Can a hair dryer burn? Thermodynamic considerations....

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Discussion Overview

The discussion centers around the thermodynamic considerations of whether the temperature of a target can exceed the temperature of hot air emitted from a hair dryer, specifically in the context of potential skin burning. Participants explore the implications of airflow, temperature limits, and the mechanics of heat transfer.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions if the temperature of a target can exceed that of the hot air from a hair dryer, noting that hair dryers typically produce air at around 60 degrees C, which is close to the threshold for burning skin.
  • Another participant clarifies that the concern is about skin burning rather than combustion, suggesting that the temperature of the air itself is not the only factor in determining the risk of burns.
  • It is mentioned that free-flowing air generally remains within safe temperature limits, but blockage in the exit duct of heat-producing devices can lead to significantly higher temperatures.
  • A participant raises a hypothetical scenario questioning why air at room temperature wouldn't warm a target if it were possible for air at 60 degrees C to do so.
  • Another participant suggests that machines can be designed to use a large flow of cold air to generate a smaller flow of hot air, implying a complex interaction between airflow and temperature.
  • A reference to aerodynamic heating is provided, suggesting that blowing air forcefully could lead to temperature increases in the target, although this remains speculative in the context of the discussion.

Areas of Agreement / Disagreement

Participants express differing views on the mechanics of heat transfer and the conditions under which a target's temperature might exceed that of the air from a hair dryer. The discussion remains unresolved with multiple competing perspectives on the topic.

Contextual Notes

There are limitations regarding assumptions about airflow dynamics, the specific conditions under which temperature increases might occur, and the definitions of burning versus heating. The discussion does not resolve these complexities.

Merlin05
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Hi all,
I actually work in physics (quantum physics) but my thermodynamics knowledge is a bit lacking these days. The following problem has had me puzzled for quite a long time.

Basically, if I point the hot air coming out of a hairdryer at a target, will that target's temperature ever go higher than the temperature of the hot air? I recall reading somewhere that hairdryers product air at 60 degrees C, which is just below the threshold that can cause burning.

Thanks.
 
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Burning of the skin, not bursting into flames, is what they probably mean.
 
Free flowing air probably stays within temperature limits most of the time . Problem with all heat gun devices is that if exit duct is partially blocked then temperature can rise considerably . Modern equipment is usually fitted with an over temperature trip out device or full thermostatic control for safety .
 
Nidum said:
Free flowing air probably stays within temperature limits most of the time . Problem with all heat gun devices is that if exit duct is partially blocked then temperature can rise considerably . Modern equipment is usually fitted with an over temperature trip out device or full thermostatic control for safety .
Thanks for the reply.
To be clear, I'm talking about the hairdryer burning the skin, not the dryer bursting into flames. In fact I just gave the hairdryer as an example, I'm really interested in understanding the physics here: i.e. if I blow air at 60 degrees C at a wall can that wall's temperature exceed 60 degrees?
 
If that were possible, why not just blow air at room temperature and expect things to warm up?
 
nasu said:
If that were possible, why not just blow air at room temperature and expect things to warm up?
Thanks for that answer!
 
It is possible to build machines which use a large flow of cold air to produce a small flow of hot air .
 
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