scholarly journals Heat Transfer in a Rotating Cavity With a Peripheral Inflow and Outflow of Cooling Air

1997 ◽  
Author(s):  
Iraj Mirzaee ◽  
Xiaopeng Gan ◽  
Michael Wilson ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Radial Component ◽  
Tangential Component ◽  
Speed Increase ◽  
Nusselt Numbers ◽  
Rotating Cavity ◽  
Outflow Region ◽  
Experimental Values ◽  
Cooling Air ◽  
Made In

This paper describes a combined computational and experimental study of the heat transfer in a rotating cavity with a peripheral inflow and outflow of cooling air for a range of rotational speeds and flow rates. Measurements are made in a purpose-built rig, with one of the two rotating discs heated, and computations are conducted using an axisymmetric elliptic solver incorporating the Launder-Sharma low-Reynolds-number k-ε turbulence model. Measured values of the tangential component of velocity, Vϕ, exhibit Rankine-vortex behaviour which is not accurately modelled by the computations. Both computed and measured values of the radial component of velocity, Vr, confirm the recirculating nature of the flow. In the outflow region, agreement between computed and measured values of Vr is mainly good, but in the inflow region the computations exhibit a “peaky” distribution which is not shown by the measurements. The measured and computed Nusselt numbers show that Nu increases as the magnitudes of the flow rate and the rotational speed increase. The computed Nusselt numbers (allowing for the effects of conduction through and radiation to the unhealed disc) reproduce the measured trends but tend to underestimate the experimental values at the larger radii.

Heat Transfer in a Rotating Cavity With a Peripheral Inflow and Outflow of Cooling Air

1998 ◽  
Vol 120 (4) ◽  
pp. 818-823 ◽  
Author(s):  
I. Mirzaee ◽  
X. Gan ◽  
M. Wilson ◽  
J. M. Owen
Keyword(s):  
Heat Transfer ◽  
Radial Component ◽  
Tangential Component ◽  
Speed Increase ◽  
Nusselt Numbers ◽  
Rotating Cavity ◽  
Outflow Region ◽  
Experimental Values ◽  
Cooling Air ◽  
Made In

This paper describes a combined computational and experimental study of the heat transfer in a rotating cavity with a peripheral inflow and outflow of cooling air for a range of rotational speeds and flow rates. Measurements are made in a purpose-built rig, with one of the two rotating discs heated, and computations are conducted using an axisymmetric elliptic solver incorporating the Launder-Sharma low-Reynolds-number k–ε turbulence model. Measured values of the tangential component of velocity, Vπ, exhibit Rankine-vortex behaviour which is not accurately modelled by the computations. Both computed and measured values of the radial component of velocity, Vr, confirm the recirculating nature of the flow. In the outflow region, agreement between computed and measured values of Vr is mainly good, but in the inflow region the computations exhibit a “peaky” distribution which is not shown by the measurements. The measured and computed Nusselt numbers show that Nu increases as the magnitudes of the flow rate and the rotational speed increase. The computed Nusselt numbers (allowing for the effects of conduction through and radiation to the unheated disk) reproduce the measured trends but tend to underestimate the experimental values at the larger radii.

Rotating Cavity With Axial Throughflow of Cooling Air: Heat Transfer

1992 ◽  
Vol 114 (1) ◽  
pp. 229-236 ◽  
Author(s):  
P. R. Farthing ◽  
C. A. Long ◽  
J. M. Owen ◽  
J. R. Pincombe
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Simple Correlation ◽  
Nusselt Numbers ◽  
Rotating Cavity ◽  
Wide Range ◽  
Effects Of Radiation ◽  
Increasing Temperature ◽  
Cooling Air ◽  
Made In

Heat transfer measurements were made in two rotating cavity rigs, in which cooling air passed axially through the center of the disks, for a wide range of flow rates, rotational speeds, and temperature distributions. For the case of a symmetrically heated cavity (in which both disks have the same temperature distribution), it was found that the distributions of local Nusselt numbers were similar for both disks and the effects of radiation were negligible. For an asymmetrically heated cavity (in which one disk is hotter than the other), the Nusselt numbers on the hotter disk were similar to those in the symmetrically heated cavity but greater in magnitude than those on the colder disks; for this case, radiation from the hot to the cold disk was the same magnitude as the convective heat transfer. Although the two rigs had different gap ratios (G = 0.138 and 0.267), and one rig contained a central drive shaft, there was little difference between the measured Nusselt numbers. For the case of “increasing temperature distribution” (where the temperature of the disks increases radially), the local Nusselt numbers increase radially; for a “decreasing temperature distribution,” the Nusselt numbers decrease radially and become negative at the outer radii. For the increasing temperature case, a simple correlation was obtained between the local Nusselt numbers and the local Grashof numbers and the axial Reynolds number.

