scholarly journals Development of Pulsating Twin Jets Mechanism for Mixing Flow Heat Transfer Analysis

2014 ◽  
Vol 2014 ◽  
pp. 1-8
Author(s):  
Ali Ahmed Gitan ◽  
Rozli Zulkifli ◽  
Shahrir Abdullah ◽  
Kamaruzzaman Sopian
Keyword(s):  
Heat Transfer ◽  
Velocity Profile ◽  
Heat Transfer Analysis ◽  
Pulsation Frequency ◽  
Pulse Profile ◽  
Pulsed Jet ◽  
Impingement Heat Transfer ◽  
Twin Jets ◽  
Flow Heat ◽  
Transfer Problems

Pulsating twin jets mechanism (PTJM) was developed in the present work to study the effect of pulsating twin jets mixing region on the enhancement of heat transfer. Controllable characteristics twin pulsed jets were the main objective of our design. The variable nozzle-nozzle distance was considered to study the effect of two jets interaction at the mixing region. Also, the phase change between the frequencies of twin jets was taken into account to develop PTJM. All of these factors in addition to the ability of producing high velocity pulsed jet led to more appropriate design for a comprehensive study of multijet impingement heat transfer problems. The performance of PTJM was verified by measuring the pulse profile at frequency of 20 Hz, where equal velocity peak of around 64 m/s for both jets was obtained. Moreover, the jet velocity profile at different pulsation frequencies was tested to verify system performance, so the results revealed reasonable velocity profile configuration. Furthermore, the effect of pulsation frequency on surface temperature of flat hot plate in the midpoint between twin jets was studied experimentally. Noticeable enhancement in heat transfer was obtained with the increasing of pulsation frequency.

Twin Pulsating Jets Impingement Heat Transfer for Fuel Preheating in Automotives

2014 ◽  
Vol 663 ◽  
pp. 322-328 ◽  
Author(s):  
Ali Ahmed Gitan ◽  
Rozli Zulkifli ◽  
Kamaruzaman Sopian ◽  
Shahrir Abdullah
Keyword(s):  
Heat Transfer ◽  
Ignition Process ◽  
Pulsation Frequency ◽  
Ir Camera ◽  
Copper Target ◽  
Air Jets ◽  
Air Jet ◽  
Impingement Heat Transfer ◽  
Pulsating Jet ◽  
Pulsating Jets

The problem of environmental pollution and depletion of fossil fuel can be reduced in automotives by using an alternative bio-fuel and improve the ignition process in engine. Both solutions need to use the fuel preheating technique. This work presents the idea of fuel preheating by using exhaust impingement on the fuel tank. Heat transfer between twin pulsating hot air jets and flat copper target was investigated as an application for preheating of automotive fuel to improve ignition process in the engine. The nozzle of 20 mm was used to produce air jet of Reynolds number, Re ≃ 5500 and a temperature of 54°C. The impinged target was imposed to still air surrounding at temperature of 24°C. Pulsating frequencies of 10-50 Hz were applied on air jets by using twin pulsating jet mechanism. The effect of pulsation frequency on heat transfer was measured using IR camera and heat flux-temperature micro foil sensor. The results obtained by both of these methods showed well agreement. Also, the results revealed significant influence of flow rate difference between steady and pulsating jet cases. In addition, the highest Nusselt number, Nu ≃ 7.2, was obtained at pulsation frequency of 20 Hz.

Two phase flow heat transfer analysis at different flow patterns in the wellbore

2017 ◽  
Vol 117 ◽  
pp. 544-552 ◽  
Author(s):  
Yonghai Gao ◽  
Yanchun Cui ◽  
Boyue Xu ◽  
Baojiang Sun ◽  
Xinxin Zhao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Heat Transfer Analysis ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Heat

Do We Really Need “Entransy”? A Critical Assessment of a New Quantity in Heat Transfer Analysis

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
H. Herwig
Keyword(s):  
Heat Transfer ◽  
Classical Theory ◽  
Critical Assessment ◽  
Heat Transfer Analysis ◽  
Classical Approach ◽  
The Past ◽  
Transfer Problems

Recently, a group of scientists introduced a new quantity for the analysis of heat transfer problems. They called it entransy since according to their understanding it is both, an indication of the nature of energy as well as that of the heat transfer ability. This concept is critically assessed on the background of two questions: Is entransy as an extension of the well established theory of heat transfer consistent with this classical approach? And: Is there a real need for the extension of the classical theory by introducing entransy as a quantity that was missing in the past?

