scholarly journals Full Surface Heat Transfer Characteristics of Stator Ventilation Duct of a Turbine Generator

2020 ◽  
Author(s):  
Shinyoung Jeon ◽  
Changmin Son ◽  
Jangsik Yang
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Cross Flow ◽  
Surface Heat ◽  
Operating Conditions ◽  
Scale Model ◽  
Turbine Generator ◽  
Surface Heat Transfer ◽  
Ventilation Duct ◽  
Flow Case

Turbine generator operates with complex cooling system due to the challenge in controlling the peak temperature of the stator bar caused by ohm loss, which is unavoidable. Therefore, it is important to characterise and quantifies the thermal performance of the cooling system. The focus of the present research is to investigate the heat transfer and pressure loss characteristics of typical cooling system, so-called stator ventilation duct. A real scale model was built at its operating conditions for the present study. The direction of cooling air is varied to consider its operation condition, so that there are (1) outward flow and (2) inward flow cases. In addition, the effect of (3) cross flow (inward with cross flow case) is also studied. The transient heat transfer method using thermochromic liquid crystals is implemented to measure full surface heat transfer distribution. A series of Computational Fluid Dynamics analysis is also conducted to support the observation from the experiment. For the inward flow case, the results suggest that the average Nusselt number of the 2nd duct is about 30% higher than the 3rd duct. The trend is similar with the effect of cross flow. The CFD results are in good agreement with the experimental data.

scholarly journals Full Surface Heat Transfer Characteristics of Stator Ventilation Duct of a Turbine Generator

Energies ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 4137
Author(s):  
Shinyoung Jeon ◽  
Changmin Son ◽  
Jangsik Yang ◽  
Sunghoon Ha ◽  
Kyeha Hwang
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Cross Flow ◽  
Surface Heat ◽  
Operating Conditions ◽  
Scale Model ◽  
Operation Condition ◽  
Surface Heat Transfer ◽  
Ventilation Duct ◽  
Flow Case

Turbine generators operate with complex cooling systems due to the challenge in controlling the peak temperature of the stator bar caused by Ohm loss, which is unavoidable. Therefore, it is important to characterize and quantify the thermal performance of the cooling system. The focus of the present research is to investigate the heat transfer and pressure loss characteristics of a typical cooling system, the so-called stator ventilation duct. A real scale model was built at its operating conditions for the present study. The direction of cooling air was varied to consider its operation condition, so that there are: (1) outward flow; and (2) inward flow cases. In addition, the effect of (3) cross flow (inward with cross flow case) was also studied. The transient heat transfer method using thermochromic liquid crystals is implemented to measure full surface heat transfer distribution. A series of computational fluid dynamics (CFD) analyses were also conducted to support the observation from the experiment. For the outward flow case, the results suggest that the average Nusselt numbers of the 2nd and 3rd ducts are at maximum 100% and 30% higher, respectively, than the inward flow case. The trend was similar with the effect of cross flow. The CFD results were in good agreement with the experimental data.

Full surface heat transfer characteristics of rotor ventilation duct of a turbine generator

2016 ◽  
Vol 94 ◽  
pp. 385-394 ◽  
Author(s):  
Wonkyung Yoo ◽  
Shinyoung Jeon ◽  
Changmin Son ◽  
Jangsik Yang ◽  
Daihyun Ahn ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Surface Heat ◽  
Heat Transfer Characteristics ◽  
Turbine Generator ◽  
Surface Heat Transfer ◽  
Transfer Characteristics ◽  
Ventilation Duct

Full Surface Heat Transfer Measurement of a Turbine Internal Cooling System Using a Large Scaled Model

2018 ◽  
Author(s):  
Nojin Park ◽  
Changmin Son ◽  
Jangsik Yang ◽  
Changyong Lee ◽  
Kidon Lee
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Pressure Loss ◽  
Cooling System ◽  
Surface Heat ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Scaled Model ◽  
Surface Heat Transfer

