618 Effects of Diameter of Test Heater and Period of Heat Generation Rate on Quasi-steady-state and Transient Heat Transfer for Forced Convection Flow of Helium Gas over a Horizontal Cylinder

2004 ◽  
Vol 2004.79 (0) ◽  
pp. _6-35_-_6-36_
Author(s):  
Toshiya Nishikawa ◽  
Zheng Zhang ◽  
Qiusheng Liu ◽  
Katsuya Fukuda
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Forced Convection ◽  
Heat Generation ◽  
Horizontal Cylinder ◽  
Convection Flow ◽  
Quasi Steady State ◽  
Heat Generation Rate ◽  
Helium Gas ◽  
Forced Convection Flow

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 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.

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