scholarly journals CONVECTIVE HEAT TRANSFER ON STENOSED BLOOD FLOW THROUGH PERMEABLE MICROCIRCULATION IN THE PRESENCE OF A MAGNETIC FIELD

2020 ◽  
Author(s):  
Alana Sankar ◽  
Sreedhara Rao Gunakala ◽  
Donna Comissiong
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Reynolds Number ◽  
Blood Flow ◽  
Nusselt Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Hartmann Number ◽  
Darcy Number ◽  
Flow Through

Blood flow through permeable microcirculation in the presence of a composite stenosis, an external magnetic field and convective heat transfer was examined. A two-layered model for the blood consisting of a fluid-particle suspension in the core region with a peripheral cell-free plasma layer was used. The proposed system of equations was solved and plots were generated. In the presence of permeable walls, an external magnetic field and convective heat transfer, the temperature of the blood, friction-factor Reynolds number and Nusselt number were investigated. The temperature of the blood increased when the Hartmann number increased, Darcy number increased, haematocrit level increased or the peripheral layer thinned. The friction-factor Reynolds number product increased as the haematocrit, Hartmann number, stenosis height or Darcy number increased. The Nusselt number decreased as the Hartmann number, haematocrit, stenosis height or Darcy number increased. These results were interpreted in terms of the physical situation. This study aids in understanding the effects of wall permeability, a magnetic field and the presence of heat transfer on different diseased arterial systems in the future.

Role of magnetic field on forced convection of nanofluid in a branching channel

2019 ◽  
Vol 30 (4) ◽  
pp. 1755-1772 ◽  
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Öztop ◽  
Ali J. Chamkha
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat Transfer ◽  
Forced Convection ◽  
Convective Heat ◽  
Transfer Rate ◽  
Base Fluid ◽  
Hartmann Number ◽  
Content Type

Purpose Numerical study of nanofluid forced convection within a branching channel was performed under the influence of a uniform magnetic field. The purpose of this study is to enhance the heat transfer performance of the separated flow at the branching channel with the use of magnetic field and nanofluid. The use of magnetic field and enhancement in both the thermal conductivity and electrical conductivity with the inclusion of the nanoparticles provides favorable thermophysical properties of the nanofluid when it used as a heat transfer fluid in a branching channel. The results of this study may be used to control the thermal performance in a branching channel and further optimization studies in the presence of magnetic field. Design/methodology/approach Galerkin weighted residual finite element method was used for the simulations. The numerical simulation results are performed by changing the inclination angle of the lower branching channel (between 0° and 90°), thermophysical properties of the fluid via inclusion of nanoparticles (between 0 and 0.04), Reynolds number (between 100 and 400) and magnetic field strength (Hartmann number changes between 0 and 15). Findings It was observed that the recirculation zones and reattachment length of the upper and lower branching channels are affected by the variation of those parameters. Reattachment lengths increase with the augmentation of the Reynolds number and deterioration of the Hartmann number. Average Nusselt number becomes higher for higher values of Hartmann number and solid particle volume fraction. Inclusion of the nanoparticle to the base fluid is very effective for the configuration with higher values of Hartmann number. An optimum value of the inclination angle of the lower branching channel is observed, beyond which heat transfer rate is significantly reduced due to the establishment of a large vortex in the upper branching channel and restriction of the fluid motion. Originality/value In this study, forced convection of nanofluid flow in a branching channel under the effect of magnetic field was numerically studied. Magnetic field effects with nanoparticle inclusion to the base fluid on the convective heat transfer was analyzed for various inclination angles of the lower branching channel. Flow separation at the junction of the channels and thus convective heat transfer rate are influenced by the variation of these parameters. There are many studies related to application of the magnetic field with nanofluids, and a few of them are related to configurations with separated flows. To the best of the authors’ knowledge, there exist no studies for the application of nanofluids and magnetic field for the convective heat transfer in a branching channel. This topic is of importance as there are many engineering applications of the branching channels.

scholarly journals Research on convective heat transfer characteristics of Fe3O4magnetic nanofluids under vertical magnetic field

2021 ◽  
pp. 151-151
Author(s):  
Ruihao Zhang ◽  
Sixian Wang ◽  
Shan Qing ◽  
Zhumei Luo ◽  
Zhang Xiaohui
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Reynolds Number ◽  
Field Strength ◽  
Convective Heat Transfer ◽  
Magnetic Field Strength ◽  
Convective Heat ◽  
Heat Transfer Characteristics ◽  
Magnetic Nanofluids ◽  
The Magnetic Field

