Determination of the Thermal Constants of the Heat Flow Equations of Electrical Machines

1969 ◽  
Vol 184 (9) ◽  
pp. 84-92 ◽  
Author(s):  
T. J. Roberts
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flow ◽  
Sheet Steel ◽  
Electrical Machine ◽  
Transfer Coefficients ◽  
Flow Equations ◽  
Heat Transfer Coefficients ◽  
Thermal Constants

One of the major problems in obtaining accurate predictions of temperature distribution within an electrical machine is the values of the thermal constants used in the solution of the heat flow equations. A line source method is developed for anisotropic materials and is used to determine the thermal conductivity of sheet steel laminations. Results are given for three typical sheet steels showing the effect of varying core clamping pressure. The thermal conductivity of high-voltage insulation is obtained from tests on production machine coils and values are given for typical insulation systems. A model test is described for the evaluation of the heat transfer coefficients from the cooling surfaces of the radial air ducts, based on the assumption of a uniform distribution of air across the duct entrance. The heat transfer coefficients from the other cooled surfaces within the machine are determined from full-scale temperature measurements on production machines. The limitation of this latter method of determination of heat transfer coefficient is evaluated.

scholarly journals Nanofluid properties for forced convection heat transfer :a review

2015 ◽  
Vol 3 (1) ◽  
pp. 145 ◽  
Author(s):  
Mohsen Darabi ◽  
Reza Naeimi ◽  
Hamid Mohammadiun ◽  
Saeed Mortazavi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Base Fluid ◽  
Convection Heat Transfer ◽  
Theoretical Models ◽  
Transfer Coefficients ◽  
Practical Applications ◽  
Heat Transfer Coefficients ◽  
The Stability

<p>The thermal conductivity of nanofluids depends on various parameters, such as concentration, temperature, particle size, pH, shape, material, and possibly on the manufacturing process of the nanoparticles. Data on the viscosity of nanofluids, available in the literature, are very limited. Theoretical models for the determination of the thermal conductivity and viscosity of nanofluids have been pursued. Experiments with nanofluids indicate that they higher heat transfer coefficients than the base fluid. No significant increase in a pressure drop is reported with nanofluids, compared with values with the base fluid. However, the stability of nanofluids with regard to settlement/agglomeration, especially at higher concentrations, is still a problem for practical applications.</p>

scholarly journals Heat Transfer in Rotating Serpentine Passages With Trips Normal to the Flow

1992 ◽  
Vol 114 (4) ◽  
pp. 847-857 ◽  
Author(s):  
J. H. Wagner ◽  
B. V. Johnson ◽  
R. A. Graziani ◽  
F. C. Yeh
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Large Scale ◽  
Flow Direction ◽  
Operating Conditions ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Flow Equations ◽  
Turbine Blade Cooling ◽  
Heat Transfer Coefficients

Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large-scale, multipass, heat transfer model with both radially inward and outward flow. Trip strips on the leading and trailing surfaces of the radial coolant passages were used to produce the rough walls. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature ratio, Rossby number, Reynolds number, and radius-to-passage hydraulic diameter ratio. The first three of these four parameters were varied over ranges that are typical of advanced gas turbine engine operating conditions. Results were correlated and compared to previous results from stationary and rotating similar models with trip strips. The heat transfer coefficients on surfaces, where the heat transfer increased with rotation and buoyancy, varied by as much as a factor of four. Maximum values of the heat transfer coefficients with high rotation were only slightly above the highest levels obtained with the smooth wall model. The heat transfer coefficients on surfaces where the heat transfer decreased with rotation, varied by as much as a factor of three due to rotation and buoyancy. It was concluded that both Coriolis and buoyancy effects must be considered in turbine blade cooling designs with trip strips and that the effects of rotation were markedly different depending upon the flow direction.

Determination of heat transfer coefficients for complex spray cooling arrangements

2016 ◽  
Vol 11 (3/4) ◽  
pp. 229 ◽  
Author(s):  
Sebastian Herbst ◽  
Kim Florian Steinke ◽  
Hans Jürgen Maier ◽  
Andrzej Milenin ◽  
Florian Nürnberger
Keyword(s):  
Heat Transfer ◽  
Spray Cooling ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Diffusion Layer Theory for Turbulent Vapor Condensation With Noncondensable Gases

1993 ◽  
Vol 115 (4) ◽  
pp. 998-1003 ◽  
Author(s):  
P. F. Peterson ◽  
V. E. Schrock ◽  
T. Kageyama
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mass Transfer ◽  
Vapor Condensation ◽  
Sensible Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Noncondensable Gas ◽  
Noncondensable Gases ◽  
Vertical Tubes

In turbulent condensation with noncondensable gas, a thin noncondensable layer accumulates and generates a diffusional resistance to condensation and sensible heat transfer. By expressing the driving potential for mass transfer as a difference in saturation temperatures and using appropriate thermodynamic relationships, here an effective “condensation” thermal conductivity is derived. With this formulation, experimental results for vertical tubes and plates demonstrate that condensation obeys the heat and mass transfer analogy, when condensation and sensible heat transfer are considered simultaneously. The sum of the condensation and sensible heat transfer coefficients becomes infinite at small gas concentrations, and approaches the sensible heat transfer coefficient at large concentrations. The “condensation” thermal conductivity is easily applied to engineering analysis, and the theory further demonstrates that condensation on large vertical surfaces is independent of the surface height.

Sign in / Sign up

Export Citation Format

Share Document