Flow and Heat Transfer in a Rotating Cavity With a Stationary Stepped Casing

2000 ◽  
Author(s):  
Abdul A. Jaafar ◽  
Fariborz Motallebi ◽  
Michael Wilson ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Laser Doppler Anemometry ◽  
Tangential Component ◽  
Rotating Disc ◽  
Turbine Engine ◽  
Flow And Heat Transfer ◽  
Rotating Cavity ◽  
Rotating Discs ◽  
Cooling Air

In this paper, new experimental results are presented for the flow in a co-rotating disc system with a rotating inner cylinder and a stationary stepped outer casing. The configuration is based on a turbine disc-cooling system used in a gas turbine engine. One of the rotating discs can be heated, and cooling air is introduced through discrete holes angled inward at the periphery of this disc. The cooling air leaves the system through axial clearances between the discs and the outer casing. Some features of computed flows, and both measured and computed heat transfer, were reported previously for this system. New velocity measurements, obtained using Laser Doppler Anemometry, are compared with results from axisymmetric, steady, turbulent flow computations obtained using a low-Reynolds-number k-ε turbulence model. The measurements and computations show that the tangential component of velocity is invariant with axial location in much of the cavity, and the data suggest that Rankine (combined free and forced) vortex flow occurs. The computations fail to reproduce this behaviour, and there are differences between measured and computed details of secondary flow recirculations. Possible reasons for these discrepancies, and their importance for the prediction of associated heat transfer, are discussed.

scholarly journals Heat Transfer in a Rotating Cavity With a Stationary Stepped Casing

1998 ◽  
Author(s):  
Iraj Mirzaee ◽  
Paul Quinn ◽  
Michael Wilson ◽  
J. Michael Owen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Parameter ◽  
Rotating Disc ◽  
Flow Rates ◽  
Nusselt Numbers ◽  
Rotating Cavity ◽  
Wide Range ◽  
Heated Disc ◽  
Cooling Air

In the system considered here, corotating “turbine” discs are cooled by air supplied at the periphery of the system. The system comprises two corotating discs, connected by a rotating cylindrical hub and shrouded by a stepped, stationary cylindrical outer casing. Cooling air enters the system through holes in the periphery of one disc, and leaves through the clearances between the outer casing and the discs. The paper describes a combined computational and experimental study of the heat transfer in the above system. In the experiments, one rotating disc is heated, the hub and outer casing are insulated, and the other disc is quasi-adiabatic. Thermocouples and fluxmeters attached to the heated disc enable the Nusselt numbers, Nu, to be determined for a wide range of rotational speeds and coolant flow rates. Computations are carried out using an axisymmetric elliptic solver incorporating the Launder-Sharma low-Reynolds-number k-ε turbulence model. The flow structure is shown to be complex and depends strongly on the so-called turbulent flow parameter, λT, which incorporates both rotational speed and flow rate. For a given value of λT, the computations show that Nu increases as Reϕ, the rotational Reynolds number, increases. Despite the complexity of the flow, the agreement between the computed and measured Nusselt numbers is reasonably good.

