Investigation of Circular and Shaped Effusion Cooling Arrays for Combustor Liner Application—Part 1: Experimental Analysis

2009 ◽  
Author(s):  
Bruno Facchini ◽  
Lorenzo Tarchi ◽  
Lorenzo Toni ◽  
Giuseppe Cinque ◽  
Salvatore Colantuoni
Keyword(s):  
Experimental Analysis ◽  
Heat Removal ◽  
Wide Band ◽  
Heat Fluxes ◽  
3D Fem ◽  
Elliptical Cross ◽  
Injection Angle ◽  
Flow Parameters ◽  
Circular Holes ◽  
Combustor Liner

An experimental analysis of two different effusion cooled plates, with a feasible arrangement for combustor liner application, is presented in this paper. Though having the same porosity and very shallow injection angle (17 deg), the first configuration presents a “standard” circular drilling (D = 2.65 mm; L/D = 16.4), while the other has “shaped” holes with such an elliptical cross-section that leads to a circular imprint on the cooled surface (Dh = 3.39 mm; L/Dh = 12.8). Either geometry is to be studied on two different samples made of both an adiabatic and a high conductivity material. Tests performed on the adiabatic plates were required to obtain adiabatic effectiveness bidimensional distributions; a full 3D FEM post-processing procedure for the evaluation of the remnant and undesired heat fluxes across the surface was employed as well. Objective of the tests carried out on the conductive samples, having the same flow parameters as the adiabatic ones, was the estimation of overall efficiency, given by the combined effect of film protection and heat removal by convection inside the holes. Hot gas side heat transfer coefficient spanwise averaged values have been evaluated employing the outcome of both adiabatic and conductive tests. Experimental measurements were performed imposing two different coolant jet Reynolds numbers, 12500 and 20000, and varying blowing ratio from 5.0 to 9.0; effectiveness was evaluated with a steady-state technique, using TLC (Thermochromic Liquid Crystals) wide band formulation. Results reveal that the reduced coolant jet penetration achievable by means of shaped configuration leads to an increased wall protection in terms of both peak and spanwise averaged values, even if circular holes guarantee a more uniform effectiveness distribution.

Investigation of Circular and Shaped Effusion Cooling Arrays for Combustor Liner Application—Part 2: Numerical Analysis

2009 ◽  
Author(s):  
A. Andreini ◽  
C. Bianchini ◽  
A. Ceccherini ◽  
B. Facchini ◽  
L. Mangani ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Cross Flow ◽  
Lateral Spreading ◽  
Elliptical Cross ◽  
Injection Angle ◽  
Blowing Ratio ◽  
Combustor Liner ◽  
Effectiveness Data ◽  
Overall Effectiveness ◽  
Good Agreement

A numerical analysis of two different effusion cooled plates, with a feasible arrangement for combustor liner application, is presented in this paper. Though having the same porosity and very shallow injection angle (17°), the first configuration presents a “conventional” circular drilling, while the other has “shaped” holes with such an elliptical cross-section that leads to a circular imprint on the cooled surface. Either geometries were the object of an experimental survey in which both adiabatic and overall effectiveness were measured. In order to compensate for the lack of detailed aerodynamic measurements, 3D CFD computations were performed for the two geometries. Steady state RANS calculations were carried out using a k–ε Two Layer turbulence model, both in the standard isotropic and in an algebraically corrected non isotropic version specifically tuned to better predict the lateral spreading of jets in a cross flow. Flow characteristic reproduce typical effusion cooled combustor liner conditions with blowing ratio of 5 and coolant jet Reynolds number of 12500. Even though good agreement could not be obtained comparing thermal adiabatic effectiveness with experiments, the findings of the experiments regarding the rating of the cooling efficiency of the two configurations were confirmed. Additionally, conjugate simulations were performed for the circular hole geometry in order to quantify heat transfer effects and to directly compare them with raw experimental overall effectiveness data.

Heat Transfer Coefficient Measurements on the Film-Cooled Pressure Surface of a Transonic Airfoil

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Paul M. Kodzwa ◽  
John K. Eaton
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Steady State ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Wide Band ◽  
Heat Fluxes ◽  
Pressure Surface ◽  
Lift Off ◽  
Transonic Airfoil

