Use of Analytical Expressions of Convection in Conjugated Heat Transfer Problems

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
R. Karvinen
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Surface Temperature ◽  
Flow Direction ◽  
Superposition Principle ◽  
Industrial Applications ◽  
Transfer Coefficients ◽  
Flat Plates ◽  
Surface Temperature Distribution ◽  
Analytical Expressions

The heat transfer coefficient of convection from the wall to the flow depends on flow type, on surface temperature distribution in a stream-wise direction, and in transient cases also on time. In so-called conjugated problems, the surface temperature distribution of the wall and flow are coupled together. Thus, the simultaneous solution of convection between the flow and wall, and conduction in the wall are required because heat transfer coefficients are not known. For external and internal flows, very accurate approximate analytical expressions have been derived for heat transfer in different kinds of boundary conditions which change in flow direction. Due to the linearity of the energy equation, the superposition principle can be adopted to couple with these expressions the surface temperature and heat flux distributions in conjugated problems. In the paper, this type of approach is adopted and applied to a number of industrial applications ranging from flat plates of electroluminecence displays to the optimization of heat transfer in fins, fin arrays and mobile phones.

Use of Analytical Expressions of Convection in Conjugated Heat Transfer Problems

2010 ◽  
Author(s):  
R. Karvinen
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Surface Temperature ◽  
Flow Direction ◽  
Superposition Principle ◽  
Industrial Applications ◽  
Transfer Coefficients ◽  
Flat Plates ◽  
Surface Temperature Distribution ◽  
Analytical Expressions

The heat transfer coefficient of convection from the wall to the flow depends on flow type, on surface temperature distribution in a stream-wise direction, and in transient cases also on time. In so-called conjugated problems, the surface temperature distribution of the wall and flow are coupled together. Thus, the simultaneous solution of convection between the flow and wall, and conduction in the wall is required because heat transfer coefficients are not known. For external and internal flows very accurate approximate analytical expressions have been derived for heat transfer in different kinds of boundary conditions which change in flow direction. Due to the linearity of the energy equation the superposition principle can be adopted to couple with these expressions the surface temperature and heat flux distributions in conjugated problems. In the paper this type of approach is adopted and applied to a number of industrial applications ranging from flat plates of electroluminecence displays to the optimization of heat transfer in fins, fin arrays and mobile phones.

scholarly journals Surface Temperature Distribution Characteristics of Marangoni Condensation for Ethanol–Water Mixture Vapor Based on Thermal Infrared Images

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 6057
Author(s):  
Guilong Zhang ◽  
Ziqiang Ma ◽  
Heng Li ◽  
Jinshi Wang
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Surface Temperature ◽  
Thermal Infrared ◽  
Water Mixture ◽  
Distribution Characteristics ◽  
Infrared Images ◽  
Single Droplet ◽  
Surface Temperature Distribution ◽  
Thermal Infrared Images

Marangoni condensation is formed due to the surface tension gradient caused by the local temperature or concentration gradient on the condensate surface; thus, the investigation of the surface temperature distribution characteristics is crucial to reveal the condensation mechanism and heat transfer characteristics. Few studies have been conducted on the temperature distribution of the condensate surface. In this study, thermal infrared images were used to measure the temperature distributions of the condensate surface during Marangoni condensation for ethanol–water mixture vapor. The results showed that the surface temperature distribution of the single droplet was uneven, and a large temperature gradient, approximately 15.6 °C/mm, existed at the edge of the condensate droplets. The maximum temperature difference on the droplet surface reached up to 8 °C. During the condensation process, the average surface temperature of a single droplet firstly increased rapidly and then slowly until it approached a certain temperature, whereas that of the condensate surface increased rapidly at the beginning and then changed periodically in a cosine-like curve. The present results will be used to obtain local heat flux and heat transfer coefficients on the condensing surface, and to further establish the relationship between heat transfer and temperature distribution characteristics.

Angular Dependency on Film Boiling Heat Transfer From Relatively Long Inclined Flat Plates

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
Chan Soo Kim ◽  
Kune Y. Suh
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Boiling Heat Transfer ◽  
Flow Direction ◽  
Film Boiling ◽  
Transfer Coefficients ◽  
Flat Plates ◽  
Heat Transfer Coefficients ◽  
Inclination Angles ◽  
Angular Dependency

The effect of inclination angle of the downward facing flat plate on the interfacial wavy motion is investigated utilizing the water quenching test apparatus downward ebullient laminar transition apparatus flat surface (DELTA-FS) in a quasi-steady state. Film boiling heat transfer coefficients are obtained on the relatively long surface in the flow direction. Interfacial velocities at the various inclination angles and wall superheat conditions are determined through the analysis of the visualized continuous snapshots with 1000 fps. Visualization of the vapor film reveals that the interfacial wavelength increases and the interfacial velocity decreases as the flat plate moves from the vertical to downward facing locations. A new semi-empirical correlation is developed from the measured heat transfer coefficients and interfacial velocities. The correlation shows good agreement with the previous water test results on vertical plates. In the case of the previous other fluid experimental results on the vertical plates, the correlation overpredicts the film boiling heat transfer coefficients at the experimental condition.

