Study on Micropump Using Boiling Bubbles

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Yasuo Koizumi ◽  
Hiroyasu Ohtake
Keyword(s):  
Cross Section ◽  
Flow Rate ◽  
Equation Of Motion ◽  
Flow Channel ◽  
Stationary Condition ◽  
Short Channel ◽  
Short Side ◽  
Liquid Plug ◽  
Average Flow Velocity ◽  
Long Channel

A micropump was developed using boiling and condensation in a microchannel. The length and hydraulic diameter of the semi-half-circle cross-section microchannel having two open tanks at both ends were 26mm and 0.465mm, respectively. A 0.5×0.5mm2 electrically heated patch was located at the offset location from the center between both ends of the microchannel, at a distance of 8.5mm from one end and at a distance of 17mm from the other end. The microchannel and the two open tanks were filled with distilled water. The heating patch was heated periodically to cause cyclic formation of a boiling bubble and its condensation. By this procedure, flow from the short side (8.5mm side) to the long side was created. The flow rate increased as the heating rate was increased. The obtained maximum average flow velocity and flow rate were 10.4mm∕s and 2.16mm3∕s, respectively. The velocity of an interface between the bubble and the liquid plug during the condensing period was much faster than that during the boiling period. During the condensing period, the velocity of the interface at the short channel side (8.5mm side) was faster than that at the long channel side (17mm side). The equation of motion of liquid in the flow channel was solved in order to calculate the travel of liquid in the flow channel. The predicted velocities agreed well with the experimental results. The velocity differences between the short side and the long side, as well as those between the boiling period and the condensing period, were expressed well by the calculation. Liquid began to move from the stationary condition during both the boiling and the condensing periods. The liquid in the inlet side (short side) moved faster than that in the outlet side (long side) during the condensing period because the inertia in the short side was lower than that in the long side. Since the condensation was much faster than boiling, this effect was more prominent during the condensing period. By iterating these procedures, the net flow from the short side to the long side was created.

Study on Micro-Pump Using Boiling Bubbles

2006 ◽  
Author(s):  
Yasuo Koizumi ◽  
Hiroyasu Ohtake
Keyword(s):  
Flow Rate ◽  
Flow Channel ◽  
Stationary Condition ◽  
Micro Channel ◽  
Short Channel ◽  
Short Side ◽  
Average Flow Velocity ◽  
Micro Pump ◽  
The One ◽  
Long Channel

By making use of boiling and condensation in a micro channel, a micro pump was developed. The length and the diameter of the half-circle cross-section micro-channel which had two open tanks at both ends were 26 mm and 0.5 mm, respectively. A 0.5×0.5 mm patch electrically heated was located at the offset location from the center between both ends of the micro channel; at 8.5 mm from the one end and at 17 mm from the other end. The micro channel and the two open tanks were filled with distilled water. The heating patch was heated periodically to cause periodical formation of a boiling bubble and its condensation. By this procedure, flow from the short side (8.5 mm side) to the long side was created. The flow rate increased as the heating rate was increased. The average flow velocity and flow rate obtained were approximately ∼ 12 mm/s and ∼ 3 mm3/s, respectively. The velocity of a interface between the bubble and liquid during the condensation period was much faster than that during the boiling period. During the condensation period, the velocity of the interface at the short channel side (8.5 mm side) was faster than that at the long channel side (17 mm side). The equation of motion of liquid in the flow channel was solved to calculate the traveling of liquid in the flow channel. Predicted velocities agreed well with the experimental results. The velocity differences between the short side and the long side as well as between the boiling period and the condensing period were expressed well by the calculation. Liquid began to move from the stationary condition during both boiling and condensing periods. Liquid in the inlet side (short side) moves faster than that in the outlet side (long side) during the condensation period because of less inertia than that in the long side. Since the condensation was much faster than boiling, this effect is more prominent during the condensation period. By iterating this, the net flow from the short side to the long side was created.