A series of experiments were conducted to investigate the detailed heat transfer characteristics of a large scaled model of a turbine blade internal cooling system. The cooling system has one passage in the leading edge and a triple passage for the remained region with two U-bends. A large scaled model (2 times) is designed to acquire high resolution measurement. The similarity of the test model was conducted with Reynolds number at the inlet of the internal cooling system. The model is designed to simulate the flow at engine condition including film extractions to match the changes in flowrates through the internal cooling system. Also, 45 deg ribs were installed for heat transfer enhancement. The experiments were performed varying Reynolds number in the range of 20,000 to 100,000 with and without ribs under stationary condition. This study employs transient heat transfer technique using thermochromic liquid crystal (TLC) to obtain full surface heat transfer distributions. The results show the detailed heat transfer distributions and pressure loss. The characteristics of pressure loss is largely dependent on the changes in cross-sectional area along the passages, the presence of U-bends and the extraction of coolant flow through film holes. The local and area averaged Nusselt number were compared to available correlations. Finally, the thermal performance counting the heat transfer enhancement as well as pressure penalty is presented.

The Effect of Initial Cross Flow on the Cooling Performance of a Narrow Impingement Channel

2005 ◽  
Vol 127 (4) ◽  
pp. 358-365 ◽  
Author(s):  
Andrew C. Chambers ◽  
David R. H. Gillespie ◽  
Peter T. Ireland ◽  
Geoffrey M. Dailey
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Heat Transfer Performance ◽  
Cooling System ◽  
Cross Flow ◽  
Scale Model ◽  
Transfer Performance ◽  
Test Technique ◽  
Turbine Blade Cooling ◽  
Turbine Cooling

Impingement channels are often used in turbine blade cooling configurations. This paper examines the heat transfer performance of a typical integrally cast impingement channel. Detailed heat transfer coefficient distributions on all heat transfer surfaces were obtained in a series of low temperature experiments carried out in a large-scale model of a turbine cooling system using liquid crystal techniques. All experiments were performed on a model of a 19-hole, low aspect ratio impingement channel. The effect of flow introduced at the inlet to the channel on the impingement heat transfer within the channel was investigated. A novel test technique has been applied to determine the effect of the initial cross flow on jet penetration. The experiments were performed at an engine representative Reynolds number of 20,000 and examined the effect of additional initial cross flow up to 10 percent of the total mass flow. It was shown that initial cross flow strongly influenced the heat transfer performance with just 10 percent initial cross flow able to reduce the mean target plate jet effectiveness by 57 percent.

Cooling Performance of a Narrow Impingement Channel Including the Introduction of Cross Flow Upstream of the First Hole

2003 ◽  
Author(s):  
Andrew C. Chambers ◽  
David R. H. Gillespie ◽  
Peter T. Ireland ◽  
Geoffrey M. Dailey
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Cooling System ◽  
Cross Flow ◽  
Scale Model ◽  
Test Technique ◽  
Turbine Blade Cooling ◽  
Turbine Cooling ◽  
Impingement Heat Transfer ◽  
Large Scale Model

Impingement channels are often used in turbine blade cooling configurations. This paper examines the heat transfer performance of a typical integrally cast impingement channel. Detailed heat transfer coefficient distributions on all heat transfer surfaces were obtained in a series of low temperature experiments carried out in a large-scale model of a turbine cooling system using liquid crystal techniques. All experiments were performed on a model of a 19-hole, low aspect ratio impingement channel. The effect of flow introduced at the inlet to the channel on the impingement heat transfer within the channel was investigated. A novel test technique has been applied to determine the effect of the initial cross flow on jet penetration. The experiments were performed at an engine representative Reynolds number of 20,000 and examined the effect of additional initial cross flow up to 10% of the total mass flow.

