Thermocouple Temperature Disturbances in Low Conductivity Materials

1962 ◽  
Vol 84 (2) ◽  
pp. 124-131 ◽  
Author(s):  
James V. Beck
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Conduction Problem ◽  
Transient Heat Conduction ◽  
Time Variable ◽  
Thermocouple Measurement ◽  
Transient Heat Conduction Problem ◽  
Thermocouple Reading ◽  
Thermocouple Temperature ◽  
Thermocouple Junction

The axisymmetric transient heat conduction problem of a thermocouple embedded in a low thermal conductivity material is analytically investigated. The thermocouple is positioned normal to a surface which is heated by a time-variable heat flux. The results of the analysis are presented as dimensionless curves for a variation of several dimensionless parameters. The analysis may be used to calculate: (a) The temperature of a thermocouple temperature measurement for a known heat flux. (b) The undisturbed temperature at the location of the thermocouple junction from the transient thermocouple measurement. (c) The undisturbed heat flux just before thermocouple from the thermocouple measurement. It is found that the temperature disturbances in the thermocouple reading due to the presence of the thermocouple itself may be very large. It is shown that in certain cases the disturbance could be as large as 50 per cent of the temperature rise. An example is given in which the disturbance reaches 700 deg F.

Conservation laws and associated Lie point symmetries admitted by the transient heat conduction problem for heat transfer in straight fins

Open Physics ◽  
2013 ◽  
Vol 11 (8) ◽  
Author(s):  
Partner Ndlovu ◽  
Rasselo Moitsheki
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Conduction ◽  
Conservation Laws ◽  
Linear Function ◽  
Power Law ◽  
Heat Conduction Problem ◽  
Transient Heat Conduction ◽  
Lie Point Symmetries ◽  
Transient Heat Conduction Problem

AbstractSome new conservation laws for the transient heat conduction problem for heat transfer in a straight fin are constructed. The thermal conductivity is given by a power law in one case and by a linear function of temperature in the other. Conservation laws are derived using the direct method when thermal conductivity is given by the power law and the multiplier method when thermal conductivity is given as a linear function of temperature. The heat transfer coefficient is assumed to be given by the power law function of temperature. Furthermore, we determine the Lie point symmetries associated with the conserved vectors for the model with power law thermal conductivity.

Transient Heat Conduction in Functionally Graded Materials by LT-MFS

2011 ◽  
Vol 189-193 ◽  
pp. 1664-1669 ◽  
Author(s):  
Ning Zhao ◽  
Lei Lei Cao ◽  
Hui Guo
Keyword(s):  
Heat Conduction ◽  
Functionally Graded Materials ◽  
Heat Conduction Problem ◽  
Transient Heat Conduction ◽  
Fundamental Solutions ◽  
Functionally Graded ◽  
Time Variable ◽  
Graded Materials ◽  
Time Space ◽  
Transient Heat Conduction Problem

: The LT-MFS approach is proposed to solve two-dimensional transient heat conduction problem in functionally graded materials (FGMs). First, a Laplace transform approach is used to move the time variable. Then, a fundamental solution in Laplace space for FGMs is constructed. Next, the solution in Laplace space is approximated by the linear combination of fundamental solutions. Further, Stefest’s algorithm is employed to convert the results in Laplace space back into the time–space domain. Finally, the method is tested on several benchmark examples. The results demonstrate well the efficiency and accuracy of the proposed method.

scholarly journals An Efficient Method to Find Solutions for Transcendental Equations with Several Roots

2015 ◽  
Vol 2015 ◽  
pp. 1-4 ◽  
Author(s):  
Rogelio Luck ◽  
Gregory J. Zdaniuk ◽  
Heejin Cho
Keyword(s):  
Null Space ◽  
Heat Conduction Problem ◽  
Hankel Matrix ◽  
Polynomial Equation ◽  
Transient Heat Conduction ◽  
Transcendental Equation ◽  
Integral Theorem ◽  
Transient Heat Conduction Problem ◽  
Cauchy’S Integral Theorem ◽  
Roots Of A Polynomial

This paper presents a method for obtaining a solution for all the roots of a transcendental equation within a bounded region by finding a polynomial equation with the same roots as the transcendental equation. The proposed method is developed using Cauchy’s integral theorem for complex variables and transforms the problem of finding the roots of a transcendental equation into an equivalent problem of finding roots of a polynomial equation with exactly the same roots. The interesting result is that the coefficients of the polynomial form a vector which lies in the null space of a Hankel matrix made up of the Fourier series coefficients of the inverse of the original transcendental equation. Then the explicit solution can be readily obtained using the complex fast Fourier transform. To conclude, the authors present an example by solving for the first three eigenvalues of the 1D transient heat conduction problem.

