• posted
I do not have an opition off useing other software this is what i'
stuck with
The basic problem is this
I'm modeling a computer case. Inisde is a motherboard, a cpu, a hea
sink, powersupply, hard drive and dvd drive
I am trying to model a system with 3 fans
1 large fan blowing into the case, right now is being setup just lik
the turtioal, so pabst 405 @ 100 rad/
similar fan blowing on the heatsink, but is just setup as blowin
perpendicular to the face (internal fan, blowing towrads the cpu
similar fan on the power supply internal fan blowing towards th
outside of case
working fluid = ai
cpu = alumin to simulate the heatspread it has on it
heat sink coppe
also have an outlet behind the power supply thats setup as a stati
pressure boundary
power supply, dvd drive, hard drive, all steal
cpu is a heat generator, generation 110
power supply, hard drive, dvd drive, all 10w surface heat sources
initial air temp = 110 degrees,
initial solid temp = 110 degrees, both
hmmm I think thats most of it
goals =
global = flui
surface on heat sink /cp
vg = cp
something else but do not remeber right now
problem i
Cosmos is caculating the fuild temprate to go DOWN
Its going down to about 60 degrees F, where is the heat going? if th
air is coming in at 110 Degrees, are cooling compents, and should b
heating up
How is my working Temp Not going up
It goes up locally, around the heatsink, and around the heat sources
but overall It is cooler then when is started.
does not seem possible
this is for a final project and I need to at least know why this i
happening
• posted
The first thing I would do is a simple problem. Maybe a box open on both ends with a heat source inside and flow through it.
Use the tools in FW to check the total mass flow into and out of the case as well as pressures at inlets and outlets.
What is the temperature of the inside walls of the case?
You have done well to recognize that the answer doesn't make sense. You will have to be systematic in eliminating possible causes. FW should have no problem giving a reasonable answer to this problem.
• posted
actualy the results do not look to bad. The low tempratures i wa seeing where in solver.
and they are different from what happens when I finally see the fna
it gets to a 'steady state' fluid temp, which is running at about 12
degrees F. which is very good, because while my fan specs are no prefect yet, just doing thermal anaylis on the system using a contro volume, and steady state analyis, keeping air standrards, fixin pressure, and Mdotin = Mdotout. I fixed my states to be 110 degrees in, and 120 degrees out. (this i from math
Floworks, gives me a fluid temp fof 123 degrees at solid state
thanks
so my question is, the numbers that are shown in solver, how do the relate to the final result
• posted
When watching the solver you are looking at an unconverged answer.
I believe FW has a setting which controls the "quality" of the answer. You know you have a converged answer (usually) when the difference between one run and another at the next higher step is very small (a few percent.)
FW and any other CFD system has to iterate to find an answer.
• posted
ok I have to add, that upon close inspection the fluid temp does g below 110 Degrees F in a few small areas of the fluid. What i do not see is how to set the air temp to be a constant 110 coming in, in the wizard I see that I can set the inital condition to be at 110 F, and the solids to be 110 F. But no where do I se the opition to set the fulid coming in to be 110 degrees. It seem that it defaults to the 68 degrees for the temp, and then builds i back up
after its all done, I can insert a boundary temp to 110 degress, bu thats only in the result

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