Heat Transfer Characteristics of Gaseous Flow in a Micro-Tube

2004 ◽  
Author(s):  
Yutaka Asako
Keyword(s):  
Heat Transfer ◽  
Incompressible Flow ◽  
Bulk Temperature ◽  
Stagnation Temperature ◽  
Arbitrary Lagrangian Eulerian ◽  
Heat Transfer Characteristics ◽  
Gaseous Flow ◽  
Transfer Characteristics ◽  
Total Temperature ◽  
Energy Equations

Two-dimensional compressible momentum and energy equations are solved numerically to obtain the heat transfer characteristics of gaseous flow in a micro-tube with isothermal wall. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The stagnation temperature is fixed at 300 K and the computations were done for the wall temperatures of 305 K, 310 K and 350 K. The bulk temperature based on the static temperature is compared with that of the incompressible flow in a conventional sized tube. The static bulk temperature of the gaseous flow in a micro-tube decreases approaching to the outlet due to the energy conversion into the kinetic energy, when flow is fast. The total temperatures are also compared witht he bulk temperature of the incompressible flow in a conventional sized tube. The total temperature is slightly higher than the bulk temperature of the incompressible flow. This is due to the additional heat transfer near the outlet. A correlation for the prediction of the heat transfer rate of the gaseous flow in the micro tube is proposed.

Heat Transfer Characteristics of Gaseous Flows in Micro-Channels

2003 ◽  
Author(s):  
Yutaka Asako ◽  
Harumi Toriyama
Keyword(s):  
Heat Transfer ◽  
Parallel Plate ◽  
Bulk Temperature ◽  
Channel Height ◽  
Arbitrary Lagrangian Eulerian ◽  
Heat Transfer Characteristics ◽  
Adiabatic Wall ◽  
Transfer Characteristics ◽  
Micro Channels ◽  
Gaseous Flows

Two-dimensional compressible momentum and energy equations are solved to obtain the heat transfer characteristics of gaseous flows in parallel-plate micro-channels. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The computations were performed for channels with adiabatic walls to obtain the adiabatic wall temperature. The channel height ranges from 10 to 100 μm and the channel length is fixed at 30 mm. The stagnation pressure varies from 1.1×105 to 4×106 Pa. The outlet pressure is fixed at the atmosphere. The computations were also performed for channels with isothermal walls. The aspect ratio of the channel height and length is 100 or 200. The bulk temperature is compared with that of the incompressible flow in the conventional sized parallel plate channel.

Heat Transfer Characteristics of Compressible Laminar Flow Through Microtubes

2011 ◽  
Vol 134 (1) ◽  
Author(s):  
Chungpyo Hong ◽  
Takaharu Yamamoto ◽  
Yutaka Asako ◽  
Koichi Suzuki
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Gas Flow ◽  
Atmospheric Condition ◽  
Stagnation Temperature ◽  
Heat Transfer Characteristics ◽  
Constant Wall Temperature ◽  
Gaseous Flow ◽  
Transfer Characteristics ◽  
Flow Through

This paper describes experimental results on heat transfer characteristics of gaseous flow in a microtube with constant wall temperature. The experiments were performed for nitrogen gas flow through three microtubes of 123 μm, 163 μm, and 243 μm in diameter with 50mm in length, respectively. The wall temperature was maintained at 310 K, 330 K, and 350 K by circulating water around the microtube, respectively. The stagnation pressure is chosen in such a way that the exit Mach number ranges from 0.1 to 1.0. The outlet pressure was fixed at the atmospheric condition. The total temperature at the outlet, the inlet stagnation temperature, the mass flow rate, and the inlet pressure were measured. The numerical computations based on the Arbitrary-Lagrangian-Eulerian (ALE) method were also performed with the same conditions of the experiment for validation of numerical results. Both the results are in excellent agreement. In some cases, the total temperatures obtained by the present experimental study are higher than the wall temperature. This is due to the additional heat transfer from the wall to the gas near the microtube outlet caused by the temperature fall due to the energy conversion into the kinetic energy. A quantitative correlation for the prediction of the heat transfer rate of the gaseous flow in microtubes which had been proposed in our previous study (Hong and Asako, 2007, “Heat Transfer Characteristics of Gaseous Flows in a Microchannel and a Microtube with Constant Wall Temperature,” Numer. Heat Transfer, Part A, 52, pp. 219–238) was validated.

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.

Total Temperature Measurements of Gaseous Flow at Micro-Tube Outlet

2009 ◽  
Author(s):  
Takaharu Yamamoto ◽  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Koichi Suzuki
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Gas Flow ◽  
Atmospheric Condition ◽  
Stagnation Temperature ◽  
Constant Wall Temperature ◽  
Gaseous Flow ◽  
Circulating Water ◽  
Total Temperature ◽  
Exit Mach Number

This paper presents experimental results on heat transfer characteristics of gaseous flow in a micro-tube with constant wall temperature. The experiment was performed for nitrogen gas flow through a micro-tube with 166 micro meters in diameter and 50mm in length. The wall temperature was maintained at 305K, 310K, 330K and 350K by circulating water around the micro-tube, respectively. The stagnation pressure is chosen in such a way that the exit Mach number ranges from 0.1 to 1.0. The outlet pressure was fixed at the atmospheric condition. The total temperature at the outlet, the inlet stagnation temperature, the mass flow rate, and the inlet pressure were measured. The numerical computations based on the Aribitary - Langrangian - Eulerian (ALE) method were also performed for the same cases of the experiment for validation of numerical computation. The both results are in excellent agreement. The total temperatures obtained by the present study are slightly higher than those of the incompressible flow. This is due to the additional heat transfer near the micro-tube outlet caused by the temperature decrease due to the energy conversion into the kinetic energy. A quantitative correlation for the prediction of the heat transfer rate of the gaseous flow in a micro-tube was proposed.

