Heat Transfer and Combustion Homework

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Discussion Overview

The discussion revolves around a homework problem related to heat transfer and combustion, specifically focusing on calculating the heat loss by natural convection from a pipe. Participants are reviewing calculations and equations used to estimate the heat transfer rate per meter of pipe.

Discussion Character

  • Homework-related, Technical explanation

Main Points Raised

  • One participant shares their working out and seeks feedback on its correctness.
  • Another participant notes the absence of part D and assumes it involves calculating the heat transfer rate using the heat transfer coefficient, pipe diameter, and temperature difference.
  • Several participants provide the equation for heat transfer, Q=hA(DeltaT), and detail their calculations, arriving at a heat loss estimate of approximately 167.9855 W/m.
  • There is a discussion about the accuracy of the results, with one participant questioning if there was anything missed in the calculations, while another mentions a slightly different result of 167.1 W/m due to roundoff.

Areas of Agreement / Disagreement

Participants generally agree on the approach to calculate the heat loss, but there is a minor discrepancy in the final numerical results, indicating some uncertainty regarding precision in the calculations.

Contextual Notes

Participants have not resolved potential issues related to rounding or the assumptions made in their calculations, such as the consistency of units and the accuracy of the heat transfer coefficient.

MaisieMitchell
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Homework Statement
The outer surface of the insulation on a horizontal steam pipe has a radius of 50mm and is at a temperature of 90Deg C. The atmospheric air surrounding the pipe is at a temperature of 14 Deg C, and has the property values listed in part (c) above. Estimate the rate of heat loss by natural convection to the atmosphere by each metre length of pipe.

Only require help with part (D).
Relevant Equations
Nu = 0.53Gr^0.25Pr^0.25
Q3.png
Q3.1.png


Does this working out look okay? Thanks in advance.
 

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I'm not going to check your arithmetic. I assume you used consistent units so that the dimensionless groups actually came out dimensionless..

I don't see any part D here. I assume part D requires you to calculate the heat transfer rate per meter of pipe, given the heat transfer coefficient, the pipe diameter, and the temperature difference. Let's see your equations for doing this.
 
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Correct part D is the question sorry - Estimate the rate of heat loss by natural convection to the atmosphere by each metre length of pipe.

The equation for doing this is

Q=hA(DeltaT)

therefore..

Q=h(2Pi*rL)(DeltaT)

Q=1.34*(90-14/0.1)^0.25
*0.1*Pi * 1 * (90-14)

Q = 167.9855 w/m
 
MaisieMitchell said:
Correct part D is the question sorry - Estimate the rate of heat loss by natural convection to the atmosphere by each metre length of pipe.

The equation for doing this is

Q=hA(DeltaT)

therefore..

Q=h(2Pi*rL)(DeltaT)

Q=1.34*(90-14/0.1)^0.25
*0.1*Pi * 1 * (90-14)

Q = 167.9855 w/m
Based on the heat transfer coefficient you calculated in part C, I get about the same result.
 
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Thanks, when you say about the same result - is there something that I have missed?
 
MaisieMitchell said:
Thanks, when you say about the same result - is there something that I have missed?
I don't think so (other than roundoff). I get 167.1
 
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Thanks again!
 
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