Baffled tubes with superimposed oscillatory flow: experimental study of the fluid mixing and heat transfer at low net Reynolds numbers

2020 ◽  
pp. 110324
Author(s):  
J. Muñoz-Cámara ◽  
D. Crespí-Llorens ◽  
J.P. Solano ◽  
P. Vicente
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Oscillatory Flow ◽  
Reynolds Numbers ◽  
Fluid Mixing

Numerical and Experimental Study of Flow and Convective Heat Transfer on a Rotor of a Discoidal Machine with Eccentric Impinging Jet

2019 ◽  
pp. 1-29
Author(s):  
Chadia Haidar ◽  
Rachid Boutarfa ◽  
Mohamed Sennoune ◽  
Souad Harmand
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Steady State ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Air Flow ◽  
Impinging Jet ◽  
Rotating Disk ◽  
Reynolds Numbers ◽  
Air Jet

This work focuses on the numerical and experimental study of convective heat transfer in a rotor of a discoidal the machine with an eccentric impinging jet. Convective heat transfers are determined experimentally in steady state on the surface of a single rotating disk. The experimental technique is based on the use of infrared thermography to access surface temperature measurement, and on the numerical resolution of the energy equation in steady-state, to evaluate local convective coefficients. The results from the numerical simulation are compared with heat transfer experiments for rotational Reynolds numbers between 2.38×105 and 5.44×105 and for the jet's Reynolds numbers ranging from 16.5×103 to 49.6 ×103. A good agreement between the two approaches was obtained in the case of a single rotating disk, which confirms us in the choice of our numerical model. On the other hand, a numerical study of the flow and convective heat transfer in the case of an unconfined rotor-stator system with an eccentric air jet impinging and for a dimensionless spacing G=0.02, was carried out. The results obtained revealed the presence of different heat transfer zones dominated either by rotation only, by the air flow only or by the dynamics of the rotation flow superimposed on that of the air flow. Critical radii on the rotor surface have been identified

An Experimental Study of Forced Heat Convection in Concentric and Eccentric Annular Channels

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
N. Kline ◽  
S. Tavoularis
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Mixed Convection ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Outer Diameter ◽  
Narrow Gap ◽  
Convection Regime ◽  
Annular Channels ◽  
Internal Surfaces

An experimental study of the effect of eccentricity on forced convective heat transfer was conducted for upward flows in vertical, open-ended annular channels with a diameter ratio of 0.61, a length to outer diameter ratio of 18:1, and both internal surfaces heated uniformly. Flows with Reynolds numbers Re = 5450, 10,000, and 27,500 and eccentricities varying from 0 to 0.9 were examined. These results are deemed to be mostly in the forced convection regime with some possible overlap with the mixed convection regime at the lowest Reynolds number considered. This work complements our previous work on natural and mixed convection using the same facility. The effect of eccentricity was not significant at lower eccentricities, but, in highly eccentric cases, the wall temperature in the narrow gap was much higher than in the wide gap and the average heat transfer coefficient was as low as one-fifth of the concentric value. For Re > 10,000, the average Nusselt number for the concentric case was nearly four times higher than the value predicted by the Dittus–Boelter correlation.

An Experimental Investigation of Impingement Heat Transfer in Narrow Space With Full-Height Pin Fins

2016 ◽  
Author(s):  
Yu Rao ◽  
Chaoyi Wan ◽  
Yuyang Liu ◽  
Jiang Qin
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Reynolds Numbers ◽  
Target Plate ◽  
Pin Fin ◽  
Impingement Heat Transfer ◽  
Pin Fins ◽  
Narrow Space ◽  
Pin Fin Arrays ◽  
Full Height

An experimental study has been conducted on multiple-jet impingement heat transfer in a narrow space with full-height pin fins under maximum cross flow scheme. Transient liquid crystal thermography method has been used to obtain the detailed impingement heat transfer distribution for the Reynolds numbers from 15,000 to 30,000. The experimental study shows that the spanwisely-averaged Nusselt number ratio Nu/(Re0.8 Pr1/3) is almost independent of Reynolds numbers, and the full-height pin-fin arrays can slightly improve the average Nusselt number on the endwall of the target plate by about 5.0%, and increase the pressure loss by up to about 17.9%. It is also found that heat transfer uniformity is also improved on the endwall of the target plate with pin fin arrays.

