Transient Damped Wave Conduction and Relaxation in Human Skin and Thermal Wear During Winter

2008 ◽  
Author(s):  
Kal Renganathan Sharma
Keyword(s):  
Steady State ◽  
Human Skin ◽  
Separation Of Variables ◽  
Relaxation Times ◽  
Thermal Relaxation ◽  
Transient Temperature ◽  
Heat Sources ◽  
Maximum Heat ◽  
Steady State Temperature ◽  
Fabric Layer

Damped wave conduction and relaxation in the human skin layer and thermal fabric layer are modeled with a temperature dependent heat source in the human tissue layer. Steady state temperature profiles are derived from the Fourier heat conduction equation. The general solution for the temperature is assumed to be a sum of the transient temperature and steady state temperature. This makes the boundary conditions in space for the skin and fabric layers homogeneous for the transient temperarature. The hyperbolic PDE is solved for by the method of separation of variables. The use of final condition in time in addition to the initial temperature condition leads to bounded infinite Fourier series solutions. These solutions are bounded and does not violate second law of thermodynamics. The model can be used to interpret experimental observations of maximum heat flux that is a parameter of the warm/cool feeling of human skin in winter. For large relaxation times of human skin tissue, τrs>(1+U*)2(b−a)216π2αs, the transient temperature can be expected to undergo oscillations. These oscillations will be supercritical and grow with time for strong heat sources, U* > 1 and may be subcritical damped oscillatory for weak heat sources, U* < 1. For large thermal relaxation times of thermal fabric material, τrf>a24π2αs, the transient temperature in the thermal fabric layer may be expected to be subcritical damped oscillatory.

A Study of High-Temperature Heat Pipes With Multiple Heat Sources and Sinks: Part II—Analysis of Continuum Transient and Steady-State Experimental Data With Numerical Predictions

1991 ◽  
Vol 113 (4) ◽  
pp. 1010-1016 ◽  
Author(s):  
A. Faghri ◽  
M. Buchko ◽  
Y. Cao
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Heat Pipe ◽  
Pipe Wall ◽  
Heat Sources ◽  
Maximum Heat ◽  
Sources And Sinks ◽  
Numerical Predictions ◽  
Wick Structure ◽  
Transient And Steady State

The experimental data presented in Part I were analyzed concerning the heat pipe performance characteristics and design. Postexperiment examination of the loosely wrapped screen wick revealed annular gaps both between the wick and the heat pipe wall and between adjacent screen layers, which greatly enhanced the maximum heat capacity of the heat pipe compared to the analytical capillary limit for a tightly wrapped screen wick. A numerical simulation for transient heat pipe performances including the vapor region, wick structure, and the heat pipe wall is given. Numerical results for continuum transient and steady-state operations with multiple heat sources were compared with experimental results and found to be in good agreement.

Steady-State Temperatures in an Anisotropic Strip

1990 ◽  
Vol 112 (1) ◽  
pp. 16-20 ◽  
Author(s):  
Zhang Xiangzhou
Keyword(s):  
Steady State ◽  
Solution Method ◽  
Heat Conduction Problem ◽  
Separation Of Variables ◽  
Rigorous Solution ◽  
Steady State Temperature ◽  
Distribution Features ◽  
Matching Technique ◽  
Principal Directions ◽  
Strip Geometry

This article deals with the development of a rigorous solution to the steady-state temperature in an anisotropic strip. The solution is given with respect to a coordinate system (x, y), which conforms with the strip geometry but does not necessarily coincide with the principal directions of the anisotropic material. Using a partitioning–matching technique and the separation of variables method, exact expressions are obtained for temperatures in the strip under prescribed boundary temperature conditions. Numerical values of the temperatures and heat flux are provided in graphic form. Also, a discussion is presented regarding the solution method and the temperature distribution features in the heat conduction problem of an anisotropic medium.

Experimental Study of Deicing Process in an Airfoil Application

2013 ◽  
Author(s):  
Pablo Perez Pereira ◽  
Luis D. Vilar-Carrasquillo ◽  
Gerardo Carbajal
Keyword(s):  
Steady State ◽  
Flow Characteristics ◽  
Temperature Response ◽  
Leading Edge ◽  
Transient Temperature ◽  
Experimental Setup ◽  
Trailing Edge ◽  
Steady State Temperature ◽  
Fluid Flow Characteristics ◽  
Transient Temperature Response

A customized airfoil for deicing process was designed, built and tested in order to investigate the effect of icing on the airfoil and the process of removing it by heating processed. A numerical simulation was performed to provide more details of the fluid flow characteristics of the presence of the ice and the temperature distribution on the airfoil when it reached the steady state conditions. An experimental setup was developed to measure and record the transient temperature response on the trailing and leading edge respectively. The experimental results suggest that from a minimum temperature of −10°C on the trailing edge, and 0°C in the leading edge with ice on the surface, the time to reach the steady state temperature of 46°C in the leading edge and 38°C in the trailing edge was close to 8 minutes approximately.

Transient Temperature Profiles in Tissues With Nonuniform Blood Flow Distributions

1982 ◽  
Vol 104 (3) ◽  
pp. 202-208 ◽  
Author(s):  
A. B. Elkowitz ◽  
A. Shitzer ◽  
R. C. Eberhart
Keyword(s):  
Heat Transfer ◽  
Blood Flow ◽  
Steady State ◽  
Flow Distribution ◽  
Tissue Blood Flow ◽  
Transient Temperature ◽  
Temperature Profiles ◽  
Heat Transfer Equation ◽  
Blood Flow Distribution ◽  
Steady State Temperature

Numerical methods and the bio-heat transfer equation are employed to calculate temperature profiles in tissues subjected to nonuniform blood flow distributions, for initial and boundary conditions which simulate experimental physiological situations. Results indicate that one can infer, from sudden changes in temperature distribution, the occurrence of sudden changes in tissue blood flow. However, prediction of blood flow distribution from near equilibrium or steady-state temperature profiles is of poor resolution, and does not appear useful as a practical technique. The methods and results are useful for predictions of temperature profiles in the absence of significant endogenous or exogenous heating; they can be extended to such applications by straightforward methods.

Heat Transfer Finite Element Analysis of an Adhesive Bonding Process

1995 ◽  
Author(s):  
Roger L. Veldman ◽  
Dennis J. VandenBrink
Keyword(s):  
Finite Element ◽  
Steady State ◽  
Adhesive Bonding ◽  
Adhesive Layer ◽  
Bonding Process ◽  
Heat Sources ◽  
Element Analysis ◽  
Steady State Condition ◽  
Steady State Temperature ◽  
Time Required

Abstract The finite element method was used to model an adhesive bonding process between a sheet of glass and a long strip of flexible PVC. The effect of the thickness of the PVC strip, the number of heat sources, the temperature of the heat sources, the size of the heat sources, and convection on the steady state temperature distribution in the adhesive layer was studied. The time required to reach the steady-state condition was also determined.

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