Net Power Transfer by Radiation

In summary, the net power transfer by radiation for a person with a skin temperature of 33 C and emissivity of .9 in a room at 24 C with an area of 1.8 m2 is 6.03x10-4 Watts. This was calculated using the Stefan-Boltzman Law and the equation IradA=Power.
  • #1
ethanabaker1
4
0

Homework Statement



A person with a skin temperature of 33 C and an emissivity of .9 is in a room at 24 C. What is the net power transfer by radiation. Let the area of the body be 1.8 m2.

Homework Equations


I=[itex]\frac{P}{A}[/itex]
[itex]\Delta[/itex]Irad=[itex]\epsilon[/itex][itex]\sigma[/itex]T4 (Stefan-Boltzman Law)


The Attempt at a Solution


Temperature difference is 33-24=9 C
Irad=(.9)(5.67x10-8)(94)
Irad=3.34x10-4
IradA=Power
(3.34x10-4)(1.8)=6.03x10-4
 
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  • #2
It probably would be nice to show a few more units in your calculations.
 
  • #3
Well, power should have units of Watts. Emissivity has no units, and I know the Boltzman constant is Wm-2K-4, so I wasn't sure if that means I should convert the temperature difference to Kelvin or not. I left it because both Kelvin and Celsius should have the same temperature difference. But I don't even know if that solution is reasonable.
 

FAQ: Net Power Transfer by Radiation

What is "Net Power Transfer by Radiation"?

"Net Power Transfer by Radiation" refers to the transfer of thermal energy through the emission and absorption of electromagnetic radiation. This process is important in understanding the heating and cooling of objects in the natural world and in various technological applications.

How does radiation transfer energy?

Radiation occurs when an object emits electromagnetic waves, such as infrared or visible light. These waves carry energy and can be absorbed by other objects, causing them to increase in temperature. The amount of energy transferred depends on the temperature and emissivity of the objects involved.

What factors affect the net power transfer by radiation?

The net power transfer by radiation is affected by several factors including the temperature and emissivity of the objects involved, the distance between them, and the nature of the surface (e.g. reflective or absorptive). The type of radiation being emitted, such as infrared or visible light, also plays a role.

How is net power transfer by radiation related to the greenhouse effect?

The greenhouse effect is a natural process in which certain gases in the Earth's atmosphere, such as carbon dioxide and water vapor, trap heat from the sun and prevent it from escaping into space. This is similar to how the Earth's surface absorbs and emits radiation, resulting in a net power transfer by radiation. However, the greenhouse effect is being enhanced by human activities, leading to an increase in global temperatures.

How is net power transfer by radiation used in technology?

Net power transfer by radiation is an essential process in various technological applications such as heating and cooling systems, solar panels, and thermal imaging devices. It is also used in industries such as metallurgy, where heat transfer through radiation is utilized in processes like welding and heat treatment.

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