Exploring Applicability of Acoustic Heat Transfer Enhancement Across Various Perturbation Elements

2020 ◽  
Author(s):  
Tapish Agarwal ◽  
Maximilian Stratmann ◽  
Simon Julius ◽  
Beni Cukurel
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Static Pressure ◽  
Pressure Fluctuations ◽  
Acoustic Excitation ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Number Range ◽  
Flow Modulation ◽  
Spatially Resolved

Abstract The requirements of improved heat transfer performance on turbine surfaces and internal cooling passages drive the research into exploring new methods for efficiency enhancements. Addition of ribbed structures inside the cooling ducts has proven to be most practical, which increases heat transfer from surfaces to fluid flow at the cost of some pressure loss. Many active and passive methods have been proposed for enhancing the heat transfer, where acoustic excitation has been recently shown to be an effective option. Moreover, the existing pressure fluctuations due to rotor-stator interactions can also be utilized as a source of excitation. However, the sensitivity of the phenomenon to various flow and geometric parameters has not been fully characterized. The present study investigates various aspects of convective heat transfer enhancement and turbulent flow modulation caused by acoustic forcing on separating and reattaching flow over isolated rib obstacles. A parametric study is conducted; rib obstacles of various sizes and shapes (including rectangular, squared, triangular, semi-cylindrical, etc.) are installed in a low-speed, fully turbulent wind tunnel and measurements are taken at different velocities and excitation frequencies. Static pressure and spatially resolved surface temperature measurements are performed to quantify the ramifications of acoustic excitation on the wetted wall. Within the favorable Strouhal number range of 0.1–0.25, an optimum value of 0.16 is observed. It is shown that triangular ribs are more prone to acoustic heat transfer enhancement than rectangular or cylindrical perturbations. A linear correlation between static pressure recovery rate and acoustic heat transfer enhancement is observed, which is invariant to change in size/shape of the rib as well as flow and excitation parameters.

Exploring Applicability of Acoustic Heat Transfer Enhancement Across Various Perturbation Elements

2021 ◽  
Vol 143 (3) ◽  
Author(s):  
Tapish Agarwal ◽  
Maximilian Stratmann ◽  
Simon Julius ◽  
Beni Cukurel
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Static Pressure ◽  
Pressure Fluctuations ◽  
Acoustic Excitation ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Number Range ◽  
Flow Modulation ◽  
Spatially Resolved

Abstract The requirements of improved heat transfer performance on turbine surfaces and internal cooling passages drive the research into exploring new methods for efficiency enhancements. The addition of ribbed structures inside the cooling ducts has proven to be most practical, which increases heat transfer from surfaces to fluid flow at the cost of some pressure loss. Many active and passive methods have been proposed for enhancing the heat transfer, where acoustic excitation has been recently shown to be an effective option. Moreover, the existing pressure fluctuations due to rotor–stator interactions can also be utilized as a source of excitation. However, the sensitivity of the phenomenon to various flow and geometric parameters has not been fully characterized. The present study investigates various aspects of convective heat transfer enhancement and turbulent flow modulation caused by acoustic forcing on separating and reattaching flow over isolated rib obstacles. A parametric study is conducted; rib obstacles of various sizes and shapes (including rectangular, squared, triangular, and semi-cylindrical) are installed in a low-speed, fully turbulent wind tunnel, and measurements are taken at different velocities and excitation frequencies. Static pressure and spatially resolved surface temperature measurements are performed to quantify the ramifications of acoustic excitation on the wetted wall. Within the favorable Strouhal number range of 0.1–0.25, an optimum value of 0.16 is observed. It is shown that triangular ribs are more prone to acoustic heat transfer enhancement than rectangular or cylindrical perturbations. A linear correlation between static pressure recovery rate and acoustic heat transfer enhancement is observed, which is invariant to change in size/shape of the rib as well as flow and excitation parameters.

Heat Transfer Enhancement in a Rectangular Channel With the Combination of Ribs, Dimples and Protrusions

2011 ◽  
Author(s):  
Jibing Lan ◽  
Yonghui Xie ◽  
Di Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Rectangular Channel ◽  
Low Pressure ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Number Range ◽  
Baseline Case ◽  
The One

Rib turbulators can enhance the heat transfer successfully, but in most cases this is associated with large pressure loss penalties. Recently, dimple techniques become an attractive method for gas turbine blade internal cooling because dimples enhance heat transfer with low pressure penalty. In the present paper, a compound heat transfer enhancement technique, heat transfer enhancement in rectangular channel (Aspect ratio = 4) with the combination of ribs, dimples and protrusions, are investigated. The calculations are conducted on five different channel configurations. Case 1 which is the baseline configuration is a rectangular channel with rectangular ribs (e/Dh = 0.078, P/e = 10). In case 2, one row of dimples are placed between two ribs. In case 3, instead of dimples, one row of protrusions are placed between two ribs. In case 4, three rows of dimples are place between two ribs. Case 5 places three rows of protrusions between two ribs instead of dimples. The present paper focuses on Reynolds numbers (based on the channel hydraulic diameter) ranging from 10000 to 60000. In all configurations, the non-dimensional dimple/protrusion depths are 0.2. The results show that the rib+dimple cases provide minor increase in Nu/Nu0, f/f0 and thermal performance. Within the Reynolds number range studied, the Nu/Nu0 values of the three row rib+protrusion case is 17% ∼ 7% higher than that of the baseline case, and the decrease in f/f0 is about 10%. The thermal performance of the three row rib+protrusion case is about 16% higher than that of the baseline case. The Nu/Nu0 values of the one row rib+protrusion case is about 9% higher than that of the baseline case, and the decrease in f/f0 is about 12%. The thermal performance of the one row rib+protrusion case is about 14% higher than that of the baseline case. It can be concluded that rib+protrusion technique in rectangular channel has the potential to provide heat transfer enhancement with low pressure penalty.

