Would a linear relationship between pump speed and the flow rate from the pump be expected?

I am building a water cooling system for my pc whereby the water can be individually redirected to each of the three individual graphics cards depending on temperature. Can the relationship between flow rate and angular velocity be expressed thusly so that I can then to proceed to solve for K or is the relationship more complicated? Thanks. :

$$\frac {dV}{dt} = kA$$ (where A is the angular velocity of the impeller and k is a constant)