A Simplified ‘Effective Circuit’ Fluid Flow Model for Forced Convection in Oblique Fin Configuration

2014 ◽  
Author(s):  
Nasi Mou ◽  
Poh Seng Lee ◽  
Saif A. Khan
Keyword(s):  
Fluid Flow ◽  
Mass Flow ◽  
Flow Model ◽  
Electrical Circuit ◽  
Flow Paths ◽  
Micro Channels ◽  
Discrete Flow ◽  
Actual Flow ◽  
The Difference ◽  
Full Domain

In this paper, a simplified ‘effective circuit’ fluid flow model is proposed to complement full-domain (geometry based) simulations of fluid flow in novel discrete oblique fin heat sinks. In the proposed model, the discrete flow paths are modeled as effective resistances, and the intersections between discrete flow paths are modeled as ‘nodes’. In an electrical circuit, the current of each branch can be derived from the current division rule, and hence the actual flow rates in the effective circuit are determined by the effective resistances. Simulink R2011b, a graphical extension to MATLAB for modeling and simulation of systems, is chosen to construct the equivalent circuit. The effective resistances are calculated using the well-known friction factor expressions for laminar flow in micro-channels. A full-domain geometry-based simulation is performed on CFX 14.0 serving as a benchmark for the developed ‘effective circuit’ fluid flow model. The results show that for a given total current value and mass flow rate, the difference of pressure drop over the whole heat sink between the simplified flow model and CFX simulation is within 13%. The mass flow distributions obtained from the simplified flow model and the CFX simulation exhibit a common distribution pattern. Interestingly, the simplified flow model is even able to capture flow migration — a distinctive phenomenon of flow in oblique fin geometries. We thus confirm the feasibility of the method of construction of our simplified ‘effective circuit’ fluid flow model.

Experimental Research on the Viscosity of Polymer Melts Filling through Micro Channels

2011 ◽  
Vol 314-316 ◽  
pp. 1346-1349
Author(s):  
Bin Xu ◽  
Yu Bin Lu ◽  
Guang Ming Li ◽  
Song Xue
Keyword(s):  
Shear Rate ◽  
Flow Model ◽  
Capillary Flow ◽  
Polymer Melt ◽  
Characteristic Size ◽  
Micro Channel ◽  
Test Results ◽  
Micro Channels ◽  
Rate Test ◽  
The Difference

Experimental observations indicate that the viscosity of polymer melt flowing through micro channel is altered with variation of characteristic size of micro channels. The explanation about the trend of various viscosity is inconsistent. In this paper, the micro channel dies of 1000μm ,500μm and 350μm diameter were developed and with several polymers, including PP , PS and HDPE, depending on the capillary flow model, the measurement experiments of polymer melt viscosity were investigated at various shear rate. Test results show that with micro-channel size decrease, the percentage reduction in viscosity increases and the difference of viscosities in different micro channels reduces with increasing shear rate.

A Non-Newtonian Fluid Flow Model for the Slip Condition on Blood Flow through a Stenosed Artery using Power-law Fluid

2018 ◽  
Vol 9 (7) ◽  
pp. 871-879
Author(s):  
Rajesh Shrivastava ◽  
R. S. Chandel ◽  
Ajay Kumar ◽  
Keerty Shrivastava and Sanjeet Kumar
Keyword(s):  
Blood Flow ◽  
Fluid Flow ◽  
Newtonian Fluid ◽  
Power Law ◽  
Flow Model ◽  
Slip Condition ◽  
Power Law Fluid ◽  
Stenosed Artery ◽  
Flow Through

scholarly journals Selective Transport of Airborne Microparticles Through Micro-channels Under Microgravity

2021 ◽  
Vol 33 (1) ◽  
Author(s):  
Monia Makhoul ◽  
Philippe Beltrame
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Bifurcation Analysis ◽  
Metal Particles ◽  
Microgravity Environment ◽  
Ratchet Effect ◽  
Selective Transport ◽  
Microgravity Experiments ◽  
Particle Drift ◽  
Micro Channels

