Correlations of the Convection Heat Transfer in Annular Channels With Rotating Inner Cylinder

1999 ◽  
Vol 121 (4) ◽  
pp. 670-677 ◽  
Author(s):  
R. Jakoby ◽  
S. Kim ◽  
S. Wittig
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Stability Boundary ◽  
Vortex Formation ◽  
Taylor Vortex ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Annular Channels ◽  
Steady State Method ◽  
The Impact

In the internal air system of gas turbine engines or generators, a large variety of different types of annular channels with rotating cylinders are found. Even though the geometry is very simple, the flow field in such channels can be completely three-dimensional and also unsteady. From the literature it is well-known that the basic two-dimensional flow field breaks up into a pattern of counter-rotating vortices as soon as the critical speed of the inner cylinder is exceeded. The presence of a superimposed axial flow leads to a helical shape of the vortex pairs that are moving through the channel. For the designer of cooling air systems there are several open questions. Does the formation of a Taylor-vortex flow field significantly affect the convective heat transfer behavior of the channel flow? Is there a stability problem even for high axial Reynolds-numbers and where is the location of the stability boundary? After all, the general influence of rotation on the heat transfer characteristics has to be known. By the results of flow field and heat transfer measurements, the impact of rotation and the additional influence of Taylor-vortex formation on the heat transfer characteristics in annular channels with axial throughflow will be discussed. The flow field was investigated by time-dependant LDA-measurements, which revealed detailed information about the flow conditions. By a spectral analysis of the measured data, the different flow regimes could be identified. Based on these results, the heat transfer from the hot gas to the rotating inner shaft was determined with a steady-state method. Thus, the influence of the different physical phenomena such as rotation with and without Taylor-vortex formation or the flow development could be separated and quantified. Finally, correlations of the measured results were derived for technical applications.

Correlations of the Convective Heat Transfer in Annular Channels With Rotating Inner Cylinder

1998 ◽  
Author(s):  
Ralf Jakoby ◽  
Soksik Kim ◽  
Sigmar Wittig
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Vortex Formation ◽  
Taylor Vortex ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Annular Channels ◽  
The Impact

In the internal air system of gas turbine engines or generators, a large variety of different types of annular channels with rotating cylinders are found. Even though the geometry is very simple, the flow field in such channels can be completely three-dimensional and also unsteady. From the literature it is well-known, that the basic two-dimensional flow field breaks up into a pattern of counter-rotating vortices, as soon as the critical speed of the inner cylinder is exceeded. The presence of a superimposed axial flow leads to a helical shape of the vortex pairs, which are moving through the channel. For the designer of cooling air systems there are several open questions. Does the formation of a Taylor-vortex flow field significantly affect the convective heat transfer behaviour of the channel flow? Is there a stability problem even for high axial Reynolds-numbers and where is the location of the stability boundary? After all, the general influence of rotation on the heat transfer characteristics has to be known. By the results of flow field and heat transfer measurements, the impact of rotation and the additional influence of Taylor-vortex formation on the heat transfer characteristics in annular channels with axial throughflow will be discussed. The flow field was investigated by time-dependant LDA-measurements, which revealed detailed information about the flow conditions. By a spectral analysis of the measured data, the different flow regimes could be identified. Based on these results, the heat transfer from the hot gas to the rotating inner shaft was determined with a steady-state method. Thus, the influence of the different physical phenomena such as rotation with and without Taylor-vortex formation or the flow development could be separated and quantified. Finally, correlations of the measured results were derived for technical applications.

Influences of Small Jet-to-Wall Spacings on Heat Transfer Characteristics and Flow-Field Entrainment Effects of Microscale Jets

2021 ◽  
Vol 143 (3) ◽  
Author(s):  
Prabhakar Subrahmanyam ◽  
B. K. Gnanavel
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Jet Impingement ◽  
Impinging Jets ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Inlet System ◽  
Potential Core ◽  
Transfer Characteristics ◽  
The Impact

Abstract Detailed heat transfer distributions of multiple microscaled tapered jets orthogonally impinging on the surface of a high-power density silicon wall is presented. The tapered jets issued from two different impingement setup are studied—(a) single circular nozzle and (b) dual circular nozzles. Jets are issued from the inlet(s) at four different Reynolds numbers {Re = 8000, 12,000, 16,000, 20,000}. The spacing between the tapered nozzle jets and the bare die silicon wall (z/d) is adjusted to be 4, 8, 12, and 16 jet nozzle diameters away from impinging influence. The impact of varying the nozzle to the silicon wall (z/d) standoff spacing up to 16 nozzle jet diameters and its effects on flow fields on the surface of the silicon, specifically the entrainment pattern on the silicon surface, is presented. Heat transfer characteristics of impinging jets on the hot silicon wall is investigated by means of large eddy simulations (LES) at a Reynolds of 20,000 on each of the four z/d spacing and compared against its equivalent Reynolds-averaged Navier–Stokes (RANS) cases. Highest heat transfer coefficients are obtained for the dual inlet system. A demarcation boundary region connecting all the microvortices between impinging jets is prominently visible at smaller z/d spacing—the region where the target silicon wall is within the sphere of influence of the potential core of the jet. This research focuses on the underlying physics of multiple tapered nozzles jet impingement issued from single and dual nozzles and its impact on turbulence, heat transfer distributions, entrainment, and other pertinent flow-field characteristics.

