Internal Flow in a Chimney Flue

1
Internal Flow in a Chimney Flue

• Brad Borchert

2
Objectives

• Scale a standard chimney
• Determine the flue inlet, exit, and outer surface
  temperatures using a thermocouple
• Compare the experimental value of the exit
  temperature with the theoretical values of
• Dittus
• Sieder
• Petukhov
• Gnielinsky

3
Experimental Flue Data
Tentrance 151.2 C 424.35 K
Texit 133.3 C 406.45 K
Ts,o 61.5 C 334.65 K
Tinf 9.2 C 282.35 K
D 0.0889 m      
H 1.67 m      
V 234 m/s m/s    
Asurface 0.466 m2 m2    
Scaled Chimney
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Theoretical Exit Temperatures

• Dittus
• 423.51 K
• Sieder
• 423.44 K
• Petukhov
• 423.46 K
• Gneilinsky
• 423.40 K
• Std. Deviation
• .048

Backpacking Stove
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Results

• Correlations predicted similar temps
• Correlation error
• Dittus
• 4.20
• Sieder
• 4.18
• Petukhov
• 4.19
• Gneilinsky
• 4.17

6
Conclusions and Recommendations

• The best correlation is Gneilinsky (Barely)
• Correlations are similarly inaccurate
• Error is within the 10 prescribed
• Where possible, use the simplest correlation
  the gain in accuracy is negligible
• Dont rely on correlations - Experiment