Quantitative measurements of heat transfer coefficient of impinging round jets at high Reynolds number on a perpendicular and inclined heated plate.

Abstract An experimental and numerical study of the convective heat transfer enhancement provided by two rib families (W and Broken W) is presented, covering Reynolds numbers (Re) between 300,000 to 900,000 in a straight channel with a rectangular cross section (AR=1.29). These high Reynolds numbers were selected for the current study since most data in the available literature typically pertain to investigations at lower Reynolds numbers. The objective of this study is to assess the local heat transfer coefficient (HTC) enhancement (compared with a smooth channel) and the overall thermal performance, taking into account the effect of increased roughness on the friction factor, of a group of W shaped turbulators over a wide range of Reynolds numbers. Furthermore, the effects of increasing the rib spacing on the thermal performance of the Broken W configuration are presented and discussed. The numerical results are compared against heat transfer measurements obtained using the Transient Liquid Crystal (TLC) method. The research shows that for the Broken W turbulators, increasing the Reynolds number is associated with an overall decrease of the thermal performance while the thermal performance of the W configuration is relatively insensitive to Reynolds number. Nevertheless, the Broken W configuration delivers higher thermal performance and heat transfer compared with the W configuration for the range of Re investigated. The Broken W configuration with a pitch spacing of 10 times the rib height was shown to provide the optimal thermal performance in the configurations investigated here.

Download Full-text

Gas Solids Suspension Convective Heat Transfer at a Reynolds Number of 130,000

Journal of Heat Transfer ◽

10.1115/1.3597543 ◽

1968 ◽

Vol 90 (4) ◽

pp. 464-468 ◽

Cited By ~ 11

Author(s):

R. Briller ◽

R. L. Peskin

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Convective Heat Transfer ◽

Convective Heat ◽

Particle Temperature ◽

Convective Heat Transfer Coefficient ◽

Loading Ratio ◽

High Reynolds

An experiment was performed to determine the convective heat-transfer coefficient to heated and cooled gas solids suspensions at a Reynolds number of 130,000. Measurements of the heat transfer were performed by traversing the stream at various locations along the pipe with specially designed probes which measured air and particle temperature locally. The results showed that for a high Reynolds number, the heat-transfer coefficient for the suspension appears to be equal to that of the pure gas at the same Reynolds number, and independent of solids loading ratio, heating or cooling, and particle size (between 0.0011 and 0.0058 in. dia).

Download Full-text

Flow and Thermal Fields in a Pendant Droplet Moving on Lyophobic Surface

2010 14th International Heat Transfer Conference, Volume 2 ◽

10.1115/ihtc14-22520 ◽

2010 ◽

Cited By ~ 1

Author(s):

Basant Singh Sikarwar ◽

K. Muralidhar ◽

Sameer Khandekar

Keyword(s):

Heat Transfer ◽

Contact Angle ◽

Reynolds Number ◽

Shear Stress ◽

Heat Transfer Coefficient ◽

Wall Shear Stress ◽

Transfer Coefficient ◽

Maximum Shear Stress ◽

Computational Domain ◽

Wall Shear

Clusters of liquid drops growing and moving on physically or chemically textured lyophobic surfaces are encountered in drop-wise mode of vapor condensation. As opposed to film-wise condensation, drops permit a large heat transfer coefficient and are hence attractive. However, the temporal sustainability of drop formation on a surface is a challenging task, primarily because the sliding drops eventually leach away the lyophobicity promoter layer. Assuming that there is no chemical reaction between the promoter and the condensing liquid, the wall shear stress (viscous resistance) is the prime parameter for controlling physical leaching. The dynamic shape of individual droplets, as they form and roll/slide on such surfaces, determines the effective shear interaction at the wall. Given a shear stress distribution of an individual droplet, the net effect of droplet ensemble can be determined using the time averaged population density during condensation. In this paper, we solve the Navier-Stokes and the energy equation in three-dimensions on an unstructured tetrahedral grid representing the computational domain corresponding to an isolated pendant droplet sliding on a lyophobic substrate. We correlate the droplet Reynolds number (Re = 10–500, based on droplet hydraulic diameter), contact angle and shape of droplet with wall shear stress and heat transfer coefficient. The simulations presented here are for Prandtl Number (Pr) = 5.8. We see that, both Poiseuille number (Po) and Nusselt number (Nu), increase with increasing the droplet Reynolds number. The maximum shear stress as well as heat transfer occurs at the droplet corners. For a given droplet volume, increasing contact angle decreases the transport coefficients.

