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I thought the chimney approach would be more 'obvious' too, so few examples of it. My own JLH project is based on making a pair of chimneys, one for each channel. The final amp should sit on tall feet to allow the air to flow underneath and up the chimney.
I got the idea from looking at coal fired power station cooling towers in the UK. there's a lot of science to it if you want.
http://www.diyaudio.com/forums/solid-state/3075-jlh-10-watt-class-amplifier-99.html#post2584968
A nice pair of chimneys in one amp, Bigun! And some internal finning... At a basic level, what made you decide to make two small chimneys instead of one large one? Seemed to make a better-proportioned chimney in a reasonable-height box?
Now, if you stuck a smaller-diameter practically indestructible cheap clear plastic pipe or maybe a pretty glass tube on top of each of your chimneys do you think it would make a huge difference in cooling during long periods of running?
Now, if you stuck a smaller-diameter practically indestructible cheap clear plastic pipe or maybe a pretty glass tube on top of each of your chimneys do you think it would make a huge difference in cooling during long periods of running?
-Very very interesting, I like a man who thinks. Even the steam-punk appearance will -have its fans in contemporary design schools.
Well I'm an architect so maybe logical that it has a "Tower-like" appearance
-What's the temp like at different heights,
In a room that's 21C I can get as high as 58C right at the very edge of the MOSFET. Two inches away my infrared thermometer gun says 29C but that seems low. Papa Pass says I think that you have to be able to hold your hands on the heatsinks about 8 seconds I think, but in his chassis that's about 3" from the MOSFETS . The only place my tube is that hot is at the same level as the MOSFETS. A band about 6" 150 mm.
-what does your hand feel at the top, how warm or cool does it run and how much air can you feel moving, blowing out the top?
At the very top I can leave my fingers on the tube all day but its reasonably warm. The tube is 30" tall 75cm and 6" 15cm square. I've always heard that output devices should be about 40% from the bottom of the sink, but in this case the bottom 6" 15cm are barely warm, so the chimney is different. I can feel the heat rising out of the top but it is pretty mild.
-Do you think it's more important to not restrict the flow, or would it help to have some disruption to add turbulance right near the transistors to maximize the heat exchange right there (like insert a stationary fan blade near the midpoint or maybe lower)?
There are wires loose inside that should be plenty to stir things up a bit. Yes I think its important to break up the hot air layer next to the inner tube. I DO think that small fins would be a great idea to break up the laminar flow and transfer more heat. They shouldn't be vertical, but at an angle or horizontal I think.
-Now that you've been there/done that, you endorse thicker aluminum; what about 1/3 the diameter, round section, internal fins, transistors lower nearer the coldest end of the chimney, and the upper half of the chimney made of some much cheaper material like thin plastic pipe or clear acrylic tube? I'm thinking round pipe is an optimum chimney shape, and in standard sizes would mate nicely to clear acrylic tube. Then again, if I have the lower metal section internally finned, then an unfinned upper plastic pipe might be smaller diameter and get higher velociy of the air, Would definitely be interesting to put a light at the top and blow some smoke into it, just to observe the air flow visually.
I don't think round pipe is necessary or an improvement. Certainly the sq tube is better where you mount the MOSFETS! the tube is warm all the way up, so plastic wouldn't be that great I don't think unless it was added on to the top of the metal tube the height of mine. But you have an innaccurate idea of the air flow, its pretty low So eventually the friction of a taller tower is going to effect things negatively. A smaller diameter is going to have more friction too. My final analysis is that the tower would be just fine with the bottom 6" 15cm cut off so only 24" 60cm tall with the Mosfets starting about 6" from the bottom. I'd make the wall thickness 1/4" 6mm at least instead of the 3/16" I have. 3/8" would probably be awesome but pricey. The two 30" sections of 3/16" cost about $100, so two shorter lengths of 3/8" should be under $200, and with how well these work I wish I had spend more so the heat isn't as concentrated and even in hotter climates they'd be fine.. I'll probably bolt some 1" x1" aluminum angle to the inside at the MOSFETS for about 18" with heatsink grease someday , but here in San Francisco it seldom gets hot enough to worry about. And yes, I have blue LEDS inside the towers so they glow like reactors out the top!
Well I'm an architect so maybe logical that it has a "Tower-like" appearance
-What's the temp like at different heights,
In a room that's 21C I can get as high as 58C right at the very edge of the MOSFET. Two inches away my infrared thermometer gun says 29C but that seems low. Papa Pass says I think that you have to be able to hold your hands on the heatsinks about 8 seconds I think, but in his chassis that's about 3" from the MOSFETS . The only place my tube is that hot is at the same level as the MOSFETS. A band about 6" 150 mm.