Experimental Study on Flow Behavior and Heat Transfer Enhancement with Distinct Dimpled Gas Turbine Blade Internal Cooling Channel

2021 ◽  
pp. 1-28
Author(s):  
Farah Nazifa Nourin ◽  
Ryoichi S. Amano
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Thermal Performance ◽  
Diameter Ratio ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Transfer Enhancement

Abstract The study presents the investigation on heat transfer distribution along a gas turbine blade internal cooling channel. Six different cases were considered in this study, using the smooth surface channel as a baseline. Three different dimples depth-to-diameter ratios with 0.1, 0.25, and 0.50 were considered. Different combinations of partial spherical and leaf dimples were also studied with the Reynolds numbers of 6,000, 20,000, 30,000, 40,000, and 50,000. In addition to the experimental investigation, the numerical study was conducted using Large Eddy Simulation (LES) to validate the data. It was found that the highest depth-to-diameter ratio showed the highest heat transfer rate. However, there is a penalty for increased pressure drop. The highest pressure drop affects the overall thermal performance of the cooling channel. The results showed that the leaf dimpled surface is the best cooling channel based on the highest Reynolds number's heat transfer enhancement and friction factor. However, at the lowest Reynolds number, partial spherical dimples with a 0.25 depth to diameter ratio showed the highest thermal performance.

scholarly journals Mixed convective heat transfer enhancement in a ventilated cavity by flow modulation via rotating plate

Heat Transfer ◽  
2020 ◽  
Author(s):  
Aminul Islam ◽  
Monoranjan Debnath Rony ◽  
Mahmudul Islam ◽  
Emdadul Haque Chowdhury ◽  
Mohammad Nasim Hasan
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Convective Heat ◽  
Transfer Enhancement ◽  
Flow Modulation ◽  
Ventilated Cavity ◽  
Rotating Plate ◽  
Convective Heat Transfer Enhancement

The Numerical Simulation Research on Heat Transfer Enhancement of the Interpolation-Tubular Air Pre-Heater with Semi-Elliptic Cylinder Shell Vortex Generator

2013 ◽  
Vol 397-400 ◽  
pp. 230-234
Author(s):  
De Fan Qing ◽  
Qing Feng Ai
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Vortex Generator ◽  
Elliptic Cylinder ◽  
Attack Angle ◽  
Width Ratio ◽  
Transfer Enhancement ◽  
Simulation Research ◽  
Number Range ◽  
Dip Angle

The semi-elliptic cylinder shell vortex generator set in the interpolation-tubular air pre-heater was studied. And by changing the high-width Ratiov, dip angleα, attack angleβ, spacingsof vortex generator to research the heat transfer and resistance properties under different working conditions, and the optimization structure of vortex generator was determined. The heating medium of the air pre-heater is the flue gas that passes across tube outside, and the cooling air as the cooling medium in the tube longitudinal scoured. The Reynolds number range is 25000 ~ 40000. The research shows that: semi-elliptic cylinder vortex generator can obviously improve the heat transfer performance, the optimization structure of the semi-elliptic cylinder vortex generator: high-width ratiov= 0.45, attack angleβ= 65 °, dip angleα= 15 °, spans= 90 mm, the heat transfer enhancement comprehensive effect raised about 43.2%~72.6%.

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.

Heat Transfer in a Rotating Cooling Channel (AR = 2:1) With Rib Turbulators and a Tip Turning Vane

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Andrew F. Chen ◽  
Hao-Wei Wu ◽  
Nian Wang ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Rotation Number ◽  
Internal Cooling ◽  
Cooling Channel ◽  
Transfer Enhancement ◽  
Rib Turbulators ◽  
Effects Of Rotation ◽  
Cooling Passage ◽  
Turbine Airfoils

Experimental investigation on rotation and turning vane effects on heat transfer was performed in a two-pass rectangular internal cooling channel. The channel has an aspect ratio of AR = 2:1 and a 180 deg tip-turn, which is a scaled up model of a typical internal cooling passage of gas turbine airfoils. The leading surface (LS) and trailing surface (TS) are roughened with 45 deg angled parallel ribs (staggered P/e = 8, e/Dh = 0.1). Tests were performed in a pressurized vessel (570 kPa) where higher rotation numbers (Ro) can be achieved with a maximum Ro = 0.42. Five Reynolds numbers (Re) were examined (Re = 10,000–40,000). At each Reynolds number, five rotational speeds (Ω = 0–400 rpm) were considered. Results showed that rotation effects are stronger in the tip regions as compared to other surfaces. Heat transfer enhancement up to four times was observed on the tip wall at the highest rotation number. However, heat transfer enhancement is reduced to about 1.5 times with the presence of a tip turning vane at the highest rotation number. Generally, the tip turning vane reduces the effects of rotation, especially in the turn portion.