Download Full-text

Thermo-mechanical analysis of a FGM plate subjected to thermal shock – A new numerical approach considering real time temperature dependent material properties

Materials Testing ◽

10.1515/mt-2020-0050 ◽

2021 ◽

Vol 63 (4) ◽

pp. 341-349

Author(s):

Mete Onur Kaman ◽

Nevin Celik ◽

Resul Das

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Thermal Shock ◽

Temperature Variation ◽

Material Properties ◽

Ambient Air ◽

Transient Temperature ◽

Heated Plate ◽

The Heat Transfer Coefficient

Abstract In present the study, sudden cooling, in other words thermal shock, is applied to a plate that is originally a functionally graded material (FGM). The flat plate is assumed to have an edge crack on it. Hence a numerical couple-field analysis is performed on the plate. The FGM is a combination of Ni and Al2O3. The thermal and mechanical properties of the FGM are assumed to depend on temperature variation. The mixing percentages of the Ni and Al2O3 throughout the plate are considered to vary (i) linearly, (ii) quadratically and (iii) in half-order. In order to solve the problem, a new subroutine depending on temperature is written using APDL (ANSYS Parametric Design Language) codes. Three values of the heat transfer coefficient are applied to the initially heated plate. As a result, the transient temperature variation and stress intensity factor are presented to show the thermo-mechanical relation of the plate. The material properties changing with temperature results in more reliable temperature values. Increasing the heat transfer coefficient results in better cooling and in a lesser amount of time to reach ambient air temperature.

Download Full-text

A Numerical Investigation Into the Heat Transfer Performance and Particle Dynamics of a Compressible, Highly Mass Loaded, High Reynolds Number, Particle Laden Flow

Journal of Heat Transfer ◽

10.1115/1.4052437 ◽

2021 ◽

Author(s):

Kyle Hassan ◽

Robert F. Kunz ◽

David Hanson ◽

Michael Manahan

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Computational Model ◽

High Reynolds Number ◽

Heat Transfer Performance ◽

Particle Dynamics ◽

Transfer Performance ◽

Temperature Distributions ◽

High Reynolds ◽

Particle Laden Flow

Abstract In this work, we study the heat transfer performance and particle dynamics of a highly mass loaded, compressible, particle-laden flow in a horizontally-oriented pipe using an Eulerian-Eulerian (two-fluid) computational model. An attendant experimental configuration [1] provides the basis for the study. Specifically, a 17 bar co-flow of nitrogen gas and copper powder are modeled with inlet Reynolds numbers of 3×104, 4.5×104, and 6×104 and mass loadings of 0, 0.5, and 1.0. Eight binned particle sizes were modeled to represent the known powder properties. Significant settling of all particle groups are observed leading to asymmetric temperature distributions. Wall and core flow temperature distributions are observed to agree well with measurements. In high Reynolds number cases, the predictions of the multiphase computational model were satisfactorily aligned with the experimental results. Low Reynolds number model predictions were not as consistent with the experimental measurements.

Download Full-text

Row Removal Heat Transfer Study for Pin Fin Arrays

Volume 5A: Heat Transfer ◽

10.1115/gt2014-25348 ◽

2014 ◽

Cited By ~ 4

Author(s):

Kathryn L. Kirsch ◽

Jason K. Ostanek ◽

Karen A. Thole ◽

Eleanor Kaufman

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

High Reynolds Number ◽

Pin Fin ◽

Heat Transfer Augmentation ◽

Aspect Ratios ◽

Pin Fins ◽

High Reynolds ◽

Pin Fin Arrays ◽

Transfer Study

Arrays of variably-spaced pin fins are used as a conventional means to conduct and convect heat from internal turbine surfaces. The most common pin shape for this purpose is a circular cylinder. Literature has shown that beyond the first few rows of pin fins, the heat transfer augmentation in the array levels off and slightly decreases. This paper provides experimental results from two studies seeking to understand the effects of gaps in pin spacing (row removals) and alternative pin geometries placed in these gaps. The alternative pin geometries included large cylindrical pins and oblong pins with different aspect ratios. Results from the row removal study at high Reynolds number showed that when rows four through eight were removed, the flow returned to a fully-developed channel flow in the gap between pin rows. When larger alternative geometries replaced the fourth row, heat transfer increased further downstream into the array.

Download Full-text

Toward improved heat dissipation of the turbulent regime over backward-facing step for the AL2O3-water nanofluids: An experimental approach

Thermal Science ◽

10.2298/tsci170606236a ◽

2019 ◽

Vol 23 (3 Part B) ◽

pp. 1779-1789 ◽

Cited By ~ 1

Author(s):

Syed Ahmed ◽

Salim Kazi ◽

Ghulamullah Khan ◽

Mohd Zubir ◽

Mahidzal Dahari ◽

...

Keyword(s):

Heat Transfer ◽

Experimental Study ◽

Reynolds Number ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Turbulent Regime ◽

Al2o3 Nanoparticles ◽

Backward Facing Step ◽

Constant Weight ◽

Weight Concentration

Experimental study of nanofluid flow and heat transfer to fully developed turbulent forced convection flow in a uniformly heated tubular horizontal backward-facing step has reported in the present study. To study the forced convective heat transfer coefficient in the turbulent regime, an experimental study is performed at a different weight concentration of Al2O3 nanoparticles. The experiment had conducted for water and Al2O3 -water nanofluid for the concentration range of 0 to 0.1 wt.% and Reynolds number of 4000 to 16000. The average heat transfer coefficient ratio increases significantly as Reynolds number increasing, increased from 9.6% at Reynolds number of 4000 to 26.3% at Reynolds number of 16000 at the constant weight concentration of 0.1%. The Al2O3 water nanofluid exhibited excellent thermal performance in the tube with a backwardfacing step in comparison to distilled water. However, the pressure losses increased with the increase of the Reynolds number and/or the weight concentrations, but the enhancement rates were insignificant.

