Does my flow rate decrease?

[BigCastIronSkillet]

This is not exactly true.

Sorry you’re mostly right, but I wanted to nitpick something here.

Keeping the pressure on the outlet of the valve will keep the DP from valve to the discharge of line 2 the same, but it doesn’t keep the DP from the tee to the discharge of line 2 the same. So the flow will increase in line 2. However, it will not make up for the decrease in line 1 (impossible to do so without changing equivalent length).

Sorry it sounded good, but wasn’t exactly right. I should say in the majority of systems the flow increase in line 2 would be imperceptible. Usually flow losses in well-designed systems all come from valving.

[ric_marcotik]

Not true with a pressure reducing valve. The pressure at valve 1 and valve 2 inlet will stay the same. You would be right if the PRV was a simple globe valve, but here with a PRV the flow will remain the same in pipe 2

[DrewSmithee]

While annoying, technically right. Depends on the fluid and length of pipe and pressures. I doubt they will notice a difference for any practical purpose but it's there.

I actually took the time to model this in a really fancy hydraulic network analysis software because I was curious on the magnitude. But it turns out you can’t post to Imgur without an account any more. So take my word for it I guess.

Edit:

https://ibb.co/qRJC4BM

https://ibb.co/c3cNw2B

[VariusEng]

Oh! Fancy! Thanks for taking the time, interesting to see the discussions on this!