Heat Transfer in a Rotating Cavity With a Stationary Stepped Casing

1999 ◽  
Vol 121 (2) ◽  
pp. 281-287 ◽  
Author(s):  
I. Mirzaee ◽  
P. Quinn ◽  
M. Wilson ◽  
J. M. Owen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Parameter ◽  
Rotating Disk ◽  
Nusselt Numbers ◽  
Rotating Cavity ◽  
Wide Range ◽  
Heated Disc ◽  
Turbine Disks ◽  
Cooling Air

In the system considered here, corotating “turbine” disks are cooled by air supplied at the periphery of the system. The system comprises two corotating disks, connected by a rotating cylindrical hub and shrouded by a stepped, stationary cylindrical outer casing. Cooling air enters the system through holes in the periphery of one disk, and leaves through the clearances between the outer casing and the disks. The paper describes a combined computational and experimental study of the heat transfer in the above-described system. In the experiments, one rotating disk is heated, the hub and outer casing are insulated, and the other disk is quasi-adiabatic. Thermocouples and fluxmeters attached to the heated disc enable the Nusselt numbers, Nu, to be determined for a wide range of rotational speeds and coolant flow rates. Computations are carried out using an axisymmetric elliptic solver incorporating the Launder–Sharma low-Reynolds-number k–ε turbulence model. The flow structure is shown to be complex and depends strongly on the so-called turbulent flow parameter, λT, which incorporates both rotational speed and flow rate. For a given value λT, the computations show that Nu increases as Reφ, the rotational Reynolds number, increases. Despite the complexity of the flow, the agreement between the computed and measured Nusselt numbers is reasonably good.

Heat Transfer in a “Cover-Plate” Preswirl Rotating-Disk System

1999 ◽  
Vol 121 (2) ◽  
pp. 249-256 ◽  
Author(s):  
R. Pilbrow ◽  
H. Karabay ◽  
M. Wilson ◽  
J. M. Owen
Keyword(s):  
Heat Transfer ◽  
Rotating Disk ◽  
Reynolds Numbers ◽  
Turbine Disk ◽  
Cover Plate ◽  
Blade Cooling ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Cooling Air ◽  
Plate System

In most gas turbines, blade-cooling air is supplied from stationary preswirl nozzles that swirl the air in the direction of rotation of the turbine disk. In the “cover-plate” system, the preswirl nozzles are located radially inward of the blade-cooling holes in the disk, and the swirling airflows radially outward in the cavity between the disk and a cover-plate attached to it. In this combined computational and experimental paper, an axisymmetric elliptic solver, incorporating the Launder–Sharma and the Morse low-Reynolds-number k–ε turbulence models, is used to compute the flow and heat transfer. The computed Nusselt numbers for the heated “turbine disk” are compared with measured values obtained from a rotating-disk rig. Comparisons are presented, for a wide range of coolant flow rates, for rotational Reynolds numbers in the range 0.5 X 106 to 1.5 X 106, and for 0.9 < βp < 3.1, where βp is the preswirl ratio (or ratio of the tangential component of velocity of the cooling air at inlet to the system to that of the disk). Agreement between the computed and measured Nusselt numbers is reasonably good, particularly at the larger Reynolds numbers. A simplified numerical simulation is also conducted to show the effect of the swirl ratio and the other flow parameters on the flow and heat transfer in the cover-plate system.

Convection from an isolated heated horizontal cylinder rotating about its axis

1953 ◽  
Vol 217 (1131) ◽  
pp. 555-562 ◽  
Keyword(s):  
Heat Transfer ◽  
Free Convection ◽  
Critical Speed ◽  
Rotating Cylinder ◽  
Critical Value ◽  
Horizontal Cylinder ◽  
Constant Heat ◽  
Rotating Surface ◽  
Experimental Values ◽  
Made In

The heat transfer by convection from an isolated heated horizontal cylinder rotating about its axis in air was measured for varying rotational speeds, cylinder temperatures and diameters; some measurements were also made in air at 4 atm pressure. The results show that the heat transfer is nearly constant at the free convection value for rotational speeds from zero to a critical value, and then increases in proportion to the 2/3 power of the rotational speed. The explanation of the constant heat transfer below the critical speed is shown to be that the heat transfer on the ascending side of the cylinder is higher, and that on the descending side lower, than the free convection at zero speed. The critical speed occurs when the circumferential speed of the rotating surface becomes approximately equal to the upward free convection velocity at the side of the heated stationary cylinder. Theory predicts this to occur at approximately R √( P/G ) = 0.9, which agrees well with the experimental values. Photographs of the flow also confirm these conclusions. Above the critical speed the irregular turbulent motion near the cylinder is shown to be similar to that which occurs in free convection above a heated horizontal surface facing upwards. Starting with known values for the free convection in the latter case, the heat transfer from the rotating cylinder above the critical speed was deduced and agrees well with the experimental results.