This paper focuses on the convective heat transfer characteristics of Fe3O4 /Water magnetic nanofluids under laminar and turbulent conditions. After verifying the accuracy of the experimental apparatus, the effects of magnetic field strength, concentration, Reynolds number and temperature on the convective heat transfer coefficient have been studied. The convective heat transfer characteristics of nanofluids under laminar and turbulent flow conditions were studied in depth, and the influence of each factor on the heat transfer coefficient was analyzed by orthogonal experimental design method. Under the laminar flow conditions, the convective heat transfer of magnetic nanofluids performed best when the Reynolds number was 2000, the magnetic field strength was 600, the temperature was 30? and the concentration was 2%. And the convective heat transfer coefficient (h) increased by 3.96% than the distilled water in the same conditions. In turbulent state, the convective heat transfer of magnetic nanofluids performed the best when the Re was 6000, the magnetic field strength was 600, the temperature was 40? and the concentration was 2%. The h increased by 11.31% than the distilled water in the same Reynolds number and the magnetic field strength conditions.

scholarly journals Determination of Heat Transfer Coefficients Over Ribbed Surfaces With Infrared Thermography

1997 ◽  
Author(s):  
Francisco P. Brójo ◽  
Luís C. Gonçalves ◽  
Pedro D. Silva
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convective Heat Transfer Coefficient ◽  
Stanton Number ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

The scope of the present work is to characterize the heat transfer between a ribbed surface and an air flow. The convective heat transfer coefficients, the Stanton number and the Nusselt number were calculated in the Reynolds number range, 5.13 × 105 to 1.02 × 106. The tests were performed inside a turbulent wind tunnel with one roughness height (e/Dh = 0.07). The ribs had triangular section with an attack angle of 60°. The surface temperatures were measured using an infrared (IR) thermographic equipment, which allows the measurement of the temperature with a good spatial definition (10.24 × 10−6 m2) and a resolution of 0.1°C. The experimental measures allowed the calculation of the convective heat transfer coefficient, the Stanton number and the Nusselt number. The results obtained suggested a flow pattern that includes both reattachment and recirculation. Low values of the dimensionless Stanton number, i.e. Stx*, are obtained at the recirculation zones and very high values of Stx* at the zones of reattachment. The reattachment is located at a dimensionless distance of 0.38 from the top of the rib. That distance seems to be independent of the Reynolds number. The local dimensionless Stanton number remains constant as the Reynolds number varies. The convective heat transfer coefficient presents an uncertainty in the range of 3 to 6%.

Effect of Reynolds Number, Hole Patterns and Hole Inclination on Cooling Performance of an Impinging Jet Array: Part I — Convective Heat Transfer Results and Optimization

2016 ◽  
Author(s):  
Weihong Li ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang ◽  
Li Yang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Impinging Jet ◽  
Target Plate ◽  
New Correlation

This study comprehensively illustrates the effect of Reynolds number, hole spacing, jet-to-target distance and hole inclination on the convective heat transfer performance of an impinging jet array. Highly resolved heat transfer coefficient distributions on the target plate are obtained utilizing transient liquid crystal over a range of Reynolds numbers varying between 5,000 and 25,000. Effect of streamwise and spanwise jet-to-jet spacing (X/D, Y/D: 4–8) and jet-to-target plate distance (Z/D: 0.75–3) are employed composing a test matrix of 36 different geometries. Additionally, the effect of hole inclination (θ: 0°–40°) on the heat transfer coefficient is investigated. Optical hole spacing arrangements and impingement distance are pointed out to maximize the area-averaged Nusselt number and minimize the amount of cooling air. Also included is a new correlation, based on that of Florschuetz et al., to predict row-averaged Nusselt number. The new correlation is capable to cover low Z/D∼0.75 and presents better prediction of row-averaged Nusselt number, which proves to be an effective impingement design tool.

