perhaps its easier to understand with some numbers
it is (now) generally accepted that a higher (volumetric) flow rate through a wb will result in 'better' cooling
not 'more' cooling, not 'faster' cooling; it is actually decreased thermal resistance
- the higher flow rate, in a given wb, results in higher fluid velocity which increases the heat convection
rate
- as the convection rate increases the thermal resistance decreases necessitating a lower thermal gradient for the heat to move
- the decreased gradient results in a lower wb bp temp, which - given that the TIM joint's thermal resistant is a constant - then is seen as a reduction in the CPU temp
at 70W with a heat die (~ 100W per Radiate)
so what then is the effect of the same increase in the flow rate on the performance of the rad ?
this is a graph not in the original rad article but shown because it is the most (apparently) simple
[all of the revised graphs can be seen
here and were updated due to the incorrect calibration of the flow meter used; the article itself is several weeks away from completion]
the dissipation was calculated using the equation on pg 1 of the article
while a slight benefit (almost) always derives from higher coolant flow, it becomes appreciable really when accompanied also with higher air flow rates
what is not apparent is the coolant temperature drop across the radiator, which is in contradiction to the dissipation;
as the dissipation increases with an increase in the flow rate, so is the temperature difference between the inlet and outlet decreasing
from a system viewpoint this is not really so significant since the temperature rise across the wb is also decreasing as the flow rate increases
- except that a higher coolant equilibrium temperature is going to result, in turn raising the wb bp temp and the CPU temp
the way that this higher temperature can be avoided is by having substantial overcapacity in the radiator
changes in the capacity can most easily be visualized in terms of the coolant residence time
- the most simple would be to make the rad's tubes longer (2 rads in series), but this will increase the flow resistance
- a better approach is to add additional tubes (2 rads in parallel), providing the additional benefit of decreased flow resistance
must close for now as its WAY too late
be cool