Transient Heat Transfer for Parallel Flow of Helium Gas Over a Horizontal Plate

2007 ◽  
Author(s):  
Qiusheng Liu ◽  
Katsuya Fukuda ◽  
Makoto Shibahara ◽  
Shingo Kikumoto
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Steady State ◽  
Heat Generation ◽  
Transient Heat Transfer ◽  
Quasi Steady State ◽  
Horizontal Plate ◽  
Heat Generation Rate ◽  
Helium Gas

Forced convection transient heat transfer for helium gas at various periods of exponentially increase of heat input to a horizontal plate (ribbon) was experimentally and theoretically studied. In the experimental studies, the authors measured heat flux, surface temperature, and transient heat transfer coefficients for forced convection flow of helium gas over a horizontal plate under wide experimental conditions. The gas flow velocities ranged from 4 to 10 m/s, the gas temperatures ranged from 313 to 353 K, and the periods of heat generation rate, τ, ranged from 46 ms to 17 s. The pressures were from 400 to 800 kPa. It was clarified that the heat transfer coefficient approaches the quasi-steady-state one for the period longer than about 1 s, and it becomes higher for the period shorter than around 1 s. Empirical correlations for quasi-steady-state heat transfer and transient heat transfer were obtained based on the experimental data. In the theoretical study, transient heat transfer was numerically solved based on a turbulent flow model. It was obtained that the surface superheat and heat flux increase exponentially as the heat generation rate increases with the exponential function. The values of numerical solutions for surface temperature and heat flux at the velocity of 6 m/s agree well with the experimental data, though they show some differences at other velocities.

Transient Forced Convection Heat Transfer for Helium Gas Flowing Over a Horizontal Plate

2006 ◽  
Author(s):  
Qiusheng Liu ◽  
Makoto Shibahara ◽  
Katsuya Fukuda
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Steady State ◽  
Heat Generation ◽  
Generation Rate ◽  
Quasi Steady State ◽  
Horizontal Plate ◽  
Heat Generation Rate ◽  
Helium Gas ◽  
The Heat Transfer Coefficient

Transient heat transfer coefficients for helium gas flowing over a horizontal plate (ribbon) were measured under wide experimental conditions. The platinum plate with a thickness of 0.1 mm was used as test heater and heated by electric current. The heat generation rate was exponentially increased with a function of Q0exp(t/τ). The gas flow velocities ranged from 4 to 10 m/s, the gas temperatures ranged from 313 to 353 K, and the periods of heat generation rate, τ, ranged from 50 ms to 17 s. The surface superheat and heat flux increase exponentially as the heat generation rate increases with the exponential function. It was clarified that the heat transfer coefficient approaches the quasi-steady-state one for the period τ longer than about 1 s, and it becomes higher for the period shorter than around 1 s. The dependence of transient heat transfer on the gas flowing velocity becomes weaker when the period becomes very shorter. The gas temperature in this study shows little influence on the heat transfer coefficient. Empirical correlation for quasi-steady-state heat transfer was obtained based on the experimental data.

Transient Heat Transfer for Helium Gas Flowing Over a Horizontal Flat-Plate With Different Widths

2013 ◽  
Author(s):  
Zhou Zhao ◽  
Qiusheng Liu ◽  
Katsuya Fukuda
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Steady State ◽  
Heat Generation ◽  
Generation Rate ◽  
Transient Heat Transfer ◽  
Quasi Steady State ◽  
Heat Generation Rate ◽  
Helium Gas ◽  
The Heat Transfer Coefficient

This study is aimed to clarify transient heat transfer process between the surface of solid and the neighboring helium gas in Very High Temperature Reactor (VHTR) or intermediate heat exchanger (IHX). In this paper a series of platinum heaters with different widths under different pressures inside a circular channel have been tested for forced convection flow. The heat generation rate of the platinum heater was increased with a function of Q0exp(t/τ) (where t is time and τ is period of heat generation rate or e-fold time). The heaters were platinum plates with a thickness of 0.1 mm and widths of 2 mm, 4 mm and 6 mm. In the present study, the heat flux, surface temperature, and transient heat transfer coefficients were measured for helium gas passing by horizontal plates under wide experimental conditions such as velocities, pressures and periods of heat generation rate. It was clarified that the heat transfer coefficient approaches the quasi-steady-state when the period is more than around 1 s and it becomes higher when the period shorter than around 1 s. Based on the experimental data, empirical correlations for both quasi-steady-state heat transfer and transient state one at various plate-widths were obtained. It was also found that the heat transfer coefficient becomes higher with the increases of gas pressure.

