Detailed Flow and Heat Transfer Coefficient Measurements in a Model of an Internal Cooling Geometry Employing Orthogonal Intersecting Channels

2000 ◽  
Author(s):  
David R. H. Gillespie ◽  
Peter T. Ireland ◽  
Geoff M. Dailey
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Large Scale ◽  
Structural Integrity ◽  
Local Heat Transfer ◽  
Bulk Temperature ◽  
Internal Cooling ◽  
Gas Temperature ◽  
Transfer Coefficients

Cast interconnecting passage Lattice cooling geometries offer the gas turbine designer higher structural integrity and improved convective efficiency when compared to traditional aerofoil rear cooling strategies. In this paper, local heat transfer coefficient distributions were measured in a model of an idealised engine lattice cooling geometry, with flow ejection through film-cooling holes. The measurements were made using the transient liquid crystal technique in a large-scale perspex model at low temperature. The technique allows very high data resolution. Heat transfer patterns on all surfaces of the device including the internal web are presented at engine representative Reynolds numbers. The results are discussed in terms of the interpreted flow field. Furthermore, a subsequent analysis which accounted for the changing driving gas temperature and mass flow rate through the model has allowed the heat transfer coefficients to be derived based on the mixed bulk temperature, and local passage Reynolds number.

Fuzzy logic and bed-to-wall heat transfer in a large-scale CFBC

2018 ◽  
Vol 28 (1) ◽  
pp. 254-266 ◽  
Author(s):  
Jaroslaw Krzywanski ◽  
Marta Wesolowska ◽  
Artur Blaszczuk ◽  
Anna Majchrzak ◽  
Maciej Komorowski ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fuzzy Logic ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Large Scale ◽  
Weighted Average ◽  
Local Heat Transfer ◽  
Wall Heat Transfer ◽  
Transfer Coefficients ◽  
Content Type

Purpose The purpose of this paper is to first present the key features of the fuzzy logic (FL) approach as a cost-effective technique in simulations of complex systems and then demonstrate the formulation and application of the method. Design/methodology/approach The FL approach is used as an alternative method of data handling, considering the complexity of analytical and numerical procedures and high costs of empirical experiments. The distance from gas distributor, the temperature and the voidage of the bed, flue gas velocity and the load of the boiler are the input parameters, whereas the overall heat transfer coefficient for the membrane walls constitutes the output. Five overlapping sigmoid and constant linguistic terms are used to describe the input and the output data, respectively. The Takagi–Sugeno inference engine and the weighted average defuzzification methods are applied to determine the fuzzy and crisp output value, respectively. Findings The performed FL model allows predicting the bed-to-wall heat transfer coefficient in a large-scale 670 t/h circulating fluidized bed (CFB) boiler. The local heat transfer coefficients evaluated using the developed model are in very good agreement with the data obtained in complementary investigations. Originality/value The performed model constitutes an easy-to-use and functional tool. The new approach can be helpful for further research on the bed-to-wall heat transfer coefficient in the CFB units.

Heat Transfer Enhancement by Turbulent Impinging Jets

2000 ◽  
Author(s):  
M. Kumagai ◽  
R. S. Amano ◽  
M. K. Jensen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Stokes Equations ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Impinging Jets ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Abstract A numerical and experimental investigation on cooling of a solid surface was performed by studying the behavior of an impinging jet onto a fixed flat target. The local heat transfer coefficient distributions on a plate with a constant heat flux were computationally investigated with a normally impinging axisymmetric jet for nozzle diameter of 4.6mm at H/d = 4 and 10, with the Reynolds numbers of 10,000 and 40,000. The two-dimensional cylindrical Navier-Stokes equations were solved using a two-equation k-ε turbulence model. The finite-volume differencing scheme was used to solve the thermal and flow fields. The predicted heat transfer coefficients were compared with experimental measurements. A universal function based on the wave equation was developed and applied to the heat transfer model to improve calculated local heat transfer coefficients for short nozzle-to-plate distance (H/d = 4). The differences between H/d = 4 and 10 due to the correlation among heat transfer coefficient, kinetic energy and pressure were investigated for the impingement region. Predictions by the present model show good agreement with the experimental data.

scholarly journals A Statistical Evaluation of the Influence of Different Material and Process Parameters on the Heat Transfer Coefficient in Gravity Die Casting

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1367
Author(s):  
Nino Wolff ◽  
Golo Zimmermann ◽  
Uwe Vroomen ◽  
Andreas Bührig-Polaczek
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Die Casting ◽  
Local Heat Transfer ◽  
Mold Temperature ◽  
Local Heat ◽  
Mold Material ◽  
Transfer Coefficients ◽  
The Heat Transfer Coefficient

Local heat transfer in gravity die casting is of great importance for precision in terms of distortion, mechanical properties, and the quality of the castings due to its effect on solidification. Depending on contact conditions such as liquid melt to solid mold, a gap between mold and component, or contact pressure between casting and mold as a result of shrinkage, there are very large differences in heat transfer. The influences of mold material, mold coating and its influence of aging, mold temperature control, and layout on the heat transfer coefficient (HTC) were investigated experimentally for different contact cases. The experiments were carried out on a rotationally symmetrical experimental setup with modular exchangeable die inserts and cores using an AlSi7Mg0.3 alloy. From the results of the individual test series, the quantitative shares of the above-mentioned influencing variables in the respective effective heat transfer coefficients were determined by means of analysis of variance. From this, the parameters having the most significant influence on the local heat balance were derived.

