Roughness Effects on Flow and Heat Transfer for Additively Manufactured Channels

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Curtis K. Stimpson ◽  
Jacob C. Snyder ◽  
Karen A. Thole ◽  
Dominic Mongillo
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Flow Conditions ◽  
Roughness Effects ◽  
Flow And Heat Transfer ◽  
Technological Advances ◽  
Rectangular Channels ◽  
Significant Augmentation ◽  
Flow Through

Recent technological advances in the field of additive manufacturing (AM), particularly with direct metal laser sintering (DMLS), have increased the potential for building gas turbine components with AM. Using the DMLS for turbine components broadens the design space and allows for increasingly small and complex geometries to be fabricated with little increase in time or cost. Challenges arise when attempting to evaluate the advantages of the DMLS for specific applications, particularly because of how little is known regarding the effects of surface roughness. This paper presents pressure drop and heat transfer results of flow through small, as produced channels that have been manufactured using the DMLS in an effort to better understand roughness. Ten different coupons made with the DMLS all having multiple rectangular channels were evaluated in this study. Measurements were collected at various flow conditions and reduced to a friction factor and a Nusselt number. Results showed significant augmentation of these parameters compared to smooth channels, particularly with the friction factor for minichannels with small hydraulic diameters. However, augmentation of Nusselt number did not increase proportionally with the augmentation of the friction factor.

Roughness Effects on Flow and Heat Transfer for Additively Manufactured Channels

2015 ◽  
Author(s):  
Curtis K. Stimpson ◽  
Jacob C. Snyder ◽  
Karen A. Thole ◽  
Dominic Mongillo
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Roughness Effects ◽  
Flow And Heat Transfer ◽  
Technological Advances ◽  
Rectangular Channels ◽  
Mini Channels ◽  
Significant Augmentation ◽  
Flow Through

Recent technological advances in the field of additive manufacturing (AM), particularly with direct metal laser sintering (DMLS), have increased the potential for building gas turbine components with AM. Using DMLS for turbine components broadens the design space and allows for increasingly small and complex geometries to be fabricated with little increase in time or cost. Challenges arise when attempting to evaluate the advantages of DMLS for specific applications, particularly because of how little is known regarding the effects of surface roughness. This paper presents pressure drop and heat transfer results of flow through small, as produced channels that have been manufactured using DMLS in an effort to better understand roughness. Ten different coupons made with DMLS all having multiple rectangular channels were evaluated in this study. Measurements were collected at various flow conditions and reduced to a friction factor and a Nusselt number. Results showed significant augmentation of these parameters compared to smooth channels, particularly with the friction factor for mini-channels with small hydraulic diameters. However, augmentation of Nusselt number did not increase proportionally with the augmentation of the friction factor.

scholarly journals Investigating the impacts of included angles on flow and heat transfer in cross-corrugated triangular ducts with field synergy principle

2013 ◽  
Vol 17 (3) ◽  
pp. 823-832 ◽  
Author(s):  
Zuoyi Chen ◽  
Lizhi Zhang ◽  
Han Song
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Reynolds Numbers ◽  
Field Synergy ◽  
Field Synergy Principle ◽  
Included Angle ◽  
Flow And Heat Transfer ◽  
Performance Evaluation Criterion ◽  
Vital Effect

Included angles (?) have vital effect on the flow and heat transfer in cross-corrugated triangular ducts. The friction factor and Nusselt number were estimated at different Reynolds numbers from both experiments and simulations. Results show that the flow in the duck with ?=90 has the largest friction factor and Nusselt number. However, the included angle influences the flow and heat transfer in cross-corrugated triangular ducts in different ways. The field synergy principle was used to explore the mechanism of the different impacts of the included angle. Results show that the flow in the cross-corrugated triangular duct with ?=90o has the smallest domain averaged included angle (?m), which implies the best synergy performance. The results of the field synergy principle were also validated by analyzing the performance evaluation criterion and studying the velocity vector and temperature distributions.

