Calculating Net Heat Flow for an Aluminum Disk in a Room

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Homework Help Overview

The discussion revolves around calculating the net heat flow of an aluminum disk with specific properties placed in a room at a different temperature. The problem involves concepts from thermodynamics, particularly heat transfer and radiation.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the application of the heat flow equation and share their numerical results. There is questioning about potential errors in calculations and the validity of the answer choices provided.

Discussion Status

Participants have shared their calculations and noted discrepancies with the expected answer choices. Some suggest that the difference may be due to a factor of √2, while others express uncertainty about the correctness of their results and the possibility of errors in the source material.

Contextual Notes

There is mention of the need to include units in calculations, and participants are considering the implications of a negative sign in their results. The discussion also highlights the importance of verifying the answer choices provided in the context of the problem.

lonelypancreas
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Homework Statement


What is the net heat flow of an aluminum disk (emissivity = 0.05) with radius
10 cm and temperature 293K placed inside a room where the temperature is 300K?


Asurface = π*r2 = 0.01π m2

Homework Equations


Hnet = A*e*σ(Tradiate4-Tabsorb4)

The Attempt at a Solution


By simply plugging in the values, I get a value of 0.13. However, the answer is not among the choices.

Where did I possibly go wrong?
 
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lonelypancreas said:

Homework Statement


What is the net heat flow of an aluminum disk (emissivity = 0.05) with radius
10 cm and temperature 293K placed inside a room where the temperature is 300K?


Asurface = π*r2 = 0.01π m2

Homework Equations


Hnet = A*e*σ(Tradiate4-Tabsorb4)

The Attempt at a Solution


By simply plugging in the values, I get a value of 0.13. However, the answer is not among the choices.

Where did I possibly go wrong?
That's the numerical answer that I got (don't forget to include your units in the future), with the possible exception of a negative sign.

What are the other choices?
 
collinsmark said:
That's the numerical answer that I got (don't forget to include your units in the future), with the possible exception of a negative sign.

What are the other choices?

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lonelypancreas said:
Hmm. The given answer choices differ from our answer by a factor of around √2, for what that's worth.

Unless there's more to the problem though I think our answer of 0.13 W is correct*. I don't know, maybe it's a mistake in the book/coursework?

*I'll let you figure out if it's into or out of the disk.
 
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