Local Heat Transfer Coefficient of Flow Boiling in Microchannels With Artificial Reentrant Cavities

2007 ◽  
Author(s):  
Chih-Jung Kuo ◽  
Yoav Peles
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Fluxes ◽  
Transfer Coefficients ◽  
Bubble Generation ◽  
Parallel Microchannels

Flow boiling in parallel microchannels with structured reentrant cavities was experimental studied. Flow patterns, boiling inceptions and heat transfer coefficients were obtained and studied for G = 83 kg/m2-s to G = 303 kg/m2-s and heat fluxes up to 643 W/cm2. The heat transfer coefficient-mass velocity and quality relations had been analyzed to identify boiling mechanism. Comparisons of the performance of the enhanced and plain-wall microchannels had also been made. The microchannels with reentrant cavities were shown to promote nucleation of bubbles and to support significantly better reproducibility and uniformity of bubble generation.

Effects of Channel Height and Bulk Temperature Considerations on Heat Transfer Coefficient of Wetted Surfaces in a Single Inline Row Impingement Channel

2008 ◽  
Author(s):  
Mark Ricklick ◽  
Stephanie Kersten ◽  
V. Krishnan ◽  
J. S. Kapat
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Side Wall ◽  
Bulk Temperature ◽  
Channel Height ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Jet Impact ◽  
Side Walls

High performance turbine airfoils are typically cooled with a combination of internal cooling channels and impingement/film cooling. In such applications, the jets impinge against a target surface, and then exit along the channel formed by the jet plate, target plate, and side walls. Local convection coefficients are the result of both the jet impact, as well as the channel flow produced from the exiting jets. Numerous studies have explored the effects of jet array and channel configurations on both target and jet plate heat transfer coefficients. However, little work has been done in examining effects on the channel side walls, which may be a major contributor to heat transfer in real world applications. This paper examines the local and averaged effects of channel height and on heat transfer coefficients, with special attention given to the channel side walls. The effects on heat transfer results due to bulk temperature variations were also investigated. High resolution local heat transfer coefficient distributions on target and side wall surfaces were measured using temperature sensitive paint and recorded via a scientific grade charge-coupled device (CCD) camera. Streamwise pressure distributions for both the target and side walls was recorded and used to explain heat transfer trends. Results are presented for average jet based Reynolds numbers between 17,000 and 45,000. All experiments were carried out on a large scale single row, 15 hole impingement channel, with X/D of 5, Y/D of 4, and Z/D of 1, 3 and 5. The results obtained from this investigation will aid in the validation of predictive tools and development of physics-based models.

Three-Dimensional Transient Heat Conduction Equation Solution for Accurate Quantification of Heat Transfer Coefficient in Transient Liquid Crystal Experiments

2019 ◽  
Author(s):  
Shoaib Ahmed ◽  
Prashant Singh ◽  
Srinath V. Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Crystal ◽  
Transfer Coefficient ◽  
Three Dimensional ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Conduction Model

Abstract Liquid crystal thermography and infrared thermography techniques are typically employed to measure detailed surface temperatures, where local heat transfer coefficient (HTC) values are calculated by employing suitable conduction models. One such practice, which is very popular and easy to use, is the transient liquid crystal thermography using one-dimensional semi-infinite conduction model. In these experiments, a test surface with low thermal conductivity and low thermal diffusivity (e.g. acrylic) is used where a step-change in coolant air temperature is induced and surface temperature response is recorded. An error minimization routine is then employed to guess heat transfer coefficients of each pixel, where wall temperature evolution is known through an analytical expression. The assumption that heat flow in the solid is essentially in one-dimension, often leads to errors in HTC determination and this error depends on true HTC, wall temperature evolution and HTC gradient. A representative case of array jet impingement under maximum crossflow condition has been considered here. This heat transfer enhancement concept is widely used in gas turbine leading edge and electronics cooling. Jet impingement is a popular cooling technique which results in high convective heat rates and has steep gradients in heat transfer coefficient distribution. In this paper, we have presented a procedure for solution of three-dimensional transient conduction equation using alternating direction implicit method and an error minimization routine to find accurate heat transfer coefficients at relatively lower computational cost. The HTC results obtained using 1D semi-infinite conduction model and 3D conduction model were compared and it was found that the heat transfer coefficient obtained using the 3D model was consistently higher than the conventional 1D model by 3–16%. Significant deviations, as high as 8–20% in local heat transfer at the stagnation points of the jets were observed between h1D and h3D.