scholarly journals EXPERIMENTAL STUDY OF HEAT TRANSFER OF A SINGLE-ROW BUNDLE OF FINNED TUBES IN MIXED CONVECTION OF AIR

2017 ◽  
Vol 60 (4) ◽  
pp. 352-366 ◽  
Author(s):  
A. B. Sukhotskii ◽  
G. S. Sidorik
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Reynolds Number ◽  
Free Convection ◽  
Mixed Convection ◽  
Forced Convection ◽  
Reynolds Numbers ◽  
Convection Flow ◽  
Single Bundle ◽  
Single Row

The technique and results of experimental study of heat transfer of a single bundle consisting of bimetallic tubes with helically knurled edges, in natural and mixed convection of air are presented. Mixed convection, i.e. a heat transfer, when the contribution of free and forced convection is comparable, was created with the help of the exhaust shaft mounted above the heat exchanger bundle and forced air movement was created by the difference in density of the air in the shaft and the environment. The experimental dependence of the heat transfer of finned single row of bundles in the selected ranges of Grashof and Reynolds numbers has been determined. It is demonstrated that heat transfer in the mixed convection is 2.5−3 times higher than in free one and the growth rate of heat transfer with increasing Reynolds number is more than in the forced convection. Different forms of representation of results of experiments were analyzed and it was determined that the Nusselt number has a single power dependence on the Reynolds number at any height of the exhaust shafts. A linear dependence of the Reynolds number on the square root of the Grashof number was determined as well as the proportionality factors for different shaft heights. It is noted that the characteristics of the motion of air particles in the bundle in free convection is identical to the motion of particles in forced convection at small Reynolds numbers, i.e. a free convection flow smoothly flows into a forced convection one without the typical failures or surges if additional driving forces arise.

Experimental Study on the Heat Transfer Enhancement by the Combination of Transverse Groove Tube and Twisted Tape Inserts

2016 ◽  
Author(s):  
Miao Gui ◽  
Qincheng Bi ◽  
Yajun Guo
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Enhancement ◽  
Reynolds Numbers ◽  
Geometrical Parameters ◽  
Twisted Tape ◽  
Transfer Enhancement ◽  
Tube Heat Exchanger ◽  
Twisted Tapes ◽  
Performance Of Heat Transfer

Both transverse groove tube and twisted tape, as an alternative to traditional smooth tube in shell and tube heat exchanger, are useful techniques for the enhancement of heat transfer. In this paper, an experimental study for the combination of transverse groove tube and twisted tapes was carried out. The flow and heat transfer characteristics of heat transfer oil flowing in the transverse groove tube (TGT) fitted with continuous twisted tape (CT), discontinuous twisted tape (DT) and perforated twisted tape (PT) was investigated with the Reynolds numbers ranging from 600 to 8000, respectively. The effect of the geometrical parameters of twisted tapes on the heat transfer performance was considered. Finally, experimental correlations for friction factor and Nusselt number were developed. The comprehensive performance of heat transfer of the transverse groove tube fitted with twisted tapes was analyzed using traditional method and Entropy Generation Analysis, and the same conclusions can be obtained that the modified heat transfer enhancement tubes, TGT-CT, DT and PT, all show better effects of heat transfer enhancement than ST and ST-CT.

21802 Experimental Study on Boiling Heat Transfer of Subcooled Flow under Oscillatory Flow and Vibration Conditions

2007 ◽  
Vol 2007.13 (0) ◽  
pp. 107-108
Author(s):  
Norihumi HIGONO ◽  
Hiroyasu OHTAKE ◽  
Yasuo KOIZUMI ◽  
Yohei KUSAMA ◽  
Shuhei WATANABE
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Boiling Heat Transfer ◽  
Oscillatory Flow ◽  
Subcooled Flow
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