I'm about to build an Aleph X using water cooled heatsinks for the first time. The heatsink will be machined from a 10" X 5" X 1" piece of copper block. 1/2" holes will be bored through the 5" long side and U shaped copper pipes will be silver soldered to these holes to complete the circuit back and forth through the copper block. I end up with one input and output for the coolant. Actually going the copper block route is much less expensive than buying new alumnium heatsinks large enough for this X. Copper cost is just under 50.00 U.S. for this size. Heatsinks at least a hundred dollars per channel for new, plus a long wait to get em. I can make each heatsink in a weekends worth of spare time.
All said and done I remember that Nelson mentioned in one of his posts that the output devices need to reach normal operating temperature for best transconductance and lowest distortion. My concern is that the water cooling may be so efficient that the O.P. devices may not get to optimum operating temp and best transconductance. Has anyone that has used water cooling out there experienced this problem at all? I suppose I could vary the water flow to achieve optimum device temperature, however the whole idea behind doing the water thing is to keep the room and the amp cool. It will also allow me to keep the amp much smaller as well. The X will be P to P wired right on the copper sink using those nifty turrett terminals that I used in my 2's. I can also mount the input devices to the sink and perhaps achieve better thermal equiliberium in a shorter amount of time as an added benefit.
Any comments or suggestions would be appreciated.
Mark
All said and done I remember that Nelson mentioned in one of his posts that the output devices need to reach normal operating temperature for best transconductance and lowest distortion. My concern is that the water cooling may be so efficient that the O.P. devices may not get to optimum operating temp and best transconductance. Has anyone that has used water cooling out there experienced this problem at all? I suppose I could vary the water flow to achieve optimum device temperature, however the whole idea behind doing the water thing is to keep the room and the amp cool. It will also allow me to keep the amp much smaller as well. The X will be P to P wired right on the copper sink using those nifty turrett terminals that I used in my 2's. I can also mount the input devices to the sink and perhaps achieve better thermal equiliberium in a shorter amount of time as an added benefit.
Any comments or suggestions would be appreciated.
Mark
About the only bright spot in my recent heat pump crisis was that I came out of it with two more heat exchangers, scavenged from the dead gear. Don't need them at present, but who knows what the future might bring?
Still need to buy a dedicated pump, though.
I haven't tried to modulate the temperature of my rig, but it's easy enough to do. Suggestions:
--Use a valve to reduce water flow. Disadvantage: you're loading the pump unnecessarily.
--Use a light dimmer to reduce the flow rate of the pump. The downside to this one being that the dimmer would throw hash into the AC line.
--Probably the easiest thing to do, at least for me, would be to place a piece of cardboard, wood, or fabric over the heat exchanger to reduce the air flow. Cheap, too. In my case, I'm still using passive air flow, i.e. convective. If you're using forced air, you could always vary the fan speed.
Given the thermal mass of my system, I'd have to wait at least twenty or thirty minutes for things to stabilize, possibly longer. Given the way that folks have to go at this, no two people are likely to have the same system. Because of that, anything I say has to be adapted carefully to any other system. Too much cooling won't hurt anything, but too little could be disasterous. So could water leaks, for that matter. So far, no problems here, though.
One thing I can say is that my system as it stands now easily dissipates the heat from four Aleph 2 channels (about 1200W of waste heat). I've considered the possibility of building an Aleph-X Verson 2.0 with a decent amount of power, but the project will have to wait for other projects to complete and for finances to recover.
Incidentally, I suppose that it goes without saying that the guys who installed the heat pumps were very, very interested in that funny looking heat exchanger with the braided water hoses coming out of it...
Grey
Still need to buy a dedicated pump, though.
I haven't tried to modulate the temperature of my rig, but it's easy enough to do. Suggestions:
--Use a valve to reduce water flow. Disadvantage: you're loading the pump unnecessarily.
--Use a light dimmer to reduce the flow rate of the pump. The downside to this one being that the dimmer would throw hash into the AC line.
--Probably the easiest thing to do, at least for me, would be to place a piece of cardboard, wood, or fabric over the heat exchanger to reduce the air flow. Cheap, too. In my case, I'm still using passive air flow, i.e. convective. If you're using forced air, you could always vary the fan speed.
Given the thermal mass of my system, I'd have to wait at least twenty or thirty minutes for things to stabilize, possibly longer. Given the way that folks have to go at this, no two people are likely to have the same system. Because of that, anything I say has to be adapted carefully to any other system. Too much cooling won't hurt anything, but too little could be disasterous. So could water leaks, for that matter. So far, no problems here, though.