Scaling Roughness Effects on Pressure Loss and Heat Transfer of Additively Manufactured Channels

2016 ◽  
Author(s):  
Curtis K. Stimpson ◽  
Jacob C. Snyder ◽  
Karen A. Thole ◽  
Dominic Mongillo
Keyword(s):  
Heat Transfer ◽  
Metal Powder ◽  
Pressure Loss ◽  
Complex Flow ◽  
Roughness Effects ◽  
Flow Paths ◽  
Flow And Heat Transfer ◽  
Flow Through ◽  
High Temperature Components ◽  
Small Channels

Additive manufacturing (AM) with metal powder has made possible the fabrication of gas turbine components with small and complex flow paths that cannot be achieved with any other manufacturing technology presently available. The increased design space of AM allows turbine designers to develop advanced cooling schemes in high temperature components to increase cooling efficiency. Inherent in AM with metals is the large surface roughness that cannot be removed from small internal geometries. Such roughness has been shown in previous studies to significantly augment pressure loss and heat transfer of small channels. However, the roughness on these channels or other surfaces made from AM with metal powder has not been thoroughly characterized for scaling pressure loss and heat transfer data. This study examines the roughness of the surfaces of channels of various hydraulic length scales made with direct metal laser sintering (DMLS). Statistical roughness parameters are presented along with other parameters that others have found to correlate with flow and heat transfer. The pressure loss and heat transfer previously reported for the DMLS channels studied in this work are compared to the physical roughness measurements. Results show that the relative arithmetic mean roughness correlates well with the relative equivalent sand grain roughness. A correlation is presented to predict the Nusselt number of flow through AM channels which gives better predictions of heat transfer than correlations currently available.

Numerical Study of Flow and Heat Transfer in Rectangular Channel With Periodic Longitudinal Vortex Generators Under Pulsating Flow

2012 ◽  
Author(s):  
Lin Tian ◽  
Wei Bai ◽  
Shanhu Xue ◽  
Zipeng Huang ◽  
Qiuwang Wang
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Vortex Generators ◽  
Longitudinal Vortex ◽  
Small Scale ◽  
Inlet Velocity ◽  
Flow And Heat Transfer

The unsteady turbulent flow and heat transfer in rectangular channel with periodic longitudinal vortex generators on up and bottom walls are investigated by standardized k-ε two equation turbulent model combined with standardized wall function which has been validated by steady experimental data. Influence of varying frequency and amplitude of inlet velocity varying by sine function on heat transfer and friction factor are discussed. It is found that parameters such as Tout, Tf, Tw, Nusselt number and the friction factor f vary with time periodically, phase difference occurred compared with inlet velocity. Pulsating frequency has little impact on time averaged Nusselt number. However, when amplitude increases from 0.2us to 0.8us, the heat transfer rate is augmented by about 4%. Furthermore, a critical frequency has been captured when amplitude equals to 0.8us for the channel studied. The current study will deepen understanding of unsteady flow in plate fuel assembly, which can be used in small-scale reactors.

Scaling Roughness Effects on Pressure Loss and Heat Transfer of Additively Manufactured Channels

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Curtis K. Stimpson ◽  
Jacob C. Snyder ◽  
Karen A. Thole ◽  
Dominic Mongillo
Keyword(s):  
Heat Transfer ◽  
Metal Powder ◽  
Pressure Loss ◽  
Complex Flow ◽  
Roughness Effects ◽  
Flow Paths ◽  
Flow And Heat Transfer ◽  
Flow Through ◽  
High Temperature Components ◽  
Small Channels

