The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Design >> RF Design >> Water cooling for RF electrode
https://designers-guide.org/forum/YaBB.pl?num=1408463850

Message started by Asta on Aug 19^th, 2014, 8:57am

Title: Water cooling for RF electrode
Post by Asta on Aug 19^th, 2014, 8:57am

Hi,

I would like to ask some information about a the impact of a water cooling system on a RF circuit (13.56MHz, a few kW).

The circuit would look like this:

.

So, the water would be in contact with the electrode and connects it to ground via a plastic tube. Sadly it will have to be tap water (DI water would solve the problem).

What is unclear to me is if at 13.56 MHz, the water has to be considered mostly as a conductor (with a resistance of 20-200 Ohm/m) or if there are effects similar to the skin effect one would find in a conductor?

More generally, I've searched but couldn't find reliable sources for the impedance of water (with real and imaginary parts) at 13.56 MHz or around and would be happy if anyone knows where to find the info.

So, in the end, is this system just a simple R from the water in parallel to the electrode capacitance or is it more complex?

Thank for the support.

Asta

Title: Re: Water cooling for RF electrode
Post by loose-electron on Aug 19^th, 2014, 1:38pm

characteristics of water changes so much with the dissolved contents.

there are other fluids used for thermal conduction methods, as well as high volume flow air.

Do you really need a direct contact water system? I know 50KW broadcast transmitters that get away with air and do quite well.

Title: Re: Water cooling for RF electrode
Post by Asta on Aug 19^th, 2014, 11:06pm

Hi,

Thanks for the suggestion of using air but I doubt that high flow of hot air in the middle of a lab would be fully appreciated. But I'll keep the idea in mind in case water proves too challenging.

And yes water properties (or at least its DC resistance) change a lot, but I'm still quite curious regarding its general RF properties.

Asta

Title: Re: Water cooling for RF electrode
Post by loose-electron on Aug 20^th, 2014, 5:15pm

consider mineral oil if it is a lab setup