I know higer flowrate means more water going through the cpu block faster, but it also means less time in the radiator.
Would there be a large difference between 100gph and 300gph, or maybe a couple of degrees??
Personal computing discussed
Moderators: renee, Starfalcon
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Q = m x Cp x Temperature rise
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m = V x 8.34 lb/gal
I know higer flowrate means more water going through the cpu block faster, but it also means less time in the radiator.
Buub wrote:I believe that you just proved that there is no minimum speed. Heat In = Heat Out.As long as the water is moving fast enough (i.e. above a minimum speed) it will carry and emit exactly the same amount of heat. Each cubic centimeter either carries a lot of heat slowly, or a little bit of heat fast. Either way, it's the same amount of heat in the end.
If the water flow is really low, then the heat losses to the inside of the case from the oustide of the fittings and tubing can become significant. Eventually, you will boil the water in the block.If it's moving too slowly, it can't get the heat away from the waterblock before excess heat builds up
I am confused by these "other losses." If the water moves too fast (say 30 ft/s), it can erode your tubing and fittings. You want it to move fast enough that flow is turbulent. (Avoid Reynolds numbers below 2100. 10000 to 100000 is good.)If it's moving too fast (which is not possible with the kind of pumps we use), there will be other losses involved that alter the picture.
An easy way to measure the actual flow is to run your return line into a bucket and use a stop watch.Now, the next issue is just how much flow you actually get. Standard pumps that are used in watercooling computers don't have a lot of head pressure (I believe that's the correct term). And watercooling systems are notoriously flow restrictive. This means you will actually get a lot less than your 100 to 300 GPH in real use. Maybe like 10 to 15 GPH in a really restrictive system.
This depends on what you mean by a "bigger" pump. For centrifugal pumps, larger diameter impellers provide more head. Thicker impellers provide more flow at the same head. Spinning the pump faster provides more head and more flow. Generally, flow through your system is probably proportional to the square root of the supplied head. Doubling the pressure supplied will increase flow by just 41%.putting in a bigger pump won't really give you very much more flow rate, because you're already at the limit of what the pump can supply at the head pressure your system puts it under.
The heat will flow at the rate that it is generated. Heat In = Heat Out. You really want a block that has a high overall heat transfer coefficient (low thermal resistance) and a large contact area between the cooling fluid and the block. A block that does not restrict the water flow too much is good because it allows a higher water flow rate. Since the heat source is a flat square, for a fixed inlet temperature and fixed block design, higher water flow will cause less temperature rise and therefore result in a lower CPU temperature.In general, in a water cooling system, you want heat moving as fast as possible through the water block. This means low-restrictive blocks are generally better.
The flow doesn't necessarily have to be slow. What you want is a radiator that internally has a fairly large surface area for the liquid to contact the radiator. At a given length, a large diameter pipe has more surface area than a small one, but you would like to keep the flow turbulent. Laminar flow does not transfer heat as well. A long run of small-diameter tubing has more area than a short run, but it is also more restrictive to flow than shorter or larger tubing. At a given supply pressure, total flow is about proportional to the square of the tubing diameter and inversely proportional to the tubing length.you want flow rate to be slower through the radiator so you can extract maximum heat. You don't want a restrictive radiator (cause that slows the whole system)
As long as the water is moving fast enough (i.e. above a minimum speed) it will carry and emit exactly the same amount of heat. Each cubic centimeter either carries a lot of heat slowly, or a little bit of heat fast. Either way, it's the same amount of heat in the end.
I believe that you just proved that there is no minimum speed. Heat In = Heat Out.
If it's moving too slowly, it can't get the heat away from the waterblock before excess heat builds up
If the water flow is really low, then the heat losses to the inside of the case from the oustide of the fittings and tubing can become significant. Eventually, you will boil the water in the block.
If it's moving too fast (which is not possible with the kind of pumps we use), there will be other losses involved that alter the picture.
I am confused by these "other losses." If the water moves too fast (say 30 ft/s), it can erode your tubing and fittings. You want it to move fast enough that flow is turbulent. (Avoid Reynolds numbers below 2100. 10000 to 100000 is good.)
putting in a bigger pump won't really give you very much more flow rate, because you're already at the limit of what the pump can supply at the head pressure your system puts it under.
This depends on what you mean by a "bigger" pump. For centrifugal pumps, larger diameter impellers provide more head. Thicker impellers provide more flow at the same head. Spinning the pump faster provides more head and more flow. Generally, flow through your system is probably proportional to the square root of the supplied head. Doubling the pressure supplied will increase flow by just 41%.
In general, in a water cooling system, you want heat moving as fast as possible through the water block. This means low-restrictive blocks are generally better.
The heat will flow at the rate that it is generated. Heat In = Heat Out. You really want a block that has a high overall heat transfer coefficient (low thermal resistance) and a large contact area between the cooling fluid and the block. A block that does not restrict the water flow too much is good because it allows a higher water flow rate. Since the heat source is a flat square, for a fixed inlet temperature and fixed block design, higher water flow will cause less temperature rise and therefore result in a lower CPU temperature.