Application of numerical procedure for thermal diagnostics of the delamination of strengthening material at concrete construction

2019 ◽  
Vol 30 (5) ◽  
pp. 2655-2668 ◽  
Author(s):  
Wojciech Piotr Adamczyk ◽  
Marcin Gorski ◽  
Ziemowit Ostrowski ◽  
Ryszard Bialecki ◽  
Grzegorz Kruczek ◽  
...  
Keyword(s):  
Heat Conduction ◽  
Thermal Resistance ◽  
Quantitative Assessment ◽  
Heat Conduction Problem ◽  
Transient Heat Conduction ◽  
Decision Variable ◽  
Assessment Procedure ◽  
Ir Camera ◽  
Content Type ◽  
Transient Heat Conduction Problem

Purpose Large structural objects, primarily concrete bridges, can be reinforced by gluing to their stretched surface tapes of fiber-reinforced polymer (FRP). The condition for this technology to work requires the quality of the bonding of FRP and the concrete to be perfect. Possible defects may arise in the phase of construction but also as a result of long-term fatigue loads. These defects having different forms of voids and discontinuities in the bonding layer are difficult to detect by optical inspection. This paper aims to describe the development of a rapid and nondestructive method for quantitative assessment of the debonding between materials. Design/methodology/approach The applied technique belongs to the wide class of active infrared (IR) thermography, the principle of which is to heat (or cool) the investigated object, and determine the properties of interest from the recorded, by an IR camera, temperature field. The methodology implemented in this work is to uniformly heat for a few seconds, using a set of halogen lamps, the FRP surface attached to the concrete. The parameter of interest is the thermal resistance of the layer separating the polymer tape and the concrete. The presence of voids and debonding will result in large values of this resistance. Its value is retrieved by solving an inverse transient heat conduction problem. This is accomplished by minimizing, in the sense of least squares, the difference between the recorded and simulated temperatures. The latter is defined as a solution of a 1D transient heat conduction problem with the already mentioned thermal resistance treated as the only decision variable. Findings A general method has been developed, which detects debonding of the FRP tapes from the concrete. The method is rapid and nondestructive. Owing to a special selection of the compared dimensionless measured and simulated temperatures, the method is not sensitive to the surface quality (roughness and emissivity). Measurements and calculation may be executed within seconds. The efficiency of the technique has been shown at a sample, where the defects have been artificially introduced in a controlled manner. Originality/value A quantitative assessment procedure which can be used to determine the extent of the debonding has been developed. The procedure uses inverse technique whose result is the unknown thermal resistance between the member and the FRP strip.

A New Method for Thermal Analysis of Die Casting

1993 ◽  
Vol 115 (2) ◽  
pp. 284-293 ◽  
Author(s):  
M. R. Barone ◽  
D. A. Caulk
Keyword(s):  
Heat Conduction ◽  
Heat Conduction Problem ◽  
Die Casting ◽  
Three Dimensional ◽  
Transient Heat Conduction ◽  
Steady Solution ◽  
Cavity Surface ◽  
Varying Coefficients ◽  
Transient Heat Conduction Problem ◽  
Time Varying Coefficients

A new approach is developed for solving the initial value, steady periodic heat conduction problem in steady-state die casting. Three characteristics found in nearly all die casting processes are exploited directly: The casting is thin compared with its overall size, its thermal conductivity is high compared with that of the mold, and the cycle time is short compared with the start-up transient of the process. Under these conditions, it is reasonable to neglect the transverse temperature gradients in the casting and assume that all die temperatures below a certain depth from the cavity surface are independent of time. The transient die temperatures near the cavity surface are represented by a polynomial expansion in the depth coordinate, with time-varying coefficients determined by a Galerkin method. This leads to a set of ordinary differential equations on the cavity surface, which govern the transient interaction between the casting and the die. From the time-averaged solution of these equations, special conditions are derived that relate the transient solution near the cavity surface to the three-dimensional steady solution in the die interior. With these conditions, the steady temperatures in the bulk of the die can be determined independently of the explicit surface transients. This reduces the effort of solving a complex transient heat conduction problem to little more than finding a steady solution alone. The overall approach provides a general analytical tool, which is capable of predicting complex thermal interactions in large multicomponent dies.

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