scholarly journals Investigation of effects on heat transfer and flow characteristics of Cr-Ni alloy and aluminum pins placed in AISI 304 tube

2020 ◽  
Vol 24 (3 Part B) ◽  
pp. 1999-2011
Author(s):  
Adnan Berber ◽  
Kazım Bagirsakci ◽  
Mehmet Gurdal
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Numerical Study ◽  
Fluid Velocity ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Forced Flow ◽  
Aisi 304 ◽  
Ni Alloy ◽  
Plain Tube

In this study, the effects of cylindrical aluminum and Cr-Ni alloy pins placed in different arrangements on the inner wall of the pipe in the turbulent flow, the effects of heat transfer and flow characteristics on different Reynolds numbers have been experimentally investigated. The experiments were carried out under forced flow and constant heat flow conditions. Air is preferred as the fluid and the fluid velocity is adjusted between Reynolds number of 10000 and 50000. It has been observed that the Nusselt values obtained over the number of Reynolds number for the 5 different test tubes are arranged in a line from large to small, sequential row aluminum pin, sequential row Cr-Ni alloy pin, diagonal row aluminum pin, diagonal row Cr-Ni alloy pin, plain tube. There are also CFD analysis for each material, arrangements and pins geometry sets. On the other hand, it was determined that friction coefficient is directly proportional to the increase of heat transfer coefficient. As a result, it is observed that experimental results are compatible with both literature and numerical study.

scholarly journals Numerical study of gas dynamics and heat transfer in matrix channels at various rib angles

2021 ◽  
Vol 2057 (1) ◽  
pp. 012026
Author(s):  
A V Barsukov ◽  
V V Terekhov ◽  
V I Terekhov
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Gas Dynamics ◽  
Average Velocity ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Separation Flow ◽  
Maximum Heat ◽  
Maximum Heat Transfer

Abstract The results of numerical simulation of the separation flow in matrix channels by the RANS method are presented. The simulation is performed at the Reynolds number Re = 12600, determined by the mass-average velocity and the height of the channel. The distribution of the local Nusselt number is obtained for various Reynolds numbers in the range of 5÷15⋅103 and several rib angles. It is shown that the temperature distribution on the surface is highly nonuniform; in particular, the maximum heat transfer value is observed near the upper edge facets, in the vicinity of which the greatest velocity gradient is observed.

Numerical Investigation on Turbulence Statistics and Heat Transfer of a Circular Jet Impinging on a Roughened Flat Plate

2021 ◽  
Vol 13 (4) ◽  
Author(s):  
Abdulrahman Alenezi ◽  
Abdulrahman Almutairi ◽  
Hamad Alhajeri ◽  
Abdulaziz Gamil ◽  
Faisal Alshammari
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Numerical Study ◽  
Roughness Element ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Target Plate ◽  
Cross Sectional ◽  
Flow Physics ◽  
Baseline Case

Abstract A detailed heat transfer numerical study of a three-dimensional impinging jet on a roughened isothermal surface is presented and is investigated from flow physics vantage point under the influence of different parameters. The effects of the Reynolds number, roughness location, and roughness dimension on the flow physics and heat transfer parameters are studied. Additionally, the relations between average heat transfer coefficient (AHTC) and flow physics including pressure, wall shear and flow vortices with thermodynamic nonequilibrium are offered. This paper studies the effect of varying both location and dimension of the roughness element which took the shape of square cross-sectional continuous ribs to deliver a favorable trade-off between total pressure loss and heat transfer rate. The roughness element was tested for three different radial locations (R/D) = 1, 1.5, and 2 and at each location its height (i.e., width) (e) was changed from 0.25 to 1 mm in incremental steps of 0.25. The study used a jet angle (α) of 90 deg, jet-to-target distance (H/D = 6), and Re ranges from 10,000 to 50,000, where H is the vertical distance between the target plate and jet exit. The results show that the AHTC can be significantly affected by changing the geometry and dimensions of the roughness element. This variation can be either an augmentation of, or decrease in, the (HTC) when compared with the baseline case. An enhancement of 12.9% in the AHTC was achieved by using optimal location and dimensions of the roughness element at specific Reynolds number. However, a diminution between 10% and 30% in (AHTC) was attained by the use of rib height e = 1 mm at Re = 50k. The variation of both rib location and height showed better contribution in increasing heat transfer for low-range Reynolds numbers.

Numerical Study of Developing Flow and Heat Transfer in a Wavy Passage

1999 ◽  
Vol 121 (4) ◽  
pp. 713-719 ◽  
Author(s):  
K. Stone ◽  
S. P. Vanka
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Numerical Study ◽  
Spatial Location ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
The Core ◽  
Flow And Heat Transfer ◽  
Developing Flow ◽  
Energy Equations

Developing flow and heat transfer in a wavy passage are studied using a numerical scheme that solves the two-dimensional unsteady flow and energy equations. Calculations are presented for a wavy channel consisting of 14 waves. Time-dependent simulations have been performed for several Reynolds numbers. At low Reynolds numbers, the flow is steady in the complete channel. As the Reynolds number is progressively increased, the flow becomes unsteady. As a result of the unsteadiness, there is increased mixing between the core and the wall fluids, thereby increasing the heat transfer rate. With further increase in Reynolds number, the flow becomes unsteady at a much earlier spatial location.

scholarly journals The Effect of Inclination Angle and Reynolds Number on the Performance of a Direct Contact Membrane Distillation (DCMD) Process

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2824 ◽  
Author(s):  
Adnan Alhathal Alanezi ◽  
Mohammad Reza Safaei ◽  
Marjan Goodarzi ◽  
Yasser Elhenawy
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Inclination Angle ◽  
Temperature Difference ◽  
Direct Contact ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Membrane Distillation ◽  
Number Range ◽  
Direct Contact Membrane Distillation

In this numerical study, a direct contact membrane distillation (DCMD) system has been modeled considering various angles for the membrane unit and the Reynolds number range of 500 to 2000. A two-dimensional model developed based on the Navier–Stokes, energy, and species transport equations were used. The governing equations were solved using the finite volume method (FVM). The results showed that with an increase in the Reynolds number of up to 1500, the heat transfer coefficient for all membrane angles increases, except for the inclination angle of 60°. Also, an increase in the membrane angle up to 90° causes the exit influence to diminish and the heat transfer to be augmented. Such findings revealed that the membrane inclination angle of 90° (referred to as the vertical membrane) with Reynolds number 2000 could potentially have the lowest temperature difference. Likewise, within the Reynolds numbers of 1000 and 2000, by changing the inclination angle of the membrane, temperature difference remains constant, however, for Reynolds numbers up to 500, the temperature difference reduces intensively.

Effects of a High Porous Material on Heat Transfer and Flow in a Circular Tube

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
Koichi Ichimiya ◽  
Tetsuaki Takeda ◽  
Takuya Uemura ◽  
Tetsuya Norikuni
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Porous Material ◽  
Entropy Generation ◽  
Circular Tube ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Equivalent Diameter

This paper describes the heat transfer and flow characteristics of a heat exchanger tube filled with a high porous material. Fine copper wires (diameter: 0.5 mm) were inserted in a circular tube dominated by thermal conduction and forced convection. The porosity was from 0.98 to 1.0. The working fluid was air. The hydraulic equivalent diameter was cited as the characteristic length in the Nusselt number and the Reynolds number. The Nusselt number and the friction factor were expressed as functions of the Reynolds number and porosity. The thermal performance was evaluated by the ratio of the Nusselt number with and without a high porous material and the entropy generation. It was recognized that the high porous material was effective in low Reynolds numbers and the Reynolds number, which minimized the entropy generation existed.

