scholarly journals A study of sensing heat flow through thermal walls by using thermoelectric module

2015 ◽  
Vol 19 (5) ◽  
pp. 1497-1505 ◽  
Author(s):  
Noppawit Sippawit ◽  
Thananchai Leephakpreeda
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Thermoelectric Module ◽  
Plane Wall ◽  
Thermal Engineering ◽  
Transfer Coefficients ◽  
Thermoelectric Effects ◽  
Flow Through ◽  
Flow Detection ◽  
Engineering Practices

Demands on heat flow detection at a plane wall via a thermoelectric module have drawn researchers? attention to quantitative understanding in order to properly implement the thermoelectric module in thermal engineering practices. Basic mathematical models of both heat transfer through a plane wall and thermoelectric effects are numerically solved to represent genuine behaviors of heat flow detection by mounting a thermoelectric module at a plane wall. The heat transfer through the plane wall is expected to be detected. It is intriguing from simulation results that the heat rejected at the plane wall is identical to the heat absorbed by the thermoelectric module when the area of the plane wall is the same as that of the thermoelectric module. Furthermore, both the area sizes of the plane walls and the convective heat transfer coefficients at the wall influence amount of the heat absorbed by the thermoelectric module. Those observational data are modeled for development of sensing heat flow through a plane wall by a thermoelectric module in practical uses.

Turbulent Heat and Momentum Transports in an Infinite Rod Array

1987 ◽  
Vol 109 (3) ◽  
pp. 599-605 ◽  
Author(s):  
An-Shik Yang ◽  
Ching-Chang Chieng
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Equation Model ◽  
Temperature Fields ◽  
Turbulent Heat ◽  
Fluid Temperature ◽  
Transfer Coefficients ◽  
Anisotropic Factor ◽  
Flow Through ◽  
Rod Array

An anisotropic factor is carefully selected from eleven distributions and adopted to the k–ε two-equation model of turbulence to obtain detailed velocity and temperature fields for steady-state, fully developed turbulent flow through infinite triangular/square rod array. The present study covers the ranges of pitch-to-diameter ratio from 1.123 to 1.5, and Reynolds number from 2.4 × 104 to 106. Velocity and wall shear stress are calculated and compared to experimental data. Normalized fluid temperature, friction factor, and heat transfer coefficient are also computed. The correlations of friction factor and heat transfer coefficients for flow inside circular pipe and flow through finite rod arrays are compared with the results for flow through infinite rod arrays.

The Reynolds Analogy Applied to a Cylinder Rotating in Air

1954 ◽  
Vol 58 (519) ◽  
pp. 205-208 ◽  
Author(s):  
Y. R. Mayhew
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Heat Flow ◽  
Solid Surface ◽  
Fluid Flows ◽  
Flat Plates ◽  
Reynolds Analogy ◽  
Transfer Data ◽  
Turbulent Fluid ◽  
Flow Through

When a turbulent fluid flows past a solid surface whose temperature differs from that of the fluid, the shear stress at the surface and the heat flow from it can be related by means of the Reynolds analogy. This analogy has been improved by Prandtl, Taylor, von Kármán and others, and its validity has been tested for flow through tubes and past flat plates by several investigators. In this note the analogy is checked against shear stress data and heat transfer data for a cylinder rotating in “still” air, when the flow is turbulent.

scholarly journals Heat flow and heat transfer coefficient during crystallization under the pressure

2018 ◽  
Vol 157 ◽  
pp. 02036
Author(s):  
Richard Pastirčák ◽  
Ján Ščury ◽  
Tomáš Fecura
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Solidification Process ◽  
Metal Mold ◽  
Transfer Coefficients ◽  
Microstructure Modeling ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Solidification Processes ◽  
Precise Prediction

Estimation of the heat flow at the metal-mold interface is necessary for accurate simulation of the solidification processes. For the numerical simulation, a precise prediction of boundary conditions is required to determine the temperature distribution during solidification, porosity nucleation, microstructure development, and residual stresses. Determination of the heat transfer coefficients at the metal-mold interface is a critical aspect for simulation of the solidification process and the microstructure modeling of the castings. For crystallization under the pressure and for thin-walled castings, HTC evaluation is important due to the very limited freezing time.

An Analytical Study of the Optimized Performance of an Impingement Heat Sink

2004 ◽  
Vol 126 (4) ◽  
pp. 528-534 ◽  
Author(s):  
S. B. Sathe ◽  
B. G. Sammakia
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
High Performance ◽  
Cross Flow ◽  
High Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
High Heat Transfer ◽  
Flow Through

The results of a study of a new and unique high-performance air-cooled impingement heat sink are presented. An extensive numerical investigation of the heat sink performance is conducted and is verified by experimental data. The study is relevant to cooling of high-power chips and modules in air-cooled environments and applies to workstations or mainframes. In the study, a rectangular jet impinges on a set of parallel fins and then turns into cross flow. The effects of the fin thickness, gap nozzle width and fin shape on the heat transfer and pressure drop are investigated. It is found that pressure drop is reduced by cutting the fins in the central impingement zone without sacrificing the heat transfer due to a reduction in the extent of the stagnant zone. A combination of fin thicknesses of the order of 0.5 mm and channel gaps of 0.8 mm with appropriate central cutout yielded heat transfer coefficients over 1500 W/m2 K at a pressure drop of less than 100 N/m2, as is typically available in high-end workstations. A detailed study of flow-through heat sinks subject to the same constraints as the impingement heat sink showed that the flow-through heat sink could not achieve the high heat transfer coefficients at a low pressure drop.

