Can someone check my work, please? 4

[gt5pilot]

This is a bit out of my area:

For air @ 80F:

d = 1.5mm (dia lumen)
L = 15cm (lumen length)
mu = 2.07 Pa.s
rho = 0.9996 kg.m^3
V = 1 m/s

Re = (rho * V * d)/ mu

Re = 0.00072 - is that really right?

Q = (V * pi * d * d)/4

Q = 1.77E-06 cc/min

That would mean a pressure loss of:

delatP = (128 * mu * L * Q)/ Pi * d * d * d * d)

= 4.42E+6 Pa or 640 psi - something seems off...but, I did say this is not my comfort zone.

Thanks for any help you can give me.

Kirk


Kirk B Olson
Senior Principal Engineer
HEII, Inc.

 

[gt5pilot]

TTFN,

In the current systemm the fluid is introduced into a thin walled silicon balloon - we will use the same delivery system with our new fluid, gas. Yes, it is problematic - at best. Diffuser design for the gas is proving to be tightly coupled with the other parameters perviously mentioned to get even heat distribution in the balloon.

We actually disect the tissue, then stain it to determine the level of neucrosis.

I would be interested in hearing of your plights and challenges further...

Kirk

Kirk B Olson
Senior Principal Engineer
HEII, Inc.

 

[IRstuff]

We never got much farther than the planning stage. We had intended to work with a doctor at USC to collect data on varying degrees of burn and use a spectrally tunable source to collect imagery and then dissect the tissue to get the objective measurement and try to correlate to the hyperspectral images.

Did you mean silicone? Silicon is thermally quite conductive and would probably have horrible uniformity. I think that even silicone would have the same problem, unless you had a VERY high gas velocity, otherwise, convection effects will result in lots of non-uniformity. You may need to have a stirring fan inside the balloon.

TTFN

 

[gt5pilot]

Yep, silicone - I need to re-read before hitting the "reply" button...sorry.

Right now, we are running experiments using Helium and CO2 - we need to run quite high velocities/volumes, as you have thought would be necessary. Temperature uniformity is an issue for us - we have been desiging and experimenting with different types of diffusers to help minimize the problem. What we do find is that one particular diffuser will work better in smaller cavities, another in a larger cavity, etc. We have been doing a fair amount of modeling to find the best compromise and then trying to back up the models with experimentation.

Kirk

Kirk B Olson
Senior Principal Engineer
HEII, Inc.

 

[IRstuff]

My guess then, is that you'll need a decent CFD program to model it. The convection formulas that exist are for VERY simple geometries and will probably choke on anything half-way complicated. Even at that, their uncertainties are quite large.

TTFN

 

[gt5pilot]

That portion of the analysis is being handled by

http://www.stthomas.edu/technology/Faculty/sparrowpage.htm

...anyone here ever worked with him or know his works?

Kirk

Kirk B Olson
Senior Principal Engineer
HEII, Inc.