The effects of the orifice geometry and the surface boundary condition on the heat transfer distribution to a flat surface of an impinging jet array were investigated. The jet array impinged normally onto the surface which was either isothermal or had a uniform heat flux. The experiments were performed for...
The present study proposes to investigate the flow structure of different arrays of jets impinging on a flat surface enclosed by three walls, creating a channel that forces the air to leave in one preferential direction, generating a self sustain crossflow. Details of both the mean and some turbulence quantities...
The characteristics of the free surface in an orifice driven by a periodic forcing function have been studied both theoretically and experimentally. In the theoretical study, two wall boundary condition cases were examined: 1) the radial velocity at the wall of the orifice is zero; and 2) the axial velocity...
The effect of jet flow pulsing and blowing ratio on a jet in cross flow has been investigated. Preliminary jet flow studies were performed without cross flow and an extensive study of jet with cross flow was done for a total of nine test cases. The effect of velocities ratios...
Micro-fluid mixing is an important aspect of many of the various micro-fluidic systems used in biochemical production, biomedical industries, micro-energy systems and some electronic devices. Typically, because of size constraints and laminar flow conditions, different fluids may only have the opportunity to mix by diffusion, which is extremely rate limited....
A computational model is developed to study the effects of alumina layer formation on an ablative surface when exposed to high temperature particle laden gas flow. The solidification dynamics i.e., the solid and liquid alumina layer growth rate, and the heat transferred to the ablative surface are investigated. A one-dimensional...
Droplet formation from a rigid and a vibration nozzle driven by a pulsing pressure is simulated. Droplet formation is simulated by using one-dimensional model. For the case of droplet formation from a vibration nozzle, the nozzle vibration is simulated by large deflection plate vibration equation. Droplet formation from a rigid...
A constrained thin film desorption scheme has been experimentally tested to determine the desorption rates for water from an aqueous lithium bromide mixture through a confining membrane. Variable conditions include the inlet concentration, pressure differential across the membrane, and channel height. Desorption takes place in a channel created between two...
Jets in crossflow are used in a wide range of engineering applications and have been studied for more than 60 years. The transversal penetration and structure of a jet placed in a crossflow is known to be strongly three-dimensional. It is believed that, by using a pulsed jet inclined in...
An experimental investigation into the behavior of micro-bubbles flowing
through a micro-channel has been conducted. Experiments were performed within a
rectangular micro-channel with dimensions of 5 cm x 13.2 mm x l30 jim. Bubbles
were generated in an electrolyte solution by electrolysis at the lower channel wall near
the inlet....
The droplet formation process in the vicinity of the nozzle exit and the behavior of a spreading droplet during impingement on a smooth glass surface were studied. Two nozzle geometries were tested. The first case was a stiff stainless steel nozzle plate 0.787 mm thick. The second case was a...
For piezoelectric stack (PZT) driven droplet generator, the driving waveform
and driving frequency effect on liquid filament shape and droplet characteristics have
been experimentally studied. The experimental study was based on a PZT driven
droplet generator with known geometric design parameters and working fluid
properties. A lumped-element-model (LEM) constructed to...
Droplet formation from a flexible nozzle plate driven by a prescribed-waveform excitation of a piezoelectric is numerically investigated using a computational fluid dynamics (CFD) model with the VOF method. The droplet generator with a flexible nozzle plate, which is free to vibrate due to the pressure acting on the plate,...
Based on experimental investigations the present study evaluates flow instability and
void fraction in a fractal-like branching microchannel network with rectangular cross-section. The hydraulic diameter of the channels ranged from 308μm at the inlet to 143μm at the outlet. The flow network used is characterized by set branching ratios for...
A one-dimensional numerical model has been developed to study diabatic and adiabatic
flow boiling in microchannels. This model accounts for developing flow effects and
variable property effects. The model uses correlations for void fraction and two-phase
multipliers found in the literature. The model has been used to study the performance...
The pressure drop of convective boiling flow may be reduced by extracting vapor locally since the entire generated vapor does not have to travel through the entire channel length. In this study, the theoretical model was developed to simulate a convective boiling flow through a fractal-like branching microchannel network with...
A method was sought to predict the flight paths and collisions for closely spaced ink droplets of various sizes as a design aid for ink-jet printing development. Computational fluid dynamics models of two rigid aligned spheres, as a proxy for ink droplets, were initiated in atmospheric pressure air at constant...
As drop-on-demand (DOD) applications continue to gain ground in desktop inkjet-printing, 3D printing, fluid mixing, and other areas the demand for higher frequency operations are beginning to push against the current physical boundaries in DOD technology. The current research is exploring the possibility of controlling drop volume and velocity at...
Porous media flows are encountered in many natural and man-made systems such as gas adsorption, filtration, heat exchangers, combustion, catalytic reactors and groundwater hydrology. This study experimentally investigates these flows as function of pore Reynolds number, Re[subscript pore]. The pore Reynolds number is based on the porous bed hydraulic diameter,...
In-situ vapor extraction is performed by applying a pressure differential across a hydrophobic porous membrane that forms a wall of the channel as a means of reducing the local quality of flow boiling within the channel. As the local quality is reduced, the heat transfer capability can be improve while...