Presents a set of data for flow and heat transfer of finned-tube bundle under the condition of high air flow velocity. Air flow and heat transfer over a 4 × 4 （ columns × rows） finned-tube heat exchanger w...Presents a set of data for flow and heat transfer of finned-tube bundle under the condition of high air flow velocity. Air flow and heat transfer over a 4 × 4 （ columns × rows） finned-tube heat exchanger with rectangular fins was investigated experimentally in a wind tunnel with constant wall temperatures condition. The air flow velocity based on the minimum flow cross-section area over flow channel ranged from 13.8 to 50. 2 m/s, the heal transfer rate ranged from 21.8 to47. 1 kW, and the air temperatures increase ranged from 10. 9 to 19. 8 ℃. The present results were compared with results calculated from correlations proposed by CSPE. For air flow velocity less than 25 m/s, these two results of heat transfer agreed well with each other, whereas for larger velocity, our test data disagreed with the CSPE correlations. For the friction factor, present data are much higher than the predicted results in the whole range. Finally, correlations for friction factors and heat transfer coefficients are DrODosed based on the experimental results.展开更多
The article presents the influence of winglet vortex generators （WVGs） placed in the core flow area on ther- mal performance enhancement of a tube heat exchanger. The experiment was carried out in a uniform wall hea...The article presents the influence of winglet vortex generators （WVGs） placed in the core flow area on ther- mal performance enhancement of a tube heat exchanger. The experiment was carried out in a uniform wall heat-fluxed tube by varying turbulent airflow for Reynolds number ranging from 5300 to 24000. In the pres- ent work, the WVGs with an attack angle of 30° were inserted into the test tube at four different winglet pitch ratios （Rp = P/D） and three winglet-width or blockage ratios （Ra = e/D）. The experimental results at various Rp and RB values were evaluated and compared with those for smooth tube and tubes with twist- ed tape or wire coil. The measurement reveals that the WVGs enhance considerably the heat transfer and friction loss above the plain tube, wire coil and twisted tape. The Nusselt number and friction factor increase with the increment Of RB and Re but with the decreasing Rp. The average Nusselt numbers for the WVGs with various Ra are in the range of 2.03-2.34 times above the plain tube. The thermal performance for the WVGs is found to be much higher than that for the wire coil and twisted tape and is in a range of 1.35-1.59. Also, a numerical investigation is conducted to study the flow structure and heat transfer enhancement mecha- nisms in the winglet-inserted tube.展开更多
基金Sponsored by the National Natural Science Special Foundation of China(Grant No.50323001)Xi'an Jiaotong University Doctoral Foundation forTeacher.
文摘Presents a set of data for flow and heat transfer of finned-tube bundle under the condition of high air flow velocity. Air flow and heat transfer over a 4 × 4 （ columns × rows） finned-tube heat exchanger with rectangular fins was investigated experimentally in a wind tunnel with constant wall temperatures condition. The air flow velocity based on the minimum flow cross-section area over flow channel ranged from 13.8 to 50. 2 m/s, the heal transfer rate ranged from 21.8 to47. 1 kW, and the air temperatures increase ranged from 10. 9 to 19. 8 ℃. The present results were compared with results calculated from correlations proposed by CSPE. For air flow velocity less than 25 m/s, these two results of heat transfer agreed well with each other, whereas for larger velocity, our test data disagreed with the CSPE correlations. For the friction factor, present data are much higher than the predicted results in the whole range. Finally, correlations for friction factors and heat transfer coefficients are DrODosed based on the experimental results.
基金Supported by the Thailand Research Fund(TRF)(Grant No.PhD/0143/2552)
文摘The article presents the influence of winglet vortex generators （WVGs） placed in the core flow area on ther- mal performance enhancement of a tube heat exchanger. The experiment was carried out in a uniform wall heat-fluxed tube by varying turbulent airflow for Reynolds number ranging from 5300 to 24000. In the pres- ent work, the WVGs with an attack angle of 30° were inserted into the test tube at four different winglet pitch ratios （Rp = P/D） and three winglet-width or blockage ratios （Ra = e/D）. The experimental results at various Rp and RB values were evaluated and compared with those for smooth tube and tubes with twist- ed tape or wire coil. The measurement reveals that the WVGs enhance considerably the heat transfer and friction loss above the plain tube, wire coil and twisted tape. The Nusselt number and friction factor increase with the increment Of RB and Re but with the decreasing Rp. The average Nusselt numbers for the WVGs with various Ra are in the range of 2.03-2.34 times above the plain tube. The thermal performance for the WVGs is found to be much higher than that for the wire coil and twisted tape and is in a range of 1.35-1.59. Also, a numerical investigation is conducted to study the flow structure and heat transfer enhancement mecha- nisms in the winglet-inserted tube.
