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Thread: I have a really wierd question.

  1. #1 I have a really wierd question. 
    Forum Freshman
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    First of all i would like to apologize if this question doesn't strictly fall into the physics category. I have posted it here because i wished for a Physic's substantiated answer. SO please forgive me. (i have tried researching online and there was absolutely nothing i could find)


    We all have air-conditioners in our houses now. It so happens that i also have a Fan in the same room.
    If i switch on the air-con, the temperature should drop to about 22 degrees. Now if i switch on the electric fan, how would it affect the temperature? For some funny reason i always feel it becomes hotter when i on the electric fan... Is it just me or by blowing the already cold air would it increase the temperature of the 'air'?

    Or will the fan disrupt the convectional flow of the air? thus making the air-con less efficient?

    Once again i seek your forgiveness if this is a dumb question to ask.


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  3. #2  
    Time Lord
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    This is not a physics answer but

    remember what you feel as "cold" is actually an unsustainably high rate of body heat loss, and

    what you feel as "hot" is an inability to shed body heat.

    The body must constantly generate heat and shed it.


    Air that is cooler than 37C will take away some heat, and much more so if it's blowing. It will feel cooler, though a thermometer doesn't show wind-chill. Evaporation of skin moisture will cool you even further, and also improves when there's a breeze.


    Any fan motor generates some heat, but I guess we can discount that. I guess your idea about the fan disrupting air flow is the answer. If the a/c normally creates a circuit of air moving around the room before recycling through the unit, does the extra fan "short circuit" this flow?


    A pong by any other name is still a pong. -williampinn
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  4. #3  
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    The fan will add some heat, but I don't think it would be significant.

    The air conditioner, if it does not circulate the air around the room very well, could create a layer of cool air near the floor. Then the fan might be stirring it around and mixing it with the warmer air near the ceiling, which would have the effect of making the room warmer at floor level. Or, if the air conditioner is only in one room, without the fan blowing it might make only that room cool. The fan would mix the cool air around the rest of the house, which would make the air conditioned room warmer.

    Another thing that could be happening is the fan may blow cool air on the thermostat, which would shut it off when the overall room temperature is somewhat warmer than without the fan blowing.
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  5. #4 Re: I have a really wierd question. 
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    Quote Originally Posted by tikai
    First of all i would like to apologize if this question doesn't strictly fall into the physics category. I have posted it here because i wished for a Physic's substantiated answer. SO please forgive me. (i have tried researching online and there was absolutely nothing i could find)


    We all have air-conditioners in our houses now. It so happens that i also have a Fan in the same room.
    If i switch on the air-con, the temperature should drop to about 22 degrees. Now if i switch on the electric fan, how would it affect the temperature? For some funny reason i always feel it becomes hotter when i on the electric fan... Is it just me or by blowing the already cold air would it increase the temperature of the 'air'?

    Or will the fan disrupt the convectional flow of the air? thus making the air-con less efficient?

    Once again i seek your forgiveness if this is a dumb question to ask.
    The fan dpes work on the air in the room, so the average temperature will rise a small amount if you run it. But it will also homogenize the air, and the temperature will become more uniform.

    Also the movement of air in the room will reduce the thickness of the stagnant air near your skin and increase heat transfer and evaporation from the skin. So if the room temperature is below body temperature you will feel cooler. This is the same thing as "wind chill.

    If the room temperatue is 22 degrees then I hope you are measuring temperature in centigrade.
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  6. #5  
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    lol, it is in degree Celsius. Sorry guys , i forgot to mention that the whoile scenario is in a small room and the doors are closed when i switch on the air-con. Thus i suppose the fan will homogenize the air in the room, and in some ways make it hotter right. Thanks a lot.
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