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Thread: Venting dc outside

  1. #61
    Makeup are comes in from the top of my 14' high garage door (12' high). It has a 3/4" gap up there and doesn't have an air stop strip like the sides to.

    But that is nothing compared to the spray room fan that is 17,000 CFM That takes the heat out faster than I can make it.

  2. #62
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    Quote Originally Posted by Carl Beckett View Post
    As for heating of the air itself - I like this equation: Q=m*Cp*deltaT.
    Carl,
    The equation I used above is a form of this one. Your equation will work for any solid, liquid, or gas, as long as you use the correct Cp, as you stated. My equation is arranged to use specific units, Btu/hr and CFM. The 1.08 comes from .075 x 60 x 0.24. Standard air density is .075, Cp for air is 0.24, and 60 minutes/hr. This is a well known and used form of the heat equation for HVAC and Industrial Ventilation engineers.

    Its just a shortcut, thought you might be interested. I use the equation you referenced, when dealing with something other than air.
    Last edited by Michael W. Clark; 04-26-2012 at 11:56 PM.

  3. #63
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    Quote Originally Posted by Leo Graywacz View Post
    But that is nothing compared to the spray room fan that is 17,000 CFM That takes the heat out faster than I can make it.
    You probably don't want to try to heat that.
    If you could separate the finish room and let it draw its make-up from somewhere besides the shop, it might help? At least only the finish room would be cold. A lot of good that would do you...
    Last edited by Michael W. Clark; 04-27-2012 at 12:07 AM.

  4. #64
    Quote Originally Posted by Michael W. Clark View Post
    So if you pick up a weight and move it across the shop, you have done nothing except generate heat? Moving the weight was not "free". Useful work was done and that took energy.
    Hi Michael. No one is disputing anything you've said above. Moving the weight does "use" energy, but it doesn't make energy disappear, it just converts it. And yes, that statement is counter-intuitive, which is why I think it's interesting. If anyone else is interested in the topic the book "E=mc2: A Biography of the World's Most Famous Equation" by David Bodanis is an easy to read history of man's understanding of physics through the centuries. It includes the evolution of the concepts of the conservation of mass and the conservation of energy and how these principles informed Einstein's famous theory. I read this book a short while ago and was excited to see what looks to me like a "real life" example in this thread. I didn't mean to start an argument and my apologies to the OP,Paul, for what turned out to be a hijacking of his thread.
    Last edited by Mark Rakestraw; 04-27-2012 at 6:55 AM.
    Mark R

  5. #65
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    If you simply pick up a weight and move it across the room and set it down at the same height, have you done any work?? I thought in order to have net work, you needed to have changed energy state ( kinetic or potential ). If you just move a bunch of energy around within the control boundary without changing state, I'm not sure any net change ( of course tHere are losses associated with this)

  6. #66
    Quote Originally Posted by Michael W. Clark View Post
    You probably don't want to try to heat that.
    If you could separate the finish room and let it draw its make-up from somewhere besides the shop, it might help? At least only the finish room would be cold. A lot of good that would do you...
    It is in a separate room. I have two 1300 sq ft areas, two side by side bays. I still heat it and it does pretty good. But below 20F and more than 10 minutes of fan and you can feel the cold get into the room. I usually turn the fan on and off when needed. In the summer I just let it run to keep the room as nice as possible.

  7. #67
    Quote Originally Posted by Carl Beckett View Post
    If you simply pick up a weight and move it across the room and set it down at the same height, have you done any work?? I thought in order to have net work, you needed to have changed energy state ( kinetic or potential ). If you just move a bunch of energy around within the control boundary without changing state, I'm not sure any net change ( of course there are losses associated with this)
    You moved the weight. You did work.

  8. #68
    In terms of the physics question, when you run your DC, you are moving air. Moving the air is the work, most of the electrical energy gets converted to this movement of air. Some heat is created because of resistance in the ducts, and because the motor is not 100% efficient. So some of the electrical energy is converted to heat.

    So the energy being supply by your utility company is being converted to some work (the moving of air with entrained particles), and some heat.

  9. #69
    Quote Originally Posted by Carl Beckett View Post
    If you simply pick up a weight and move it across the room and set it down at the same height, have you done any work?? I thought in order to have net work, you needed to have changed energy state ( kinetic or potential ). If you just move a bunch of energy around within the control boundary without changing state, I'm not sure any net change ( of course tHere are losses associated with this)
    Yes, you have done work. You have consumed food, and burned calories in order to move the weight.

  10. #70
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    Quote Originally Posted by Mark Rakestraw View Post
    Hi Michael. No one is disputing anything you've said above. Moving the weight does "use" energy, but it doesn't make energy disappear, it just converts it. And yes, that statement is counter-intuitive, which is why I think it's interesting. If anyone else is interested in the topic the book "E=mc2: A Biography of the World's Most Famous Equation" by David Bodanis is an easy to read history of man's understanding of physics through the centuries. It includes the evolution of the concepts of the conservation of mass and the conservation of energy and how these principles informed Einstein's famous theory. I read this book a short while ago and was excited to see what looks to me like a "real life" example in this thread. I didn't mean to start an argument and my apologies to the OP,Paul, for what turned out to be a hijacking of his thread.
    Hey, it's been fascinating, and it brought up aspects I had never considered.
    Its the longest thread I've ever started!
    Paul

  11. #71
    But did your question get answered?

  12. #72
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    yeah, not sure, to be honest.
    Paul

  13. #73
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    Quote Originally Posted by Carl Beckett View Post
    If you simply pick up a weight and move it across the room and set it down at the same height, have you done any work?? I thought in order to have net work, you needed to have changed energy state ( kinetic or potential ). If you just move a bunch of energy around within the control boundary without changing state, I'm not sure any net change ( of course tHere are losses associated with this)
    Well let me ask it this way:

    If you pick it up and set it back down... say, 100 times. (lets assume in the same spot)

    Did you do any work?

  14. #74
    Absolutely. But did you accomplish anything, not really. You burned up some calories and probably paid an aspirin company for their product...

  15. #75
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    Quote Originally Posted by paul cottingham View Post
    yeah, not sure, to be honest.
    Paul,
    I would estimate your SP losses at around an 1" of SP, maybe a little less by adding the fittings you are talking about. It is likely that the filter has more loss than this, so if you bypass it and vent outside, you will probably increase the CFM of the system. Try not to put the elbow directly on the blower outlet if possible.

    I apologize for my part in leading away from your question. I think you will like venting outside better, when its practical. I have a friend that does this with a small blower and loves it. He sends chips and all to the outside, no cyclone or filter.
    Mike

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