Numerical Simulations on Turbulent Heat Transfer Characteristics of Supercritical Pressure Fluids

2009 ◽  
Author(s):  
Toru Nakatsuka ◽  
Kazuyuki Takase ◽  
Hiroyuki Yoshida ◽  
Takeharu Misawa
Keyword(s):  
Heat Transfer ◽  
Prediction Accuracy ◽  
Experimental Studies ◽  
Supercritical Pressure ◽  
Turbulent Heat Transfer ◽  
High Heat Flux ◽  
Turbulent Heat ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Annular Channels

As one of next generation nuclear reactors, development of a supercritical pressure water reactor (SCWR) has been performed. In order to design the SCWR, it is necessary to investigate thermal-hydraulic characteristics in the SCWR core precisely. As for those characteristics, many experimental studies have been conducted from the former in each country using circular tubes, annular channels, and the simulated fuel bundles. An objective of this study is to clarify the prediction accuracy of the turbulent heat transfer characteristics in the supercritical pressure fluids for the SCWR design. From the experimental results of the supercritical pressure fluids flowing upward in a vertical circular tube, it was confirmed that the turbulent heat transfer coefficient suddenly decreases under the high heat flux condition. Although many numerical studies have been done in order to confirm the deterioration of turbulent heat transfer in supercritical pressure fluids, it is important to choose a suitable turbulence model to obtain high prediction accuracy. Then, the present study was performed to investigate numerically the effect of turbulent models on the deteriorated turbulent heat transfer.

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.

Assessment of the Thermal Performance of Alternate Firing Schemes in Oxygen-Fired Glass Melting Furnaces

2003 ◽  
Author(s):  
Kris L. Jorgensen ◽  
Satish Ramadhyani ◽  
Raymond Viskanta
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Computer Model ◽  
Thermal Performance ◽  
Glass Melting ◽  
Side Wall ◽  
Shear Stresses ◽  
Heat Transfer Characteristics ◽  
Unstable Flow ◽  
Transfer Characteristics

Three firing schemes for an industrial oxygen-fired glass melting furnace were examined to determine the thermal performance and relative merits of each scheme. A comprehensive computer model was used to investigate the effects of each scheme on the combustion and heat transfer in the furnace. The three-dimensional computer model, suitable for predicting and analyzing fluid flow, combustion and heat transfer has been used to simulate the combustion space of the furnace. The turbulent flow field is obtained by solving the Favre averaged Navier-Stokes equations and using the k-ε model to calculate the turbulent shear stresses and close the equation set. The combustion model consists of a single step, irreversible, infinitely fast reaction. A mixture fraction is used to track the mixing of fuel and oxidant and thus reaction progress in this mixing limited model. An assumed shape PDF method is utilized to account for turbulent fluctuations. Radiative heat transfer in the combustion gases and between surfaces is modeled using the discrete ordinates method coupled with the weighted-sum-of-gray-gases model. The model furnace for all three firing schemes was the same size and shape, was charged from the rear end wall and was pulled from the front wall. The three schemes investigated were: 1) non-interlaced side-wall fired, 2) interlaced side-wall fired, and 3) end fired. The results show that all three arrangements provide similar thermal performance and heat transfer characteristics. However, the flow field for the non-interlaced arrangement is very complex in the region where jets from opposing walls meet at the furnace center line. This type of jet interference can lead to unstable flow, particularly at the centerline of the furnace. Unstable flow conditions can affect the heat transfer characteristics of the furnace and make the furnace difficult to operate. Conversely, the interlaced and end-fired schemes do not exhibit the jet interference seen in the non-interlaced arrangement. While the results indicate that the thermal performance of all three arrangements were similar, the possibility of jet interference suggests that an interlaced or end-fired arrangement is preferable.

Effect of NGV Lean Under Influence of Inlet Temperature Traverse

2013 ◽  
Author(s):  
A. Rahim ◽  
B. Khanal ◽  
L. He ◽  
E. Romero
Keyword(s):  
Heat Transfer ◽  
Computational Study ◽  
Navier Stokes ◽  
Tangential Displacement ◽  
Inlet Temperature ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Inlet Conditions ◽  
Hot Streak ◽  
The Impact

One of the most widely studied parameters in turbine blade shaping is blade lean, i.e. the tangential displacement of spanwise sections. However, there is a lack of published research that investigates the effect of blade lean under non-uniform temperature conditions (commonly referred to as a ‘hot-streak’) that are present at the combustor exit. Of particular interest is the impact of such an inflow temperature profile on heat transfer when the NGV blades are shaped. In the present work a computational study has been carried out for a transonic turbine stage using an efficient unsteady Navier-Stokes solver (HYDRA). The configurations with a nominal vane and a compound leaned vane under uniform and hot-streak inlet conditions are analysed. After confirming the typical NGV loading and aero-loss redistributions as seen in previous literature on blade lean, the focus has been directed to the rotor aerothermal behavior. Whilst the overall stage efficiencies for the configurations are largely comparable, the results show strikingly different rotor heat transfer characteristics. For a uniform inlet, a leaned NGV has a detrimental effect on the rotor heat transfer. However, once the hot-streak is introduced, the trend is reversed; the leaned NGV leads to favourable heat transfer characteristics in general and for the rotor tip region in particular. The possible causal links for the observed aerothermal features are discussed. The present findings also highlight the significance of evaluating NGV shaping designs under properly conditioned inflow profiles, rather than extrapolating the wisdom derived from uniform inlet cases. The results also underline the importance of including rotor heat transfer and coolability during the NGV design process.

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