Computational Investigation of Heat Transfer Characteristics of Counter-Rotating Turbine Disks With Annulus

2015 ◽  
Author(s):  
Dongdong Liu ◽  
Xiang Luo ◽  
Zhi Tao
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Vortex Pair ◽  
Rotating Disks ◽  
Heat Transfer Characteristics ◽  
Complex Flow ◽  
Transfer Characteristics ◽  
Air Inlet ◽  
Inlet Conditions ◽  
Cooling Air

The heat transfer characteristics of counter-rotating disks with annulus flow were investigated numerically in this paper, in which the effects of coolant inlet conditions (inlet geometry, turbulent parameter and inlet preswirl) of the cavity were emphasized. The axial Reynolds number of annulus Rew was set to be 5.99×105 and rotating Reynolds number Reϕ was set to be 2.35×105. Two kinds of cooling air inlet, radial inlet from the middle of cavity and axial inlet from one side of cavity, were adopted and investigated. The turbulent parameter and preswil ratio varied from 0.028 to 0.197 and −1.5 to 1.5, respectively. According to the calculation results:a vortex pair that generated by the radial inlet and non-preswirling cooling air is somehow unstable which rendered a complex flow field and wall heat transfer pattern in the cavity. For the influence of pumping effect of rotating disks, preswirling of cooling air led to uneven division of cooling air for two counter-rotating disks in radial cooling air inlet type. More cooling air flows towards the disk with same rotating direction of preswirl cooling air and leads to higher Nu in that wall which was enhanced by the increase of preswirl ratio. Axial cooling air inlet results in a much more stable flow than that with radial inlet. The Nu of the wall that cooling air flow towards was higher than that of the other one and this difference increased with the increase of turbulent parameter λT.

Numerical Simulation on Heat Transfer Characteristics of Turbulent Gas Flow in Micro-Tubes

2011 ◽  
Author(s):  
Kyohei Isobe ◽  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Ichiro Ueno
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Wall Temperature ◽  
Gas Flow ◽  
Tube Diameter ◽  
Turbulence Energy ◽  
Stagnation Temperature ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Turbulent Gas Flow

Numerical simulations were performed to obtain for heat transfer characteristics of turbulent gas flow in micro-tubes with constant wall temperature. The numerical methodology was based on Arbitrary-Lagrangian-Eulerinan (ALE) method to solve compressible momentum and energy equations. The Lam-Bremhorst Low-Reynolds number turbulence model was employed to evaluate eddy viscosity coefficient and turbulence energy. The tube diameter ranges from 100 μm to 400 μm and the aspect ratio of the tube diameter and the length is fixed at 200. The stagnation temperature is fixed at 300 K and the computations were done for wall temperature, which ranges from 305 K to 350 K. The stagnation pressure was chosen in such a way that the flow is in turbulent flow regime. The obtained Reynolds number ranges widely up to 10081 and the Mach number at the outlet ranges from 0.1 to 0.9. The heat transfer rates obtained by the present study are higher than those of the incompressible flow. This is due to the additional heat transfer near the micro-tube outlet caused by the energy conversion into kinetic energy.

scholarly journals Heat transfer and flow region characteristics study in a non-annular channel between rotor and stator

2012 ◽  
Vol 16 (2) ◽  
pp. 593-603 ◽  
Author(s):  
M. Nili-Ahmadabadi ◽  
H. Karrabi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Characteristics ◽  
Annular Channel ◽  
Flow Region ◽  
Air Gap ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Slip Ring

This paper will present the results of the experimental investigation of heat transfer in a non-annular channel between rotor and stator similar to a real generator. Numerous experiments and numerical studies have examined flow and heat transfer characteristics of a fluid in an annulus with a rotating inner cylinder. In the current study, turbulent flow region and heat transfer characteristics have been studied in the air gap between the rotor and stator of a generator. The test rig has been built in a way which shows a very good agreement with the geometry of a real generator. The boundary condition supplies a non-homogenous heat flux through the passing air channel. The experimental devices and data acquisition method are carefully described in the paper. Surface-mounted thermocouples are located on the both stator and rotor surfaces and one slip ring transfers the collected temperature from rotor to the instrument display. The rotational speed of rotor is fixed at three under: 300rpm, 900 rpm and 1500 rpm. Based on these speeds and hydraulic diameter of the air gap, the Reynolds number has been considered in the range: 4000<Rez<30000. Heat transfer and pressure drop coefficients are deduced from the obtained data based on a theoretical investigation and are expressed as a formula containing effective Reynolds number. To confirm the results, a comparison is presented with Gazley?s (1985) data report. The presented method and established correlations can be applied to other electric machines having similar heat flow characteristics.

