The human body is adaptable to the extreme climatic conditions and keep the body core and skin temperature within the comfort zone by regulating the metabolic heat generation rate. For example, in extreme cold conditions, human body will maintain the body temperature by increasing metabolic heat generation rate while in very hot environment, human body will sweat and release heat generated within the body. To understand this effect of ambient conditions on human body repeat Example 3–14 in the text and consider a case, where climatic conditions change from 220°C and 20°C. For this change in ambient air temperature calculate the metabolic heat generation rate required within the different human body types with the skin/fat thickness of 0.0075, 0.005 and 0.0025 m so as to maintain the skin temperature at 34°C. Assume that inspite of the change in ambient air temperature the perspiration rate remains constant at 0.0005 s^-1. Plot a graph of metabolic heat generation rate against the ambient temperature with a temperature increment of 5°C.

Example 3-14

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EXAMPLE 3-14 Application of Bioheat Transfer Equation We are interested in heat transfer analysis from a human body subjected to certain environmental conditions. For this purpose consider a region of muscle with a skin/ fat layer over it under steady state conditions as shown in Fig. 3-51. For simplicity approximate this region as a one-dimensional plane wall with surface area A. The muscle thickness is Lm covered by a layer of skin/fat with a thickness Lsf. The met- abolic heat generation rate (em) and perfusion rate (p) are both constant throughout the muscle. The blood density and specific heat are p, and cb, respectively. The core body temperate (T) and the arterial blood temperature (T₂) are both assumed to be the same and constant. The muscle and the skin/fat layer thermal conduc- tivities are km and ks, respectively. The skin has an emissivity of & and the body is subjected to an air environment with a temperature of To, a convection heat trans- fer coefficient of hconv, and a radiation heat transfer coefficient of hrad. Assuming blood properties and thermal conductivities are all constant, (a) develop an expres- sion for the interface temperature (T) between the muscle and the outer skin/fat layer, and (b) determine the temperature T, and the rate of heat loss from the body (Q), and the skin temperature (T) for the following conditions: