The Effects of Variable Properties on MHD Flow in Finite Ducts

1970 ◽  
Vol 37 (4) ◽  
pp. 954-958 ◽  
Author(s):  
W. J. Thomson ◽  
G. R. Bopp
Keyword(s):  
Numerical Solutions ◽  
Mhd Flow ◽  
Duct Flow ◽  
Variable Properties ◽  
Temperature Dependent ◽  
Constant Property ◽  
Flow Rates ◽  
Friction Factors ◽  
Fluid Properties ◽  
Fluid Parameters

Numerical solutions are obtained of the coupled partial differential equations which describe variable property MHD flow in finite rectangular ducts. The fluid properties are allowed to vary to the extent that electrical conductivity and viscosity are assumed to be temperature-dependent. It is shown that it is not possible to account for fluid property variations in terms of “weighted” fluid parameters such as average Hartmann numbers. Analysis leads to the conclusion that it is the nature of the current distributions in the duct which is important in predicting the behavior of nonisothermal MHD duct flow. It is possible that this conclusion may aid in the evaluation and correlation of experimental data. It is also shown that consideration of variable fluid properties results in friction factors and flow rates which differ from constant property solutions by as much as a factor of two and by 50 percent, even for small variations.

Numerical study on the effects of variable properties and nanoparticle diameter on nanofluid flow and heat transfer through micro-annulus

2017 ◽  
Vol 27 (8) ◽  
pp. 1851-1869 ◽  
Author(s):  
Morteza Heydari ◽  
Hossein Shokouhmand
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Numerical Study ◽  
Simple Algorithm ◽  
Variable Properties ◽  
Temperature Dependent ◽  
Constant Property ◽  
Content Type ◽  
Nanoparticle Diameter ◽  
Flow And Heat Transfer

Purpose The purpose of this paper is to evaluate differences between the results of constant property and variable property approaches in solving the problem of Al2O3-water nanofluid heat transfer in an annular microchannel. Also, the effect of nanoparticle diameter on flow and heat transfer characteristics is investigated. Design/methodology/approach Thermo-physical properties of the nanofluid including density, specific heat, viscosity and thermal conductivity are assumed to be temperature dependent. Governing equations are descritized using the finite volume method and solved by SIMPLE algorithm. Findings The results reveal that the constant property assumption is unable to predict the correct trend of variations along the microchannel for some of the characteristics, especially when the range of temperature change near the wall is considerable. In the fully developed region, constant property solution overestimates the values of shear stress near the walls of the microchannel. In addition, the values of Nusselt numbers are different for the two solutions. Furthermore, a decrease in wall’s shear stress has been observed as a result of increasing nanoparticle size. Originality/value This paper reflects that how the friction factor and heat transfer vary along the microchannel in temperature dependent modeling, which is not reflected in the results of constant property approach. To the best of the authors’ knowledge, there is no similar investigation of the effect of nanofluid variable properties with Pr=5 or in annular geometry.

Thermal Performance Analysis of a Rectangular Longitudinal Finned Solar Air Heater With Semicircular Absorber Plate

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Satyender Singh ◽  
Prashant Dhiman
Keyword(s):  
Thermal Performance ◽  
Numerical Solutions ◽  
Solar Air Heater ◽  
Duct Flow ◽  
Balance Equations ◽  
Absorber Plate ◽  
Ansys Fluent ◽  
Air Heater ◽  
Glass Cover ◽  
Good Agreement

Thermal performance of a single-pass single-glass cover solar air heater consisting of semicircular absorber plate finned with rectangular longitudinal fins is investigated. The analysis is carried out for different hydraulic diameters, which were obtained by varying the diameter of the duct from 0.3–0.5 m. One to five numbers of fins are considered. Reynolds number ranges from 1600–4300. Analytical solutions for energy balance equations of different elements and duct flow of the solar air heater are presented; results are compared with finite-volume methodology based numerical solutions obtained from ansys fluent commercial software, and a fairly good agreement is achieved. Moreover, analysis is extended to check the effect of double-glass cover and the recycle of the exiting air. Results revealed that the use of double-glass cover and recycle operation improves the thermal performance of solar air heater.

scholarly journals Microfluidic Network Simulations Enable On-Demand Prediction of Control Parameters for Operating Lab-On-A-Chip-Devices

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1320
Author(s):  
Julia Sophie Böke ◽  
Daniel Kraus ◽  
Thomas Henkel
Keyword(s):  
Fluid Management ◽  
Lab On A Chip ◽  
Microfluidic System ◽  
Flow Rates ◽  
Demand Prediction ◽  
Fast Running ◽  
Microfluidic Network ◽  
Fluid Properties ◽  
Network Simulations ◽  
User Friendly

