Convective Heat Transfer in a Rotor–Stator System Airgap With a Centered Natural Suction of Fluid

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
Julien Pellé ◽  
Souad Harmand
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Rotating Disk ◽  
Air Gap ◽  
Nusselt Numbers ◽  
Spacing Interval ◽  
Single Disk ◽  
Rotor Surface

The present work relates to an experimental study of the local convective heat transfer over the rotor surface in the air-gap of a discoidal rotor–stator system. This configuration is of interest namely, in electrical machines or tubomachinery. Following precedent studies obtained for a single rotating disk or a closed (but unshrouded) rotor–stator system, an air suction comes through the stator and enters the air-gap in this particular work. Determination of Nusselt numbers is based on the use of infrared thermography. The influence of the suction is discussed for an interdisk dimensionless spacing interval, G ranging from 0.01 to 0.16 and for a rotational Reynolds number, Re between 30,000 and 5,16,000. Results shows that the suction could locally provide better cooling than in the closed rotor–stator and in the single disk configurations, even if the main influence is a decrease in the convective heat transfer.

Convective Heat Transfer in a Rotor Stator System Air Gap With Multiple Suctions of Fluid Through the Stator

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
Julien Pellé ◽  
Souad Harmand
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Nusselt Numbers ◽  
Spacing Interval ◽  
Rotor Surface ◽  
Thermal Balance Equation ◽  
Full Disk

The experimental work presented in this paper relates to the local convective heat transfer on the rotor surface in the airgap of a discoidal rotor stator system. The stator used in these experiments is a multiperforated disk in which an air suction due to the rotation of the rotor comes through and enters the airgap. A thermal balance equation was used to identify the local convective heat transfer coefficient, with temperatures as boundary conditions, which have been measured by infrared thermography. The influence of the suctions is discussed for an interdisk dimensionless spacing interval G ranging from 0.01 to 0.16 and for Re between 129,000 and 516,000. Results are compared with precedent studies in which we obtained Nusselt numbers with a closed rotor stator system in which stator is a full disk and a rotor stator system with one hole at the stator center. It is shown that multiperforated stator can or cannot improve the rotor cooling, depending on G and Re.

APPLICATION OF ADSORPTION METHOD FOR DETERMINATION OF LOCAL CONVECTIVE HEAT TRANSFER RATES

1974 ◽  
Author(s):  
S. Koncar-Djurdjevic ◽  
M. Mitrovic ◽  
S. Cvijovic ◽  
G. Popovic ◽  
Dimitrije Voronjec
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Adsorption Method ◽  
Transfer Rates

Simulation of electrically conductive liquid convection in a spherical layer when heat is applied to the inner sphere

2019 ◽  
Author(s):  
С.В. Соловьев
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Magnetic Induction ◽  
Spherical Layer ◽  
Gravity Vector ◽  
Joule Dissipation ◽  
Conductive Liquid ◽  
Nusselt Numbers

Представлены результаты численного моделирования конвективного теплообмена электропроводящей жидкости между концентрическими сферами при подводе тепла к внутренней сфере. Исследовано влияние числа Грасгофа и джоулевой диссипации на структуру течения жидкости, поля температуры, магнитной индукции и распределение локальных чисел Нуссельта. Получено уравнение подобия теплообмена, когда ускорение свободного падения направлено к центру сферического слоя. The Boussinesq approximation is used for modelling a large class of problems of convective heat transfer in spherical concentric layers in which the gravity vector is directed vertically downwards. But for problems of geophysics and astrophysics there is a fundamental difference, the gravity vector is directed along the radius to the center of the spherical layer. Therefore, the study of convective heat transfer in spherical layers, when the vector of gravitational acceleration is directed along the radius to the center of the spherical layer, is of independent interest. In this paper, the influence of the Grashof number, the Joule dissipation heat on the fluid flow structure, temperature field, magnetic induction, and the distribution of Nusselt numbers when heat is applied from below are studied. To solve the problem, the finite element method is used. In a dimensionless formulation, the problem is solved taking into account both the heat of the Joule dissipation, magnetic, inertial, viscous and lifting forces in a spherical coordinate system and the symmetry in longitude. The stationary fields of temperature, stream functions, vortex strength, radial and meridional components of magnetic induction and the distribution of local Nusselt numbers of electro conductive liquid in a concentric spherical layer for different Grashof numbers with and without accounting for the heat of Joule dissipation are obtained when heat is applied to the inner sphere. Two critical values of the Grashof number are numerically determined. The equation of heat exchange similarity is obtained, when the acceleration of gravity is directed to the center of the spherical layer. The mathematical model and the presented results may be useful for the study of convective heat exchange of electrically conducting fluid in space technologies and in the geophysical and astrophysical problems.

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

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