African elephants have a large body with a surface area of the trunk as A=11 m². Typically, elephants roll into wet mud in summer time. The evaporation of moisture from skin surface enhances the convection heat transfer rate to h=30 W/m²K (without evaporation the h value is very small ~ h= 8 W/m²K). The normal metabolism of elephants (the total heat generation rate in the elephant body) is Qgen = 2500 W. Based on what you learned in ENME321, the surface temperature of the elephant (or any object with heat generate rate) is calculated using the following equation: T₁=Too+Qgen /(h A). The air temperature Too is 32°C. Elephants are not considered as being overheated if the surface temperatures are lower than 37°C. a. The elephant has not rolled into wet mud. Use h=8 W/m²K, estimate the surface temperature of the elephant. Do you think that the elephant will be overheated? b. The elephant has rolled into wet mud. Use h = 30 W/m²K, estimate the surface temperature of the elephant. Do you think that the elephant will be overheated? c. Now, consider thermal contribution of elephant ear. One side of the ear is about 5 feet by 4 feet. First estimate the total surface area of the ears of an elephant (two sides, and two ears). Add the total surface area of the ears to the surface area of the trunk. Recalculate the surface temperature of the elephant, assuming that the elephant has rolled into wet mud. Do you think that the elephant will be overheated?

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)
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ISBN:9781305387102
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Chapter9: Heat Transfer With Phase Change
Section: Chapter Questions
Problem 9.37P
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African elephants have a large body with a surface area of the trunk as A= 11
m². Typically, elephants roll into wet mud in summer time. The evaporation of moisture
from skin surface enhances the convection heat transfer rate to h= 30 W/m²K (without
evaporation the h value is very small ~ h=8 W/m²K). The normal metabolism of
elephants (the total heat generation rate in the elephant body) is Qgen = 2500 W. Based
on what you learned in ENME321, the surface temperature of the elephant (or any object
with heat generate rate) is calculated using the following equation: Ts = Too+ Qgen /(h A).
The air temperature Too is 32°C. Elephants are not considered as being overheated if the
surface temperatures are lower than 37°C.
a. The elephant has not rolled into wet mud. Use h=8 W/m²K, estimate the surface
temperature of the elephant. Do you think that the elephant will be overheated?
b. The elephant has rolled into wet mud. Use h=30 W/m²K, estimate the surface
temperature of the elephant. Do you think that the elephant will be overheated?
c. Now, consider thermal contribution of elephant ear. One side of the ear is about 5
feet by 4 feet. First estimate the total surface area of the ears of an elephant (two
sides, and two ears). Add the total surface area of the ears to the surface area of
the trunk. Recalculate the surface temperature of the elephant, assuming that the
elephant has rolled into wet mud. Do you think that the elephant will be
overheated?
Transcribed Image Text:African elephants have a large body with a surface area of the trunk as A= 11 m². Typically, elephants roll into wet mud in summer time. The evaporation of moisture from skin surface enhances the convection heat transfer rate to h= 30 W/m²K (without evaporation the h value is very small ~ h=8 W/m²K). The normal metabolism of elephants (the total heat generation rate in the elephant body) is Qgen = 2500 W. Based on what you learned in ENME321, the surface temperature of the elephant (or any object with heat generate rate) is calculated using the following equation: Ts = Too+ Qgen /(h A). The air temperature Too is 32°C. Elephants are not considered as being overheated if the surface temperatures are lower than 37°C. a. The elephant has not rolled into wet mud. Use h=8 W/m²K, estimate the surface temperature of the elephant. Do you think that the elephant will be overheated? b. The elephant has rolled into wet mud. Use h=30 W/m²K, estimate the surface temperature of the elephant. Do you think that the elephant will be overheated? c. Now, consider thermal contribution of elephant ear. One side of the ear is about 5 feet by 4 feet. First estimate the total surface area of the ears of an elephant (two sides, and two ears). Add the total surface area of the ears to the surface area of the trunk. Recalculate the surface temperature of the elephant, assuming that the elephant has rolled into wet mud. Do you think that the elephant will be overheated?
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