Massively-Parallel DNS and LES of Turbine Vane Endwall Horseshoe Vortex Dynamics and Heat Transfer

2011 ◽  
Author(s):  
Markus Schwa¨nen ◽  
Michael Meador ◽  
Josh Camp ◽  
Shriram Jagannathan ◽  
Andrew Duggleby
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulence Intensity ◽  
Vortex Dynamics ◽  
Turbulent Viscosity ◽  
Horseshoe Vortex ◽  
Surface Heat ◽  
Scale Model ◽  
Pass Filter ◽  
Surface Heat Transfer

Higher turbine inlet temperatures enable increased gas turbine efficiency but significantly reduce component lifetimes through melting of the blade and endwall surfaces. This melting is exacerbated by the horseshoe vortex that forms as the boundary layer stagnates in front of the blade, driving hot gasses to the surface. Furthermore, this vortex exhibits significant dynamical motions that increase the surface heat transfer above that of a stationary vortex. To further understand this heat transfer augmentation, the dynamics of the horseshoe vortex must be characterized in a 3D time-resolved fashion which is difficult to obtain experimentally. In this paper, a 1st stage high pressure stator passage is examined using a spectral element direct numerical simulation at a Reynolds number Re = U∞C/v = 10,000. Although the Re is lower than engine conditions, the vortex already exhibits similar strong aperiodic motions and any uncertainty due to sub-grid scale modeling is avoided. The vortex dynamics are analyzed and their impact on the surface heat transfer is characterized. Results from a baseline case with a smooth endwall are also compared to a passage with film cooling holes. Higher Reynolds number simulations require a Large Eddy Simulation turbulent viscosity model that can handle the high accelerations around the blade. A high-pass-filter sub-grid scale model is tested at the same low Reynolds number to test its effectiveness by direct comparisons to the DNS. This resulted in a significant drop in turbulence intensity due to the high strain rate in the freestream, resulting in different dynamics of the vortex than observed in the DNS. Appropriate upstream engine conditions of high freestream turbulence and large integral length scales for all cases are generated via a novel inflow turbulence development domain using a periodic solution of Taylor vortices that are convected over a square grid. The size of the vortices and grid spacing is used to control the integral length scale, and the intensity of the vortices and upstream distance is used to control the turbulence intensity. The baseline DNS exhibits a bi-modal horseshoe vortex, and the presence of cooling-holes qualitatively increases the number of vortex cores resulting in more complex interactions.

scholarly journals Heat Transfer Enhancement for Finned-Tube Heat Exchangers With Winglets

2000 ◽  
Author(s):  
James E. O’Brien ◽  
Manohar S. Sohal
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Circular Tube ◽  
Reynolds Numbers ◽  
Surface Heat ◽  
Operating Conditions ◽  
Transfer Enhancement ◽  
Height Ratio ◽  
Surface Heat Transfer ◽  
Delta Winglet

Abstract This paper presents the results of an experimental study of forced convection heat transfer in a narrow rectangular duct fitted with a circular tube and/or a delta-winglet pair. The duct was designed to simulate a single passage in a fin-tube heat exchanger. Heat transfer measurements were obtained using a transient technique in which a heated airflow is suddenly introduced to the test section. High-resolution local fin-surface temperature distributions were obtained at several times after initiation of the transient using an imaging infrared camera. Corresponding local fin-surface heat transfer coefficient distributions were then calculated from a locally applied one-dimensional semi-infinite inverse heat conduction model. Heat transfer results were obtained over an airflow rate ranging from 1.51 × 10−3 to 14.0 × 10−3 kg/s. These flow rates correspond to a duct-height Reynolds number range of 670–6300 with a duct height of 1.106 cm and a duct width-to-height ratio, W/H, of 11.25. The test cylinder was sized such that the diameter-to-duct height ratio, D/H is 5. Results presented in this paper reveal visual and quantitative details of local fin-surface heat transfer distributions in the vicinity of a circular tube, a delta-winglet pair, and a combination of a circular tube and a delta-winglet pair. Comparisons of local and average heat transfer distributions for the circular tube with and without winglets are provided. Overall mean fin-surface Nusselt-number results indicate a significant level of heat transfer enhancement associated with the deployment of the winglets with the circular cylinder. At the lowest Reynolds numbers (which correspond to the laminar operating conditions of existing geothermal aircooled condensers), the enhancement level is nearly a factor of two. At higher Reynolds numbers, the enhancement level is close to 50%.

