Specific Absorption Rate and Temperature Increase in Human Eye Subjected to Electromagnetic Fields at 900 MHz

2012 ◽  
Vol 134 (9) ◽  
Author(s):  
Teerapot Wessapan ◽  
Phadungsak Rattanadecho
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Electromagnetic Fields ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Specific Absorption ◽  
Eye Model ◽  
Human Eye

Human eye is one of the most sensitive parts of the entire human body when exposed to electromagnetic fields. These electromagnetic fields interact with the human eye and may lead to cause a variety of ocular effects from high intensity radiation. However, the resulting thermo-physiologic response of the human eye to electromagnetic fields is not well understood. In order to gain insight into the phenomena occurring within the human eye with temperature distribution induced by electromagnetic fields, a detailed knowledge of absorbed power distribution as well as temperature distribution is necessary. This study presents a numerical analysis of specific absorption rate (SAR) and heat transfer in the heterogeneous human eye model exposed to electromagnetic fields. In the heterogeneous human eye model, the effect of power density on specific absorption rate and temperature distribution within the human eye is systematically investigated. In particular, the results calculated from a developed heat transfer model, considered natural convection and porous media theory, are compared with the results obtained from a conventional heat transfer model (based on conduction heat transfer). In all cases, the temperatures obtained from the developed heat transfer model have a lower temperature gradient than that of the conventional heat transfer model. The specific absorption rate and the temperature distribution in various parts of the human eye during exposure to electromagnetic fields at 900 MHz, obtained by numerical solution of electromagnetic wave propagation and heat transfer equation, are also presented. The results show that the developed heat transfer model, which is the more accurate way to determine the temperature increase in the human eye due to electromagnetic energy absorption from electromagnetic field exposure.

Numerical Analysis of Specific Absorption Rate and Heat Transfer in Human Head Subjected to Mobile Phone Radiation: Effects of User Age and Radiated Power

2012 ◽  
Vol 134 (12) ◽  
Author(s):  
Teerapot Wessapan ◽  
Phadungsak Rattanadecho
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Mobile Phone ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Human Head ◽  
Head Model ◽  
Specific Absorption ◽  
Radiated Power ◽  
Mobile Phone Radiation

The human head is one of the most sensitive parts of the human entire body when exposed to electromagnetic radiation. This electromagnetic radiation interacts with the human head and may lead to detrimental effects on human health. However, the resulting thermophysiologic response of the human head is not well understood. In order to gain insight into the phenomena occurring within the human head with temperature distribution induced by electromagnetic field, a detailed knowledge of absorbed power distribution as well as temperature distribution is necessary. This study presents a numerical analysis of specific absorption rate and heat transfer in the heterogeneous human head model exposed to mobile phone radiation. In the heterogeneous human head model, the effects of user age and radiated power on distributions of specific absorption rate and temperature profile within the human head are systematically investigated. This study focuses attention on organs in the human head in order to investigate the effects of mobile phone radiation on the human head. The specific absorption rate and the temperature distribution obtained by numerical solution of electromagnetic wave propagation and unsteady bioheat transfer equation in various tissues in the human head during exposure to mobile phone radiation are presented.

Study on Effective Radial Thermal Conductivity of Gas Flow through a Methanol Reactor

2015 ◽  
Vol 13 (1) ◽  
pp. 103-112 ◽  
Author(s):  
Kun Lei ◽  
Hongfang Ma ◽  
Haitao Zhang ◽  
Weiyong Ying ◽  
Dingye Fang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Reynolds Number ◽  
Temperature Distribution ◽  
Large Scale ◽  
Gas Flow ◽  
Fixed Bed ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Particle Reynolds Number

Abstract The heat conduction performance of the methanol synthesis reactor is significant for the development of large-scale methanol production. The present work has measured the temperature distribution in the fixed bed at air volumetric flow rate 2.4–7 m3 · h−1, inlet air temperature 160–200°C and heating tube temperature 210–270°C. The effective radial thermal conductivity and effective wall heat transfer coefficient were derived based on the steady-state measurements and the two-dimensional heat transfer model. A correlation was proposed based on the experimental data, which related well the Nusselt number and the effective radial thermal conductivity to the particle Reynolds number ranging from 59.2 to 175.8. The heat transfer model combined with the correlation was used to calculate the temperature profiles. A comparison with the predicated temperature and the measurements was illustrated and the results showed that the predication agreed very well with the experimental results. All the absolute values of the relative errors were less than 10%, and the model was verified by experiments. Comparing the correlations of both this work with previously published showed that there are considerable discrepancies among them due to different experimental conditions. The influence of the particle Reynolds number on the temperature distribution inside the bed was also discussed and it was shown that improving particle Reynolds number contributed to enhance heat transfer in the fixed bed.