Transient Heat Transfer From a Horizontal Plate in Forced Flow of Various Gases

2011 ◽  
Author(s):  
Qiusheng Liu ◽  
Makoto Shibahara ◽  
Katsuya Fukuda
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Gas Flow ◽  
Transient Heat Transfer ◽  
Quasi Steady State ◽  
Horizontal Plate ◽  
Heat Generation Rate ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
The Heat Transfer Coefficient

In this research, to obtain fundamental experimental data of transient heat transfer and to clarify the transient heat transfer process at wide experimental conditions for the safety assessment of very high temperature reactor (VHTR), forced convection transient heat transfer coefficients were measured for Helium, Carbon dioxide, Argon and Nitrogen gases flowing over a horizontal plate due to exponentially increasing heat input. The platinum ribbon with a thickness of 0.1 mm and a width of 4.0 mm was used as the test heater and heated by electric current. The heat generation rate was controlled and measured by a heat input control system, it was exponentially increased with a function of Q0exp(t/τ). The periods (e-fold times) of heat generation rate, τ, ranged from 46 ms to 17 s, the gas flow velocities ranged from 1 to 10 m/s, the pressures ranged from 400 kPa to 800 kPa, and the gas temperatures ranged from 290 to 353 K. It was clarified that the heat transfer coefficient approaches the quasi-steady-state one for the period longer than about 1 s, and it becomes higher for the period shorter than around 1 s. The heat transfer coefficient increases with the increases in pressure and velocity, and it shows some dependence on temperature at the experimental range of this research. The dependence of transient heat transfer on the gas flow velocity becomes weaker when the period becomes very shorter. Effect of gas thermal physical properties on heat transfer was investigated, and helium gas shows higher heat transfer coefficients than those of other gases due to its higher thermal conductivity. Empirical correlations for quasi-steady-state heat transfer and transient one for various gases were obtained based on the experimental data.

Transient Heat Transfer From Single Horizontal Heaters in Forced Flow of Helium Gas at Exponentially Increasing Heat Inputs

2008 ◽  
Author(s):  
Qiusheng Liu ◽  
Katsuya Fukuda ◽  
Makoto Shibahara
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Surface Temperature ◽  
Numerical Solution ◽  
Transient Heat Transfer ◽  
Quasi Steady State ◽  
Helium Gas ◽  
The Heat Transfer Coefficient

Forced convection transient heat transfer for helium gas at various periods of exponential increase of heat input to a horizontal cylinder and a plate (ribbon) was experimentally and theoretically studied. It was clarified that the heat transfer coefficient approaches the quasi-steady-state one for the period longer than about 1 s, and it becomes higher for the period shorter than around 1 s. The dependence of transient heat transfer on the gas flowing velocity becomes weaker when the period becomes very shorter. However, the gas temperature in this study shows little influence on the heat transfer coefficient. Empirical correlations for quasi-steady-state heat transfer and transient heat transfer were obtained based on the experimental data. In the theoretical study, transient heat transfer was numerically solved based on a turbulent flow model. The values of numerical solution for surface temperature and heat flux were compared and discussed with authors’ experimental data. It was clarified that the surface superheat and heat flux increase exponentially as the heat generation rate increases with the exponential function. The temperature distribution near the heater becomes larger as the surface temperature increases. The values of numerical solution for surface temperature and heat flux agree well with the experimental data for the cylinder diameter of 1 mm. However, the heat fluxes show some differences from the experimental values for the cylinder diameters of 0.7 mm and 2.0 mm. And for the numerical solution for a plate, the values of numerical solutions for surface temperature and heat flux at the velocity of 6 m/s agree well with the experimental data, though they show some differences at other velocities.

Experimental Study on Transient Heat Transfer for Helium Gas Flowing in a Minichannel

2020 ◽  
Author(s):  
Feng Xu ◽  
Qiusheng Liu ◽  
Satoshi Kawaguchi ◽  
Makoto Shibahara
Keyword(s):  
Heat Transfer ◽  
Heat Generation ◽  
Heat Transfer Process ◽  
Test Tube ◽  
Generation Rate ◽  
Transient Heat Transfer ◽  
Heat Generation Rate ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Helium Gas

Abstract The blanket modules of first wall need bear tremendous heat flux due to the very high temperature of plasma in the nuclear fusion reactor. Therefore, it is significant to clarify the knowledge of transient heat transfer process for helium gas flowing in the tubes installed in the blanket modules. In this research, the transient heat transfer process of turbulent forced convection for helium gas flowing in a horizontal minichannel was experimentally investigated. The test tube made of platinum with the inner diameter of 1.8 mm, the wall thickness of 0.1 mm and the effective length of 90 mm was heated by a direct current from power source. The heat generation rate of the test tube, Q̇, was raised with an exponential function, Q̇ = Q0 exp(t/τ), where Q0 is the initial heat generation rate, t is time, and τ is e-folding time of heat generation rate. The heat generation rates of the test tube were controlled and measured by a heat input control system. The flow rates were adjusted by the bypass of gas loop and measured by the turbine flow meter. The experiment was conducted under the e-folding time of heat generation rate ranged from 40 ms to 15 s. Based on experimental data, it is obvious that the heat flux and temperature difference between surface temperature of test tube and bulk temperature of helium gas increased with the exponentially increasing of heat generation rate. At the same flow velocity, the heat transfer coefficients approached constant values when the e-folding time is longer than about 1 s (quasi-steady state), but increased with a decrease of e-folding time when the e-folding time is smaller than about 1 s (transient state). The heat transfer coefficients increased with the increase in flow velocities but showed less dependent on flow velocities at shorter e-folding time. Furthermore, the Nusselt number under quasi-steady and transient condition was affected by the Reynolds number and the Fourier number.