Shroud Heat Transfer Measurements From a Rotating Cavity With an Axial Throughflow of Air

1994 ◽  
Vol 116 (3) ◽  
pp. 525-534 ◽  
Author(s):  
C. A. Long ◽  
P. G. Tucker
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Surface Temperature ◽  
Vortex Breakdown ◽  
Rossby Number ◽  
Temperature Level ◽  
Centripetal Acceleration ◽  
Surface Temperature Distribution ◽  
Nusselt Numbers ◽  
Rotating Cavity

The paper discusses measurements of heat transfer obtained from the inside surface of the peripheral shroud. The experiments were carried out on a rotating cavity, comprising two 0.985-m-dia disks, separated by an axial gap of 0.065 m and bounded at the circumference by a carbon fiber shroud. Tests were conducted with a heated shroud and either unheated or heated disks. When heated, the disks had the same temperature level and surface temperature distribution. Two different temperature distributions were tested; the surface temperature either increased, or decreased with radius. The effects of disk, shroud, and air temperature levels were also studied. Tests were carried out for the range of axial throughflow rates and speeds: 0.0025 ≤ m ≤ 0.2 kg/s and 12.5 ≤Ω≤ 125 rad/s, respectively. Measurements were also made of the temperature of the air inside the cavity. The shroud Nusselt numbers are found to depend on a Grashof number, which is defined using the centripetal acceleration. Providing the correct reference temperature is used, the measured Nusselt numbers also show similarity to those predicted by an established correlation for a horizontal plate in air. The heat transfer from the shroud is only weakly affected by the disk surface temperature distribution and temperature level. The heat transfer from the shroud appears to be affected by the Rossby number. A significant enhancement to the rotationally induced free convection occurs in the regions 2≤Ro≤4 and Ro≥20. The first of these corresponds to a region where vortex breakdown has been observed. In the second region, the Rossby number may be sufficiently large for the central throughflow to affect the shroud heat transfer directly. Heating the shroud does not appear to affect the heat transfer from the disks significantly.

Study of Surface Temperature Distribution in Plastic Sheet Spraying

2010 ◽  
Vol 43 ◽  
pp. 703-706
Author(s):  
Zai Liang Chen ◽  
Ji Zhong Yan
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Temperature Distribution ◽  
Surface Temperature ◽  
Ansys Software ◽  
Plastic Sheet ◽  
Surface Temperature Distribution ◽  
Heat Transfer Theory ◽  
The Right ◽  
Surface Temperature Field

The heater’s setting temperature is calculated by using the heat transfer theory. Using the thermal module of ANSYS software to simulate the plastic sheet’s surface temperature field, acquired the distribution of the plastic sheet’s surface temperature field. The results show to get even spraying with the right temperature for spraying experiments.

Advanced Calculation Method for the Surface Temperature Distribution of Turbine Blades

1996 ◽  
Vol 118 (1) ◽  
pp. 18-22 ◽  
Author(s):  
A. S. Dorfman
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
Turbine Blade ◽  
Thermal History ◽  
Turbine Blades ◽  
Boundary Layer Equation ◽  
Surface Temperature Distribution

A method of solution of the thermal boundary layer equation for a gas, together with the heat conduction equation for the turbine blade, using the boundary condition of the fourth kind (conjugate problem), is presented. The effect of the surface temperature distribution on the heat transfer coefficient (the effect of thermal history) is considered. This effect is important for gas turbine blades because the difference in temperatures between the blade’s surface and gas usually varies considerably along the blade’s surface; hence, the effect of thermal history can be significant. It is shown that the results, obtained accounting for thermal history, can differ substantially from results calculated with the assumption that the blade’s surface is isothermal. This might be one of the reasons why there is a marked difference between the actual temperature distribution of the turbine blade and the calculated one. It is important to consider the effect of thermal history since it is a fact that the major unknown in the design of turbine blade cooling systems is in the estimation of external heat transfer coefficient (Hannis and Smith, 1989).

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