Using Gradient Heat Flux Measurement to Experimentally Determine Local Heat Transfer Coefficient on Combustion Chamber Surface in a Diesel Engine

2019 ◽  
pp. 87-96
Author(s):  
V.B. Sapozhnikov ◽  
V.Yu. Mityakov ◽  
A.V. Mityakov ◽  
A.V. Vintsarevich ◽  
D.V. Gerasimov
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Combustion Chamber ◽  
Local Heat Transfer ◽  
Flux Measurement ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Engine Operation ◽  
Heat Transfer Coefficients

We used gradient thermometry to determine local heat transfer coefficients on the fire deck surface. We studied two modes of engine operation, that is, motored and fired. We show that the heat transfer coefficient distribution over the fire deck surface is inhomogeneous. Our investigation results may be used to validate existing models of heat transfer in a combustion chamber.

Distribution of local heat transfer coefficient values in the wall region of an agitated vessel

2008 ◽  
Vol 62 (1) ◽  
Author(s):  
Magdalena Cudak ◽  
Joanna Karcz
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbulent Regime ◽  
Transfer Coefficients ◽  
Measuring Point ◽  
Agitated Vessel ◽  
Heat Transfer Coefficients

AbstractExperimentally found local heat transfer coefficients are analyzed as a function of the measuring point on the heat transfer surface area of the agitated vessel wall and of the impeller eccentricity. Eccentric Rushton turbine and A 315 impeller are considered. Local heat transfer coefficients were measured by means of the computer-aided electrochemical method. The measurements were performed in an agitated vessel with inner diameter 0.3 m, filled with liquid up to the height equal to the vessel diameter. The experiments were carried out within the turbulent regime of the Newtonian liquid flow in the agitated vessel. The results were compared with the data obtained for the agitated vessel equipped with an eccentrically located axial flow propeller or an HE 3 impeller. Experimental studies show that the distributions of the heat transfer coefficient values depend on the impeller eccentricity, impeller type and the direction of the liquid circulation in the agitated vessel.

Detailed Experimental Characterization of Heat Transfer Coefficient Over the Internal Cooling Passages of an Additive Manufactured Turbine Airfoil

2016 ◽  
Author(s):  
Sin Chien Siw ◽  
Minking K. Chyu ◽  
Jae Y. Um ◽  
Ching-Pang Lee
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Local Heat Transfer Coefficient ◽  
Scale Model ◽  
Internal Cooling ◽  
Trailing Edge

This report describes the detailed experimental study to characterize the local heat transfer coefficient distribution over the internal cooling passages of a simplified generic airfoil. The airfoil is manufactured through additive manufacturing based on actual geometry and dimensions (1X scale model) of row one airfoil, applicable in large gas turbine system. At the mainbody section, the serpentine channel consists of three passages without any surface features or vortex generators. Both the leading edge and trailing edge sections are subjected to direct impingement. The trailing edge section is divided into three chambers, separated by two rows of blockages. This study employs the well-documented transient liquid crystal technique, where the local heat transfer coefficient on both pressure and suction sides is deduced. The experiments were performed at varying Reynolds number, ranging from approximately 31,000–63,000. The heat transfer distribution on the pressure side and suction side is largely comparable in the first and third pass, except for the second pass. Highest heat transfer occurs at the trailing edge region, which is ultimately dominated by impingement due to the presence of three rows of blockages. A cursory numerical calculation is performed using commercially available software, ANSYS CFX to obtain detailed flow field distribution within the airfoil, which explains the heat transfer behavior at each passage. The flow parameter results revealed that the pressure ratio is strongly proportional with increasing Reynolds number.

Pin-Fin Heat Transfer: Contribution of the Wall and the Pin to the Overall Heat Transfer

1992 ◽  
Author(s):  
A. M. Ai Dabagh ◽  
G. E. Andrews
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Diameter Ratio ◽  
Duct Flow ◽  
Transfer Coefficients ◽  
Pin Fin ◽  
Heat Transfer Coefficients

The differences in the heat transfer coefficient between the pin and the wall in pin-fin heat transfer was determined for three pin length to diameter ratios. A staggered pin-fin array was used with a 50% duct flow blockage by the pins. The axial pitch-to-pin diameter ratio, X/D, was 1.5 and the transverse pitch-to-diameter ratio, S/D, was 2.0. Three pin length-to-diameter ratios, T/D, of 0.7. 1.0 and 2.2 were investigated. The mean heat transfer coefficient results were very similar to previous work for similar geometries. The axial variation of heat transfer coefficient showed this to be fairly uniform with a small peak at the fourth row. Around each pin four measurements of the heat transfer coefficients were made with four on the fin surface at each end. Thus 12 local heat transfer coefficients were made per pin-fin. These showed that for all three geometries the wall or fin heat transfer was always greater by 15–35% than the pin for the same velocity and Re.

Sign in / Sign up

Export Citation Format

Share Document