How Do "Heat Fins" Work In a Vacuum? - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 11th April 2008, 02:19 AM   #1
diyAudio Member
 
Join Date: Oct 2007
Default How Do "Heat Fins" Work In a Vacuum?

I was just reading about some tubes that have "heat fins" attached at the plate. I was just sort of wondering how this does a whole lot of good in the evacuated environment inside of the tubes' glass bottle. I can see how it might add a VERY small amount of area to the plate which could help radiate some heat but does it really help? Or are these fins really there for some other reason? Making the plate more rigid or something?
  Reply With Quote
Old 11th April 2008, 02:30 AM   #2
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
How is heat dissipated in "outer space" as there are no dense molecules to "sink" it", and "transport" it away yet spacecraft get rid of it.

It is "radiated"

This is a very good question.
  Reply With Quote
Old 11th April 2008, 02:45 AM   #3
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
One of the things that you learn by abusing tubes at dissipations far in excess of the ratings is that most of the heat dissipated by the plate comes from a small area of the plate structure. This is the area that glows when you crank up the juice. The fins that are welded to the plate are usually added to the area that glows and can double that area. What I don't understand it why there are sometines fins welded to the INSIDE of the plate structure.

Since there is a vacuum inside the tube there is very little heat conducted out of the tube. Most of the heat is radiated out of the tube. This why metal objects, especially black metal objects like OPT's that are near the hottest tubes (the output tubes) get hot. The fins allow more surface area to radiate more heat. I have tested tubes with and without the fins that are otherwize identical and can state that the fins can allow for a much higher plate dissipation.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 11th April 2008, 06:39 PM   #4
diyAudio Member
 
Ty_Bower's Avatar
 
Join Date: Mar 2007
Location: Newark, DE
As others have said, yes the fins do increase the area available to radiate energy. The plates aren't very large to begin with, so even small fins make a difference.

I found this short answer as to how it is possible for energy to radiate through a vacuum:
http://answers.yahoo.com/question/in...6033051AAxxTL1
  Reply With Quote
Old 11th April 2008, 07:01 PM   #5
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
It's always a combination: conduction, convection and radiation.

Since there is a vacuum, convection is nil. There is of couse radiation, as mentioned. But there is also conduction through the structure to the pins and the socket.

Jan Didden
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W. S. Maugham
Check out Linear Audio!
  Reply With Quote
Old 11th April 2008, 10:37 PM   #6
diyAudio Member
 
smoking-amp's Avatar
 
Join Date: Dec 2001
Location: Hickory, NC
re: Tubelab
"What I don't understand it why there are sometines fins welded to the INSIDE of the plate structure."

I believe the fins on the inside of the plate are called Barkhausen plates. They help short out UHF space charge oscillations near saturation. (space charge cloud oscillating back and forth thru the screen grid when the plate voltage drops suddenly) Usually found on TV Horizontal output tubes which get abused with pulses that stimulate these Barkhausen oscillations.

Don
__________________
I want a Huvr-Board!!
  Reply With Quote
Old 11th April 2008, 11:40 PM   #7
diyAudio Member
 
Join Date: Sep 2004
Location: UK
Default Heat, Light & Sound

Quote:
Originally posted by janneman
It's always a combination: conduction, convection and radiation.

Since there is a vacuum, convection is nil. There is of couse radiation, as mentioned. But there is also conduction through the structure to the pins and the socket.

Jan Didden
"Heat, Light & Sound" was our Physics text nearly 50 years ago.

Heat was divided into Convection, Conduction and Radiation.

Sub-chapters covered the experiments of all the greats: Newton, Kelvin, Boyle, etc etc

Do they still do all that at school?

Sorry! I am an old fart and reminiscing!
  Reply With Quote
Old 11th April 2008, 11:49 PM   #8
ilimzn is offline ilimzn  Croatia
diyAudio Member
 
Join Date: Feb 2005
Location: Zagreb
Quote:
Originally posted by smoking-amp
re: Tubelab
"What I don't understand it why there are sometines fins welded to the INSIDE of the plate structure."

I believe the fins on the inside of the plate are called Barkhausen plates. They help short out UHF space charge oscillations near saturation. (space charge cloud oscillating back and forth thru the screen grid when the plate voltage drops suddenly) Usually found on TV Horizontal output tubes which get abused with pulses that stimulate these Barkhausen oscillations.

Don
I wonder if they could also be there to enhance heat transfer from the grids and cathode?
The thing with radiation is that it really works both ways, depending on the temperature of the objects in question. It is often forgotten that the plate actually radiates most of the heat produced by all the structures shrouded by it, because heat from those is mostly radiated onto the inner surface of the plate, then conducted to the outer surface and then radiated outwards (some is of course picked up by the bulb and then radiated on the outside). The rest would be conduction (for example through the grid wire support rods which frequently have fins attached on top and sometimes on the bottom).

Regarding fins on the outside, because there is no convection, these have to be strategically placed, unlike fins on a heatsink - to prevent them radiating too much onto other parts of the plate. The effective area of parallel fins such as found on heatsinks, would be much smaller than expected if this was done on a tube plate, because they 'shadow' each other as far as radiation is concerned. However, similar structures can still be used as heat spreaders to prevent hot spots.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
What makes an amplifier "bright", "warm", or "neutral"? JohnS Solid State 51 13th December 2009 06:42 PM
How can I add a "Digital In" to my current cd player ? (Make it work as a DAC ) b_online Digital Source 2 20th December 2007 10:52 AM
Randy Slone "Fig 11.6" amp, modded: will work? tcpip Solid State 85 29th May 2007 10:31 PM
Will this work? "Mixed" 300B PPP IT ppereira Tubes / Valves 4 24th April 2004 05:29 PM


New To Site? Need Help?

All times are GMT. The time now is 07:08 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2