One thing I can say is that my system as it stands now easily dissipates the heat from four Aleph 2 channels (about 1200W of waste heat). I've considered the possibility of building an Aleph-X Verson 2.0 with a decent amount of power, but the project will have to wait for other projects to complete and for finances to recover.
Incidentally, I suppose that it goes without saying that the guys who installed the heat pumps were very, very interested in that funny looking heat exchanger with the braided water hoses coming out of it...
Grey
Yea, actually that gave me an idea regarding the pump flow thing...... adjusting the intake of the pump rather than loading it down by limiting the output flow would be the better way to control via the pump. I believe that the pump should be allowed to run at its normal speed for best motor life anyway. The pump could also be controled with a small variac anyway and be practically noisless. I want to include a hall effect drive motor on my pump though for highest reliability. There will also be overtemp and water flow sensors as well.
The other idea that Grey pointed out and which I will most likely follow though would be to vary the speed of the fan with a temperature servo system fed back from the overtemp sensor. This would be by far the better route IMHO. It not only allows unimpeeded pump operation but it would allow me to actually have an operating temperature adjustment feature. I could set the operating temp of the X with a distortion analyzer and know when the 2nd harmonic is lowest that the best tranconductance point has been reached. I also do believe that the actual heat sink will end up running very cool to just warm to the touch while the chip/device temp is still actually quite hot. Fortunately I have quite a bit of experience with water cooling large film projectors and believe me all the water jackets are copper. Copper conducts much faster than alumnium does. Silver plating the copper substantially increases the heat conduction as well. A silver flash plating is also cheap to do. Coolant will be 50/50 antifreeze and distilled water. Antifreeze also helps drastically at increasing heat conduction.
Any thoughts on advantages/disadvantages of fastening the input devices to the sink would allow for faster DC offset and thermal stabilization? In fact perhaps making a plexi cover that is like a small shallow box to cover the entire parts side of the sink would also be to advantage....or simply potting the entire P to P circuit less O.P. devices....... Either of these would in effect allow every part to operate at the same temperature very quickly.
Mark
The other idea that Grey pointed out and which I will most likely follow though would be to vary the speed of the fan with a temperature servo system fed back from the overtemp sensor. This would be by far the better route IMHO. It not only allows unimpeeded pump operation but it would allow me to actually have an operating temperature adjustment feature. I could set the operating temp of the X with a distortion analyzer and know when the 2nd harmonic is lowest that the best tranconductance point has been reached. I also do believe that the actual heat sink will end up running very cool to just warm to the touch while the chip/device temp is still actually quite hot. Fortunately I have quite a bit of experience with water cooling large film projectors and believe me all the water jackets are copper. Copper conducts much faster than alumnium does. Silver plating the copper substantially increases the heat conduction as well. A silver flash plating is also cheap to do. Coolant will be 50/50 antifreeze and distilled water. Antifreeze also helps drastically at increasing heat conduction.
Any thoughts on advantages/disadvantages of fastening the input devices to the sink would allow for faster DC offset and thermal stabilization? In fact perhaps making a plexi cover that is like a small shallow box to cover the entire parts side of the sink would also be to advantage....or simply potting the entire P to P circuit less O.P. devices....... Either of these would in effect allow every part to operate at the same temperature very quickly.
Mark
Mark A. Gulbrandsen said:
Industrial applications that need to power down their pump, are always encouraged to use speed regulators instead of valves. Valves wil cavitate in the water flow, wear down and eventually need service. It produces noise in your water flow. Next to that, (but that isn't really an argument in Class A amps) if you run your pump with a speed regulator, it saves about 40 - 60% energy.
If you plan to use a hall effect motor (brushless DC machine) you can't use a variac to power down, because the motor is field-vector operated (hence the hall effect devices). You will need a field-vector speed controller. (e.g. complex switchmode stuff) Only normal asynchronous AC motors or DC motors can be used for voltage (current) control.
A simple aquarium pump with a variac or dimmer will work just fine
Bouke
Yes, I am aware that a Hall effect cannot be controled with a variac. The Hall motors require their own specialized control circuitry. Fortunately I have a bit of experience with them.
Gary, Installing a heater in line is probably not the route that I'd go but I do know what you're getting at. Although the temp feedback would be a bit more complicated it would serve to do two things....sense over temp and shut the amp down in that condition, and it would be the feedbck element in the temp. control circuit...so no clixon sensor would be needed. Water flow loss is another option but in a closed circuit very little water is lost.
