Humans are able to control their heat production rate and heat loss rate to maintain a nearly constant core temperature 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 surroundings, we focus on a layer of skin and fat, with its outer surface exposed to the environment and its inner surface at a temperature slightly less than the core temperature, T₁ = 35°C = 308 K. Consider a person with a skin/fat layer of thickness L= 3 mm 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 emissivity of the skin is ε = 0.95. 1. When the person is in still air at T = 297 K, what is the skin surface temperature and rate of heat loss to the environment? Convection heat transfer to the air is characterized by a free convection coefficient of h = 2 W/m² K. 2. When the person is in water at T = 297 K, what is the skin surface temperature and heat loss rate? Heat transfer to the water is characterized by a convection coefficient of h=200 W/m² K. T= 308 K- -T₂ Skin/fat re= 0.95 T=297 K- 9rad acond grony Air or water k=0.3 W/m-K 1-3 mm HL 11 HI 1 T = 297 K h-2 W/m²K (Air) h=200 W/m²K (Water)
Humans are able to control their heat production rate and heat loss rate to maintain a nearly constant core temperature 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 surroundings, we focus on a layer of skin and fat, with its outer surface exposed to the environment and its inner surface at a temperature slightly less than the core temperature, T₁ = 35°C = 308 K. Consider a person with a skin/fat layer of thickness L= 3 mm 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 emissivity of the skin is ε = 0.95. 1. When the person is in still air at T = 297 K, what is the skin surface temperature and rate of heat loss to the environment? Convection heat transfer to the air is characterized by a free convection coefficient of h = 2 W/m² K. 2. When the person is in water at T = 297 K, what is the skin surface temperature and heat loss rate? Heat transfer to the water is characterized by a convection coefficient of h=200 W/m² K. T= 308 K- -T₂ Skin/fat re= 0.95 T=297 K- 9rad acond grony Air or water k=0.3 W/m-K 1-3 mm HL 11 HI 1 T = 297 K h-2 W/m²K (Air) h=200 W/m²K (Water)
Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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Transcribed Image Text:Humans are able to control their heat production rate and heat loss rate to maintain a nearly constant core
temperature Te = 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 surroundings, we focus on a
layer of skin and fat, with its outer surface exposed to the environment and its inner surface at a temperature
slightly less than the core temperature, T₁= 35°C = 308 K. Consider a person with a skin/fat layer of thickness
L= 3 mm 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 emissivity of the skin is ε = 0.95.
1. When the person is in still air at T = 297 K, what is the skin surface temperature and rate of heat loss to the
environment? Convection heat transfer to the air is characterized by a free convection coefficient of h = 2
W/m² K.
2. When the person is in water at T = 297 K, what is the skin surface temperature and heat loss rate? Heat
transfer to the water is characterized by a convection coefficient of h=200 W/m² K.
T= 308 K-
I.
Skin/fat
-e = 0.95
9ad
T=297 K-
conv
Air or water
k=0.3 W/m-K
9"
cond
L = 3 mm-
T = 297 K
h-2 W/m²K (Air)
h=200 W/m²K (Water)
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