Analysis of Entropy Generation of a Magneto-Hydrodynamic Flow Through the Operation of an Unlooped Pulsating Heat Pipe

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
Mobadersani Farrokh ◽  
Toolabi Goodarz ◽  
Jafarmadar Samad ◽  
Nasiri Javid ◽  
Habibzadeh Amin
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Pipe ◽  
Entropy Generation ◽  
Uniform Magnetic Field ◽  
Pipe Diameter ◽  
Bejan Number ◽  
Pulsating Heat Pipe ◽  
Viscous Effects ◽  
Evaporator Temperature

The aim of the study is the analysis of a uniform magnetic field effect on fluid flow, heat transfer, and entropy generation through the operation of a pulsating heat pipe (PHP). An open loop PHP with three neighboring vapor plugs and two liquid slugs has been considered. The governing equations such as momentum, energy, and mass equations are solved using an explicit method except for the energy equation of liquid slugs. For each case study, Bejan number has been derived to find the heat transfer share in entropy generation. According to the results, the performance of the oscillating heat pipe decreases by applying uniform magnetic field. Moreover, the obtained results illustrate the effects of the applied magnetic field position on the heat transfer and the entropy generation. The latent and sensible heat transfer into the PHP enhance as a result of increase in the pipe diameter, so that the liquid slugs oscillate with high amplitudes. In addition, the entropy generation value increases with an augmentation in the value of the pipe diameter. The evaluated Bejan numbers indicate that the viscous effects in entropy generation decrease as the pipe diameter increases. Furthermore, the results depict that the heat transfer performance of PHP improves by increasing temperature difference between evaporator and condenser sections. With an increase in the value of the evaporator temperature, the Bejan number will increase, as a result, this phenomenon reveals the inconsiderable role of viscous impacts in high evaporator temperatures. In order to validate the calculations, the calculated results have been compared with the previous studies which show good agreement.

Effects of Surface Coating of Nanoparticles on Thermal Performance of Open Loop Pulsating Heat Pipes

2012 ◽  
Author(s):  
Mehdi Taslimifar ◽  
Maziar Mohammadi ◽  
Ali Adibnia ◽  
Hossein Afshin ◽  
Mohammad Hassan Saidi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Pipe ◽  
Thermal Performance ◽  
Surface Coating ◽  
Heat Pipes ◽  
Open Loop ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Performance Of Heat Transfer

Homogenous dispersing of nanoparticles in a base fluid is an excellent way to increase the thermal performance of heat transfer devices especially Heat Pipes (HPs). As a wickless, cheap and efficient heat pipe, Pulsating Heat Pipes (PHPs) are important candidates for thermal application considerations. In the present research an Open Loop Pulsating Heat Pipe (OLPHP) is fabricated and tested experimentally. The effects of working fluid namely, water, Silica Coated ferrofluid (SC ferrofluid), and ferrofluid without surface coating of nanoparticles (ferrofluid), charging ratio, heat input, and application of magnetic field on the overall thermal performance of the OLPHPs are investigated. Experimental results show that ferrofluid has better heat transport capability relative to SC ferrofluid. Furthermore, application of magnetic field improves the heat transfer performance of OLPHPs charged with both ferrofluids.

An Investigation of Temperature Characteristics of Pulsating Heat Pipe

2005 ◽  
Author(s):  
Qingjun Cai ◽  
Chung-Lung Chen ◽  
Julie F. Asfia
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Temperature Difference ◽  
Operating Temperature ◽  
Temperature Fluctuations ◽  
Optimal Operation ◽  
Large Temperature ◽  
Pulsating Heat Pipe ◽  
Operation Condition ◽  
Evaporator Temperature

Pulsating heat pipe (PHP) is an interesting heat transfer device. This paper focuses on PHP heat transfer characteristics versus its operating temperature. In experiments of copper and stainless steel PHPs, results indicate that, at a same input power, both temperature differences (from the evaporator to condenser) and evaporator temperature fluctuations are relevant to operating temperature. The minimal temperature difference and fluctuation appear at an operating temperature ranging from 120 to 160°C. Experimental analysis of the evaporator temperature fluctuations show that single phase cooling in PHP causes a large temperature difference (between the evaporator and condenser) and fluctuation. Phase change proportion increases at the optimal operation condition. Static mechanical balance combining with dynamic elastic oscillation system is used to interpret PHP temperature variations versus operating temperature.