Performance Indicators for Steady-State Heat Transfer Through Fin Assemblies

1996 ◽  
Vol 118 (2) ◽  
pp. 310-316 ◽  
Author(s):  
A. S. Wood ◽  
G. E. Tupholme ◽  
M. I. H. Bhatti ◽  
P. J. Heggs
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Heat Flow ◽  
Performance Indicators ◽  
Physical Parameters ◽  
State Heat ◽  
Extended Surface ◽  
Flow Through ◽  
Steady State Heat ◽  
Steady State Heat Transfer

A comparative study is presented of several models describing steady-state heat flow through an assembly consisting of a primary surface (wall) and attached extended surface (fin). Attention is focused on the validity of four performance indicators. The work shows that the augmentation factor is the only indicator capable of correctly predicting the behavioral trends of the rate of heat flow through the assembly as the influencing physical parameters are varied.

scholarly journals Thermal Step Response of N-Layer Composite Walls—Accurate Approximative Formulas

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Carl-Eric Hagentoft ◽  
Simon Pallin
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Flow ◽  
Numerical Solutions ◽  
Step Change ◽  
Step Response ◽  
Surface Boundary ◽  
Multilayer Composites ◽  
Flow Through ◽  
Multiple Variables

Abstract For many industrial applications, heat flow through composites relates directly to energy usage and thus is of highest interest. For multilayer composites, the heat flow is a result of multiple variables, such as the temperature gradient over the surface boundaries and each material's thermal conductivity, specific heat, and thickness. In addition, the transient heat flux also depends on how the materials are aligned together. The heat flow through composites can be estimated using advanced computer simulations for applied heat transfer. Although these tools are powerful, they are also time consuming. Therefore, approximations that allow the estimation of heat flow through composites can be very useful. This paper presents approximations to solve transient heat transfer in multilayer composites, with and without an interior surface resistance. Since the energy use for various applications relates to the heat transferred at the surface boundary, the main focus of this paper is to define approximate solutions for interior heat flow. In other words, these approximations are found by applying a unit step change in temperature on one side of a composite and then in real-time emulating the surface heat flux on the opposite side from which the step change occurs. The approximations are presented based on lumped analyses and Laplace network solutions and are validated against analytical and numerical solutions.

scholarly journals To the determination of heat exchange conditions near the inner surface of walls with reflective thermal insulation from aluminium foil

2018 ◽  
Vol 196 ◽  
pp. 02035 ◽  
Author(s):  
Nina Umnyakova ◽  
Mikhail Gandzhuntsev
Keyword(s):  
Heat Transfer ◽  
Thermal Insulation ◽  
Experimental Studies ◽  
Building Envelope ◽  
Surface Radiation ◽  
Thermal Engineering ◽  
Transfer Coefficients ◽  
Concrete Wall ◽  
Heat Transfer Coefficients ◽  
Inner Surface

Materials with a low coefficient of surface radiation intensively reflect the radiant component of the heat flux and reduce heat losses through the building envelope. When designing building structures with reflective thermal insulation it is necessary to evaluate the efficiency of its application. However, at present there are no methods for calculating the value of thermal losses through external walls in the presence of reflective thermal insulation on internal surface of the wall, as well as there are no data on the values of heat transfer coefficients at the inner surface of building envelope with reflective thermal insulation. In this regard, in the climatic chambers of NIISF RAABS, complex thermal engineering studies were carried out. For this a cellular concrete wall 2,8 x1,2 m was put up into the chamber with reflective thermal insulation on the inner surface and without it. The obtained results of experimental studies, presented in the work, allowed obtaining numerical values of heat transfer coefficients at the inner surface of walls with reflective thermal insulation, and use the obtained data in further calculations.

scholarly journals The possibilities of application of radiant wall cooling in existing buildings as a part of their retrofit

2019 ◽  
Vol 111 ◽  
pp. 03008
Author(s):  
Michal Krajčík ◽  
Ondřej Šikula
Keyword(s):  
Heat Transfer ◽  
Heat Flow ◽  
Numerical Simulations ◽  
Environmental Impacts ◽  
Thermal Response ◽  
Cooling Capacity ◽  
Existing Buildings ◽  
Negative Effects ◽  
Flow Through ◽  
Moderate Climate

In the following years and decades the increase in cooling capacity will put tremendous pressure on the energy infrastructure and severely increase the environmental impacts. In a moderate climate and well thermally insulated buildings like, e.g., in Europe, installation of low-exergy radiant systems could help alleviate these negative effects. Wall systems may be especially suitable for installation in existing buildings, however, their possible applications in buildings retrofit have not been fully explored. We therefore investigate the possible applications of wall cooling in existing buildings by numerical simulations of two-dimension heat flow through a wall fragment. Three wall systems are proposed and compared in terms of thermal response and heat transfer. The effect of various parameters is investigated to facilitate the design of the wall systems.

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