Resin Flow, Cure and Heat Transfer Analysis for Pultrusion Process

1994 ◽  
Vol 28 (6) ◽  
pp. 486-506 ◽  
Author(s):  
R. Gorthala ◽  
J. A. Roux ◽  
J. G. Vaughan
Keyword(s):  
Heat Transfer ◽  
Velocity Profile ◽  
Variable Viscosity ◽  
Control Volume ◽  
Pressure Profile ◽  
Heat Transfer Analysis ◽  
Direct Result ◽  
Resin Flow ◽  
Degree Of Cure ◽  
Pultrusion Process

This work presents temperature and degree of cure profiles within a pultruded composite and focuses on the development of different models used for predicting the velocity profile including a slip velocity model. This study uses a variable viscosity model and highlights the results for the velocity profile, viscosity of resin within a pultrusion die, gelation lengths, iso-gelation lines, and axial pressure profile. Gelation was predicted to occur at about one-third the distance down the die length and the degree of cure at gelation was computed to be about 0.34. The composite systems considered in this study are graphite/epoxy and fiberglass/epoxy. A comprehensive two-dimensional mathematical model in cylindrical coordinates was developed for resin flow, cure and heat transfer associated with the pultrusion process. A control-volume-based finite difference method (Patankar method) was used for solving the governing equations. The model can be utilized for ascertaining the effects of pultrusion process variables on the characteristics of the cured composite; this primarily reduces to a large extent the trial and error experimentation often required. Moreover, insight for characterization and optimization of the pultrusion process is a direct result of this modeling.

Numerical Prediction of the Flow Field and Impingement Heat Transfer Caused by a Laminar Slot Jet

1976 ◽  
Vol 98 (4) ◽  
pp. 654-658 ◽  
Author(s):  
A. R. P. van Heiningen ◽  
A. S. Mujumdar ◽  
W. J. M. Douglas
Keyword(s):  
Heat Transfer ◽  
Velocity Profile ◽  
Nozzle Exit ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Effect Of Temperature ◽  
Navier Stokes ◽  
Impingement Heat Transfer ◽  
Stream Function Form ◽  
Energy Equations

The effects of uniform suction and nozzle exit velocity profile on the flow and heat-transfer characteristics of a semiconfined laminar impinging slot jet were investigated numerically. The full Navier-Stokes and energy equations were solved using a hybrid or upwind finite-difference representation of the equations cast into their vorticity-stream-function form. The importance of the nozzle exit profile is shown by comparison of the computed heat-transfer distribution with the available experimental data in the laminar range. Application of suction at the impingement surface is shown to enhance the local heat-transfer rates by a constant amount. The nondimensional heat-transfer coefficient and skin friction at the plate are computed as functions of the nozzle Reynolds number, the suction rate, and the nozzle velocity profile. The effect of temperature-dependent physical properties is included in the analysis.

Conjugate Heat Transfer CFD Predictions of the Surface Averaged Impingement Heat Transfer Coefficients for Impingement Cooling With Backside Cross-Flow

2013 ◽  
Author(s):  
Abubakar M. El-Jummah ◽  
Reyad A. A. Abdul Hussain ◽  
Gordon E. Andrews ◽  
John E. J. Staggs
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Conjugate Heat Transfer ◽  
Cross Flow ◽  
Heat Transfer Analysis ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Impingement Heat Transfer ◽  
Square Array ◽  
Velocity Turbulence

A 10 row impingement heat transfer configuration with a single sided exit at the end of the impingement gap was modelled using conjugate heat transfer CFD. The predictions were compared with experimental results for an electrically heated, 6.35mm thick, metal wall of nimonic-75, which was impingement cooled. The geometry investigated was a square array of inline impingement 10 × 10 holes with X/D of 4.66 and Z/D of 3.06, where D = 3.27mm. The use of metal walls enabled the local surface averaged heat transfer coefficient h, to be estimated from an imbedded thermocouple that logged the rate of cooling when the heating was removed. Conjugate heat transfer analysis provided local h values, which were surface averaged for comparison with the measured h. The CFD results also provided velocity, turbulence and Nusselt number distributions on the target and impingement jet surfaces. The aerodynamics data enabled the pressure loss of the system to be predicted, which compared well with experimental measurements. The predicted surface distributions of Nusselt number were similar to the surface turbulence kinetic energy distributions, which demonstrated the importance of turbulence in convective heat transfer. Surface averaged heat transfer coefficients were predicted and are in good agreement with the measurements for five coolant mass flow rates. The predicted and measured results for surface averaged h were similar to measurements of other investigators for similar impingement geometries.

scholarly journals Heat Transfer Analysis for FGMs Using SPH-CSPM

2010 ◽  
Vol 452-453 ◽  
pp. 685-688 ◽  
Author(s):  
Gui Ming Rong ◽  
Hiroyuki Kisu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Particle Method ◽  
Heat Transfer Analysis ◽  
Graded Materials ◽  
Various Boundary Conditions ◽  
Particle Hydrodynamics ◽  
Spatial Coordinates ◽  
Smoothed Particle ◽  
Transfer Problems

The solution of heat transfer problems for functional graded materials (FGMs) by smoothed particle hydrodynamics, in which the thermal conductivity is a function of the spatial coordinates and the temperature, is discussed for both steady and non-steady problems under various boundary conditions. The boundary is treated using the corrective smoothed particle method to heighten the accuracy. Several calculations are performed to test the validity of the formulation. As an example of practical application, the problem of FGM cylindrical plates subjected to thermal shock is calculated, in which the thermal conductivity is temperature dependent and the heat transfer coefficient is varied in radial direction.

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