Mark
Gary, Installing a heater in line is probably not the route that I'd go but I do know what you're getting at. Although the temp feedback would be a bit more complicated it would serve to do two things....sense over temp and shut the amp down in that condition, and it would be the feedbck element in the temp. control circuit...so no clixon sensor would be needed. Water flow loss is another option but in a closed circuit very little water is lost.
Mark
Car engines are water-cooled, have an optimum temperature, and are well proven.
They use a thermostat valve at the block outlet, killing flow to the radiator when cold. A leak in this valve keeps a small flow through the radiator to keep it wet and perhaps to reduce cavitation. A passive bypass circulates coolant around the block while cold to prevent hot-spots and to limit pump cavitation. The radiator fan is often thermo-controlled, though this may be because the car has "free air" at 60MPH, can be climbing a steep grade at 5MPH, and the radiator space is limited.
I don't think your transistors' optimum temperature is anything like a car engine, and your puny 1,200 watt cooker is far smaller than the 50,000 watts that can come off a car engine, so I doubt you should actually use car parts.
There are bathroom shower controls that will take hot and cold water and give a mix of warm water at nice body (or transistor) temperature. I have not dissected one. Is it possible that if you pumped heat-block water into the "outlet", it would split water to a radiator on the "Cold In" and a bypass on the "Hot In" connections, and hold block temp similar to set-temp? Low cavitation, minimal leaks, standard hardware-store part, easy-trim hand-knob.
Dead-loss is another way to go. Run water through the block and out the window or into a drain. Yes it is inefficient, BUT the cost and global pollution of the total water you will use is perhaps no more than the water and energy consumed to manufacture pumps and radiators (and dwarfed by the electric bill). You lose the geeky "funny looking heat exchanger" that fascinated your HVAC dudes, you gain an annoying drain line to "somewhere", but the system could run at nearly zero pressure, throttled at the water source. (I know, then you don't have the "braided water hoses" to amuse the HVAC guys.)
I think most small-production heat exchangers are copper not for cooling, but because fresh water rots aluminum even more than copper, and Al is a real pain to solder and not a welder's delight (or not in thin sheets). Certainly for a water-air exchanger, the limit is all about the air, not the metal. Aluminum is a heck of a lot better than air; we used copper radiators because they rot slowly and can be repaired with a torch. Then the car makers realized that price was key and repairability was bad, and the coolant additives improved, so car radiators went to aluminum. I don't see any difference in performance, and if you use the good additives they seem to last 9/10th as long as copper. Then you throw them away, but repairing small copper has gone out of fashion too. These are all reasons you should use copper, of course: fabrication labor exceeds material cost and copper allows simple techniques and less labor; you don't want strange corrosion inhibitors dripping in the good rug.
They use a thermostat valve at the block outlet, killing flow to the radiator when cold. A leak in this valve keeps a small flow through the radiator to keep it wet and perhaps to reduce cavitation. A passive bypass circulates coolant around the block while cold to prevent hot-spots and to limit pump cavitation. The radiator fan is often thermo-controlled, though this may be because the car has "free air" at 60MPH, can be climbing a steep grade at 5MPH, and the radiator space is limited.
I don't think your transistors' optimum temperature is anything like a car engine, and your puny 1,200 watt cooker is far smaller than the 50,000 watts that can come off a car engine, so I doubt you should actually use car parts.
There are bathroom shower controls that will take hot and cold water and give a mix of warm water at nice body (or transistor) temperature. I have not dissected one. Is it possible that if you pumped heat-block water into the "outlet", it would split water to a radiator on the "Cold In" and a bypass on the "Hot In" connections, and hold block temp similar to set-temp? Low cavitation, minimal leaks, standard hardware-store part, easy-trim hand-knob.
Dead-loss is another way to go. Run water through the block and out the window or into a drain. Yes it is inefficient, BUT the cost and global pollution of the total water you will use is perhaps no more than the water and energy consumed to manufacture pumps and radiators (and dwarfed by the electric bill). You lose the geeky "funny looking heat exchanger" that fascinated your HVAC dudes, you gain an annoying drain line to "somewhere", but the system could run at nearly zero pressure, throttled at the water source. (I know, then you don't have the "braided water hoses" to amuse the HVAC guys.)
I think most small-production heat exchangers are copper not for cooling, but because fresh water rots aluminum even more than copper, and Al is a real pain to solder and not a welder's delight (or not in thin sheets). Certainly for a water-air exchanger, the limit is all about the air, not the metal. Aluminum is a heck of a lot better than air; we used copper radiators because they rot slowly and can be repaired with a torch. Then the car makers realized that price was key and repairability was bad, and the coolant additives improved, so car radiators went to aluminum. I don't see any difference in performance, and if you use the good additives they seem to last 9/10th as long as copper. Then you throw them away, but repairing small copper has gone out of fashion too. These are all reasons you should use copper, of course: fabrication labor exceeds material cost and copper allows simple techniques and less labor; you don't want strange corrosion inhibitors dripping in the good rug.