Numerical Investigation on Heat Transfer of Al2O3/Water Nanofluid in a Shell and Tube Heat Exchanger

2014 ◽  
Vol 591 ◽  
pp. 3-6
Author(s):  
M. Raja ◽  
R. Vijayan ◽  
R. Vivekananthan ◽  
M.A. Vadivelu
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Exchanger ◽  
Numerical Investigation ◽  
Volume Concentration ◽  
Heat Transfer Characteristics ◽  
Tube Heat Exchanger ◽  
Transfer Characteristics ◽  
Shell And Tube ◽  
Suspended Nanoparticles

In the present work, the effect of nanofluid in a shell and tube heat exchanger was studied numerically. The effects of Reynolds number, volume concentration of suspended nanoparticles on the heat transfer characteristics were investigated using CFD software. Finally, the effect of the nanofluid on Shell and tube heat exchanger performance was studied and compared to that of a conventional fluid (i.e., water).

Effect of Turbulent Intensity and Axial Gap on Turbine Heat Transfer Using Steady and Harmonic Models

2013 ◽  
Author(s):  
Sridhar Murari ◽  
Sunnam Sathish ◽  
Ramakumar Bommisetty ◽  
Jong S. Liu
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Flow Field ◽  
Turbulence Intensity ◽  
Pressure Coefficient ◽  
Heat Transfer Characteristics ◽  
Complex Flow ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Heat Loads

The knowledge of heat loads on the turbine is of great interest to turbine designers. Turbulence intensity and stator-rotor axial gap plays a key role in affecting the heat loads. Flow field and associated heat transfer characteristics in turbines are complex and unsteady. Computational fluid dynamics (CFD) has emerged as a powerful tool for analyzing these complex flow systems. Honeywell has been exploring the use of CFD tools for analysis of flow and heat transfer characteristics of various gas turbine components. The current study has two objectives. The first objective aims at development of CFD methodology by validation. The commercially available CFD code Fine/Turbo is used to validate the predicted results against the benchmark experimental data. Predicted results of pressure coefficient and Stanton number distributions are compared with available experimental data of Dring et al. [1]. The second objective is to investigate the influence of turbulence (0.5% and 10% Tu) and axial gaps (15% and 65% of axial chord) on flow and heat transfer characteristics. Simulations are carried out using both steady state and harmonic models. Turbulence intensity has shown a strong influence on turbine blade heat transfer near the stagnation region, transition and when the turbulent boundary layer is presented. Results show that a mixing plane is not able to capture the flow unsteady features for a small axial gap. Relatively close agreement is obtained with the harmonic model in these situations. Contours of pressure and temperature on the blade surface are presented to understand the behavior of the flow field across the interface.

Experimental Investigation of the Air Flow Behavior and Heat Transfer Characteristics in Microchannels With Different Channel Lengths

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Zhi Tao ◽  
Zhibing Zhu ◽  
Haiwang Li
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Critical Reynolds Number ◽  
Flow Behavior ◽  
Channel Length ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Poiseuille Number ◽  
Channel Lengths

This paper attempts to experimentally investigate the influence of channel length on the flow behavior and heat transfer characteristics in circular microchannels. The diameters of the channels were 0.4 mm and the length of them were 5 mm, 10 mm, 15 mm, and 20 mm, respectively. All experiments were performed with air and completed with Reynolds number in the range of 300–2700. Results of the experiments show that the length of microchannels has remarkable effects on the performance of flow behavior and heat transfer characteristics. Both the friction factor and Poiseuille number drop with the increase of channel length, and the experimental values are higher than the theoretical ones. Moreover, the channel length does not influence the value of critical Reynolds number. Nusselt number decrease as the increase of channel length. Larger Nusselt numbers are obtained in shorter channels. The results also indicate that in all cases, the friction factor decreases and the Poiseuille number increases with the increase of the Reynolds number. It is also observed that the value of critical Reynolds number is between 1500 and 1700 in this paper, which is lower than the value of theoretical critical Reynolds number of 2300.

Numerical Study on Flow and Heat Transfer Characteristics of Jet Impingement Cooling

2011 ◽  
Vol 148-149 ◽  
pp. 680-683
Author(s):  
Run Peng Sun ◽  
Wei Bing Zhu ◽  
Hong Chen ◽  
Chang Jiang Chen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Numerical Study ◽  
Cross Flow ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Transfer Characteristic ◽  
Heat Transfer Characteristics ◽  
Impingement Cooling ◽  
Transfer Characteristics

Three-dimensional numerical study is conducted to investigate the heat transfer characteristics for the flow impingement cooling in the narrow passage based on cooling technology of turbine blade.The effects of the jet Reynolds number, impingement distance and initial cross-flow on heat transfer characteristic are investigated.Results show that when other parameters remain unchanged local heat transfer coefficient increases with increase of jet Reynolds number；overall heat transfer effect is reduced by initial cross-flow；there is an optimal distance to the best effect of heat transfer.