Measurement and Prediction of Heat Transfer From Compressor Discs With a Radial Inflow of Cooling Air

1991 ◽  
Author(s):  
P. R. Farthing ◽  
C. A. Long ◽  
R. H. Rogers
Keyword(s):  
Heat Transfer ◽  
Source Region ◽  
Thermal Conditions ◽  
Integral Model ◽  
Transfer Rates ◽  
Nusselt Numbers ◽  
Maximum Value ◽  
Cooling Air ◽  
Experimental Rig ◽  
Acceptable Agreement

An integral theory is used to model the flow, and predict heat transfer rates, for corotating compressor discs with a superposed radial inflow of air. Measurements of heat transfer are also made, both in an experimental rig and in an engine. The flow structure comprises source and sink regions, Ekman-type layers and an inviscid central core. Entrainment occurs in the source region, the fluid being distributed into the two nonentraining Ekman-type layers. Fluid leaves the cavity via the sink region. The integral model is validated against the experimental data, although there are some uncertainties in modelling the exact thermal conditions of the experiment. The magnitude of the Nusselt numbers is affected by the rotational Reynolds number and dimensionless flowrate; the maximum value of Nu is found to occur near the edge of the source region. The heat transfer measurements using the engine data show acceptable agreement with theory and experiment. This is very encouraging considering the large levels of uncertainty in the engine data.

Computation of Heat Transfer in Rotating Cavities Using a Two-Equation Model of Turbulence

1990 ◽  
Author(s):  
A. P. Morse ◽  
C. L. Ong
Keyword(s):  
Heat Transfer ◽  
Turbulence Model ◽  
Radial Direction ◽  
Reynolds Numbers ◽  
Systematic Errors ◽  
Equation Model ◽  
Sufficient Accuracy ◽  
Nusselt Numbers ◽  
Radial Outflow ◽  
Cooling Air

The paper presents finite-difference predictions for the convective heat transfer in symmetrically-heated rotating cavities subjected to a radial outflow of cooling air. An elliptic calculation procedure has been used, with the turbulent fluxes estimated by means of a low Reynolds number k-ε model and the familiar ‘turbulence Prandtl number’ concept. The predictions extend to rotational Reynolds numbers of 3.7 × 106 and encompass cases where the disc temperatures may be increasing, constant or decreasing in the radial direction. It is found that the turbulence model leads to predictions of the local and average Nusselt numbers for both discs which are generally within ± 10% of the values from published experimental data, although there appear to be larger systematic errors for the upstream disc than for the downstream disc. It is concluded that the calculations are of sufficient accuracy for engineering design purposes, but that improvements could be brought about by further optimization of the turbulence model.

Numerical Analysis of Heat Transfer and Flow Stability in an Open Rotating Cavity Using the Maximum Entropy Production Principle

2010 ◽  
Author(s):  
D. Bohn ◽  
R. Krewinkel ◽  
A. Wolff
Keyword(s):  
Heat Transfer ◽  
Entropy Production ◽  
Maximum Entropy ◽  
Gas Turbines ◽  
Cooling System ◽  
Numerical Study ◽  
Internal Cooling ◽  
Maximum Entropy Production ◽  
Nusselt Numbers ◽  
Rotating Cavity

The flow field and heat transfer in the internal cooling system of gas turbines can be modelled using rotating-disc systems with axial throughflow. Because of the complexity of these flows, in which buoyancy-induced phenomena are of the utmost importance, numerical studies are notoriously difficult to perform and need extensive experimental validation. J.M. Owen proposed using the Maximum Entropy Production (MEP) Principle as a possible means of simplifying numerical computations for these complex flows. This theory is based on the heat flux out of the cavity. In this numerical study, the Nusselt numbers on the disc walls inside an open rotating cavity with a Rayleigh number of approximately 4.97×108 are evaluated with regard to the computed Nusselt numbers on the disc walls. These can be considered to be representative of the flow inside the cavity. It is shown that, as predicted by Owen, the flow is stable when the heat transfer out of the cavity is maximised, or, conversely, the system is unstable when the heat transfer is minimised. Furthermore, it is proven that the level of the Nusselt number plays an important role for the change between the number of vortex pairs in the flow as well.

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