Posted by Joe on April 20, 1998 at 12:42:09
In Reply to: Radiator Flow ?
posted by Bob Johnson on April 20, 1998 at 11:24:05
: So what do you guys think ?
Interesting concept but your flow calculations do not include the effects of the external loop, specifically the pump, hoses, passages through the block, etc.
The flow rate you have determined by your method is the flow with only the hydraulic head of the height of the radiator as the motive force.In real life, some (perhaps all) of this head is counterbalanced with the standing column of water that exists on the engine side of the loop.Flow through the radiator may be less than you test on this account.
Another factor you haven't considered is that of Net Positive Suction Head (NPSH) of the pump which in other words is the suction "pull" that the pump is able to impart in the suction eye on the water.Flow through the radiator may be beyond what you calculate in your method due to NPSH without pressurising the upper tank.
Also, the external coolant loop through the engine block itself may be the largest area of hydraulic resistance.You are assuming in your testing that the radiator is the sole source of hydraulic resistance in the circuit, which it is not.
However, the external loop being the same in both cases, you can make some valid comparisons.But, be careful.You have to consider the entire system to adequately model what is going on.And this really should include the airflow side too.