megalomania
June 9th, 2008, 08:47 AM
Here is a question that has irritated me for some time now that I forgot about until the beginning of the summer heat.
Consider a fast moving fan blowing air directly on you. This is intended to keep you cool because the fast moving air takes up some of your heat and is rapidly moved away. However, what if the air blowing through the fan is significantly warmer than you? Shouldn�t fast moving air that is hot actually make you warmer, or is the fact the air is moving at such a great speed and making momentary contact enough for it to momentarily get even hotter. Does this not go against the technical rules of thermodynamics, or is this allowed by the fact the air is moving so fast in can�t reach equilibrium with your body?
This problem occurred to me a couple summers ago when I was working at the steel mill. They have these large shop fans on the floor which is fine in some areas, but I wonder how much good they do for the guys around the furnaces where the ambient air is over 130 degrees F in the summer. The heat might actually be greater depending on if a furnace door is open, hot steel is being moved, how the fans may be positioned, and the time of day.
As I sit now at my computer, my fan in the window blowing on me, it looks to be another 90+ degree day. Is it actually counterproductive to have heat so much warmer than me blowing right on me? Would it be better to move the fan on the other side of me and blow the interior room air on me?
The theory would seem to indicate blowing air hotter than you should make you hotter. In my experience I am cooler sitting in front of the fan blowing on high. Of course in the winter when I go over to my parents house, as they have a fireplace that gets used all the time, I like to stand in front of the blower to get warm. It is blowing very hot air, albeit not as fast as a fan on high, but the blower still goes rather fast.
Is there some rule that defines where heat energy is allowed to go against the standard thermodynamics and make a system temporarily not at equilibrium? If so, Is there a limit to how hot the air can be and still take away heat? I would think at some point, if it got hot enough, the hot air blowing on my through my fan would actually make me warmer.
Consider a fast moving fan blowing air directly on you. This is intended to keep you cool because the fast moving air takes up some of your heat and is rapidly moved away. However, what if the air blowing through the fan is significantly warmer than you? Shouldn�t fast moving air that is hot actually make you warmer, or is the fact the air is moving at such a great speed and making momentary contact enough for it to momentarily get even hotter. Does this not go against the technical rules of thermodynamics, or is this allowed by the fact the air is moving so fast in can�t reach equilibrium with your body?
This problem occurred to me a couple summers ago when I was working at the steel mill. They have these large shop fans on the floor which is fine in some areas, but I wonder how much good they do for the guys around the furnaces where the ambient air is over 130 degrees F in the summer. The heat might actually be greater depending on if a furnace door is open, hot steel is being moved, how the fans may be positioned, and the time of day.
As I sit now at my computer, my fan in the window blowing on me, it looks to be another 90+ degree day. Is it actually counterproductive to have heat so much warmer than me blowing right on me? Would it be better to move the fan on the other side of me and blow the interior room air on me?
The theory would seem to indicate blowing air hotter than you should make you hotter. In my experience I am cooler sitting in front of the fan blowing on high. Of course in the winter when I go over to my parents house, as they have a fireplace that gets used all the time, I like to stand in front of the blower to get warm. It is blowing very hot air, albeit not as fast as a fan on high, but the blower still goes rather fast.
Is there some rule that defines where heat energy is allowed to go against the standard thermodynamics and make a system temporarily not at equilibrium? If so, Is there a limit to how hot the air can be and still take away heat? I would think at some point, if it got hot enough, the hot air blowing on my through my fan would actually make me warmer.