Flow and Heat Transfer Enhancement Characteristics of Impinging Jets in Transitional Time Periodic Flow Regimes

2010 ◽  
Author(s):  
Julian P. Gutierrez ◽  
Alfonso Ortega ◽  
Amador M. Guzman
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Temporal Evolution ◽  
Flow Regimes ◽  
Periodic Flow ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Time Average

The flow and heat transfer characteristics of an impinging jet on a perpendicular flat surface are obtained by two dimensional numerical simulations of laminar and transitional flow regimes for the Reynolds number of Re = 300, 350, and 400 for a Prandtl number of Pr = 0.7. A fixed jet to plate spacing of H/W = 5 and a given heat flux on the plate surface are considered. Temporal evolution of velocity and temperature fields, Fourier spectra of the velocity temporal evolution and time average local and global Nusselt numbers are obtained for increasing Reynolds numbers for determining the time depending behavior and its effect on the heat transfer characteristics. Numerical simulation results demonstrate that self-sustained transitional periodic flow regimes arise from a laminar regime, when the Reynolds number is further increased to Re = 400 and that these regimes spread out to the whole domain with similar time dependent characteristics due to the flow incompressibility. Evaluations of time average local and global Nusselt numbers demonstrate the asymmetric Gaussian-type spatial distribution and the increase of both parameters when the flow evolves through the transitional periodic regime, with reasonable increases on the pumping power requirements.

Heat Transfer Characteristics of an Inclined Impinging Jet on a Curved Surface in Crossflow

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
X. L. Wang ◽  
H. B. Yan ◽  
T. J. Lu ◽  
S. J. Song ◽  
T. Kim
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flat Plate ◽  
Local Heat Transfer ◽  
Impinging Jet ◽  
Local Heat ◽  
Curved Surface ◽  
Heat Transfer Characteristics ◽  
Potential Core ◽  
Transfer Characteristics

This study reports on heat transfer characteristics on a curved surface subject to an inclined circular impinging jet whose impinging angle varies from a normal position θ = 0 deg to θ = 45 deg at a fixed jet Reynolds number of Rej = 20,000. Three curved surfaces having a diameter ratio (D/Dj) of 5.0, 10.0, and infinity (i.e., a flat plate) were selected, each positioned systematically inside and outside the potential core of jet flow where Dj is the circular jet diameter. Present results clarify similar and dissimilar local heat transfer characteristics on a target surface due to the convexity. The role of the potential core is identified to cause the transitional response of the stagnation heat transfer to the inclination of the circular jet. The inclination and convexity are demonstrated to thicken the boundary layer, reducing the local heat transfer (second peaks) as opposed to the enhanced local heat transfer on a flat plate resulting from the increased local Reynolds number.

Heat Transfer Characteristics of Low Reynolds Number Turbulent Swirling LPG/Air Flame Impinging on a Flat Surface

2010 ◽  
Author(s):  
Arun Kaushal ◽  
Gurpreet Singh ◽  
Subhash Chander ◽  
Anjan Ray
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flat Surface ◽  
Low Reynolds Number ◽  
Reynolds Numbers ◽  
Heat Transfer Characteristics ◽  
Swirl Number ◽  
Transfer Characteristics ◽  
Swirling Flames ◽  
Low Reynolds

An experimental study has been conducted to determine the heat transfer characteristics for low Reynolds number turbulent swirling LPG/Air flames impinging on a flat surface. Effect of variation of Reynolds number (3000–7000), dimensionless separation distance (H/d = 1 to 6) and equivalence ratio (φ = 0.8 to 2) on heat transfer characteristics has been determined at constant swirl number of 4. Further, experiments were also conducted to investigate the effect of swirl number on heat transfer characteristics at Re = 7000, φ = 1.0 and H/d = 5. It has been concluded that the major drawback of flame impingement i.e., non-uniformity in the heating can be resolved by using swirling flames in place of non-swirling flames. With increase in Reynolds number the flame becomes longer and broader. Also, at higher Re the flame becomes noisy and violent because of the enhanced turbulences in the flame. A dip in the temperature was observed at the stagnation point at all Re and this dip was more significant at higher Re. At small separation distances (H/d = 1 and 2) and at large Reynolds numbers (Re = 7000) heating is comparatively more non-uniform because of close proximity of the visible reaction zone to the plate resulting in intense heating in the stagnation region. High average heat fluxes were obtained at low separation distances and at larger Reynolds numbers.

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