I would greatly appreciate it if someone with knowledge of fluids could check my work.

 

Alex;

 

Nice work; and interesting.  It looks good to me; but my knowledge was too limited to verify the formula for the friction factor.

 

Typically our tube diameters are less than 2”; maybe 1 – 1 ½”, which increases the percentage difference a bit.  But also in the typical system the biggest chunk of pressure drop is through the radiator, where I think the velocities in the tubes may get up to more like 10 – 15 ft/sec.  It is interesting that using the model for small diameter tube with high velocity, the difference between the coolants decreases somewhat. That seemed counterintuitive.  I realize that a flat tube is different than the round tube model, but it still may give a clue.

 

Al