Typical value free air convection heat transfer coefficient

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SUMMARY

The typical value for the free air convection heat transfer coefficient at a high temperature of 1000°C is estimated to range between 10 and 100 W/m²·K, with variations depending on specific conditions. For a vertical cylinder with a diameter of 5 cm and height of 3 cm, a conservative estimate of 20 W/m²·K is recommended based on discussions and references from Engineering Toolbox and Wikipedia. At elevated temperatures, radiation becomes a significant factor, often overshadowing convection effects. Accurate calculations should consider the geometry of the object and the influence of radiation on heat transfer.

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  • Understanding of heat transfer principles, specifically convection and radiation.
  • Familiarity with the heat transfer coefficient and its significance in thermal analysis.
  • Knowledge of relevant formulas for calculating convection heat transfer coefficients.
  • Experience with thermal measurement techniques and tools.
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  • Research the correlation for heat transfer coefficients for short cylinders and spheres at high temperatures.
  • Learn about radiation heat transfer calculations and their impact on thermal systems.
  • Explore the use of thermal controllers for measuring and managing heat transfer in practical applications.
  • Investigate the effects of temperature on convection heat transfer coefficients in various materials.
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whats would be typical value for free air convection heat transfer coefficient at high temperature of 1000 degree c?

let say i have a vertical cylinder of diameter 5 cm and 3 cm high. and i heat it to 1000 degree c. the room temperature is 20c . what would the convection heat transfer coefficient be?
 
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Note that at that temperature, radiation is probably a much bigger factor than convection, so you're going to want to calculate that.
 
the thing is engineering box say 5 and 25 W/m^2.K, i have seen some website say 5 and 50 W/m^2.K, and wikipedia 10-100 W/m^2.K so i don't really know what to chooese.

plus onvection heat transfer coefficient increase with temperature, it may be 25 W/m^2.K at 20-200 degree c but it will be higher at 1000 degree c.
 
It's a very difficult thing to estimate. I'd pick something conservative inside all three ranges. Like, 20.

What exactly the purpose of this question? Ie, how much accuracy is required? Can you measure instead of calculating? Use a controller?
 
russ_watters thanks, i alway just assumed radiation doesn't matter much but actually as you said, is it much bigger factor than convection. that's why the data i got doesn't match the result from convection
 

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