An Experimental and Numerical Study on the Aerothermal Characteristics of a Ribbed Transonic Squealer-Tip Turbine Blade With Purge Flow

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
A. Arisi ◽  
J. Phillips ◽  
W. F. Ng ◽  
S. Xue ◽  
H. K. Moon ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Purge Flow

Detailed heat transfer coefficient (HTC) and film cooling effectiveness (Eta) distribution on a squealer-tipped first stage rotor blade were measured using an infrared technique. The blade tip design, obtained from the Solar Turbines, Inc., gas turbine, consists of double purge hole exits and four ribs within the squealer cavity, with a bleeder exit port on the pressure side close to the trailing edge. The tests were carried out in a transient linear transonic wind tunnel facility under land-based engine representative Mach/Reynolds number. Measurements were taken at an inlet turbulent intensity of Tu = 12%, with exit Mach numbers of 0.85 (Reexit = 9.75 × 105) and 1.0 (Reexit = 1.15 × 106) with the Reynolds number based on the blade axial chord and the cascade exit velocity. The tip clearance was fixed at 1% (based on engine blade span) with a purge flow blowing ratio, BR = 1.0. At each test condition, an accompanying numerical study was performed using Reynolds-averaged Navier–Stokes (RANS) equations solver ansys fluent to further understand the tip flow characteristics. The results showed that the tip purge flow has a blocking effect on the leakage flow path. Furthermore, the ribs significantly altered the flow (and consequently heat transfer) characteristics within the squealer-tip cavity resulting in a significant reduction in film cooling effectiveness. This was attributed to increased coolant–leakage flow mixing due to increased recirculation within the squealer cavity. Overall, the peak HTC on the cavity floor increased with exit Mach/Reynolds number.

Numerical Investigation of 3-D Turbulent Flow in Orifice Plate within a Pipe

2015 ◽  
Vol 761 ◽  
pp. 27-31
Author(s):  
Mohamed Abed Alabas Siba ◽  
Wan Mohd Faizal Wan Mahmood ◽  
Mohd Zaki Nuawi ◽  
Rasidi Rasani
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Turbulent Flow ◽  
Finite Volume ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Orifice Plate ◽  
Navier Stokes ◽  
Volume Method

A numerical study of the turbulent flow in an orifice plate within a pipe is carried out by utilizing the Navier-Stokes (N-S) equations. The governing equations are solved using primitive variables with a finite volume method (FVM) and simulated using the finite volume based commercial CFD code ANSYS. The study investigates the influences of Reynolds numbers (Re = 5000, 10000, and 15000) and aspect ratio (β = 0.2, 0.3, and 0.5), on the flow characteristics, i.e. the velocity profile, the differential pressure, and the vorticity, and on the mechanical properties, i.e. the strain, the stress, and the total deformation of the flow around and beyond the orifice. It is found that as the Reynolds number increases, the flow velocity and the pressure increase. The vorticity images show a slightly different behavior. As the Reynolds number has its own effect on the results, it is also found that the aspect ratio affects the results more significantly. The flow patterns are presented for unsteady flow throughout the orifice plate at different values of the Reynolds number.

Heat Transfer and Flow Characteristics of the Jet Array Impingement

2021 ◽  
Author(s):  
Min Ren ◽  
Xueying Li ◽  
Jing Ren
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Cross Flow ◽  
High Heat ◽  
Thermochromic Liquid Crystal ◽  
High Heat Transfer ◽  
Transfer Region ◽  
Performance Of Heat Transfer

Abstract An experimental and numerical study is performed to investigate heat transfer and pressure loss characteristics for impingement. Experimental heat transfer is measured by the thermochromic liquid crystal. The CFD model uses a steady state RANS approach and the shear stress transport (SST). The effect of Reynolds number (5000–25000), the distance between the holes and the distance from the hole to target on the impingement is investigated in the present study. Local Nusselt number as well as area and line average values are gotten experimentally and numerically. Besides, numerical simulations provide the detailed flow characteristics of the problem and complement experimental measurements. The result shows that the heat transfer increases with Reynolds number increasing. But the qualitative distribution of local heat transfer does not change with the increase of Reynolds number, when it is sensitive to P/D and Z/D. The performance of heat transfer is best when Z/D = 2. And the high heat transfer region of Z/D = 1 is closer to the exit than that of Z/D = 2 and Z/D = 3. The main reason is the effect of cross flow and the momentum of the jet reaching the wall. The performance of heat transfer is best when P/D = 5. And the high heat transfer region of P/D = 4 is closer to the exit than that of P/D = 5 and P/D = 6. The main reason is the effect of cross flow and interactions between jets.

