Energy emitted by radiation from a pipe

AI Thread Summary
The discussion focuses on calculating the heat emission rate from a vertical steam pipe with a diameter of 8 cm and a surface temperature of 950°C, surrounded by air at 27°C. Using Stefan's law, the radiation heat transfer rate was calculated to be 511 W/m², leading to a total heat emission rate of 128 W/m for a meter length of the pipe. The conversion to calories per second resulted in approximately 30.6 Cal/sec/m, while the book's answer was 29 Cal/sec/m. The discrepancy arises from the correct temperature conversion, as 950°C corresponds to 368K, not 373K. Ultimately, the calculations highlight the importance of precise temperature conversions in thermal radiation calculations.
Karol
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Homework Statement


A vertical steam pipe of diameter 8 cm and emissivity e=0.8 has it's surface at 950C. The surrounding air and the temperature of the room and things in it are at 270C.
What is the heat emission rate H from the pipe, for meter length, by radiation?

Homework Equations


Stefan's law: R=e\sigma T^4
\sigma=5.672\times 10^{-8}\left[Watt/m^2\right]
1\left[Calorie\right]=4.186\left[Joule\right]

The Attempt at a Solution


R=0.8\cdot 5.672\times10^{-8}\left(373^4-300^4\right)=511\left[Watt/m^2\right]
H=511\cdot \pi \cdot 0.08\cdot 1=128\left[Watt/m\right]
128\left[Watt\right]\div 4.186=30.6\left[Calorie/Sec/m\right]
The answer, according to the book, is 29\left[Calorie/Sec/m\right]
 
Physics news on Phys.org
95C is ~368K not 373K, though using 368K I get only 28 cal/s/m
 
The book uses Kelvin as Celsius+273
 
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