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Unread 07-16-2002, 12:23 PM   #5
myv65
Cooling Savant
 
Join Date: May 2002
Location: home
Posts: 365
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Quote:
Originally posted by ECUPirate
I thought about trying to do a block like that, but here are two considerations.
1) the flow through the channels will be very laminar = bad.


Ah no. Not sure where you get your info, but for internal flows, the crossover occurs at a Reynold's number of about 2300. Re = rho * V * D / mu. With rho = 1000 kg/m^2, V ~ 1 m/s, D = 0.05 m, and mu = 0.001 N-s/m^2, Re ~ 50,000 which is well into the turbulent region. Laminar internal flows require extremely low velocity.

Quote:

2) If I made a block like that, I'd switch the ins/outs so that they are on opposite ends. As it is, the channels closest to the ins/outs will get the highest flow.
Maybe, but probably not. This one is very counter-intuitive, but the flow would probably be highest at the tube farthest from the entrance/exit. I work with manifolds much like this and test many in a lab. In this arrangement, flow would darn near stagnate in the first couple of cross tubes.

As to BigBen2k's original question, it comes down to velocity and surface area. Them's that provide high velocity (good convection coefficient) and lots of area (q = h*A*delta-T) win. With enough pressure, direct impingement puts a high velocity jet right above the core. Performance drops with a weak pump. Some low-loss designs can make great use of surface area, but don't get great velocity. The real trick is matching a block to a pump without buying more pump than you need.
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