Heat Transfer Enhancement of Planar Pulsating Heat Pipe Device

2006 ◽  
Author(s):  
Qingjun Cai ◽  
Chung-Lung Chen ◽  
Julie F. Asfia
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Printed Circuit Boards ◽  
Longitudinal Direction ◽  
High Heat ◽  
Electronic Cooling ◽  
Circuit Boards ◽  
Pulsating Heat Pipe ◽  
Evaporator Temperature ◽  
Key Factor

Heat pipes are widely used heat transfer devices in the electronic cooling area. In this paper, a novel pulsating heat pipe (PHP) design, which combines features of PHP and capillary microstructures, is presented to enhance heat transfer of electronic printed circuit boards (PCB). Test prototype fabrication is initiated by making dual-radius serpentine channels on a 4.0mm thick aluminum plate, followed by compressing 4.67mm diameter copper tube into the grooves, and completed by generating a millimeter sized liquid channel with micro-grooves in the PHP along the longitudinal direction. Because of this design, the planar PHP is able to circulate operating liquid by both capillary pump and oscillation motions, which eliminate the dry state in the evaporator section and supply sufficient coolant at high heat loads. Demonstrations of heat transfer performance indicate that the planar PHP has high effective thermal conductivity and low evaporator temperature fluctuations, and oscillation continuity is the key factor to reduce the temperature difference between the evaporator and condenser.

scholarly journals Heat transfer and entropy generation analysis in a horizontal channel filled with a permeable medium in the presence of aligned magnetic field and temperature gradient heat source

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
K. S. Balamurugan ◽  
N. Udaya Bhaskara Varma ◽  
J. L. Ramaprasad
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Shear Stress ◽  
Temperature Gradient ◽  
Heat Source ◽  
Entropy Generation ◽  
Fluid Velocity ◽  
Horizontal Channel ◽  
Bejan Number ◽  
Aligned Magnetic Field

AbstractThe current investigation is concerned with heat transfer and entropy generation analysis in a horizontal channel brimming with porous medium in the existence of aligned magnetic field, viscous and joules dissipation and temperature gradient heat source. The boundary conditions are treated as constant values for velocity and temperature at lower and upper walls. An explicit solution of governing equations has been attained in closed system. The repercussions of pertinent parameters on the fluid velocity, temperature, entropy generation and Bejan number are conferred and scrutinized through graphs in detail. Additionally the expressions for shear stress and the rate of heat transfer coefficients at the channel walls are derived and results obtained are physically interpreted through tables. From the conquered results, it is addressed that Brinkman number Br enhances boundary layer thickness. Entropy generation increases with intensifying values of $$M$$ M , aligned angle ϕ, temperature gradient heat source parameter Q, characteristic temperature ration $$\omega$$ ω and permeability parameter K. The shear stress is same at both the lower and upper walls.

Operating Characteristic Investigations in Pulsating Heat Pipe

2006 ◽  
Vol 128 (12) ◽  
pp. 1329-1334 ◽  
Author(s):  
Qingjun Cai ◽  
Chung-lung Chen ◽  
Julie F. Asfia
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Temperature Difference ◽  
Temperature Fluctuation ◽  
Operating Temperature ◽  
Temperature Fluctuations ◽  
Pulsating Heat Pipe ◽  
Oscillation System ◽  
Evaporator Temperature ◽  
Total Temperature

Pulsating heat pipe (PHP) is an interesting heat transfer device. In this paper we focus on PHP heat transfer characteristics versus its operating temperature. In experiments of copper and stainless steel PHPs, results indicate that, at a same input power, both the total temperature differences (from the evaporator to condenser) and the evaporator temperature fluctuations are relevant to operating temperature. The minimal total temperature difference and temperature fluctuation appear at an operating temperature ranging from 120°Cto160°C. Experimental analysis of the evaporator temperature fluctuations show that single phase cooling in PHP causes a large total temperature difference and temperature fluctuation. Phase change proportion increases at the optimal operating temperature. Static mechanical balance combining with dynamic elastic oscillation system is used to interpret PHP temperature variations versus the operating temperature.

