3-D Numerical Analysis for Fluid Flow and Heat Transfer in a Micro Chip by Using an Electro-Hydrodynamic Micro-Pump

2005 ◽  
Author(s):  
Chia-Wen Lin ◽  
Jiin-Yuh Jang
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Source ◽  
Applied Voltage ◽  
High Performance ◽  
Liquid Velocity ◽  
Working Fluid ◽  
Computational Domain ◽  
Flow And Heat Transfer ◽  
Micro Pump

A computational investigation of the heat transfer for a high performance integrated chip by using an electrohydrodynamic (EHD) pump was studied. This paper presents a fully computational system bundle with electro field, fluid flow and heat transfer for a cooling device. The micro pump provides the required pumping power by using the dipole moment generated from polarizing molecules and induces the flow to cool down the heat source. The computational domain of the micro channel for length and depth are kept in 1500μm and 500μm with parallel electrodes pitch (20μm, 40μm, 80μm). The effects of different applied voltage VE ranging from 100V to 500V, using oil as the working fluid and the heat flux of the heat source fixed at 2.5W/cm2 is investigated in detail. It is found that the EHD micro pump is more effective for lower channel pitch and higher applied voltage. For VE = 500V and electrodes pitch = 20μm, this study identifies a maximum performance of 49.36kPa in the pressure head and 9.55W/cm2 in the heat transfer. In addition, the performance of flow rate, liquid velocity and averaging Nusselt number for the specific condition are 0.94 L/min-mm2, 0.12 m/s, and 106.10. However, it also identifies the performance of the heat transfer for electrodes pitch = 40μm is about 146.0% of that for pitch = 80μm. But for pitch = 20μm, it is only 10.5% higher than that for pitch = 40μm.

Influence of Flow Acceleration on Convection Heat Transfer of CO2 at Supercritical Pressures and Air in a Vertical Micro Tube

2010 ◽  
Author(s):  
Pei-Xue Jiang ◽  
Rui-Na Xu ◽  
Zhi-Hui Li ◽  
Chen-Ru Zhao
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Wall Temperature ◽  
Convection Heat Transfer ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Convection Heat ◽  
Downward Flow ◽  
Flow Acceleration ◽  
Flow And Heat Transfer

The convection heat transfer of CO2 at supercritical pressures in a 0.0992 mm diameter vertical tube at relatively high Reynolds numbers (Rein = 6500), various heat fluxes and flow directions are investigated experimentally and numerically. The effects of buoyancy and flow acceleration resulting from the dramatic property variations are studied. The Results show that the local wall temperature varied non-linearly for both upward and downward flow when the heat flux was high. The difference in the local wall temperature between upward and downward flow is very small when the other test conditions are held the same, which indicates that for supercritical CO2 flowing in a micro tube as employed in this study, the buoyancy effect on the convection heat transfer is insignificant and the flow acceleration induced by the axial density variation with temperature is the main factor leading to the abnormal local wall temperature distribution at high heat fluxes. The predicted temperatures using the LB low Reynolds number turbulence model correspond well with the measured data. To further study the influence of flow acceleration on the convection heat transfer, air is also used as the working fluid to numerically investigate the fluid flow and heat transfer in the vertical micro tube. The results show that the effect of compressibility on the fluid flow and heat transfer of air in the vertical micro tube is significant but that the influence of thermal flow acceleration on convection heat transfer of air in a vertical micro tube is insignificant.

Characterisation of Flow and Heat Transfer Regimes in Various Horizontal Ducts Submitted to Mixed Convection

2006 ◽  
Author(s):  
C. Abid ◽  
M. Medale ◽  
F. Koffi ◽  
F. Papini ◽  
A. Benderradji
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Mixed Convection ◽  
Thermal Gradient ◽  
Thermal Instability ◽  
Vertical Gradient ◽  
Working Fluid ◽  
Circular Duct ◽  
Flow And Heat Transfer ◽  
Wide Range

The emphasis of this communication is to make a synthesis of several results we have obtained in various mixed convection configurations. This study has been conducted for circular or rectangular ducts submitted to different ways of heating (vertical or horizontal thermal gradient in the rectangular case and combined vertical and horizontal in the circular case). The bibliography is rather poor for mixed convection in liquids, so the chosen working fluid used here is water. Moreover, a wide range of forced fluid flow and heat flux rates has been considered spreading from laminar to turbulent flow. The characterization of fluid flow and heat transfer regimes is based on temporal recording of temperature measurements obtained in several locations by means of thermocouples or infrared thermography. The analysis of these temperature signals highlights several regimes depending on control parameters. The flow structure in the cases of uniformly heated circular duct and the rectangular one heated from below is constituted of two longitudinal rolls and we notice only one roll in the case of the rectangular duct submitted to the horizontal thermal gradient. For low Reynolds and Rayleigh Numbers, the behavior of all these configurations is stable, however the increasing of these parameters induces thermal instability in the case of circular and rectangular ducts heated from below. That means that the thermal vertical gradient is responsible of the occurring of the thermal instability. This result shows that the horizontal thermal gradient is a stabilizing gradient while the vertical one is a destabilizing one. As this instability enhances heat transfer, it will be very helpful to characterize and to identify the domain where it is occurring in order to prevent or to provoke it depending on the expected performance of the heat exchanger. In this paper, we propose to establish a diagram showing the domain of occurrence of this instability for the various cases cited above and to describe the fluid flow and heat transfer associated to these configurations.

High-Performance Computing for Fluid Flow and Heat Transfer

2002 ◽  
Author(s):  
Darrell W. Pepper ◽  
Joseph M. Lombardo
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
High Performance ◽  
Daily Basis ◽  
Data Sets ◽  
Graphical Displays ◽  
Levels Of Detail ◽  
Flow And Heat Transfer ◽  
Micro Level ◽  
Performance Computing

The use of computers in heat transfer and fluid flow has become so commonplace today that no one would consider working in either field without some knowledge of computing. Problems are now being solved on a daily basis that even a few years ago were considered intractable. While we once thought that a problem with a few million nodes was huge a few years ago, researchers are now addressing problems with over 100 million nodes. At such levels of detail, one can begin to model processes at the micro level of physics. When researchers are able to quickly analyze these gigantic data sets and can generate insightful graphical displays, the understanding of fundamental processes and governing relations will escalate tremendously.

Numerical Simulation of Operating Performance of Heat Exchangers in a Residential Split Air-Conditioner

2011 ◽  
Vol 250-253 ◽  
pp. 3913-3918 ◽  
Author(s):  
Shun Yu Su ◽  
Tian Tian ◽  
Jian Chen
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Exchangers ◽  
Great Influence ◽  
Working Fluid ◽  
Air Conditioner ◽  
Two Phase ◽  
Air Conditioning System ◽  
Flow And Heat Transfer ◽  
Phase Fluid

The mechanism of fluid flow and heat transfer in the heat exchangers was investigated in this paper. Using R22 as the working fluid, the steady distributed parameter models of condenser and evaporator in a residential split air-conditioner were established based on thermophysical laws such as mass, momentum and energy conservation equations. The regions of two-phase fluid and superheated gas in evaporator and the regions of superheated gas, two-phase fluid and subcooled liquid in condenser were respectively simulated under designed conditions of air-conditioning system. Based on the calculated results, the flow and heat transfer performances of heat exchangers were analyzed. The results show that the two-phase fluid regions in both evaporator and condenser have great influence on the fluid flow and heat transfer performances in it.

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