This paper presents isoenergetic temperature and steady-state film-cooled heat transfer coefficient measurements on the pressure surface of a modern, highly cambered transonic airfoil. A single passage model simulated the idealized two-dimensional flow path between blades in a modern transonic turbine. This set up offered a simpler construction than a linear cascade but produced an equivalent flow condition. Furthermore, this model allowed the use of steady-state, constant surface heat fluxes. We used wide-band thermochromic liquid crystals (TLCs) viewed through a novel miniature periscope system to perform high-accuracy (±0.2 °C) thermography. The peak Mach number along the pressure surface was 1.5, and maximum turbulence intensity was 30%. We used air and carbon dioxide as injectant to simulate the density ratios characteristic of the film cooling problem. We found significant differences between isoenergetic and recovery temperature distributions with a strongly accelerated mainstream and detached coolant jets. Our heat transfer data showed some general similarities with lower-speed data immediately downstream of injection; however, we also observed significant heat transfer attenuation far downstream at high blowing conditions. Our measurements suggested that the momentum ratio was the most appropriate variable to parameterize the effect of injectant density once jet lift-off occurred. We noted several nonintuitive results in our turbulence effect studies. First, we found that increased mainstream turbulence can be overwhelmed by the local augmentation of coolant injection. Second, we observed complex interactions between turbulence level, coolant density, and blowing rate with an accelerating mainstream.

Direct Liquid Cooling of High Flux LED Systems: Hot Spot Abatement

2013 ◽  
Author(s):  
Enes Tamdogan ◽  
Mehmet Arik ◽  
M. Baris Dogruoz
Keyword(s):  
Hot Spots ◽  
Hot Spot ◽  
Heat Removal ◽  
Heat Fluxes ◽  
Light Extraction ◽  
Junction Temperature ◽  
System Level ◽  
Design Parameters ◽  
Liquid Cooling ◽  
Wide Range

With the recent advances in wide band gap device technology, solid-state lighting (SSL) has become favorable for many lighting applications due to energy savings, long life, green nature for environment, and exceptional color performance. Light emitting diodes (LED) as SSL devices have recently offered unique advantages for a wide range of commercial and residential applications. However, LED operation is strictly limited by temperature as its preferred chip junction temperature is below 100 °C. This is very similar to advanced electronics components with continuously increasing heat fluxes due to the expanding microprocessor power dissipation coupled with reduction in feature sizes. While in some of the applications standard cooling techniques cannot achieve an effective cooling performance due to physical limitations or poor heat transfer capabilities, development of novel cooling techniques is necessary. The emergence of LED hot spots has also turned attention to the cooling with dielectric liquids intimately in contact with the heat and photon dissipating surfaces, where elevated LED temperatures will adversely affect light extraction and reliability. In the interest of highly effective heat removal from LEDs with direct liquid cooling, the current paper starts with explaining the increasing thermal problems in electronics and also in lighting technologies followed by a brief overview of the state of the art for liquid cooling technologies. Then, attention will be turned into thermal consideration of approximately a 60W replacement LED light engine. A conjugate CFD model is deployed to determine local hot spots and to optimize the thermal resistance by varying multiple design parameters, boundary conditions, and the type of fluid. Detailed system level simulations also point out possible abatement techniques for local hot spots while keeping light extraction at maximum.

scholarly journals Influence of the Spectral Model of Radiation on the Calculated Characteristics of Complex Heat Exchange in Flame Furnaces of the Petrochemical Industry

2020 ◽  
Vol 6 (6) ◽  
pp. 42-47
Author(s):  
A. Abdullin
Keyword(s):  
Petrochemical Industry ◽  
Wide Band ◽  
Combustion Products ◽  
Heat Fluxes ◽  
Spectral Model ◽  
Band Model ◽  
Total Heat Transfer ◽  
Complex Heat Exchange ◽  
Tube Furnaces ◽  
Wide Band Model

The influence of the spectral model of radiation on heat fluxes and the temperature of combustion products in the radiant chambers of tube furnaces of the petrochemical industry is analyzed. A wide-band model and a Hottel gray model are considered. It is shown that the spectral model of the combustion medium radiation weakly affects the calculated characteristics of the total heat transfer.

scholarly journals Influence of the ambient temperature on the cooling efficiency of the high performance cooling device with thermosiphon effect

2018 ◽  
Vol 180 ◽  
pp. 02073
Author(s):  
Patrik Nemec ◽  
Milan Malcho
Keyword(s):  
Ambient Temperature ◽  
High Performance ◽  
Convection Heat Transfer ◽  
Heat Removal ◽  
Measuring Method ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Cooling Efficiency ◽  
Cooling Device

This work deal with experimental measurement and calculation cooling efficiency of the cooling device working with a heat pipe technology. The referred device in the article is cooling device capable transfer high heat fluxes from electric elements to the surrounding. The work contain description, working principle and construction of cooling device. The main factor affected the dissipation of high heat flux from electronic elements through the cooling device to the surrounding is condenser construction, its capacity and option of heat removal. Experimental part describe the measuring method cooling efficiency of the cooling device depending on ambient temperature in range -20 to 40°C and at heat load of electronic components 750 W. Measured results are compared with results calculation based on physical phenomena of boiling, condensation and natural convection heat transfer.

