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Humans are able to control their heat production rate and heat loss rate to maintain a nearly constant core temperature of Tc = 37 C under a wide range of environmental conditions. This process is called thermoregulation. From the perspective of calculating heat transfer between a human body and its surrounding, we focus on a layer of skin and fat, with its outer surface exposed to the environmental and its inner surface at a temperature slightly less than the core temperature, Ti = 35 C = 308 K. Consider a person with a skin/ fat layer of thickness L= 3mm and effective thermal conductivity k = 0.3 W/m.K. The person has a surface area A = 1.8 m2 and is dressed in a bathing suit. The radiation heat transfer coefficient is hr = 5.9 W/m2.K

Humans are able to control their heat production rate and heat loss rate to maintain a nearly constant core temperature of Tc = 37 C under a wide range of environmental conditions. This process is called thermoregulation. From the perspective of calculating heat transfer between a human body and its surrounding, we focus on a layer of skin and fat, with its outer surface exposed to the environmental and its inner surface at a temperature slightly less than the core temperature, Ti = 35 C = 308 K. Consider a person with a skin/ fat layer of thickness L= 3mm and effective thermal conductivity k = 0.3 W/m.K. The person has a surface area A = 1.8 m2 and is dressed in a bathing suit. The radiation heat transfer coefficient is hr = 5.9 W/m2.K

Introductory Circuit Analysis (13th Edition)
Introductory Circuit Analysis (13th Edition)
13th Edition
ISBN:9780133923605
Author:Robert L. Boylestad
Publisher:Robert L. Boylestad
Chapter1: Introduction
Section: Chapter Questions
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EXAMPLE 3 Humans are able to control their heat production rate and heat loss rate to maintain a nearly constant core temperature of Tc = 37 C under a wide range of environmental conditions. This process is called thermoregulation. From the perspective of calculating heat transfer between a human body and its surrounding, we focus on a layer of skin and fat, with its outer surface exposed to the environmental and its inner surface at a temperature slightly less than the core temperature, Ti = 35 C = 308 K. Consider a person with a skin/ fat layer of thickness L= 3mm and effective thermal conductivity k 0.3 W/m.K. The person has a surface area A = 1.8 m2 and is dressed in a bathing suit. The radiation heat transfer coefficient is hr = 5.9 W/m2.K E'in-E'out=D0 T- 308 K qcond"-qconv"-qrad"=0 Skinvfat 0.95 T- 297 K qx' =k(T1-T2) / L = kAT/L Tcond q'=h(Ts-Too) T- 297 K h = 2 Wim-K (Air) h = 200 W/m2-K (Water) grad" =q/A =ɛEb(Ts)-aG=eo(Tsª-Tsur*) k= 0.3 Wim-K L= 3 mm K(Ti-Ts) / L=h(Ts-Too)+e0(Ts-Tsur* ) Air or water Solving for Ts, with Tsur Too, we have Ts = [k/L+(h+hr)Too ]/ [k/L + (h + hr)] h, = ɛ0 ( T, + Tgur).(T,² + T²,ur) Ts =307.2K qs = kA(Ti-Ts)/L = 0.3 x 1.8 x ( 308 - 300,7) /3 x 103 146 W
Transcribed Image Text:EXAMPLE 3 Humans are able to control their heat production rate and heat loss rate to maintain a nearly constant core temperature of Tc = 37 C under a wide range of environmental conditions. This process is called thermoregulation. From the perspective of calculating heat transfer between a human body and its surrounding, we focus on a layer of skin and fat, with its outer surface exposed to the environmental and its inner surface at a temperature slightly less than the core temperature, Ti = 35 C = 308 K. Consider a person with a skin/ fat layer of thickness L= 3mm and effective thermal conductivity k 0.3 W/m.K. The person has a surface area A = 1.8 m2 and is dressed in a bathing suit. The radiation heat transfer coefficient is hr = 5.9 W/m2.K E'in-E'out=D0 T- 308 K qcond"-qconv"-qrad"=0 Skinvfat 0.95 T- 297 K qx' =k(T1-T2) / L = kAT/L Tcond q'=h(Ts-Too) T- 297 K h = 2 Wim-K (Air) h = 200 W/m2-K (Water) grad" =q/A =ɛEb(Ts)-aG=eo(Tsª-Tsur*) k= 0.3 Wim-K L= 3 mm K(Ti-Ts) / L=h(Ts-Too)+e0(Ts-Tsur* ) Air or water Solving for Ts, with Tsur Too, we have Ts = [k/L+(h+hr)Too ]/ [k/L + (h + hr)] h, = ɛ0 ( T, + Tgur).(T,² + T²,ur) Ts =307.2K qs = kA(Ti-Ts)/L = 0.3 x 1.8 x ( 308 - 300,7) /3 x 103 146 W
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