Characteristics of Turbulent Gas Flow in Microtubes

2012 ◽  
Author(s):  
Chungpyo Hong ◽  
Shinichi Matsushita ◽  
Yutaka Asako ◽  
Ichiro Ueno
Keyword(s):  
Gas Flow ◽  
Electrical Discharge Machining ◽  
Average Diameter ◽  
Companion Paper ◽  
Isothermal Flow ◽  
One Dimensional ◽  
Adiabatic Flow ◽  
Flow Acceleration ◽  
Friction Factors ◽  
Turbulent Gas Flow

This paper presents results of an experimental investigation of turbulent gas flow in microtubes fabricated by wire cutting electrical discharge machining (EDM) in a stainless steel block. The micro-tube was designed with a main flow tube and five pressure ports, which lead to the pressure transducers. The average diameters of the main tubes were 320 μm and 369 μm. And the aspect ratio of length to the average diameter is about 190. The outlet of the tube faced to the atmosphere. The pressure distribution of turbulent gas flow in microtubes fall steeply and Mach numbers increase near the outlet with increasing the inlet pressure due to flow acceleration. Both Darcy friction factors and Fanning friction factors of turbulent flow were obtained under the assumption of isothermal flow and under the assumption of one dimensional adiabatic flow. The later data reduction was proposed in the companion paper [1]. Friction factors obtained under assumption of isothermal flow is compared with one obtained under the assumption of one dimensional adiabatic flow. The result shows that the obtained Darcy and Fanning friction factors were evaluated as a function of Reynolds number on the Moody chart.

Data Reduction of Friction Factor of Compressible Flow in Micro-Channels

2012 ◽  
Author(s):  
D. Kawashima ◽  
Y. Asako
Keyword(s):  
Friction Factor ◽  
Compressible Flow ◽  
Data Reduction ◽  
Compressible Fluid ◽  
Isothermal Flow ◽  
One Dimensional ◽  
The Past ◽  
Friction Factors ◽  
Micro Channels ◽  
Past Data

This paper focuses on data reduction of friction factor of compressible fluid flowing through micro-channels. The both pressure and temperature are required to calculate the friction factor of compressible flow. Therefore, in the past data reduction of many experiments, the friction factors have been obtained under the assumption of isothermal flow since temperature measurement of compressible flow in micro-channels is quite difficult due to the experimental technique limitation. The authors find that the temperature of the fluid can be obtained from the pressure under the assumption of one dimensional flow in an adiabatic channel (Fanno flow). In this paper, the temperatures obtained by our proposed equation are compared with results of numerical simulations and friction factors are also compared.

scholarly journals METHODOLOGY FOR DETERMINING SPEED COEFFICIENTS IN THE DESIGN OF RADIAL-AXIAL TURBINE

2020 ◽  
Vol 4 ◽  
pp. 25-36
Author(s):  
A.V. Passar ◽  
◽  
D.V. Timoshenko ◽  
E.V. Faleeva ◽  
◽  
...  
Keyword(s):  
Gas Flow ◽  
Average Diameter ◽  
Operating Parameters ◽  
Optimal Operating ◽  
Axial Turbine ◽  
One Dimensional ◽  
Optimal Geometry ◽  
Centripetal Turbine ◽  
Stationary Approximation

The article proposes a method for the interrelated determination of the speed coefficients and optimal geometry of a radial-axial centripetal turbine flow range. The method is based on a model of gas flow at an average diameter in a one-dimensional quasi-stationary approximation, supplemented with ratios to determine the optimal operating parameters of the turbine.

Experimental Investigations of Turbulent Gas Flow in a Micro-Channel

2011 ◽  
Author(s):  
Shinichi Matsushita ◽  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Ichiro Ueno
Keyword(s):  
Mach Number ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Gas Flow ◽  
Experimental Investigations ◽  
Micro Channel ◽  
Pressure Transducers ◽  
Friction Factors ◽  
Turbulent Flow Regime ◽  
Turbulent Gas Flow

This paper presents experimental investigations on turbulent gas flow characteristics of nitrogen gas through a micro-channel. The micro-channels were etched into silicon wafers, capped with glass, and their hydraulic diameter is 147.76 micro meters. The micro-channel was designed with a main flow channel and seven side channels, which lead to the pressure transducers. The stagnation pressure was designated in such a way that the flow is in turbulent flow regime. The outlet of the channel faced to the atmosphere. The pressures of the main channel at seven locations were measured by gauge pressure transducers to determine local values of Mach number. And the pressure differences of each pressure ports were measured by differential pressure transducers to obtain the pressure losses precisely. The pressure distribution of turbulent gas flow through a micro-channel falls steeply and Mach number increases near the outlet with increasing the inlet pressure due to flow acceleration. Both Darcy friction factor and Fanning friction factor were obtained for turbulent flow. The result shows that the obtained both friction factors were evaluated as a function of Reynolds number on the Moody chart. The values of Darcy friction factors differ from Blasius correlation for turbulent flow regime due to the compressibility effects, however the values of Fanning friction factors coincide with Blasius correlation.

Semi Local Friction Factor of Gas Flow Through a Micro-Tube

2017 ◽  
Author(s):  
Kenshi Maeda ◽  
Chungpyo Hong ◽  
Yutaka Asako
Keyword(s):  
Friction Factor ◽  
High Speed ◽  
Gas Flow ◽  
Electrical Discharge Machining ◽  
Tube Wall ◽  
Gas Temperature ◽  
Local Pressure ◽  
Adiabatic Wall ◽  
Friction Factors ◽  
Flow Through

Flow characteristics of laminar gas flow through a micro-tube were experimentally studied on friction factors in this paper. The experiments were performed for nitrogen flow through a stainless steel micro-tube with 123.87 μm in diameter and 50mm in length. Two static pressure tap holes were fabricated on the micro-tube wall at intervals of 5mm with electrical discharge machining. The local pressure was measured to determine the local values of Mach number, temperature and friction factor. Both the Fanning and the Darcy friction factors were obtained under the assumption of a Fanno flow (adiabatic wall) since the external micro-tube wall was covered with the foamed polystyrene. The effects of temperature decrease on friction factors were investigated because the gas temperature steeply decreases near the outlet due to energy conversion from thermal energy into kinetic energy in a high speed gas flow. The obtained friction factors were compared with those in the available literature and also with numerical results.

scholarly journals Average Friction Factors of Choked Gas Flow in Microtubes

2020 ◽  
Vol 1599 ◽  
pp. 012018
Author(s):  
D Kang ◽  
C Hong ◽  
D Rehman ◽  
G L Morini ◽  
Y Asako ◽  
...  
Keyword(s):  
Gas Flow ◽  
Friction Factors

On the theory of electrohydrodynamically driven capillary jets

1997 ◽  
Vol 335 ◽  
pp. 165-188 ◽  
Author(s):  
ALFONSO M. GAÑÁN-CALVO
Keyword(s):  
Surface Charge ◽  
Electric Fields ◽  
Gas Flow ◽  
Wave Speed ◽  
Propagation Speed ◽  
Field Equations ◽  
Steady Regime ◽  
One Dimensional ◽  
Relaxation Effects ◽  
Capillary Jets

Electrohydrodynamically (EHD) driven capillary jets are analysed in this work in the parametrical limit of negligible charge relaxation effects, i.e. when the electric relaxation time of the liquid is small compared to the hydrodynamic times. This regime can be found in the electrospraying of liquids when Taylor's charged capillary jets are formed in a steady regime. A quasi-one-dimensional EHD model comprising temporal balance equations of mass, momentum, charge, the capillary balance across the surface, and the inner and outer electric fields equations is presented. The steady forms of the temporal equations take into account surface charge convection as well as Ohmic bulk conduction, inner and outer electric field equations, momentum and pressure balances. Other existing models are also compared. The propagation speed of surface disturbances is obtained using classical techniques. It is shown here that, in contrast with previous models, surface charge convection provokes a difference between the upstream and the downstream wave speed values, the upstream wave speed, to some extent, being delayed. Subcritical, supercritical and convectively unstable regions are then identified. The supercritical nature of the microjets emitted from Taylor's cones is highlighted, and the point where the jet switches from a stable to a convectively unstable regime (i.e. where the propagation speed of perturbations become zero) is identified. The electric current carried by those jets is an eigenvalue of the problem, almost independent of the boundary conditions downstream, in an analogous way to the gas flow in convergent–divergent nozzles exiting into very low pressure. The EHD model is applied to an experiment and the relevant physical quantities of the phenomenon are obtained. The EHD hypotheses of the model are then checked and confirmed within the limits of the one-dimensional assumptions.