Transient Heat Transfer From a Horizontal Cylinder in the Low-Reynolds-Number Flow of Helium Gas

2002 ◽  
Author(s):  
Qiusheng Liu ◽  
Katsuya Fukuda ◽  
Koichi Hata
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Steady State ◽  
Heat Input ◽  
Low Reynolds Number ◽  
Horizontal Cylinder ◽  
Transient Heat Transfer ◽  
Quasi Steady State ◽  
Helium Gas ◽  
Low Reynolds

The knowledge of forced convection transient heat transfer at various periods of exponentially increasing heat input to a heater is important as a database for understanding the transient heat transfer process in a high temperature gas cooled reactor (HTGR) due to an accident in excess reactivity. In this study, the transient heat transfer coefficients for Helium gas flowing perpendicular to a horizontal cylinder were measured in the low-Reynolds-number region. The platinum heater with a diameter of 1.0 mm was heated by electric current with an exponentially increasing heat input of Q0exp(t/τ). It was clarified that the heat transfer coefficient approaches the quasi-steady-state one for the period τ over around 1 s, and it becomes higher for the period of τ shorter than about 1 s. The transient heat transfer shows less dependent on the gas flowing velocity when the period becomes very short. Based on the experimental data, the ratio of transient heat transfer to the quasi-steady-state one was correlated as a function of Reynolds number of the gas flow and the non-dimensional period of increasing heat input. For the non-dimensional period larger than about 300, the transient heat transfer approaches the steady-state one, and shows no dependence on the Reynolds number.

Transient Heat Transfer for Carbon Dioxide Flowing Over a Horizontal Plate With Exponentially Increasing Heat Input

2008 ◽  
Author(s):  
Makoto Shibahara ◽  
Qiusheng Liu ◽  
Katsuya Fukuda
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
Heat Generation ◽  
Numerical Solutions ◽  
Generation Rate ◽  
Transient Heat Transfer ◽  
Horizontal Plate ◽  
Heat Generation Rate ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Transient heat transfer coefficients for carbon-dioxide gas flowing over a horizontal plate (ribbon) at various periods of exponentially increasing heat input was experimentally and theoretically studied. In the experimental studies, transient heat transfer coefficients were measured under various velocities and periods. The platinum plate with a thickness of 0.1 mm was used as test heater and heated by electric current. The heat generation rate was exponentially increased with a function of Q0exp(t/τ). The gas flow velocities ranged from 1 to 3 m/s, the gas temperatures ranged from 313 K to 353 K, and the periods of heat generation rate ranged from 46 ms to 17 s. The surface temperature and heat flux increase exponentially as the heat generation rate increases with the exponential function. It was clarified that the heat transfer coefficient approaches the quasi-steady-state one for the period longer than about 1 s, and it becomes higher for the period shorter than around 1 s. In the theoretical study, forced convection transient heat transfer was numerically solved based on a conventional turbulent flow model. The temperature within the boundary layer around the heater increases with the increase of the surface temperature. It is understood that the gradient of the temperature distribution near the wall of the plate is higher at a higher surface temperature difference. The values of numerical solutions for the heat fluxes agree well with the experimental data, though the numerical solutions for surface temperatures show some differences with the experimental data.

Transient Forced Convection Heat Transfer Due to Exponentially Increasing Heat Input for Helium Gas Flowing on a Narrow Plate

2008 ◽  
Author(s):  
Makoto Shibahara ◽  
Qiusheng Liu ◽  
Katsuya Fukuda
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Forced Convection ◽  
Heat Input ◽  
Numerical Solutions ◽  
Transient Heat Transfer ◽  
Heat Generation Rate ◽  
Helium Gas ◽  
Narrow Plate

Steady and transient forced convection transient heat transfer due to exponentially increasing heat input to a heater is important as a database for safety assessment of the transient heat transfer process not only in a high temperature gas cooled reactor (HTGR) due to an accident in excess reactivity but also in high heat flux gas cooling devices such as a gas turbine and a rocket engine. In this research, forced convection transient heat transfer for helium gas at various periods of exponential increase of heat input (Q0exp(t/τ)) to a horizontal narrow plate was numerically solved based on a turbulent flow model. The platinum plate with a length of 50 mm was used as test heater. The velocities ranged from 4 to 10 m/s, the gas temperatures ranged from 313 to 353 K, and the periods of heat generation rate, τ, ranged from 46 ms to 8.6 s. The values of numerical solutions for surface temperature and heat flux were compared and discussed with authors’ experimental values. It was obtained that the surface temperature difference and heat flux increase exponentially as the heat generation rate increases with the exponential function. Then the temperature within the boundary layer also increases with the increase of the surface temperature. It is understood that the gradient of the temperature distribution near the wall of the plate is higher at a higher surface temperature difference. The values of numerical solutions for surface temperature and heat flux at the velocity of 6 m/s agree well with the experimental data, though they show some differences at other velocities. And also, heat transfer coefficients at the velocity of 6 m/s agree well with the experimental data, though they show some differences at other velocities. They agree within 15% at various periods and velocities.

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