Heat Transfer Characteristics of Porous Radiant Burners

1991 ◽  
Vol 113 (2) ◽  
pp. 423-428 ◽  
Author(s):  
T. W. Tong ◽  
S. B. Sathe
Keyword(s):  
Heat Transfer ◽  
Radiative Transfer ◽  
Heat Generation ◽  
Numerical Study ◽  
Radiant Energy ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
High Heat Transfer ◽  
Energy Equations ◽  
Radiant Burners

This paper reports a numerical study of the heat transfer characteristics of porous radiant burners, which have significant advantages over conventional burners. The heat transfer characteristics are investigated using a one-dimensional conduction, convection, and radiation model. The combustion phenomenon is modeled as spatially dependent heat generation. Nonlocal thermal equilibrium between the gas and solid phases is accounted for by using separate energy equations for the two phases. The solid matrix is assumed to emit, absorb, and scatter radiant energy. The spherical harmonics approximation is used to solve the radiative transfer equation. The coupled energy equations and the radiative transfer equations are solved using a numerical iterative procedure. The effects of the various factors on the performance of porous radiant burners are determined. It is revealed that for a given rate of heat generation, large optical thicknesses and high heat transfer coefficients between the solid and gas phases are desirable for maximizing radiant output. Also, low solid thermal conductivities, scattering albedos and flow velocities, and high inlet environment reflectivities produced high radiant output.

Total Temperature Measurements of Gaseous Flow at Micro-Tube Outlet: Cooled From the Wall

2009 ◽  
Author(s):  
Takaharu Yamamoto ◽  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Koichi Suzuki
Keyword(s):  
Wall Temperature ◽  
Gas Flow ◽  
Atmospheric Condition ◽  
Bulk Temperature ◽  
Inlet Temperature ◽  
Stagnation Temperature ◽  
Constant Wall Temperature ◽  
Gaseous Flow ◽  
Total Temperature ◽  
Exit Mach Number

This paper presents experimental results on heat transfer characteristics of gaseous flow in a micro-tube with constant wall temperature whose wall temperature is lower than the inlet temperature (cooled case). The experiment was performed for nitrogen gas flow through a micro-tube with 163.4 micro meters in diameter and 50 mm in length. The gas was heated at the inlet of the micro-tube to Tin = 315K, 335K and 355K. The wall temperature was maintained at 305K which was lower than the inlet temperature by circulating water around the micro-tube. The stagnation pressure was chosen in such a way that the exit Mach number ranges from 0.1 to 0.9. The outlet pressure was fixed at the atmospheric condition. The total temperature at the outlet, the inlet stagnation temperature, the mass flow rate, and the inlet pressure were measured. The numerical computations based on the aribitary-Langrangian-Eulerian (ALE) method were also performed for the same conditions of the experiment. The total and bulk temperature obtained by the present study are compared with those of the numerical cases and also compared with temperatures of the incompressible flow. The results have similar trends.

Heat Transfer Characteristics of Gaseous Slip Flow in Concentric Micro Annular Tubes

2009 ◽  
Author(s):  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Koichi Suzuki
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Incompressible Flow ◽  
Slip Flow ◽  
Outer Wall ◽  
Constant Heat Flux ◽  
Heat Transfer Characteristics ◽  
Constant Heat ◽  
Transfer Characteristics ◽  
Adiabatic Case

A concentric micro annular passage is a basic and important micro-geometry of micro-fluidic-systems from simple heat exchanger to the most complicated nuclear reactors. Therefore, heat transfer characteristics of gaseous flows in concentric micro annular tubes with constant heat flux whose value was positive or negative were numerically investigated. The slip velocity, temperature jump and shear stress work were considered on the slip boundary. The numerical methodology was based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The computations were performed for two thermal cases. This is, the heat flux was constant at the inner wall and outer wall was adiabatic (Case 1) and the heat flux was constant at the outer wall and the inner wall was adiabatic (Case 2). Each constant heat flux of 104 Wm−2 for the positive value and −104 Wm−2 for the negative value was chosen. The outer tube radius ranged from 20 to 150 μm with the radius ratio 0.02, 0.05, 0.1, 0.25 and 0.5 and the ratio of length to hydraulic diameter was 100. The stagnation pressure was chosen in such a way that the exit Mach number ranges from 0.1 to 0.7. The outlet pressure was fixed at the atmospheric pressure. The heat transfer characteristics in concentric micro annular tubes were obtained. The wall and bulk temperatures with positive heat flux are compared with those of negative heat flux cases and also compared with those of the simultaneously developing incompressible flow. The results show that the compressible slip flow Nusselt number is different from that of incompressible flow. And, the temperatures normalized by heat flux have different trends whether heat flux value is positive or negative. A correlation for the prediction of the heat transfer characteristics of gas slip flow in concentric micro annular tubes is proposed.

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