Second Law Analysis of Flow in a Circular Pipe With Uniform Suction and Magnetic Field Effects

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
G. Nagaraju ◽  
Srinivas Jangili ◽  
J. V. Ramana Murthy ◽  
O. A. Bég ◽  
A. Kadir
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Entropy Generation ◽  
Stokes Equations ◽  
Circular Pipe ◽  
Bejan Number ◽  
Magnetic Field Effects ◽  
Constant Wall Temperature ◽  
Entropy Generation Number ◽  
Uniform Suction

The present paper investigates analytically the two-dimensional heat transfer and entropy generation characteristics of axisymmetric, incompressible viscous fluid flow in a horizontal circular pipe. The flow is subjected to an externally applied uniform suction across the wall in the normal direction and a constant magnetic field. Constant wall temperature is considered as the thermal boundary condition. The reduced Navier–Stokes equations in a cylindrical coordinate system are solved to obtain the velocity and temperature distributions. The velocity distributions are expressed in terms of stream function and the solution is obtained using the homotopy analysis method (HAM). Validation with earlier nonmagnetic solutions in the literature is incorporated. The effects of various parameters on axial and radial velocities, temperature, axial and radial entropy generation numbers, and axial and radial Bejan numbers are presented graphically and interpreted at length. Streamlines, isotherms, pressure, entropy generation number, and Bejan number contours are also visualized. Increasing magnetic body force parameter shifts the peak of the velocity curve near to the axis, whereas it accelerates the radial flow. The study is relevant to thermodynamic optimization of magnetic blood flows and electromagnetic industrial flows featuring heat transfer.

Natural Convection and Entropy Generation in a Cavity Filled With Two Horizontal Layers of Nanofluid and Porous Medium in Presence of a Magnetic Field

2015 ◽  
Author(s):  
Ali Al-Zamily ◽  
M. Ruhul Amin
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Rayleigh Number ◽  
Entropy Generation ◽  
Darcy Number ◽  
Bejan Number ◽  
Flow Heat

A numerical analysis is performed to study the fluid flow, heat transfer and entropy generation inside a square cavity embedded with heat flux and subject to the horizontal magnetic field. The cavity is consist of two same width layers: first layer filled with nanofluid (Al2O3+water) and second one is saturated porous media filled with a same nanofluid. The uniform constant heat flux is applied partly at the base wall, and the other parts of the base wall are assumed adiabatic. The upper horizontal wall kept adiabatic, while the vertical walls are maintained at constant cold temperature. Finite element method based on the variational formulation is employed to solve the main equations. The results of the present study are based on visualization of heat flow via isotherms and heatfunctions (heatlines), fluid flow via streamfunctions, and irreversibility via Bejan number. Comparisons with previously numerical and experimental published works are performed and the results are found to be in a good agreement. In this study, the effect of the main pertinent parameters, such as: nanoparticles volume fraction (0≤Φ≤0.15), Rayleigh number (104≤Ra≤107), Darcy number (10−1≤Da≤10−5), Hartmann number (0≤Ha≤60) on the fluid flow, heat transfer and entropy generation are investigated. The results show that the effect of the Hartmann on Nusselt number increases as Darcy number increases especially at high Rayleigh number. Also, at Ra=107 and Φ=0.15, the percentage decreasing in Nusselt number due to present magnetic field (Ha=40) are 85.89% at Da=10−1, 87.12% at Da=10−3 and 98.69% at Da=10−5.

Sign in / Sign up

Export Citation Format

Share Document