Modeling of Temperature Distribution in Moving Webs in Roll-to-Roll Manufacturing

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Youwei Lu ◽  
Prabhakar R. Pagilla
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Thermal Strain ◽  
Heat Transfer Model ◽  
Operating Conditions ◽  
Transfer Model ◽  
Roll To Roll ◽  
Flexible Material ◽  
Process Line ◽  
The Web

A heat transfer model that can predict the temperature distribution in moving flexible composite materials (webs) for various heating/cooling conditions is developed in this paper. Heat transfer processes are widely employed in roll-to-roll (R2R) machines that are used to perform processing operations, such as printing, coating, embossing, and lamination, on a moving flexible material. The goal is to efficiently transport the webs over heating/cooling rollers and ovens within such processes. One of the key controlled variables in R2R transport is web tension. When webs are heated or cooled during transport, the temperature distribution in the web causes changes in the mechanical and physical material properties and induces thermal strain. Tension behavior is affected by these changes and thermal strain. To determine thermal strain and material property changes, one requires the distribution of temperature in moving webs. A multilayer heat transfer model for composite webs is developed in this paper. Based on this model, temperature distribution in the moving web is obtained for the web transported on a heat transfer roller and in a web span between two adjacent rollers. Boundary conditions that reflect many types of heating/cooling of webs are considered and discussed. Thermal contact resistance between the moving web and heat transfer roller surfaces is considered in the derivation of the heat transfer model. Model simulations are conducted for a section of a production R2R coating and fusion process line, and temperature data from these simulations are compared with measured data obtained at key locations within the process line. In addition to determining thermal strain in moving webs, the model is valuable in the design of heating/cooling sources required to obtain a certain desired temperature at a specific location within the process line. Further, the model can be used in determining temperature dependent parameters and the selection of operating conditions such as web speed.

Effect of the SAR Distribution of a Radio Frequency (RF) Coil on the Temperature Field Within a Human Leg: Numerical Studies

1999 ◽  
Author(s):  
J. X. Ling ◽  
Jeffrey W. Hand ◽  
Ian R. Young
Keyword(s):  
Temperature Distribution ◽  
Temperature Change ◽  
Absorption Rate ◽  
Specific Absorption Rate ◽  
Source Term ◽  
Fdtd Method ◽  
Tissue Temperature ◽  
Maximum Temperature ◽  
Rf Coil ◽  
Specific Absorption

Abstract This paper presents a three dimensional Finite Element Model for studying the effect of the specific absorption rate (SAR) distribution of a RF coil on the temperature distribution within a human leg due to the energy deposit. The model consists of fat, muscle, and bone, and has 21,158 uniform elements. The 3-D leg model was derived from the tissue maps that are obtained from the 79 sequential MR images of a volunteer’s leg. The specific absorption rate (SAR) data are from the solution to the fundamental Maxwell’s electromagnetic equations of the leg with RF coil in place using finite difference time domain (FDTD) method. The blood perfusion term, which is a function of the local tissue temperature, along with the metabolic heat as well as the SAR term, are treated as one heat source term in the classical bio-heat transfer equation. A commercial FEA code, ANSYS, was used to solve the 3-D heat conduction equation with an additional iteration method to deal with the temperature dependent source term. The 3-D temperature fields without and with the SAR term were computed, as well as the changes in temperature. They predict that the maximum temperature change occurs in approximately the same location as the maximum local SAR. The map of the temperature change clearly shows how the presence of the RF coil affect the temperature distribution within the leg. With 2 watts absorbed in the leg, about 8.8 w/kg of peak SAR value, the maximum change in temperature of the leg is about 1.74° C.

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