Reliable operation of lab-on-a-chip systems depends on user-friendly, precise, and predictable fluid management tailored to particular sub-tasks of the microfluidic process protocol and their required sample fluids. Pressure-driven flow control, where the sample fluids are delivered to the chip from pressurized feed vessels, simplifies the fluid management even for multiple fluids. The achieved flow rates depend on the pressure settings, fluid properties, and pressure-throughput characteristics of the complete microfluidic system composed of the chip and the interconnecting tubing. The prediction of the required pressure settings for achieving given flow rates simplifies the control tasks and enables opportunities for automation. In our work, we utilize a fast-running, Kirchhoff-based microfluidic network simulation that solves the complete microfluidic system for in-line prediction of the required pressure settings within less than 200 ms. The appropriateness of and benefits from this approach are demonstrated as exemplary for creating multi-component laminar co-flow and the creation of droplets with variable composition. Image-based methods were combined with chemometric approaches for the readout and correlation of the created multi-component flow patterns with the predictions obtained from the solver.

scholarly journals Perturbation Solutions For Magnetohydrodynamics (Mhd) Flow of in a Non-Newtonian Fluid Between Concentric Cylinders

2019 ◽  
Vol 24 (1) ◽  
pp. 199-211
Author(s):  
M. Yürüsoy ◽  
Ö.F. Güler
Keyword(s):  
Analytical Solutions ◽  
Numerical Solutions ◽  
Variable Viscosity ◽  
Perturbation Technique ◽  
Equations Of Motion ◽  
Mhd Flow ◽  
Model Space ◽  
Viscosity Model ◽  
Concentric Cylinders ◽  
Approximate Analytical Solutions

Abstract The steady-state magnetohydrodynamics (MHD) flow of a third-grade fluid with a variable viscosity parameter between concentric cylinders (annular pipe) with heat transfer is examined. The temperature of annular pipes is assumed to be higher than the temperature of the fluid. Three types of viscosity models were used, i.e., the constant viscosity model, space dependent viscosity model and the Reynolds viscosity model which is dependent on temperature in an exponential manner. Approximate analytical solutions are presented by using the perturbation technique. The variation of velocity and temperature profile in the fluid is analytically calculated. In addition, equations of motion are solved numerically. The numerical solutions obtained are compared with analytical solutions. Thus, the validity intervals of the analytical solutions are determined.

Numerical Solutions of Transients in Pneumatic Networks: Part 3—Network Problems With Branching

1969 ◽  
Vol 36 (3) ◽  
pp. 594-597 ◽  
Author(s):  
S. Tsao ◽  
W. Rodgers
Keyword(s):  
Boundary Condition ◽  
Fluid Flow ◽  
Transmission Lines ◽  
Numerical Solutions ◽  
Mathematical Problem ◽  
Flow Rates ◽  
Network Problems

This paper investigates the mathematical problem of fluid flow at a junction. It is shown that the junction pressure at a given time can be expressed approximately in terms of the known pressures and flow rates at and near the junction at an earlier time. After the junction pressure is determined, it serves as a boundary condition for all the transmission lines meeting at the junction. Several junction networks are computed for illustrative purposes.

Upwinding Meshfree Point Collocation Method for Unsteady Magnetohydrodynamic Flow at High Hartmann Numbers

2011 ◽  
Vol 130-134 ◽  
pp. 1668-1671
Author(s):  
Xing Hui Cai ◽  
Cheng Ying Shi ◽  
Guo Liang Wang
Keyword(s):  
Collocation Method ◽  
Numerical Solutions ◽  
Hartmann Number ◽  
Mhd Flow ◽  
Rectangular Section ◽  
Point Collocation ◽  
Coupled Equations ◽  
Meshless Collocation ◽  
Support Domain ◽  
Flow Through

In this paper, a meshfree point collocation method, with an upwinding scheme, is presented to obtain the numerical solutions of the coupled equations in the velocity field for the unsteady magnetohydrodynamic (MHD) flow through a straight duct of rectangular section with insulated walls. Computations have been carried out for the unsteady MHD flow, which is under the external applied magnetic field of arbitrary orientation, of different Hartmann number from 5 to 106 and at various time levels. As the adaptive upwinding local support domain is introduced in the meshless collocation method, numerical results show that the method can compute MHD problems with Hartmann numbers up to 106 with good accuracy. The results also show that as Hartmann number increases, the time needed to reach the steady state decreases.

A Procedure to Reduce the Effects of Variable Fluid Temperatures in the Flow Direction: Application to the Design of a Rotary Regenerator

1988 ◽  
Author(s):  
Thomas P. Lewandowski ◽  
Tah-Teh Yang
Keyword(s):  
Heat Exchanger ◽  
Analytical Procedure ◽  
Flow Direction ◽  
Operating Conditions ◽  
Single Element ◽  
Temperature Dependent ◽  
Axial Temperature ◽  
Flow Length ◽  
Fluid Properties ◽  
Element Method

The purpose of this paper is to present results of an analytical procedure which accounts for variations in temperature dependent fluid properties in the flow direction of a heat exchanger. The procedure is called the multi-element method and is used in the performance calculations of a rotary regenerator subject to axial temperature variations greater than 2:1. The multi-element method partitions the flow length and evaluates the heat exchanger by combining the performances of each length. The results show graphically the differences between using the multi-element method and a more commonly used single-element method. The differences presented are between the predicted regenerator disk thickness and between the predicted core pressure drop for a variety of operating conditions.

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