The efficiency of a turbine in a tidal channel

2007 ◽  
Vol 588 ◽  
pp. 243-251 ◽  
Author(s):  
CHRIS GARRETT ◽  
PATRICK CUMMINS
Keyword(s):  
Cross Section ◽  
Upper Bound ◽  
Free Stream ◽  
Fractional Power ◽  
Channel Cross Section ◽  
Tidal Channels ◽  
Short Channel ◽  
Flow Through ◽  
Long Channel ◽  
Turbine Wake

There is an upper bound to the amount of power that can be generated by turbines in tidal channels as too many turbines merely block the flow. One condition for achievement of the upper bound is that the turbines are deployed uniformly across the channel, with all the flow through them, but this may interfere with other uses of the channel. An isolated turbine is more effective in a channel than in an unbounded flow, but the current downstream is non-uniform between the wake of the turbines and the free stream. Hence some energy is lost when these streams merge, as may occur in a long channel. We show here, for ideal turbine models, that the fractional power loss increases from 1/3 to 2/3 as the fraction of the channel cross-section spanned by the turbines increases from 0 to close to 1. In another scenario, possibly appropriate for a short channel, the speed of the free stream outside the turbine wake is controlled by separation at the channel exit. In this case, the maximum power obtainable is slightly less than proportional to the fraction of the channel cross-section occupied by turbines.

Computational and theoretical research of the injector block function

2020 ◽  
pp. 123-126
Author(s):  
В.В. Кожемякин ◽  
Р.А. Иванов ◽  
Е.С. Игнатьева
Keyword(s):  
Hydraulic Resistance ◽  
Cross Section ◽  
Flow Rate ◽  
Pressure Dependence ◽  
Theoretical Study ◽  
Water Jet ◽  
Theoretical Research ◽  
Sudden Expansion ◽  
Operating Modes ◽  
Coefficient Of Hydraulic Resistance

Работа посвящена расчетно-теоретическому исследованию работы блока инжекторов. Рассмотрен пароводяной струйный аппарат, который применяется в качестве средства циркуляции теплоносителя первого контура. Подвод дополнительного потока осуществляется на цилиндрическом участке с внезапным расширением сечения через перемычку. Для достижения поставленной цели разработана программа для ЭМВ, в которой смоделирована зависимость давления от нагрузки в контуре, а также проведено расчетно-теоретическое исследование влияние гидравлического сопротивления на расход перемычки. В данной работе рассмотрены только рабочие режимы, т.е. все инжекторы работают как насосы. В ходе работы было установлено, что при нагрузке в 30% увеличиваются коэффициенты инжекции пароводяного струйного аппарата, но характер работы перемычек не меняется. Так же было установлено, что расход через перемычку меняется не пропорционально коэффициенту гидравлического сопротивления перемычки. The paper is devoted to the computational and theoretical study of the injector block operation. A steam-water jet apparatus is considered, which is used as a means of circulating the primary circle coolant. The additional flow is supplied on the cylindrical section with a sudden expansion of the cross-section through the bridge. To achieve this goal, a computer program was developed that modeled the pressure dependence on the load in the circuit, and also a theoretical study of the influence of hydraulic resistance on the flow of the jumper was conducted. In this paper, only operating modes are considered, i.e. all the injectors function as pumps. In the process of the research, it was found that at a load of 30%, the injection coefficients of the steam-water jet apparatus increase, but the nature of the work of the jumpers does not change. It was also found out that the flow rate through the jumper does not change in proportion to the coefficient of hydraulic resistance of the jumper.

On the Influence of the Slot Orifice in Diesel Common Rail Nozzle

2018 ◽  
Vol 11 (1) ◽  
pp. 55-69 ◽  
Author(s):  
Giancarlo Chiatti ◽  
Ornella Chiavola ◽  
Fulvio Palmieri ◽  
Roberto Pompei
Keyword(s):  
Cross Section ◽  
Flow Rate ◽  
Experimental Analysis ◽  
Common Rail ◽  
Spray Angle ◽  
The Novel ◽  
Hydraulic Behavior ◽  
Reference Information ◽  
Light Duty ◽  
Set Up

Background:The paper deals with a diesel common rail nozzle in which a novel orifice layout is implemented.Objective:Its influence on the nozzle mechanical-hydraulic behavior and on the spray shape transient development is experimentally investigated.Methods:In the research, a solenoid injector for light duty diesel engines is equipped with the novel nozzle prototype and tested. The prototype layout is described, pointing out the features of the nozzle orifices, in which a Slot cross-section is adopted; the investigation is accomplished extending the hydraulic tests and the spray visualizations to a reference nozzle with standard holes. The influence of the hole layout on the mechanical-hydraulic behavior of the nozzle is assessed by experimental analysis based on the rate of injection measurement, in comparison with the reference nozzle. Once the hydraulic behavior of the novel nozzle has been characterized in terms of mass flow rate, the slot influence on the spray shape is assessed analyzing the macroscopic features such as the penetration distance and the spray angle, in non evaporative conditions. The study is carried out under transient injection conditions, for different injection pressures, up to 1400 bar.Results:The results on spray characteristics also provide reference information to set up spray models suited to take the Slot orifice into account.

