Macroscopic Approach to Bioheat Transport

Abstract

Bioheat transport principles can be used to find heat flux and temperature in biological systems and devices as a function of both position and time. If we are interested in spatial variations of heat flux or temperature in a system, then it is necessary to use a microscopic approach, as presented in Chaps. 10 and 11. However, in many situations spatial variations are not of interest. Instead, we might be interested in predicting the rate or the amount of energy that flows in or out of the system as a whole, or we might like to know how the total energy varies with time inside the system. In such cases, a macroscopic approach can be used to describe the accumulation of energy within the system or the flow of energy through a system. Take, for example, the flow of heat from a human arm through a layer of clothing. We found in Chap. 8 that the temperature in the layer varies with radial position in a nonlinear fashion. However, we are usually interested in the heat flux from the arm, not the temperature distribution in the clothing. To compute the heat flux we only need to know the thermal resistance of the clothing layer and the temperatures at the inside and outside surface. If an additional layer, with known thermal resistance, is added to the clothing ensemble, its effect on heat loss can be computed using a macroscopic approach.