Effect of 45-Deg Rib Orientations on Heat Transfer in a Rotating Two-Pass Channel With Aspect Ratio From 4:1 to 2:1

2019 ◽  
Author(s):  
Izzet Sahin ◽  
Andrew F. Chen ◽  
Chao-Cheng Shiau ◽  
Je-Chin Han ◽  
Robert Krewinkel
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Heat Transfer Enhancement ◽  
Rotation Number ◽  
Pressure Loss ◽  
Heat Transfer Analysis ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
First Passage

Abstract The internal cooling passages of gas turbine blades mostly have varying aspect ratios from one passage to another. However, there are limited data available in the open literature that used a reduced cross-section and aspect ratio, AR, after the tip turn. Therefore, the current study presents heat transfer and pressure drop of three different α = 45° profiled rib orientations, typical parallel (usual), reversed parallel (unusual), and criss-cross patterns in a rotating two-pass rectangular channel with AR = 4:1 and 2:1 in the first radially outward flow and second radially inward flow passages respectively. For each rib orientation, regional averaged heat transfer results are obtained for both the flow passages with the Reynolds number ranging from 10,000 to 70,000 for the first passage and 16000 to 114000 for the second passage with a rotational speed range of 0 rpm to 400 rpm. This results in the highest rotation number of 0.39 and 0.16 for the first and second passage respectively. The effects of rib orientation, aspect ratio variation, 180° tip turn, and rotation number on the heat transfer and pressure drop will be addressed. According to the results, for usual, unusual and criss-cross rib patterns, increasing rotation number causes the heat transfer to decrease on the leading surface and increase on the trailing surface for the first passage and vice versa for the second passage. Overall heat transfer enhancement of the usual and unusual rib patterns is higher than criss-cross one. In terms of the pressure losses, the criss-cross rib pattern has the lowest and the usual rib pattern has the highest-pressure loss coefficients. When pressure loss and heat transfer enhancement are both taken into account together, the criss-cross or unusual rib pattern might be an option to use in the internal cooling method. Therefore, the results can be useful for turbine blade internal cooling design and heat transfer analysis.

Experimental Study of Advanced Convective Cooling Techniques for Combustor Liners

2008 ◽  
Author(s):  
Michael Maurer ◽  
Uwe Ruedel ◽  
Michael Gritsch ◽  
Jens von Wolfersdorf
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Transfer Enhancement ◽  
Number Range ◽  
Convective Cooling

An experimental study was conducted to determine the heat transfer performance of advanced convective cooling techniques at the typical conditions found in a backside cooled combustion chamber. For these internal cooling channels, the Reynolds number is usually found to be above the Reynolds number range covered by available databases in the open literature. As possible candidates for an improved convective cooling configuration in terms of heat transfer augmentation and acceptable pressure drops, W-shaped and WW-shaped ribs were considered for channels with a rectangular cross section. Additionally, uniformly distributed hemispheres were investigated. Here, four different roughness spacings were studied to identify the influence on friction factors and the heat transfer enhancement. The ribs and the hemispheres were placed on one channel wall only. Pressure losses and heat transfer enhancement data for all test cases are reported. To resolve the heat transfer coefficient, a transient thermocromic liquid crystal technique was applied. Additionally, the area-averaged heat transfer coefficient on the W-shaped rib itself was observed using the so-called lumped-heat capacitance method. To gain insight into the flow field and to reveal the important flow field structures, numerical computations were conducted with the commercial code FLUENT™.

Heat Transfer Enhancement in Tip-Turn Region of Two-Pass Channel With a 180-Degree Turn

2011 ◽  
Author(s):  
Pavin Ganmol ◽  
Minking K. Chyu ◽  
Mary Anne Alvin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Sharp Turn ◽  
Pin Fins ◽  
Series Of Experiments ◽  
Turn Region

The design geometry and transport phenomena associated with the tip internal cooling can be very complex and has been little studied. Internal cooling channel near a tip region typically inherits a sharp, 180-degree, turn and little or no enhancement installation exists. To explore potential design for enhancement cooling, a series of experiments are performed to investigate the heat transfer enhancement by placing different pin-fins configurations in the tip-turn region of a two-pass channel with a 180-degree sharp turn. Transient liquid crystal technique is applied to acquire detailed local heat transfer data both on the channel surface and pin elements, for Reynolds number between 13,000 and 28,000. Present results suggest that the pin-fins can enhance heat transfer up to 2.3 fold in the tip-turn region and up to 1.3 fold for the entire channel. The presence of the pin-fins also changes the flow pattern in the post turn region which is resulting in more evenly distributed heat transfer downstream of the turn.

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