scholarly journals A Thermo-electric Apparatus for Thermal Diffusivity and Thermal Conductivity Measurements

Energies ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 4238 ◽  
Author(s):  
Zhang ◽  
Lin ◽  
Tsai ◽  
Wu ◽  
Wu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Heat Source ◽  
Experimental Results ◽  
Measurement Device ◽  
Thermo Electric ◽  
One Dimensional ◽  
Transfer Measurement ◽  
Heat Transfer Measurement

In this study, a one-dimensional heat transfer measurement device is developed based on the mathematical theory of the Angstrom method. To conform to the mathematical assumption, it is required that the device precisely controls the heat source to generate sinusoidal temperature signal. A thermo-electric module is used as the heat source for the measurement platform. This module is connected to a computer for program control, such that the temperature can be controlled quickly, precisely, and dynamically. In this study, five common heat-conducting materials are tested to verify the proposed one-dimensional heat transfer measurement device. By substituting the experimental results into the mathematical model of the Angstrom method, the thermal diffusion and thermal conductivity of the test material is calculated. The experimental results are compared with the physical properties of the materials, and the accuracy error is extremely low. This study confirmed that the Angstrom method theory applied thermal diffusivity and thermal conductivity measurement, which can be realized by thermo-electric temperature control technology.

NATURAL CONVECTION HEAT TRANSFER FROM A DISCRETE HEAT SOURCE COUPLED WITH CONDUCTION DOMINATED PHASE CHANGE

1998 ◽  
Vol 22 (3) ◽  
pp. 269-289
Author(s):  
M. Lacroix
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Steady State ◽  
Natural Convection ◽  
Thermal Diffusivity ◽  
Heat Source ◽  
Phase Change ◽  
Numerical Study ◽  
Thermal Conductivity Ratio ◽  
Discrete Heat Source

A numerical study has been conducted for the heat transfer from a discrete heat source by natural convection in air above coupled with conduction dominated melting of a phase change material (PCM) below via a wall of finite thermal diffusivity. Results indicate that the presence of a PCM layer underneath the wall significantly delays the temperature rise of the heat source. The time delay increases as the thermal diffusivity of the wail material decreases and as the thickness of the PCM layer increases. For high thermal conductivity wall materials [Formula: see text] the steady state heat source temperatures are similar and independent of the PCM layer. On the other hand, for [Formula: see text], the steady state temperatures are higher and dependent on the thickness of the PCM layer. A correlation is proposed in terms of the thickness of the PCM layer and the thermal conductivity ratio of the wall.

scholarly journals A Hypothesis for the Redevelopment of Warm-Core Cyclones over Northern Australia

2008 ◽  
Vol 136 (10) ◽  
pp. 3863-3872 ◽  
Author(s):  
Kerry Emanuel ◽  
Jeff Callaghan ◽  
Peter Otto
Keyword(s):  
Heat Transfer ◽  
Thermal Diffusivity ◽  
Tropical Cyclones ◽  
Deep Layer ◽  
Heat Fluxes ◽  
Northern Australia ◽  
One Dimensional ◽  
Warm Core ◽  
Vertical Heat ◽  
Underlying Soil

Tropical cyclones moving inland over northern Australia are occasionally observed to reintensify, even in the absence of well-defined extratropical systems. Unlike cases of classical extratropical rejuvenation, such reintensifying storms retain their warm-core structure, often redeveloping such features as eyes. It is here hypothesized that the intensification or reintensification of these systems, christened agukabams, is made possible by large vertical heat fluxes from a deep layer of very hot, sandy soil that has been wetted by the first rains of the approaching systems, significantly increasing its thermal diffusivity. To test this hypothesis, simulations are performed with a simple tropical cyclone model coupled to a one-dimensional soil model. These simulations suggest that warm-core cyclones can indeed intensify when the underlying soil is sufficiently warm and wet and are maintained by heat transfer from the soil. The simulations also suggest that when the storms are sufficiently isolated from their oceanic source of moisture, the rainfall they produce is insufficient to keep the soil wet enough to transfer significant quantities of heat, and the storms then decay rapidly.

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