Systematic Study of Film Cooling With a Three-Dimensional Calculation Procedure

1986 ◽  
Vol 108 (1) ◽  
pp. 124-130 ◽  
Author(s):  
A. O. Demuren ◽  
W. Rodi ◽  
B. Scho¨nung
Keyword(s):  
Systematic Study ◽  
Film Cooling ◽  
Three Dimensional ◽  
Heat Fluxes ◽  
Test Cases ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
The Individual ◽  
Volume Method

The present paper describes three-dimensional calculations of film cooling by injection from a single row of holes. A systematic study of the influence of different parameters on the cooling effectiveness has been carried out. Twenty-seven test cases have been calculated, varying the injection angle (α = 10/45/90 deg), the relative spacing (s/D = 1.5/3/5) and the blowing rate (M = 0.5/1/2) for the same mainstream conditions. The governing three-dimensional equations are solved by a finite volume method. The turbulent stresses and heat fluxes are obtained from a k–ε model modified to account for nonisotropic eddy viscosities and diffusivities. Examples of predicted velocity and temperature distributions are presented and compared with available experimental data. For all the test cases, the laterally averaged cooling effectiveness is given. On the whole, the agreement with experiments is fairly good, even though there are discrepancies about details in some of the cases. The influence of the individual parameters on the film cooling effectiveness is predicted correctly in all cases. This influence is discussed in some detail and the parameter combination with the best overall cooling performance is identified.

Experimental analysis on passive residual heat removal in molten salt reactor using single cooling thimble test system

Energy ◽  
2016 ◽  
Vol 112 ◽  
pp. 1049-1059 ◽  
Author(s):  
Kailun Chen ◽  
Changqi Yan ◽  
Zhaoming Meng ◽  
Xiangcheng Wu ◽  
Shaochuang Song ◽  
...  
Keyword(s):  
Molten Salt ◽  
Experimental Analysis ◽  
Heat Removal ◽  
Test System ◽  
Molten Salt Reactor ◽  
Residual Heat

Perspiration Nano-Patch for Hot Spot Thermal Management

2007 ◽  
Author(s):  
Shankar Narayanan ◽  
Andrei G. Fedorov ◽  
Yogendra K. Joshi
Keyword(s):  
Heat Transfer ◽  
Thermal Management ◽  
Hot Spot ◽  
Evaporative Cooling ◽  
Heat Removal ◽  
Heat Fluxes ◽  
Conceptual System ◽  
Sweeping Gas ◽  
Phase Change Heat Transfer ◽  
Latent Heat Of Vaporization

A novel cooling scheme utilizing evaporative cooling for an ultra-thin, spatially confined liquid film is described for meeting the challenge of hot spot thermal management aiming at locally removing heat fluxes in excess of 200 W/cm2. This work presents the conceptual system design and results of performance calculations supporting the feasibility of the proposed cooling scheme. The phase change heat transfer is one of the most efficient means of heat transfer due to an advantage offered by the significant latent heat of vaporization of liquids. Fundamentally, evaporation could be a much more efficient method of heat removal as compared to boiling if certain conditions are met. Theoretically, we demonstrate that if a stable monolayer of liquid can be maintained on the surface and fully dry sweeping gas (e.g., air) is blown at high velocity above this liquid monolayer one can dissipate heat fluxes of the order of several hundreds of Watts per cm2. We also show that a more volatile FC-72 can outperform water in evaporative cooling using stable liquid microfilms.

Nongray Radiative Gas Analyses Using the S-N Discrete Ordinates Method

1991 ◽  
Vol 113 (4) ◽  
pp. 946-952 ◽  
Author(s):  
T. K. Kim ◽  
J. A. Menart ◽  
H. S. Lee
Keyword(s):  
Radiative Heat ◽  
Narrow Band ◽  
Wide Band ◽  
Heat Fluxes ◽  
Discrete Ordinates ◽  
Band Model ◽  
Spectral Correlation ◽  
Discrete Ordinates Method ◽  
Computational Speed ◽  
Wide Band Model

The S-N discrete ordinates method is applied to analyze radiative heat transfer in nongray gases. Spectral correlation between the terms in the equation of transfer is considered for black or nearly nonreflecting walls. Formulations to apply the S-N method using a narrow-band or the exponential wide-band model are presented. The net radiative wall heat fluxes and the radiative source distributions are obtained for uniform, parabolic, and boundary layer type temperature profiles, as well as for a parabolic concentration profile. The narrow- and wide-band nongray solutions are compared with gray-band approximations using the same band models. The computational speed of the gray-band approximation is obtained at the expense of accuracy in the internal fluxes and radiative source distributions. The wall radiative flux predictions by the gray-band approximation are satisfactory.

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