[PSUBS-MAILIST] Light Experiments

[Alec Smyth via Personal_Submersibles]

Great stuff Alan!

On Sun, Apr 16, 2017 at 12:33 AM, Alan via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> I put a temperature probe inside the housing of my 80W LED light.
> The probe was up against the acrylic lens, as I was concerned about
> what temperature the lens was seeing on the inside. The lens is 10mm
> away from the LED.
> The LED manufacturer told me that on normal LEDs the temperature
> out the front of the LED can be 338F (170C) but my flip chips should
> run cooler.
> Briefly; when run at 30W in water they stabilised at 257F after 5 minutes.
> At 45W they stabilised at 280F after 5 minutes. I stopped upping the amps
> at this stage.
> Next experiment, I filled the housing with silicone oil.
> At 45W it hit 116F in 4 minutes & temperature stabilised.
> At 76W it hit 139F in 6 minutes & stabilised.
> So oil has massive advantages in lessening temperature on the lens,
> maybe because it is a buffer from the radiant heat & also transfers the
> heat
> out through the housing quicker.
> Greg your thoughts would be appreciated on this; I am thinking that
> without the
> oil the acrylic lens would see temperatures at which it is formed
> especially
> if I went up to 80W. Although the outside of the lens was cold there would
> be a
> temperature transition across the thickness of the lens & it would be
> considerably
> weakened. I am building to 500ft, so it would potentially see 250 psi in
> operation.
>    At this stage I haven't made up my mind whether to go with a
> borosilicate lens
> or oil fill with an acrylic lens. I had a large bubble & it would be hard
> to eliminate
> all bubbles in the oil filling process.
> Will try & attach photos.
> Alan
>
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> Sent from my iPad
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