Line balancing multiple diamaters

[Mastert1]

I have a fluid dynamics question.
If I start with a 3/16" dia line then step it up to 3/8" will I lose any slowing of the flow I achieved from by 3/16" line, from a line balancing standpoint?
In other words, will the beer in the line speed back up in the 3/8" line?
thereby making any length of 3/16" line I have at the beginning of the system irrelevant to the final flow rate?

I ask because it seems to be the case in my system that the first line length doesn't have a noticeable effect on my balancing. I think in the end I got a trunk line that was too large.

Check out the included pic of my system. Not to scale.

 

[chris000]

look at the pressure drop from transition point to the next to see how much you want to loose (and subsequently calculate the length) of the 3/16:
how much pressure do you want for the type (time) of pour?
how much are you loosing in the fixed system?
how much do you have in the keg?
how much are you loosing due to static pressure (height)?
how much is then left over will give you the length of line you need

 

[day_trippr]

Woof. Yeah, 3/8" ID tubing was an epic error.
Check out the only beer line calculator worth using and plug your .375" in.
300+ feet would work

I would be inclined to essentially ignore the trunk line and its ridiculously low resistance, focus on the 3/16" choker, start with 12' of line and see what happens.

The flow rate certainly will not "speed up" in the trunk line, in fact its velocity will be slower than through the choker...

Cheers!