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  • Users: DrBiff
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  1. DrBiff

    substitute for variac

    Man, I love you guys. You've given me many options, now I just need to sit and ponder for awhile, hehe.
  2. DrBiff

    substitute for variac

    ah! beautiful explanation. That is exactly what I wanted to know. I just received an email from a coworker saying the fans are external rotor shaded-pole motors, so I guess since thats not a PSC I will need to switch to a DC fan right? (I already have a digital DC power supply) or try...
  3. DrBiff

    substitute for variac

    oh come on! killing me here..... cant you guys answer any of my questions that are not specifically related to the fan?
  4. DrBiff

    substitute for variac

    No come on guys I already read that thread, thats how I know you guys recommended the VFD, I wanted to see if there was a product that I dont know about. I am also interested in how some of this stuff works for future reference, like why would decreasing the frequency have the same effect as...
  5. DrBiff

    substitute for variac

    Ok how do I find this out? Doesn't say anything on the spec page, is there some indication written on the motor? Will look when I go down to the lab. What does a variac output? single phase 3-phase?
  6. DrBiff

    substitute for variac

    Hey guys I'm a ME so bear with me....I have an AC fan that I have been controlling the rpm with a variac, but I now need to be more precise(digital I suspect). I don't necessarily need it to be computer controlled, just need to fine tune the rpm to achieve an exact pressure drop(relatively)...
  7. DrBiff

    Icepak: determination of energy

    So my convergence criterion has been questioned when using IcePak. I can show that mass flow in equals mass flow out, but my boss wants to see energy in and energy out. I know you can do heat flow in and out, but it doesn't seem to be making sense. It says 1W flows through the entrance then...
  8. DrBiff

    icepak

    hey thanks, monitoring points and regular points are perfect, I was unaware icepak had this feature
  9. DrBiff

    icepak

    I am trying to measure and exact point in icepak, but every time I run a simulation the surface probe hits a point that is not exactly the same as last time, is there a better way to go about this or a way to setup the surface probe to measure an exact point??
  10. DrBiff

    Solver not resulting in min

    your are 100% correct in that it is finding local minima, my solution is based on if statements that make an educated initial guess that results in the correct minimum, where as before I was just sticking in 1 and the answer was 75.........
  11. DrBiff

    assembly crash, refering to two different parts

    well I think I know what the problem is, but still don't know the solution, picture something like a tripod, where there is a slider on the middle bar and the leg connects to the top of the bar and to the slider. I connect the leg to the top of the bar, but when I try and connect it to the...
  12. DrBiff

    assembly crash, refering to two different parts

    So, any one here ever have the problem of assembling a part and the entire program crashing when making references to two separate parts? Well, thats happening to me and its going to cause a big pain in my butt if I have to figure out a way to assemble this thing with each part referring to...
  13. DrBiff

    Solver not resulting in min

    ya it wasn't a cycle problem its that if the guess goes outside a constraint there are #NUM! and division by zero errors....what I ended up doing was changing the initial guesses to something more realistic and the computer seems to not go out side the constraints and hits the minimum value, so...
  14. DrBiff

    Solver not resulting in min

    oh...well crap
  15. DrBiff

    Solver not resulting in min

    ok now its going to the correct min value if I set it to only alter one value, but if I have it change two or more values it goes outside my constraints how does the solver come up with a solution? does it test values outside the constraints and then filters the results to the constraints or...
  16. DrBiff

    Solver not resulting in min

    I am trying to use excel's solver to minimize a very complex function that is subject to six constraints(optimizing the number of fins on a heat sink), but the solver never hits the minimum value, when I plot the function versus the number of fins, there is always a lower value(greater number of...
  17. DrBiff

    fluids property database

    no I haven't tried the Piping & Fluid mechanics section, whats the rule here on double posting in two different forums the http://webbook.nist.gov/chemistry/fluid/is very close to what I am looking for, but in order to search every fluid they have I would need to select every fluid individually
  18. DrBiff

    fluids property database

    I see that there are a lot of databases for metals, and I can get some properties for ceramics and polymers from my old textbooks, but now I am in need of fluid properties and cannot find anything useful. Does anyone know of a free fluids property database in which I can enter desired...

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