Additive manufacturing (AM) with metal powder has made possible the fabrication of gas turbine components with small and complex flow paths that cannot be achieved with any other manufacturing technology presently available. The increased design space of AM allows turbine designers to develop advanced cooling schemes in high-temperature components to increase cooling efficiency. Inherent in AM with metals is the large surface roughness that cannot be removed from small internal geometries. Such roughness has been shown in previous studies to significantly augment pressure loss and heat transfer of small channels. However, the roughness on these channels or other surfaces made from AM with metal powder has not been thoroughly characterized for scaling pressure loss and heat transfer data. This study examines the roughness of the surfaces of channels of various hydraulic length scales made with direct metal laser sintering (DMLS). Statistical roughness parameters are presented along with other parameters that others have found to correlate with flow and heat transfer. The pressure loss and heat transfer previously reported for the DMLS channels studied in this work are compared to the physical roughness measurements. Results show that the relative arithmetic mean roughness correlates well with the relative equivalent sand grain roughness. A correlation is presented to predict the Nusselt number of flow through AM channels, which gives better predictions of heat transfer than correlations currently available.

Numerical Investigation of Flow and Heat Transfer in Microchannels

2008 ◽  
Author(s):  
Emrah Deniz ◽  
I. Yalcin Uralcan
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Experimental Studies ◽  
Numerical Results ◽  
Turbulent Regime ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Micro Channels

Mini and microchannel applications have become an important and attractive research area during the past decades. For micro systems design purposes, numerical and experimental studies have been conducted on flow and heat transfer characteristics of mini and microchannels and various friction factor and Nusselt number correlations have been proposed. Some researchers have tried to apply conventional tube correlations to mini and micro channels, rather than deriving new correlations. In this study, using commercial CFD software, flow and heat transfer characteristics in laminar and turbulent flow through circular channels are analyzed numerically. The applicability of conventional correlations in calculating the friction factor and Nusselt number is investigated. It is concluded that, in laminar regime conventional correlations can be used to calculate the friction factor for the channel sizes considered. In turbulent regime, however, numerical results for friction factor yielded greater values than those calculated by the conventional correlations. Numerical Nusselt numbers are found to be closer to the conventional values in laminar and turbulent regimes. In turbulent regime, on the other hand, Nusselt number values calculated with the microchannel correlations are determined to be greater than the numerical results and the values calculated with the conventional correlations.

Forced Convection in a Square Duct With a Wavy Wall

2013 ◽  
Author(s):  
H. Shmueli ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Wave Amplitude ◽  
Numerical Approach ◽  
Wavy Wall ◽  
Local Flow ◽  
Square Duct ◽  
Eddy Simulation ◽  
Flow And Heat Transfer

In the present study, turbulent flow and heat transfer in a square duct with a heated wavy wall are investigated numerically using the Large Eddy Simulation (LES). A thorough validation of the numerical approach is done versus the existing results for both flat-wall square ducts and wavy-wall channels. It is demonstrated that a very good agreement is achieved with the literature in terms of global and local flow and heat transfer parameters. Heated wavy surfaces of various amplitudes are explored. The results are compared with those for a completely flat duct in terms of the friction factor and Nusselt number. It is shown that the friction factor increases practically linearly with the wave amplitude. On the other hand, the Nusselt number, averaged over the entire duct length, increases more steeply for the relatively small wave amplitude, but almost reaches a plateau for a further increase in the amplitude.

Numerical Study of the Effect of Concentric, Thermally-insulated Insert on Brinkman-Forchheimer Flow and Heat Transfer through a Cylindrical Tube

2018 ◽  
Vol 7 (4.10) ◽  
pp. 290
Author(s):  
P. G. Siddheshwar ◽  
S. Ashoka ◽  
Om P. Suthar
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Continuation Method ◽  
Difference Approximation ◽  
Computer Assisted ◽  
Flow And Heat Transfer ◽  
Linear Algebraic Equations ◽  
Non Linear ◽  
Flow Through ◽  
Forchheimer Flow