Diabatic Nozzle Flow with Constant Small Stage Efficiency

1960 ◽  
Vol 64 (598) ◽  
pp. 632-635 ◽  
Author(s):  
R. A. A. Bryant
Keyword(s):  
Gas Flow ◽  
Nozzle Flow ◽  
Flow Conditions ◽  
One Dimensional ◽  
Real Flow ◽  
Stage Efficiency ◽  
Frictional Effects

The concept of small stage efficiency is introduced when studying one-dimensional gas flow in nozzles in order to permit a closer approximation of real flow conditions than is possible from an isentropic analysis. It is more or less conventional to assume the flow conditions are adiabatic whenever the small stage efficiency is used. That is to say, small stage efficiency is generally considered in relation to flows contained within adiabatic boundaries, in which case it becomes a measure of the heat generated by internal frictional effects alone.

One-dimensional adiabatic flow of equilibrium gas–particle mixtures in long vertical ducts with friction

1989 ◽  
Vol 203 ◽  
pp. 251-272 ◽  
Author(s):  
Guido Buresti ◽  
Claudio Casarosa
Keyword(s):  
Equilibrium Mixture ◽  
Adiabatic Heating ◽  
Explosive Eruptions ◽  
Perfect Gas ◽  
Typical Application ◽  
One Dimensional ◽  
Adiabatic Flow ◽  
Flow Parameters ◽  
Constant Area ◽  
Inlet Conditions

The equations of the steady, adiabatic, one-dimensional flow of an equilibrium mixture of a perfect gas and incompressible particles, in constant-area ducts with friction, are derived taking into account the effects of gravity and of the finite volume of the particles. As is the case for a pure gas, the mixture is shown to be subject to the phenomenon of choking, and the possibility of an adiabatic heating of the mixture in a subsonic expansion is also theoretically predicted for certain flow inlet conditions. The model may be used to approximately describe the conditions existing in portions of volcanic conduits during the Plinian phases of explosive eruptions. Some results of the numerical integration of the equations for a typical application of this type are briefly discussed, thus showing the potential of the model for carrying out rapid analyses of the influence of the main geometrical and flow parameters describing the problem. A non-volcanological application is also analysed to illustrate the possibility of the adiabatic heating of the mixture.

Numerical Simulation on Heat Transfer Characteristics of Turbulent Gas Flow in Micro-Tubes

2011 ◽  
Author(s):  
Kyohei Isobe ◽  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Ichiro Ueno
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Wall Temperature ◽  
Gas Flow ◽  
Tube Diameter ◽  
Turbulence Energy ◽  
Stagnation Temperature ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Turbulent Gas Flow

Numerical simulations were performed to obtain for heat transfer characteristics of turbulent gas flow in micro-tubes with constant wall temperature. The numerical methodology was based on Arbitrary-Lagrangian-Eulerinan (ALE) method to solve compressible momentum and energy equations. The Lam-Bremhorst Low-Reynolds number turbulence model was employed to evaluate eddy viscosity coefficient and turbulence energy. The tube diameter ranges from 100 μm to 400 μm and the aspect ratio of the tube diameter and the length is fixed at 200. The stagnation temperature is fixed at 300 K and the computations were done for wall temperature, which ranges from 305 K to 350 K. The stagnation pressure was chosen in such a way that the flow is in turbulent flow regime. The obtained Reynolds number ranges widely up to 10081 and the Mach number at the outlet ranges from 0.1 to 0.9. The heat transfer rates obtained by the present study are higher than those of the incompressible flow. This is due to the additional heat transfer near the micro-tube outlet caused by the energy conversion into kinetic energy.

Sign in / Sign up

Export Citation Format

Share Document