scholarly journals Heat Transfer Enhancement for Finned-Tube Heat Exchangers With Winglets

2005 ◽  
Vol 127 (2) ◽  
pp. 171-178 ◽  
Author(s):  
James E. O’Brien ◽  
Manohar S. Sohal
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Circular Tube ◽  
Reynolds Numbers ◽  
Surface Heat ◽  
Operating Conditions ◽  
Transfer Enhancement ◽  
Height Ratio ◽  
Surface Heat Transfer ◽  
Delta Winglet

This paper presents the results of an experimental study of forced convection heat transfer in a narrow rectangular duct fitted with a circular tube and/or a delta-winglet pair. The duct was designed to simulate a single passage in a fin-tube heat exchanger. Heat transfer measurements were obtained using a transient technique in which a heated airflow is suddenly introduced to the test section. High-resolution local fin-surface temperature distributions were obtained at several times after initiation of the transient using an imaging infrared camera. Corresponding local fin-surface heat transfer coefficient distributions were then calculated from a locally applied one-dimensional semi-infinite inverse heat conduction model. Heat transfer results were obtained over an airflow rate ranging from 1.51×10−3 to 14.0×10−3kg/s. These flow rates correspond to a duct-height Reynolds number range of 670–6300 with a duct height of 1.106 cm and a duct width-to-height ratio, W/H, of 11.25. The test cylinder was sized such that the diameter-to-duct height ratio, D/H is 5. Results presented in this paper reveal visual and quantitative details of local fin-surface heat transfer distributions in the vicinity of a circular tube, a delta-winglet pair, and a combination of a circular tube and a delta-winglet pair. Comparisons of local and average heat transfer distributions for the circular tube with and without winglets are provided. Overall mean fin-surface Nusselt-number results indicate a significant level of heat transfer enhancement associated with the deployment of the winglets with the circular cylinder. At the lowest Reynolds numbers (which correspond to the laminar operating conditions of existing geothermal air-cooled condensers), the enhancement level is nearly a factor of 2. At higher Reynolds numbers, the enhancement level is close to 50%.

Experimental Study of Impingement Jet Cooling Above Pedestal Roughened Channels

2015 ◽  
Author(s):  
G. L. Peacock ◽  
S. J. Thorpe
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cross Flow ◽  
Surface Heat ◽  
Surface Heat Transfer ◽  
Liquid Crystal Thermography ◽  
Impingement Jet ◽  
Jet Cooling ◽  
Surface Heat Transfer Coefficient

An experimental investigation has been conducted into the use of a combined impingement-pedestal cooling geometry to improve uniformity of surface heat transfer coefficient over traditional combustor liner impingement arrays. Various pedestal arrangements have been investigated by altering the height-to-diameter (H/D) and pitch-to-diameter (P/D) ratios and measurements have been made over a range of impingement jet Reynolds numbers between ∼20 and 40×103. The surface heat transfer coefficient has been determined using a transient liquid crystal thermography measurement technique and the data presented in terms of Nusselt number. A ‘shielded impingement’ concept has also been defined featuring full-height pedestals positioned upstream of each impingement jet and arranged to shield the impingement jets from the developing cross-flow. Aerodynamic measurements have also been made to evaluate the influence of changes to the pedestal geometry on the pressure drop incurred across the different cooling patterns. The analysis indicates superior heat transfer performance can be achieved for the shielded impingement arrangements, with the greatest improvement over equivalent geometries displayed towards the rear of the cooling channel.

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