Temperature Measurement in Transient Heat Transport Phenomena through a Thermal Boundary Layer with High Vortex Density in He II

1996 ◽  
pp. 265-271 ◽  
Author(s):  
T. Shimazaki ◽  
M. Murakami ◽  
T. Iida
Keyword(s):  
Boundary Layer ◽  
Temperature Measurement ◽  
Heat Transport ◽  
Thermal Boundary Layer ◽  
Transport Phenomena ◽  
Vortex Density

A Study on Heat Transport Phenomena in a Developed Thermal Boundary Layer of Drag Reducing Channel Flow

2016 ◽  
Author(s):  
K. Watanabe ◽  
Y. Kaiho ◽  
S. Hara ◽  
T. Tsukahara ◽  
Y. Kawaguchi
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transport ◽  
Thermal Boundary Layer ◽  
Transport Phenomena ◽  
Surfactant Solution ◽  
Temperature Fluctuations ◽  
Large Temperature ◽  
Wall Region ◽  
Solution Flow

The heat transport phenomena in a developed thermal boundary layer of surfactant solution flow were investigated experimentally. The experiment was conducted under different surfactant additive concentrations. The temperature fluctuations in a thermal boundary layer in a smooth channel flow were measured by fine-wire thermocouple probe. Heat transfer reducing rate and temperature fluctuation characteristics including mean temperature distribution, intensity, wave form, spectral density function, and skewness factor were studied. The results showed that the turbulent transport is obstructed by additives, and the temperature field shows dramatic changes. High frequency component of temperature fluctuation of surfactant solution flow was decreased due to suppression of turbulence and viscoelasticity. Large temperature fluctuations occur in the thermal boundary layer because the development of the thermal boundary layer is obstructed, and large temperature fluctuations appear to concentrate the temperature gradient in the near-wall region (10 < y+ < 60). In contrast, viscous sublayer expands due to viscoelasticity, and the temperature gradient and turbulence fluctuation are small in the near-wall region of y+ < 10. As a result, two layers having significantly different characteristics seem to coexist. The heat transfer reduction is constant with variation of additive concentration condition, but heat transport phenomena were microscopically influenced by viscoelasticity.

Precise Measurement and Analysis of Heat Transfer to the Inlet Air Using Intake Port Model

2006 ◽  
Author(s):  
Keisuke Uchida ◽  
Takashi Suzuki ◽  
Yasufumi Oguri ◽  
Masatake Yoshida
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Nusselt Number ◽  
Temperature Measurement ◽  
Thermal Boundary Layer ◽  
Heating Temperature ◽  
Great Influence ◽  
Intake Port ◽  
Fundamental Information ◽  
System Temperature

Temperature measurement experiments with an intake port model and analysis of heat transfer phenomena were carried out to obtain the fundamental information on constructing physical model that expressed heat transfer phenomena in an engine intake system. Temperature measurement experiments on steady air flow were done, and shape inside the intake port model, heating temperature of the intake port model, mass flow rate of air, and the development conditions of the velocity boundary layer and the thermal boundary layer were changed as experiment parameters. As the results, it was clear that the change of inside shape and heating temperature had little influence to the change of Nusselt number but the development condition of the velocity and thermal boundary layer had great influence. And the equations that expressed the Nusselt number with Reynolds number and Graetz number in each case that the velocity and thermal boundary layer were developed simultaneously and individually were obtained.

Heat transfer of temperature-sensitive magnetic fluids around single heating pipe

2020 ◽  
Vol 64 (1-4) ◽  
pp. 1039-1046
Author(s):  
Yuhiro Iwamoto ◽  
Hayaki Nakasumi ◽  
Yasushi Ido ◽  
Xiao-Dong Niu
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transport ◽  
Thermal Boundary Layer ◽  
High Heat ◽  
Temperature Sensitive ◽  
Long Distance ◽  
Nanoparticle Suspension ◽  
Single Heating

Temperature-sensitive magnetic fluid (TSMF) is a magnetic nanoparticle suspension with strong temperature-dependent magnetization even at room temperature. TSMF is a refrigerant that enables high heat transport capability and pumpless long-distance heat transport. To enhance the heat transport capacity of the magnetically-driven heat transport device using TSMF, it is effective to use a heating body with a very large heat exchange surface such as a heat sink or a porous medium. In the present study, the thermal flow of TSMF around a single heating pipe under a magnetic field was investigated. Visualization of the temperature field by infrared thermography showed that the application of the magnetic field dramatically developed the thermal boundary layer and improved heat transfer. It was clarified by numerical analysis that this dramatic variation in the thermal boundary layer was associated with several vortexes generated by magnetic force in the vicinity of the heating pipe.

Effect of Nanofluid on Heat Transfer Enhancement for Mixed Convection Flow Over a Corrugated Surface

2020 ◽  
Vol 45 (4) ◽  
pp. 373-383
Author(s):  
Nepal Chandra Roy ◽  
Sadia Siddiqa
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Local Nusselt Number ◽  
Richardson Number ◽  
Thermal Boundary Layer ◽  
Volume Fraction ◽  
Convection Flow ◽  
Mixed Convection Flow

AbstractA mathematical model for mixed convection flow of a nanofluid along a vertical wavy surface has been studied. Numerical results reveal the effects of the volume fraction of nanoparticles, the axial distribution, the Richardson number, and the amplitude/wavelength ratio on the heat transfer of Al2O3-water nanofluid. By increasing the volume fraction of nanoparticles, the local Nusselt number and the thermal boundary layer increases significantly. In case of \mathrm{Ri}=1.0, the inclusion of 2 % and 5 % nanoparticles in the pure fluid augments the local Nusselt number, measured at the axial position 6.0, by 6.6 % and 16.3 % for a flat plate and by 5.9 % and 14.5 %, and 5.4 % and 13.3 % for the wavy surfaces with an amplitude/wavelength ratio of 0.1 and 0.2, respectively. However, when the Richardson number is increased, the local Nusselt number is found to increase but the thermal boundary layer decreases. For small values of the amplitude/wavelength ratio, the two harmonics pattern of the energy field cannot be detected by the local Nusselt number curve, however the isotherms clearly demonstrate this characteristic. The pressure leads to the first harmonic, and the buoyancy, diffusion, and inertia forces produce the second harmonic.

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