CurtPalme.com Home Theater Forum

ecrabb · Posted: Thu Feb 20, 2014 6:19 am Post subject:

jbmeyer13 · Joined: 03 Dec 2010 Posts: 1135

Hey Steve- I saw those same links prior to my last response as well. I'm not even sure what series aluminum is used for the LC chambers so perhaps someone can chime in on that. I don't remember hearing about Sony G70 or G90 chassis having issue with glycol. Did you ever have any issues with your G70?

ecrabb · Posted: Thu Feb 20, 2014 6:06 pm Post subject:

jbmeyer13 · Joined: 03 Dec 2010 Posts: 1135

I wish it takes a long time to develop- I think Nash had some in a 2011 or 2012 model year tube IIRC.

The solution would be to anodize the LC chambers but that would require either:

1) Destroying the existing bellows and pulling everything apart

or

2) Finding a used LC housing with bellows needing to be replaced and also bare tubes

In both cases (assuming you can find some place that can anodize the housings for a reasonable price) you would need a competent tech to pot/reinstall the tubes. By the time you add up the cost of anodizing and labor for tube installation it's likely more than the tube itself is worth in this market.

This is the type of project Dragan should do as I'm pretty sure he has coated chambers with epoxy. Perhaps he's looked into it but concluded that the cost was not worth it.

digitalayon · Joined: 02 Mar 2009 Posts: 921

See....I would rather just change the fluid and call it a day. Especially when you are talking cost of epoxy and anodizing. Prolonging with a different solution makes more sense to me. I think I am going to try Galden this year on my projector.

jbmeyer13 · Joined: 03 Dec 2010 Posts: 1135

ecrabb · Posted: Sat Feb 22, 2014 12:00 am Post subject:

mc86 · Posted: Sun Mar 02, 2014 1:09 am Post subject:

Regarding the use of something other than glycol regarding the optical properties: For a LC machine, I think the curvature of the c-element is probably a function of the distance in the bellows and the index of refraction of the fluid. Changing the index of refraction a lot could make a difference. I dunno. 1.42 or whatever down to 1.28 is a big difference, it seems to me. The sensitivity to the performance of the entire optic system to this, I couldn't venture a guess.

As per the heat transfer, I could do better than a guess. My lab also uses some fluorinated heat transfer fluid (3M brand) that is very similar. Mine is called Fluorinert 70. It was $100 for maybe 2L (1/2 gallon) 10 years ago.

Without evaluating the Raleigh # to determine if there is natural convection or not, I would imagine with fluorinert there is convection. With glycerol there may not be (or if there is, to a much smaller level). Here is why: the performance of a fluid when used as a cooling agent in natural convection cases is, amongst other things, dependent on the ratio of the buoyancy forces (think how much the density changes as temperature changes) to the viscous resistance to flow. This is a ratio called the Grashof number. Fluorinert will have a grashof number that is about 5000x that of glycerol (all other things being equal). This is b/c Fluorinert has a thermal expansion coefficient 3X that of glycercol and is 1/1600th the kinematic viscosity. Add to this the fact fluorinert is 1/5 as thermally conductive and an interesting relational understanding emerges. The heat from the tube face (a flat surface) would make a higher local temperature in fluorinert b/c it conducts less readily (I'll assume densities and heat capacities are similar, which is likely). Remember -- Fluorinert expands much more rapidly as it heats than glycerol would have AND is way less viscous than glycerol. The result is that convective currents are much more likely to form and are greater than those which might be formed by glycerol all other things being equal. Either way, the heat transfer is almost certainly going to be a lot faster with fluorinated heat transfer compounds. So...yes, fluorinated heat transfer fluids will remove heat away from the surface at a faster rate. Wink

Whether or not that matters or how much, depends on the phosphor and the glass at that point.

Also, regarding the cooling -- last May/June (2013) I prepared to do two phosphor browning experiments, but they didn't happen last summer. They may shed a little initial light on the topic of the role of temperature in phosphor browning. I'll post some updates to that in the days ahead.

PS - Today was 1st time since Jan 1 I've made time to read CRT forum -- I miss getting to tinker and think about this stuff. And to share and laugh with you all.

Matt