It is a common observation that the temperature for same distance above a candle is more than the temperature at the side of the flame. Why does it happen?

As far as I could think, at the top of a candle heat is transferred both by convection and radiation, while on the sides of the flame radiation is the only mean of heat transfer. Am I correct?

  • 1
    $\begingroup$ That would be my guess, too. For example, if you consider a gas cooktop's burners rather than a single candle, there is a considerable amount of heat in the rising hot air above the burners. Even with the burners on their low setting it is impossible to keep my hand above the flames for any length of time, but to the sides of the burners much less heat is felt. $\endgroup$
    – user93237
    Jan 9, 2016 at 5:56
  • $\begingroup$ @SamuelWeir but can we say that there will be no convection sideways to the candle? $\endgroup$
    – Abdullah
    Jan 9, 2016 at 8:37
  • 4
    $\begingroup$ @Abdullah: The direction of convection is largely determined by the direction of gravity. In a spaceship there is little convection and only diffusion brings oxygen to the site of combustion. $\endgroup$ Jan 9, 2016 at 15:02

1 Answer 1


Air starts rising upwards as soon as it gets heated at the bottom of the flame.

Its place is taken by cold air instantly, i.e. there is convective air flow. So the top of the flame has both convective and radiative heating, while the sides only radiate heat.


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