Local heat transfer and flow losses in fin-tube heat exchangers with Vortex generators: Comparison of round and flat tubes

1993 ◽  
Vol 7 (2) ◽  
pp. 130 ◽  
Author(s):  
M. Fiebig ◽  
A. Valencia ◽  
N.K. Mitra
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Vortex Generators ◽  
Flow Losses ◽  
Flat Tubes ◽  
Fin Tube

Measurements of Local Heat Transfer Coefficients in Heat Exchangers With Inclined Flat Tubes by Means of the Ammonia Absorption Method

2010 ◽  
Author(s):  
Ulf Ahrend ◽  
Angelika Hartmann ◽  
Juergen Koehler
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Detailed Knowledge ◽  
Absorption Method ◽  
Compact Heat Exchangers ◽  
Flat Tubes ◽  
Ammonia Absorption ◽  
Calibration Approach

For high efficiency compact heat exchangers one needs to gain detailed knowledge of the distribution of the local heat transfer. For a profound assessment of heat enhancing mechanisms like secondary flow structures which are often found at rather small scales it is necessary to perform heat transfer measurements with high spatial resolution. A technique that satisfies this need is the ammonia absorption method (AAM). It is based on the analogy between heat and mass transfer. The here presented paper describes a new calibration approach for the AAM. It is done through the use of a well established heat transfer correlation for the hydrodynamic and thermal entry in parallel plate channels. This calibration approach is applied to heat transfer measurements in compact heat exchangers with inclined flat tubes and plane fins at Redh = 3000. The heat transfer performance is compared to fin-and-tube heat exchangers with round tubes. It is found that the novel devices show consistently higher global Nusselt numbers than comparable round tube heat exchangers.

scholarly journals Heat Transfer Enhancement of Impingement Cooling by Adopting Circular-Ribs or Vortex Generators in the Wall Jet Region of A Round Impingement Jet

2020 ◽  
Vol 5 (3) ◽  
pp. 17 ◽  
Author(s):  
Ken-Ichiro Takeishi ◽  
Robert Krewinkel ◽  
Yutaka Oda ◽  
Yuichi Ichikawa
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Cooling System ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Vortex Generators ◽  
Wall Jet ◽  
Transfer Enhancement ◽  
Impingement Cooling ◽  
Impingement Jet

In the near future, when designing and using Double Wall Airfoils, which will be manufactured by 3D printers, the positional relationship between the impingement cooling nozzle and the heat transfer enhancement ribs on the target plate naturally becomes more accurate. Taking these circumstances into account, an experimental study was conducted to enhance the heat transfer of the wall jet region of a round impingement jet cooling system. This was done by installing circular ribs or vortex generators (VGs) in the impingement cooling wall jet region. The local heat transfer coefficient was measured using the naphthalene sublimation method, which utilizes the analogy between heat and mass transfer. As a result, it was clarified that, within the ranges of geometries and Reynolds numbers at which the experiments were conducted, it is possible to improve the averaged Nusselt number Nu up to 21% for circular ribs and up to 51% for VGs.

Numerical Investigation of Heat Transfer Enhancement on a Small Scale Vortex Generator

2009 ◽  
Author(s):  
Jiansheng Wang ◽  
Zhiqin Yang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Flow Structure ◽  
Rectangular Channel ◽  
Vortex Generator ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Vortex Generators ◽  
Small Scale ◽  
Transfer Enhancement

The heat transfer characteristic and flow structure of fluid in the rectangular channel with different height vortex generators in small scale are investigated with numerical simulation. Meantime, the properties of heat transfer and flow of fluid in the rectangular channel are compared with the channel which located small scale vortex generator. The variation law of local heat transfer and flow structure in channel is obtained. The mechanism of heat transfer enhancement of small scale vortex generators is discussed in detail. It is found that the influence of vortex generator on heat transfer is not in proportion to the size of vortex generator. What is more, turbulent flow structure near the wall, which influences the temperature distribution near the wall, induces the variety of local heat transfer. The fluid movement towards to the wall causes the heat transfer enhanced. On the contrary, the fluid movement away from the wall decreases the local heat transfer.

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