Evaporation and Viscous Flow in Triangular Grooves in Micro Heat Pipes

2005 ◽  
Author(s):  
Mulugeta Markos ◽  
Vladimir S. Ajaev ◽  
G. M. Homsy
Keyword(s):  
Cross Section ◽  
Flow Rate ◽  
Cross Sections ◽  
Wedge Angle ◽  
Heat Pipes ◽  
Type Model ◽  
Pressure Gradients ◽  
Maximum Value ◽  
Dry Out ◽  
Micro Heat Pipes

We develop a lubrication type model of a liquid flow in a wedge in the limit of small capillary numbers and negligible gravity. The model incorporates the effects of capillary pressure gradients and evaporation. Steady vapor-liquid interface shapes are found for a range of parameters. In the limit of weak evaporation the flow is the same in all cross-sections and can be controlled by changing the wedge angle. We find the wedge angle that results in the maximum value of the flow rate for a given contact angle. For high evaporation rates, both the flow rate and the amount of liquid in each cross-section along the wedge decrease until the point of dry-out is reached. The location of the dry-out point is studied as a function of evaporation. Practical suggestions about optimization of micro heat pipes are given.

A new method for prediction of the acoustic performance and design parameter sensitivity analysis of multi-chamber perforated resonators with an irregular cross-section

2021 ◽  
pp. 1-24
Author(s):  
Rong Guo ◽  
Zanzan Sun ◽  
Zhen Huang ◽  
Rui Luo
Keyword(s):  
Theoretical Prediction ◽  
Cross Section ◽  
Flow Rate ◽  
New Method ◽  
Frequency Noise ◽  
Acoustic Characteristics ◽  
Inlet Flow ◽  
Acoustic Performance ◽  
Inlet Flow Rate ◽  
Prediction Approach

Abstract Aiming at reducing the high-amplitude and wide-frequency noise in charged air intake system of the powertrain, this paper proposes a new method for predicting the acoustic characteristics of an irregular cross-section multi-chamber perforated resonator under flow conditions. By this method, the presence of three-dimensional sound waves and the effects of higher-order modes are considered, and the acoustic performance of the resonator can be evaluated through the computation of transmission loss. Moreover, by discretizing the cross-section of perforated resonator and extracting node information, this method can solve the acoustic characteristics of the perforated resonator with any cross-section. Based on the transfer matrix method, the quadrupole parameters of each chamber are obtained. Then the acoustic characteristics of the multi-chamber perforated resonator could be calculated. The theoretical prediction data and the experimental data have been compared and the results show good agreement within the entire frequency range, which verifies the accuracy of the theoretical prediction approach. Based on this prediction approach, the influence of section ratio, structure parameters and inlet flow rate on the acoustic characteristics of the resonator is explored. The results show that when the structural parameters change, the peak resonance frequency of the resonator will have a regular shift. With the increase of the inlet flow rate, the main frequency band of sound attenuation will decrease significantly. The theoretical method developed in this work can be used for the calculation and optimization of multi-chamber resonators in various applications.

Thermal and Fluid Dynamic Behavior of a Horizontal Channel With Adiabatic Moving Lower Plate

2005 ◽  
Author(s):  
Assunta Andreozzi ◽  
Vincenzo Naso ◽  
Oronzio Manca
Keyword(s):  
Heat Flux ◽  
Reynolds Number ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Horizontal Channel ◽  
Lower Plate ◽  
Stationary Condition ◽  
Moving Plate ◽  
Plate Velocity

In this study a numerical investigation of mixed convection in air in horizontal parallel walled channels with moving lower plate is carried out. The moving lower plate has a constant velocity and it is adiabatic, whereas the upper one is heated at uniform heat flux. The effects of horizontal channel height, heat flux and moving plate velocity are analyzed. Results in terms of temperature and stream function fields are given and the mass flow rate per unit of length and divided by the dynamic viscosity is reported as a function of Reynolds number based on the moving plate velocity. For stationary condition of lower plate, a typical C–loop inside the horizontal channel is detected. Different flow motions are observed in the channel and the two reservoirs, depending on the heat flux values and the distance between the heated upper stationary plate and lower adiabatic moving plate. The dimensionless induced mass flow rate presents different increase between the Reynolds number lower or greater than 1000.

