Follow-up was 100%completed,with an average follow-up period of 6.1±2.7 years(range 1–11 years).4 patients died during the follow-up.The overall 5 and 10 years’survival rates estimated by Kaplan-Meier method were 88%and 68%,respectively.Although there were no significant differences in the duration of postoperative follow-up between the death group and the survival group(p>0.05),the major systemic ventricular end-diastolic diameter(SVEDD)(p=0.018)and the degree of AVVR(p=0.001)showed significant difference between the two groups.The diameters of main pulmonary artery showed significant growth in both the death group(p=0.015)and the survival group(p=0.012)over time.SVEDD had no significant increase in the survival group(p=0.665)but was significantly larger in the death group(p=0.014).Multivariable risk factors of late mortality in patients treated with Kawashima procedure were follow-up AVVR(p=0.044;HR:3.124;95%CI:1.030–9.473)and SVEDD(p=0.031;HR:9.766;95%CI:1.226–77.8).14 patients(100