The system of non-linear algebraic equations arising from the application of the central difference approximation to the fully developed Brinkman-Forchheimer flow equation is solved using the computer assisted continuation method based on the classical, explicit Runge-Kutta method of four slopes. The continuation method is found to be very effective in capturing boundary and inertia effects in the considered flow through porous media. Further, it succeeds in giving the required solution for large values of Forchheimer number when shooting method fails to do so. Heat transport in forced convective flow through the annulus is quantified in terms of the Nusselt number. It is found that the effect of increasing the radius of the inner cylinder is to increase the Nusselt number. The results of fully-developed, non-linear flow and heat transfer through a rectangular channel and a cylindrical porous tube are obtained as limiting cases of the present study. 

scholarly journals Three-dimensional numerical investigation of turbulent flow and heat transfer inside a horizontal semi-circular cross-sectioned duct

2014 ◽  
Vol 18 (4) ◽  
pp. 1145-1158 ◽  
Author(s):  
Kamil Arslan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Forced Flow ◽  
Flow And Heat Transfer ◽  
Darcy Friction Factor

In this study, steady-state turbulent forced flow and heat transfer in a horizontal smooth semi-circular cross-sectioned duct was numerically investigated. The study was carried out in the turbulent flow condition where Reynolds numbers range from 1?104 to 5.5?104. Flow is hydrodynamically and thermally developing (simultaneously developing flow) under uniform surface heat flux with uniform peripheral wall heat flux (H2) boundary condition on the duct?s wall. A commercial CFD program, Ansys Fluent 12.1, with different turbulent models was used to carry out the numerical study. Different suitable turbulence models for fully turbulent flow (k-? Standard, k-? Realizable, k-? RNG, k-? Standard and k-? SST) were used in this study. The results have shown that as the Reynolds number increases Nusselt number increases but Darcy friction factor decreases. Based on the present numerical solutions, new engineering correlations were presented for the average Nusselt number and average Darcy friction factor. The numerical results for different turbulence models were compared with each other and similar experimental investigations carried out in the literature. It is obtained that, k-? Standard, k-? Realizable and k-? RNG turbulence models are the most suitable turbulence models for this investigation. Isovel contours of velocity magnitude and temperature distribution for different Reynolds numbers, turbulence models and axial stations in the duct were presented graphically. Also, local heat transfer coefficient and local Darcy friction factor as function of dimensionless position along the duct were obtained in this investigation.

Counter-rotation vortex flows and heat transfer mechanisms in a V-spirally-corrugated tube

2019 ◽  
Vol 233 (7) ◽  
pp. 928-952 ◽  
Author(s):  
S Eiamsa-ard ◽  
P Promthaisong
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Flow Region ◽  
Corrugated Tube ◽  
Flow And Heat Transfer ◽  
Counter Rotation ◽  
Swirl Flows ◽  
Transfer Behavior ◽  
Fluid Transfer

The flow and heat transfer behavior of newly designed V-corrugated tubes with various numbers of starts ( N = 2, 3, 4, and 5), depth ratios ( DR = 0.02–0.14), and pitch ratios ( PR = 1.0–2.0) were studied in the turbulent flow region (5000 ≤  Re ≤ 20,000). The friction factor ( f), friction factor ratio ( f/ f0), Nusselt number ( Nu), Nusselt number ratio ( Nu/ Nu0), and thermal enhancement factor ( TEF) values are reported. The computational results indicate that the conventional spirally-corrugated tube create swirl flows while V-corrugated tubes generate a counter-rotating vortex flow that impinges upon the lower zone of the tubes and enhances fluid transfer between tube core and near-wall regions. The results also show that the f, Nu, f/ f0, Nu/ Nu0 monotonically increase with decreasing PR, increasing DR and N, while the TEF is dependent on a tradeoff between f/ f0 and Nu/ Nu0. Over the studied range, the f/ f0, Nu/ Nu0, and TEF were in the ranges of 1.36–43.82, 1.00–5.35, and 0.80–2.11, respectively. The maximum TEF, 2.11, was achieved with a V-corrugated tube with an N of 4, DR of 0.06, and PR of 2.0 at Re = 5000.

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