Study of Heat Transfer Control with Magnetic Field Using Higher Order Finite Difference Scheme

2016 ◽  
Vol 8 (3) ◽  
pp. 449-463 ◽  
Author(s):  
R. Sivakumar ◽  
S. Vimala ◽  
S. Damodaran ◽  
T. V. S. Sekhar
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Nusselt Number ◽  
Temperature Field ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Experimental Studies ◽  
Higher Order ◽  
Polar Coordinates ◽  
Cylindrical Polar Coordinates

Abstract.The control of convective heat transfer from a heated circular cylinder immersed in an electrically conducting fluid is achieved using an externally imposed magnetic field. A Higher Order Compact Scheme (HOCS) is used to solve the governing energy equation in cylindrical polar coordinates. The HOCS gives fourth order accurate results for the temperature field. The behavior of local Nusselt number, mean Nusselt number and temperature field due to variation in the aligned magnetic field is evaluated for the parameters 5≤Re≤40, 0≤N≤20 and 0.065≤Pr≤7. It is found that the convective heat transfer is suppressed by increasing the strength of the imposed magnetic field until a critical value of N, the interaction parameter, beyond which the heat transfer increases with further increase in N. The results are found to be in good agreement with recent experimental studies.

The Heat Transfer Characteristics of Rolling Wheel and the Characteristic Length Determining Them

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Liangbi Wang ◽  
Yongheng Zhang ◽  
Yuan Wu ◽  
Qiuwang Wang ◽  
Zhihui Yin
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Characteristic Length ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Rolling Wheel ◽  
Wheel Radius

The convective heat transfer characteristics on the surface of a rolling wheel are investigated using the naphthalene sublimation technique. Five sizes of rolling wheel are selected in the experiments. The local and average Nusselt numbers are obtained. The results reveal that if the wheel radius is used as the characteristic length, the relationship between Nusselt number and Reynolds number is dependent on the wheel radius. This indicates that the wheel radius is not the characteristic length to determine the dimensionless convective heat transfer characteristics of the rolling wheel. Thus, a newly defined characteristic length is provided. For different radii of the wheel, the relationships between Nusselt number and Reynolds number based on this length collapse into one reasonable correlation. The correlation not only enriches the insight of convective heat transfer on rolling wheel but also extends the applicability of the present experimental data.

Numerical Analysis of Convective Heat Transfer From an Elliptic Pin Fin Heat Sink With and Without Metal Foam Insert

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Hamid Reza Seyf ◽  
Mohammad Layeghi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Numerical Analysis ◽  
Pressure Drop ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Sink ◽  
Metal Foam ◽  
Pin Fin

A numerical analysis of forced convective heat transfer from an elliptical pin fin heat sink with and without metal foam inserts is conducted using three-dimensional conjugate heat transfer model. The pin fin heat sink model consists of six elliptical pin rows with 3 mm major diameter, 2 mm minor diameter, and 20 mm height. The Darcy–Brinkman–Forchheimer and classical Navier–Stokes equations, together with corresponding energy equations are used in the numerical analysis of flow field and heat transfer in the heat sink with and without metal foam inserts, respectively. A finite volume code with point implicit Gauss–Seidel solver in conjunction with algebraic multigrid method is used to solve the governing equations. The code is validated by comparing the numerical results with available experimental results for a pin fin heat sink without porous metal foam insert. Different metallic foams with various porosities and permeabilities are used in the numerical analysis. The effects of air flow Reynolds number and metal foam porosity and permeability on the overall Nusselt number, pressure drop, and the efficiency of heat sink are investigated. The results indicate that structural properties of metal foam insert can significantly influence on both flow and heat transfer in a pin fin heat sink. The Nusselt number is shown to increase more than 400% in some cases with a decrease in porosity and an increase in Reynolds number. However, the pressure drop increases with decreasing permeability and increasing Reynolds number.

TURBULENT-FORCED CONVECTIVE HEAT TRANSFER AND PRESSURE DROP ANALYSIS OF FE3O4 MAGNETIC NANOFLUID IN A CIRCULAR MICROCHANNEL

2015 ◽  
Vol 75 (11) ◽  
Author(s):  
Nor Azwadi Che Sidik ◽  
M.M. Yassin ◽  
M.N. Musa
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Volume Concentration ◽  
Pure Water ◽  
Dimensional Structure ◽  
Outlet Section

A numerical simulation was accomplished in this study that investigated the turbulent force convective heat transfer and pressure drop in straight circular copper pipe with a hydraulic diameter of 0.0005m and 0.1m in length, as given by Lee and Mudawar [11]. The enhancement of heat transfer for water and nanofluids (Fe3O4) under 100 [W/m2] constant heat flux was applied around the wall of the pipe. In this study, standard k-ɛ turbulence model was employed and was performed at a steady state flow, incompressible turbulent flow, and three-dimensional structure. Various volume concentrations of nanoparticles were conducted in the range of 1% to 15% at constant nanoparticle diameter size, which was 32 nm. The heat transfer enhancement was obtained in the range of Reynolds number from 3000 to 10,000. The results displayed an increase in Reynolds number and volume concentrations, as well as an increase in the Nusselt number. The optimum Nusselt number gained was about 5% to 6% of volume concentration at each Reynolds number tested. Besides, with the increase of Reynolds number, the variation pressure saw a dropped for inlet, whereas an increase in the outlet section. Moreover, the  increase in volume concentration also caused a small increment in the pressure drop compared to pure water.

