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?
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!)
8th Edition
ISBN:9781305387102
Author:Kreith, Frank; Manglik, Raj M.
Publisher:Kreith, Frank; Manglik, Raj M.
Chapter9: Heat Transfer With Phase Change
Section: Chapter Questions
Problem 9.37P
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