And that's a fairly small car engine. Typical rule of thumb of fuel energy disbursement for full load operation is 30% out the crankshaft, 30% as heat out the exhaust, 30% out the radiator and 10% lost as friction and pumping losses. So for a 200kW engine (not unusual in a lot of places), that 12 inch x 24 inch heatsink incorrectly called the radiator has to dump over 200,000 watts sometimes.PRR said:
That would give your loungeroom something to think about!
Why not use one of those computer water cooling kits. This Cooling System is said to be able to handle 400 watts and has a control system using a probe that could connect to a water cooled heat spreader like this one . This set up should be able to cool a good sized Aleph X.
> 30% out the crankshaft, 30% as heat out the exhaust, 30% out the radiator
ooops. I took 30% but applied it to brake power, and should have applied it to developed (inside the cylinder) power, or just remembered that the hot-water is similar to the crank power.
> a 200kW engine
What we Yanks would call a 260 Horse engine.
Small quibble: a 260-HP passenger car does not get a 260-HP cooler, because there is nearly no way you can apply 260 HP for more than a few seconds safely or legally. Sanely-driven cars just don't need big power except in short spurts. Average power is under 50HP, and I gather that 100HP of cooling is usually ample. If you held 260HP, or anything much over 100HP, on a flat road, you would soon be doing 120+MPH, which even if legal is not safe in many of the US muscle cars of the 1970s. Anyway at 120MPH you get good cooling. Hill-climbing can demand full power at low air-speed, but cars of this class can't find a hill steep enough. Trailer-pulling can and does overheat 260-HP cars.
A truck with 260 rated HP will be using 200+HP a lot of the time and will have a far larger cooler than a 260-HP car.
> that 12 inch x 24 inch heatsink
More like 17"x28" in my last few V-8s. That's the size of the hole in the front wall, not the size they needed. My V-8 were rated "200", 130, 144, and 137HP, but they were in frames that sometimes housed "350HP" and "400HP" engines (heck, they once offered the 600-HP SOHC 427 dealer-option in my T-Bird frame). The high-HP versions got 3-row radiators stock, 4-row for trailer and police option, and just 2-row with my tame engines. Even the 2-row seemed to be more than enough for the Burd, which never overheated in the worst abuse unless it had dropped all of its water.
You may be right that my current Honda Accord is only a 12"x24" cooler, but it's just a motorcycle engine dressed up in car clothes. (And 6 more horses than my mighty 5.8L V-8 T-Burd. And less heat rejected to the world for every horse delivered to the wrong wheels....)
ooops. I took 30% but applied it to brake power, and should have applied it to developed (inside the cylinder) power, or just remembered that the hot-water is similar to the crank power.
> a 200kW engine
What we Yanks would call a 260 Horse engine.
Small quibble: a 260-HP passenger car does not get a 260-HP cooler, because there is nearly no way you can apply 260 HP for more than a few seconds safely or legally. Sanely-driven cars just don't need big power except in short spurts. Average power is under 50HP, and I gather that 100HP of cooling is usually ample. If you held 260HP, or anything much over 100HP, on a flat road, you would soon be doing 120+MPH, which even if legal is not safe in many of the US muscle cars of the 1970s. Anyway at 120MPH you get good cooling. Hill-climbing can demand full power at low air-speed, but cars of this class can't find a hill steep enough. Trailer-pulling can and does overheat 260-HP cars.
A truck with 260 rated HP will be using 200+HP a lot of the time and will have a far larger cooler than a 260-HP car.
> that 12 inch x 24 inch heatsink
More like 17"x28" in my last few V-8s. That's the size of the hole in the front wall, not the size they needed. My V-8 were rated "200", 130, 144, and 137HP, but they were in frames that sometimes housed "350HP" and "400HP" engines (heck, they once offered the 600-HP SOHC 427 dealer-option in my T-Bird frame). The high-HP versions got 3-row radiators stock, 4-row for trailer and police option, and just 2-row with my tame engines. Even the 2-row seemed to be more than enough for the Burd, which never overheated in the worst abuse unless it had dropped all of its water.
You may be right that my current Honda Accord is only a 12"x24" cooler, but it's just a motorcycle engine dressed up in car clothes. (And 6 more horses than my mighty 5.8L V-8 T-Burd. And less heat rejected to the world for every horse delivered to the wrong wheels....)
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