Convective Heat Transfer Coefficients in a Building-Integrated Photovoltaic/Thermal System

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Luis M. Candanedo ◽  
Andreas Athienitis ◽  
Kwang-Wook Park
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Average Nusselt Number ◽  
Heated Surface ◽  
Reynolds Numbers ◽  
Building Integrated Photovoltaic ◽  
T System

This paper presents an experimental study for the development of convective heat transfer correlations for an open loop air-based building-integrated photovoltaic/thermal (BIPV/T) system. The BIPV/T system absorbs solar energy on the top surface, which includes the photovoltaic panels and generates electricity while also heating air drawn by a variable speed fan through a channel formed by the top roof surface with the photovoltaic modules and an insulated attic layer. The BIPV/T system channel has a length/hydraulic diameter ratio of 38, which is representative of a BIPV/T roof system for 30–45 deg tilt angles. Because of the heating asymmetry in the BIPV/T channel, two average Nusselt number correlations are reported as a function of Reynolds number: one for the top heated surface and the other for the bottom surface. For the top heated surface, the Nusselt number is in the range of 6–48 for Reynolds numbers ranging from 250 to 7500. For the bottom insulated surface, the Nusselt number is in the range of 22–68 for Reynolds numbers ranging from 800 to 7060. This paper presents correlations for the average Nusselt number as a function of Reynolds number; this correlation is considered adequate for the design of BIPV/T systems where forced convection dominates. Local Nusselt number distributions are also presented for laminar and turbulent flow conditions.

Laminar Mixing, Heat Transfer and Pressure Losses in a Chaotic Mini-Channel: Application to the Fuel Cell Cooling

2006 ◽  
Author(s):  
Yahia Lasbet ◽  
Bruno Auvity ◽  
Cathy Castelain ◽  
Hassan Peerhossaini
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Pressure Loss ◽  
Inlet Section ◽  
Mixing Rate ◽  
Channel Geometry ◽  
Pressure Losses

Currently, the heat exchangers allowing the cooling of the low temperature fuel cells (PEMFC) are integrated in the bipolar plates and constituted of a network of straight channels. The flow regime is laminar, and thus, unfavorable to an intense convective heat transfer. In order to increase the power density of the fuel cells, the use of chaotic geometries in the cooling system is envisaged to intensify high convective heat transfer. In this numerical study, several chaotic three-dimensional mini-channels of rectangular section (2 millimeters × 1 millimeter) are evaluated in terms of heat transfer efficiency, mixing properties and pressure losses. Their performances are compared to those of a straight channel geometry currently used in the cooling systems of the PEMFC, and a serpentine 2-D channel. Hydrodynamic and thermal performances of these geometries are computed using the commercial CFD code Fluent©. At the inlet section, the velocity profile is hydrodynamically established. The thermophysical properties of the fluid are constant and equal to those of water at 300 K. The Nusselt number is evaluated for a Reynolds number equal to 200 and with a uniform density flux imposed on the walls and equal to 10,000 W/m2. For the calculation of the mixing rate, a condition of adiabatic wall is imposed. The inlet section is horizontally divided into two parts. Water in the higher part is at the temperature of 320K and in the lower part is at the temperature of 300K. The calculation of the mixing rate is made for Reynolds numbers equal to 100 and 200. The present study shows that a 3-D chaotic channel geometry significantly improves the convective heat transfer compared to regular straight or serpentine channels. Among all the studied geometries, one of them induces the higher heat transfer intensification (mean Nusselt number equal to 20) with a strong pressure loss. With an alternative geometry, we obtained a better compromise between high heat transfer and reduced pressure loss. However, all the chaotic geometries present similar mixing rate for the two studied Reynolds number. To confirm the performances of the selected geometries, an experimental study is currently undertaken. The final aim is to realize and test a prototype of chaotic heat exchanger in a bipolar plate of PEMFC.

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