AbstractThis paper analyzes the possibility of obtaining the selective transport of microparticles suspended in air in a microgravity environment through modulated channels without net displacement of air. Using numerical simulation and bifurcation analysis tools, we show the existence of intermittent particle drift under the Stokes assumption of the fluid flow. The particle transport can be selective and the direction of transport is controlled only by the kind of pumping used. The selective transport is interpreted as a deterministic ratchet effect due to spatial variations in the flow and the particle drag. This ratchet phenomenon could be applied to the selective transport of metal particles during the short duration of microgravity experiments.

scholarly journals Modelling of Humidity Dynamics for Open-Cathode Proton Exchange Membrane Fuel Cell

2021 ◽  
Vol 12 (3) ◽  
pp. 106
Author(s):  
Fengxiang Chen ◽  
Liming Zhang ◽  
Jieran Jiao
Keyword(s):  
Fuel Cell ◽  
Mass Flow ◽  
Proton Exchange Membrane ◽  
Flow Model ◽  
Transport Theory ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Output Performance ◽  
Exchange Membrane

The durability and output performance of a fuel cell is highly influenced by the internal humidity, while in most developed models of open-cathode proton exchange membrane fuel cells (OC-PEMFC) the internal water content is viewed as a fixed value. Based on mass and energy conservation law, mass transport theory and electrochemistry principles, the model of humidity dynamics for OC-PEMFC is established in Simulink® environment, including the electrochemical model, mass flow model and thermal model. In the mass flow model, the water retention property and oxygen transfer characteristics of the gas diffusion layer is modelled. The simulation indicates that the internal humidity of OC-PEMFC varies with stack temperature and operating conditions, which has a significant influence on stack efficiency and output performance. In order to maintain a good internal humidity state during operation, this model can be used to determine the optimal stack temperature and for the design of a proper control strategy.

Generalized Fluid Flow Model for Ceramic Tape Casting

1995 ◽  
Vol 78 (9) ◽  
pp. 2497-2503 ◽  
Author(s):  
Rangarajan Pitchumani ◽  
Vistasp M. Karbhari
Keyword(s):  
Fluid Flow ◽  
Flow Model ◽  
Tape Casting ◽  
Ceramic Tape

On-demand Electrohydrodynamic Jetting of an Ethylene Glycol and Water Mixture—System of Controlled Picoliter Fluid Deposition

2021 ◽  
Author(s):  
J. F. Dijksman ◽  
U. Stachewicz
Keyword(s):  
Fluid Flow ◽  
Power Amplifier ◽  
Large Diameter ◽  
Electrical Circuit ◽  
Viscous Drag ◽  
Water Mixture ◽  
Electrical Field ◽  
On Demand ◽  
Flat Substrate ◽  
Set Up

On-demand electrohydrodynamic jetting also called electrohydrodynamic atomization (EHDA) is a method to jet small amounts of fluid out of a nozzle with a relatively large diameter by switching on and off an electrical field between the nozzle and the substrate. The total amount of volume deposited is up to 5 pL. The set-up consists of a vertically placed glass pipette with a small nozzle directed downward and a flat substrate placed close to the end of the nozzle. Inside the pipette, an electrode is mounted close to the entrance of the nozzle. The electrode is connected to a high voltage power amplifier. Upon switching on the electrical field, the apparent surface tension drops, the meniscus deforms into a cone and fluid starts to flow toward the nozzle deforming the meniscus. At a certain moment the cone reaches the Taylor cone dimensions and from its tip a jet emerges that decomposes into a stream of charged fL droplets that fly toward the substrate. This process stops when the pulse is switched off. After switching off, the meniscus returns slowly to its equilibrium position. The process is controlled by different time constants, such as the slew rate of the power amplifier and the RC time of the electrical circuit composed of the electrical resistance in the fluid contained in the nozzle between the electrode and the meniscus, and the capacitance of the gap between the meniscus and the flat substrate. Another time constant deals with the fluid flow during the growth of the meniscus, directly after switching on the pulse. This fluid flow is driven by hydrostatic pressure and opposed by a viscous drag in the nozzle. The final fluid flow during droplet formation is governed by the balance between the drag of the charge carriers inside the fluid, caused by the current associated with the charged droplets leaving the meniscus and the viscous drag. These different phenomena will be discussed theoretically and compared to experimental results.

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