-what does your hand feel at the top, how warm or cool does it run and how much air can you feel moving, blowing out the top?
At the very top I can leave my fingers on the tube all day but its reasonably warm. The tube is 30" tall 75cm and 6" 15cm square. I've always heard that output devices should be about 40% from the bottom of the sink, but in this case the bottom 6" 15cm are barely warm, so the chimney is different. I can feel the heat rising out of the top but it is pretty mild.
-Do you think it's more important to not restrict the flow, or would it help to have some disruption to add turbulance right near the transistors to maximize the heat exchange right there (like insert a stationary fan blade near the midpoint or maybe lower)?
There are wires loose inside that should be plenty to stir things up a bit. Yes I think its important to break up the hot air layer next to the inner tube. I DO think that small fins would be a great idea to break up the laminar flow and transfer more heat. They shouldn't be vertical, but at an angle or horizontal I think.
-Now that you've been there/done that, you endorse thicker aluminum; what about 1/3 the diameter, round section, internal fins, transistors lower nearer the coldest end of the chimney, and the upper half of the chimney made of some much cheaper material like thin plastic pipe or clear acrylic tube? I'm thinking round pipe is an optimum chimney shape, and in standard sizes would mate nicely to clear acrylic tube. Then again, if I have the lower metal section internally finned, then an unfinned upper plastic pipe might be smaller diameter and get higher velociy of the air, Would definitely be interesting to put a light at the top and blow some smoke into it, just to observe the air flow visually.
I don't think round pipe is necessary or an improvement. Certainly the sq tube is better where you mount the MOSFETS! the tube is warm all the way up, so plastic wouldn't be that great I don't think unless it was added on to the top of the metal tube the height of mine. But you have an innaccurate idea of the air flow, its pretty low So eventually the friction of a taller tower is going to effect things negatively. A smaller diameter is going to have more friction too. My final analysis is that the tower would be just fine with the bottom 6" 15cm cut off so only 24" 60cm tall with the Mosfets starting about 6" from the bottom. I'd make the wall thickness 1/4" 6mm at least instead of the 3/16" I have. 3/8" would probably be awesome but pricey. The two 30" sections of 3/16" cost about $100, so two shorter lengths of 3/8" should be under $200, and with how well these work I wish I had spend more so the heat isn't as concentrated and even in hotter climates they'd be fine.. I'll probably bolt some 1" x1" aluminum angle to the inside at the MOSFETS for about 18" with heatsink grease someday , but here in San Francisco it seldom gets hot enough to worry about. And yes, I have blue LEDS inside the towers so they glow like reactors out the top!
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I see your interior finning is in the direction of the airflow. I keep thinking some kind of spiral internal finning would be good. And if the flow is most restriced at the heat sinks it will be moving the fastest there where it counts, unless it restricts too much and slows it all. So I wonder if you couldn't get much better cooling by putting a solid plug in the middle of your tunnel, forcing the air deep into your fins, then putting a tall pipe on the top to make it really suck the air in past the heatsinks. I really like the idea that it will work harder the hotter it gets. 'course your amp is not huge, so excuse my exaggerated ideas.
Of course all "exterior" fins are really chimneys too,...and enjoying really unrestricted airflow, making the room air circulate on either side.
An additional chimney extension could be made of pretty wood. Blown glass. Thin anodized aluminum. Light titanium. Cheap acrylic or cheaper PVC. Maybe the chimney could telescope for transport. A rectangular chimney extension could fold flat onto the top of an amp for transport.
Of course all "exterior" fins are really chimneys too,...and enjoying really unrestricted airflow, making the room air circulate on either side.
An additional chimney extension could be made of pretty wood. Blown glass. Thin anodized aluminum. Light titanium. Cheap acrylic or cheaper PVC. Maybe the chimney could telescope for transport. A rectangular chimney extension could fold flat onto the top of an amp for transport.
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I already had the 4 black heatsinks with power devices mounted on them. I thought it made sense from a construction point to build it the way I did. Also, for a chimney I think you need a large enough aspect ratio. With the two chimneys I get a decent height:width of opening ratio. As you say, it also meant the box wouldn't be twice as tall for the same aspect ratio. If you look carefully, you will see that I have 3 chimneys this way - there is another chimney made of the space between the two main chimneys and inside it there are also vertical fins. And front and back of these three chimneys are another pair of chimneys formed by the front and back panels of the chassis. This cools the rest of the electronics. that's 5 chimney's in all
I could extend the main chimneys, I don't see why that wouldn't work. If I put a light inside each chimney to illuminate them it could be quite a centre piece !
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