Humans are able to control their rates of heat production and heat loss 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 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, Ti = 35°C = 308 K. Consider a person with a skin/fat layer of thickness L = 2 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. a). When the person is in still air at T∞ = 308 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 ?2 ⋅ K b). When the person is in water at T∞ = 308, what is the skin surface temperature and rate of heat loss? Heat transfer to the water is characterized by a convection coefficient of h = 200 W ?2 ⋅ K
Humans are able to control their rates of heat production and heat loss 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 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, Ti = 35°C = 308 K. Consider a person
with a skin/fat layer of thickness L = 2 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.
a). When the person is in still air at T∞ = 308 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
?2 ⋅ K
b). When the person is in water at T∞ = 308, what is the skin surface temperature
and rate of heat loss? Heat transfer to the water is characterized by a convection
coefficient of h = 200 W
?2 ⋅ K
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