Frost-free window

[wilsonia]

I need to keep a window (300mm x 125mm) in an environmental chamber free from frost at temperatures down to -180°C.

The window is formed from 4 separate panes, since the window must also withstand 600°C.

I can keep inter-pane space clear by purging with dry gas, but outer pane in contact with ambient air always fogs. Using tin-coated glass("K-glass&quot, and passing current across it, OK for some applications, but electrical connections fry after prolonged high temperature running. Also currents and voltages necessary are kind of high for areas that can be touched by fingers!

 

[insideman]

How about directing a jet of dry air at the glass?

 

[WKTaylor]

Humm...

-180C to + 600C.... this is an exceptional and odd temp range... especially for an uncontroled environment [obviously humidity is a factor]. Must be testing aerospace materials.

Suggest You purge the chamber with dry nitrogen for several minutes before starting; then insure a positive pressure bleed-out of dry nitrogen from the chamber through-out the test.

Regards, Wil Taylor Regards, Wil Taylor

 

[Hush]

Interesting dilemma. I’m guessing insulated glass will self-destruct at these temperatures but might be worth checking out. How about taking air from inside the chamber where its bone dry, heating it, and blowing it between the panes to lower the temperature differential on the outside pane. This in conjunction with insideman‘s idea and what you’re already doing might work. Also if you put the tinned glass one pane in you'll have less chance of zapping your co-workers. One more thought, I wonder what they use on the space shuttle.