Ah, thank you for that suggestion. I hadn't really thought much about it because like-for-like a horizontal base is less ideal. BUT... yes indeed: in some situations a top-mounted heatsink could be considerably bigger, and so end up being noticeably more effective than a smaller side-mounted one.
Cheers,
Kev
turk 182,
There are a lot of papers available online that show the effects of fin orientation on cooling efficiency. I'm not sure what I can attach here due to this site's rules on copyrights but there is an especially interesting paper by Md Ruhul Amin Rana available on the University of British Columbia's website in the "Open Collections" section. It shows as much as a 75 degree difference between horizontal and vertical fin orientation, with vertical preferred. Most heat sink manufacturers also specifically recommend vertical orientation for the type of fins being discussed. How much the orientation matters is, no doubt, a function of heat sink geometry (length, fin height, etc.) and location of the heat source.
Best regards,
Bruce
I make Guitar amps and for 60-100W ones, use the aluminum back panel, (43 cm by 10 cm) as such.
No fins, but:
* ample surface anyway, just do the Math, more than many popular extruded finned heatsinks used in 100W amps
* vertical by definition 😉
* bonus: cabinet is taller than back panel, leaving an almost 1 cm wide slot above, another below, so internal panel surface also gets ventilation.
Proven by over 14000 amps delivered over 53 years 🙂
Now from 200W up: always fan cooled.
Cheaper, more practical and compact than similar performing finned heatsinks which would be huge.
And fan noise is NOT a problem within 20 meters (or more) around a drummer 😉
No fins, but:
* ample surface anyway, just do the Math, more than many popular extruded finned heatsinks used in 100W amps
* vertical by definition 😉
* bonus: cabinet is taller than back panel, leaving an almost 1 cm wide slot above, another below, so internal panel surface also gets ventilation.
Proven by over 14000 amps delivered over 53 years 🙂
Now from 200W up: always fan cooled.
Cheaper, more practical and compact than similar performing finned heatsinks which would be huge.
And fan noise is NOT a problem within 20 meters (or more) around a drummer 😉
I think they are. The 1/4" on the left are speedy speaker outputs? Over on the right the last fin hides the line ins?
Not sure
Likely they would be to left and right of the sink to separate signal and power, but they could be below the heatsink or possibly even poking through it in some cunning way. The sinks I have are too wide, so will need cutting down, and would still be more than big enough in terms of dissipation. I suppose that leaves quite a few possible options for placement.
Not sure; I'd assumed they were balanced inputs, but you could well be right. Though the picture is just a somewhat random illustration of a rear heatsink arrangement; the inputs/outputs that I'd actually use would need to be arranged for my own aims.I think they are. The 1/4" on the left are speedy speaker outputs? Over on the right the last fin hides the line ins?
Likely they would be to left and right of the sink to separate signal and power, but they could be below the heatsink or possibly even poking through it in some cunning way. The sinks I have are too wide, so will need cutting down, and would still be more than big enough in terms of dissipation. I suppose that leaves quite a few possible options for placement.
Makes me think of Mark's thermo-handling Jig (engages the fan and regulates its RPM according to temp). (No fan when no heat... useless/less useful with Class-A though)
Should safety-measures be added, just in case the fan stops working?
Yes, one of these bolted to heatsink or, in my case, back panel:
Found that a normally closed 70-75C switch works fine, it is rated to open 10A
There´s 2 ways to wire them, :
* some use it to open speaker out, so "amp keeps working" , fan keeps running, if amp is sending balanced line feed to a PA mixer that is not interrupted, so less disturbance to a Live Show,
* others plain open Mains voltage (it´s wired in series with the main Fuse) which may be safer, pick one.
Found that a normally closed 70-75C switch works fine, it is rated to open 10A
There´s 2 ways to wire them, :
* some use it to open speaker out, so "amp keeps working" , fan keeps running, if amp is sending balanced line feed to a PA mixer that is not interrupted, so less disturbance to a Live Show,
* others plain open Mains voltage (it´s wired in series with the main Fuse) which may be safer, pick one.
Aside: We listen to every screw, hood, every material, every mass-stiffness relationship on our equipment. Heat sinks are often large, heavy, vibrate terribly, which modulates the sound.
And a normally open at 65C to start the fan.Yes, one of these bolted to heatsink or, in my case, back panel:
Found that a normally closed 70-75C switch works fine, it is rated to open 10A
There´s 2 ways to wire them, :
* some use it to open speaker out, so "amp keeps working" , fan keeps running, if amp is sending balanced line feed to a PA mixer that is not interrupted, so less disturbance to a Live Show,
* others plain open Mains voltage (it´s wired in series with the main Fuse) which may be safer, pick one.
to Bruce Gillingham...could you please provide a direct link to the paper your referring to, so far i've been unable to find it.
and so as to remove the pigeon hole thinking about orientation this design is intended to work horizontal as well as vertical (but data shows it's performance is degraded when the sink is oriented points down and the heat source is at the top)
Some of the heatsinks pictured above (e.g. post 33) are not going to do well. Air has a tendency to move between fins or surfaces but only when the spacing is large enough. Otherwise there is mostly justy stagnant air except around the outside edges, which defeats the purpose of having a lot of fin area. The good old vertical fin with 1-2cm fin spacing works best. This assumes there is no fan driving the air, in which case you can get away with smaller fin-fin spacing but it has to be above some minimum value.
hence why i've opened the discussion to convection direction.
and sorry to say some of the pictured heatsinks are the epitome of new understanding and efficiency.
and sorry to say some of the pictured heatsinks are the epitome of new understanding and efficiency.
I don't think the air in the middle of the heat sink such as in #34 and #35 could remain stagnant. Any stagnant air in the center would continue to heat up, and therefore become lighter than any surrounding air (including that around the outer fins/pins/cones). It will therefore rise (within a gravity field), creating a lower pressure (partial vacuum, if you will) area beneath it, which will draw in surrounding air to equalize that pressure (advection). Air is a very low viscosity material. Hard to stop it from moving when subjected to pressure gradients. Now, I am not arguing that a heat sink with fins configured to allow free low-drag vertical flow of air across their surfaces is not superior, but in some designs the constraints may preclude using an ideal heat sink configuration.
The fractal-inspired one in #33 presumably was designed to be mounted with the channels oriented vertically. Assuming it is, I doubt the viscosity of air is high enough to prevent it from flowing through it in its attempt to equalize any heat-induced pressure gradients, but I'm not knowledgeable enough to provide an engineering analysis to support that.