Tube Transverse Pitch Effect on Heat/Mass Transfer Characteristics of Flat Tube Bank Fin Mounted With Vortex Generators

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
Song Liu ◽  
Liangbi Wang ◽  
Jufang Fan ◽  
Yongheng Zhang ◽  
Yuanxin Dong ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Enhancement ◽  
Heat Mass Transfer ◽  
Isothermal Condition ◽  
Vortex Generators ◽  
Transfer Enhancement ◽  
Tube Bank ◽  
Flat Tube ◽  
Tube Pitch

For one heat exchanger model of three-row flat tube bank fin mounted with vortex generators (VGs), the effect of transversal tube pitch on heat/mass transfer performance was investigated by the experimental method of naphthalene sublimation. For the same arrangement of VGs around the tube, it is found that the larger the transversal tube pitch, the larger the heat transfer enhancement because of less interactions of vortices generated from different VGs. Interaction of vortices decreases the heat transfer enhancement on the fin surfaces with and without VGs for the case with small transversal tube pitch. For isothermal condition, two correlated equations of average Nusselt number and friction factor considering the fin spacing, the attack angle of VG, the height of VG, the ratio of transversal tube pitch, and Reynolds number are reported.

Heat and Mass Transfer Caused by a Laminar Channel Flow Equipped With a Synthetic Jet Array

2010 ◽  
Author(s):  
Zdeneˇk Tra´vni´cˇek ◽  
Petra Dancˇova´ ◽  
Jozef Kordik ◽  
Toma´sˇ Vit ◽  
Miroslav Pavelka
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Channel Flow ◽  
Heat Mass Transfer ◽  
Low Reynolds Number ◽  
Transfer Enhancement ◽  
Laminar Channel Flow ◽  
Low Reynolds

Low-Reynolds-number laminar channel flow is used in various heat/mass transfer applications, such as cooling and mixing. A low Reynolds number implies a low intensity of heat/mass transfer processes, since they rely only on the gradient diffusion. To enhance these processes, an active flow control by means of synthetic (zero-net-mass-flux) jets is proposed. This arrangement can be promising foremost in microscale. The present study is experimental in which a Reynolds number range of 200–500 is investigated. Measurement was performed mainly in air as the working fluid by means of hot-wire anemometry and the naphthalene sublimation technique. PIV experiments in water are also discussed. The experiments were performed in macroscale at the channel cross-section (20×100)mm and (40×200)mm in air and water, respectively. The results show that the low Reynolds number channel flow can be actuated by an array of synthetic jets, operating near the resonance frequency. The control effect of actuation and the heat transfer enhancement was quantified. The stagnation Nusselt number was enhanced by 10–30 times in comparison with the non-actuated channel flow. The results indicate that the present arrangement can be a useful tool for heat transfer enhancement in various applications, e.g., cooling and mixing.

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