Instantaneous and Time-Averaged Flow Structure around Two Heated Square Cylinders in the Laminar Flow Regime

2011 ◽  
Vol 110-116 ◽  
pp. 2896-2902
Author(s):  
Amin Etminan ◽  
Abazar Barzegar
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Laminar Flow ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Viscous Drag ◽  
Two Dimensional ◽  
Number Range ◽  
Pressure Coefficients ◽  
Square Cylinders

In this paper, the flow characteristics and heat transfer over two equal square cylinders which are placed in tandem arrangement, are investigated numerically. The simulations are performed for a Reynolds number range varying from 1 to 200 and spacing between the cylinders is five widths of the cylinders. The calculations are carried out on a finite volume code for both steady and unsteady incompressible laminar flow in the two dimensional regime. In this study, the instantaneous and mean streamlines and isotherm patterns for different Reynolds numbers are presented. In addition, the effect of Reynolds number on the flow patterns around the cylinders are in detail presented. In addition, the quantities such as pressure and viscous drag coefficients and pressure coefficients are presented.

Laminar Entrance Length in Microtubes

2009 ◽  
Author(s):  
Evan C. Lemley ◽  
Tim A. Handy ◽  
Dimitrios V. Papavassiliou ◽  
Henry J. Neeman
Keyword(s):  
Reynolds Number ◽  
Fluid Velocity ◽  
Flow Characteristics ◽  
Computer Code ◽  
Reynolds Numbers ◽  
Hydraulic Diameter ◽  
Entrance Length ◽  
Surface Area Ratio ◽  
Pressure Losses ◽  
Macro Scale

The goal of this study was to determine the entrance length — the distance from a microtube entrance to the point where flow is fully developed — for laminar liquid flow in smooth, straight, circular-microtubes and trapezoidal microchannels. Knowledge of the entrance length and pressure losses in this region for microtubes are of interest in microfluidic devices, in porous media, and in other networks of small ducts or pores. Although laminar entrance length has been studied extensively in macroscale tubes, only recently has attention been paid problem of entrance length in microtubes. Some differences do exist in macro versus micro flow, sometimes attributed to the relatively small volume to surface area ratio at the microscale. The entrance length determined in this study is intended to provide a means to analyze and design microtubes or networks of microtubes. The inlet velocity was varied to provide a Reynolds number of 10 to 2000 and the length was varied based on Reynolds number to ensure the length captured the entire entrance region. Simulations of water at standard conditions were performed using FLUENT and a custom written computer code, which automated the process of creating the flow geometries, extracting results, and determining the entrance length for each run. A grid resolution study was performed to ensure grid size was not a factor. Pressure and velocity distributions as a function of position were extracted to determine flow characteristics. Fluid velocity magnitudes from the tube centerline to 95% of the distance to the tube wall were used to determine when fully developed flow was reached by finding the point at which all velocity magnitudes did not change by more than 1% for additional distance along the tube. Results were compared to results from the literature for entrance length in macro-scale tubes and found to be qualitatively the same. The entrance length (in units of the number of diameters) for circular tubes is often expressed as C times the Reynolds number. For Reynolds numbers greater than 100, this study found C to be 0.0505, which is in general agreement with macroscale experiments and simulations, where C is reported to be between 0.05 and 0.2. For trapezoidal microchannels we found a relationship for entrance length over hydraulic diameter that is proportional (slope of 0.674) to Reynolds number for Reynolds number over 100. As Reynolds numbers get small the value of entrance length over hydraulic diameter goes to 0.674.

Sign in / Sign up

Export Citation Format

Share Document