Electroosmotic Flow in Hydrophobic Microchannels of General Cross Section

2015 ◽  
Vol 138 (3) ◽  
Author(s):  
Morteza Sadeghi ◽  
Arman Sadeghi ◽  
Mohammad Hassan Saidi
Keyword(s):  
Cross Section ◽  
Flow Rate ◽  
Electroosmotic Flow ◽  
Slip Length ◽  
Debye Length ◽  
Surface Hydrophobicity ◽  
Double Layers ◽  
Slip Conditions ◽  
Wall Boundary Conditions ◽  
Electroosmotic Velocity

Adopting the Navier slip conditions, we analyze the fully developed electroosmotic flow in hydrophobic microducts of general cross section under the Debye–Hückel approximation. The method of analysis includes series solutions which their coefficients are obtained by applying the wall boundary conditions using the least-squares matching method. Although the procedure is general enough to be applied to almost any arbitrary cross section, eight microgeometries including trapezoidal, double-trapezoidal, isosceles triangular, rhombic, elliptical, semi-elliptical, rectangular, and isotropically etched profiles are selected for presentation. We find that the flow rate is a linear increasing function of the slip length with thinner electric double layers (EDLs) providing higher slip effects. We also discover that, unlike the no-slip conditions, there is not a limit for the electroosmotic velocity when EDL extent is reduced. In fact, utilizing an analysis valid for very thin EDLs, it is shown that the maximum electroosmotic velocity in the presence of surface hydrophobicity is by a factor of slip length to Debye length higher than the Helmholtz–Smoluchowski velocity. This approximate procedure also provides an expression for the flow rate which is almost exact when the ratio of the channel hydraulic diameter to the Debye length is equal to or higher than 50.

The Effect of Boundary Layer Separation on Accuracy of Flow Measurement Using the Gibson Method

2007 ◽  
Author(s):  
F. Z. Sierra ◽  
A. Adamkowski ◽  
G. Urquiza ◽  
J. Kubiak ◽  
H. Lara ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Cross Section ◽  
Flow Rate ◽  
Pressure Difference ◽  
Proper Time ◽  
Effective Cross Section ◽  
Boundary Layer Separation ◽  
Water Hammer ◽  
Time Interval ◽  
Geometry Factor

The Gibson method utilizes the effect of water hammer phenomenon (hydraulic transients) in a pipeline for flow rate determination. The method consists in measuring a static pressure difference, which occurs between two cross-sections of the pipeline as a result of a temporal change of momentum from t0 to t1. This condition is induced when the water flow in the pipeline is stopped suddenly using a cut-off device. The flow rate is determined by integrating, within a proper time interval, the measured pressure difference change caused by the water hammer (inertia effect). However, several observations demonstrate that changes of pipeline geometry like diameter change, bifurcations, or direction shift by elbows may produce an effect on the computation of the flow rate. The paper focuses on this effect. Computational simulations have shown that the boundary layer separates when the flow faces sudden changes like these mentioned to above. The separation may reduce the effective cross section area of flow modifying a geometry factor involved into the computation of the flow rate. The remainder is directed to quantify the magnitude of such a factor under the influence of pipeline geometry changes. Results of numerical computations are discussed on the basis of how cross section reductions impact on the geometry factor magnitude and consequently on the mass flow rate.

scholarly journals Experimental Investigation of a Rectangular Airlift Pump

2010 ◽  
Vol 2010 ◽  
pp. 1-5 ◽  
Author(s):  
I. I. Esen
Keyword(s):  
Experimental Investigation ◽  
Cross Section ◽  
Flow Rate ◽  
Liquid Flow ◽  
Liquid Flow Rate ◽  
Rectangular Cross Section ◽  
Hydraulic Performance ◽  
Experimental Program ◽  
Empirical Equations ◽  
Airlift Pump

Hydraulic performance of an airlift pump having a rectangular cross-section 20 mm × 80 mm was investigated through an experimental program. The pump was operated at six different submergence ratios and the liquid flow rate was measured at various flowrates of air injected. The effectiveness of the pump, defined as the ratio of the mass of liquid pumped to the mass of air injected, was determined as a function of the mass of air injected for different submergence ratios. Results obtained were compared with those for circular airlift pumps using an analytical model for circular pumps. Effectiveness of the rectangular airlift pump was observed to be comparable to that of the circular pumps. Hydraulic performance of the rectangular airlift pump investigated was then described by a set of semilogarithmic empirical equations.

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