Download Full-text

Aerodynamics and Heat Transfer Investigations on a High Reynolds Number Turbine Cascade

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration ◽

10.1115/91-gt-157 ◽

1991 ◽

Cited By ~ 6

Author(s):

Taher Schobeiri ◽

Eric McFarland ◽

Frederick Yeh

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

High Reynolds Number ◽

Test Facility ◽

Experimental Investigations ◽

Turbine Cascade ◽

Calculation Methods ◽

Transfer Coefficients ◽

Pressure Distributions ◽

High Reynolds

In this report the results of aerodynamic and heat transfer experimental investigations performed in a high Reynolds number turbine cascade test facility are analyzed. The experimental facility simulates the high Reynolds number flow conditions similar to those encountered in the space shuttle main engine. In order to determine the influence of Reynolds number on aerodynamic and thermal behavior of the blades, heat transfer coefficients were measured at various Reynolds numbers using liquid crystal temperature measurement technique. Potential flow calculation methods were used to predict the cascade pressure distributions. Boundary layer and heat transfer calculation methods were used with these pressure distributions to verify the experimental results.

Download Full-text

The Simulation Study of Turbulence Models for Conjugate Heat Transfer Analysis of a High Pressure Air-Cooled Gas Turbine

2010 14th International Heat Transfer Conference, Volume 5 ◽

10.1115/ihtc14-22088 ◽

2010 ◽

Cited By ~ 1

Author(s):

Zhenfeng Wang ◽

Peigang Yan ◽

Hongfei Tang ◽

Hongyan Huang ◽

Wanjin Han

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Gas Turbine ◽

Turbulence Model ◽

Conjugate Heat Transfer ◽

Turbulence Models ◽

Turbulence Characteristic ◽

The Heat Transfer Coefficient

The different turbulence models are adopted to simulate NASA-MarkII high pressure air-cooled gas turbine. The experimental work condition is Run 5411. The paper researches that the effect of different turbulence models for the flow and heat transfer characteristics of turbine. The turbulence models include: the laminar turbulence model, high Reynolds number k-ε turbulence model, low Reynolds number turbulence model (k-ω standard format, k-ω-SST and k-ω-SST-γ-θ) and B-L algebra turbulence model which is adopted by the compiled code. The results show that the different turbulence models can give good flow characteristics results of turbine, but the heat transfer characteristics results are different. Comparing to the experimental results, k-ω-SST-θ-γ turbulence model results are more accurate and can simulate accurately the flow and heat transfer characteristics of turbine with transition flow characteristics. But k-ω-SST-γ-θ turbulence model overestimates the turbulence kinetic energy of blade local region and makes the heat transfer coefficient higher. It causes that local region temperature is higher. The results of B-L algebra turbulence model show that the results of B-L model are accurate besides it has 4% temperature error in the transition region. As to the other turbulence models, the results show that all turbulence models can simulate the temperature distribution on the blade pressure surface except the laminar turbulence model underestimates the heat transfer coefficient of turbulence flow region. On the blade suction surface with transition flow characteristics, high Reynolds number k-ε turbulence model overestimates the heat transfer coefficient and causes the blade surface temperature is high about 90K than the experimental result. Low Reynolds number k-ω standard format and k-ω-SST turbulence models also overestimate the blade surface temperature value. So it can draw a conclusion that the unreasonable choice of turbulence models can cause biggish errors for conjugate heat transfer problem of turbine. The combination of k-ω-SST-γ-θ model and B-L algebra model can get more accurate turbine thermal environment results. In addition, in order to obtain the affect of different turbulence models for gas turbine conjugate heat transfer problem. The different turbulence models are adopted to simulate the different computation mesh domains (First case and Second case). As to each cooling passages, the first case gives the wall heat transfer coefficient of each cooling passages and the second case considers the conjugate heat transfer course between the cooling passages and blade. It can draw a conclusion that the application of heat transfer coefficient on the wall of each cooling passages avoids the accumulative error. So, for the turbine vane geometry models with complex cooling passages or holes, the choice of turbulence models and the analysis of different mesh domains are important. At last, different turbulence characteristic boundary conditions of turbine inner-cooling passages are given and K-ω-SST-γ-θ turbulence model is adopted in order to obtain the effect of turbulence characteristic boundary conditions for the conjugate heat transfer computation results. The results show that the turbulence characteristic boundary conditions of turbine inner-cooling passages have a great effect on the conjugate heat transfer results of high pressure gas turbine.

Download Full-text