Good day.

I am doing a hydraulic calculation to check the pressure balance and flow distribution in a closed loop cooling water system. I am using the as built isometric drawings for the pipe length and the K-Factor method for the pressure loss calculation in the line.

I have attached a simple diagram to further illustrate my queries.

For my question, assuming:

a. distance from point 1 to point to 2 is the same for Figures A and B

b. Figure A tee main and pipe has the same schedule number and the tee is standard (non-reducing tee)

c. flow rate from point 1 to point 2, for figures A and B, is the same

d. no other fittings in between point 1 and point 2 for both figures A and B.

I checked one website (http://www.freecalc.com/fricfram.htm) and compared the difference if I specify one piece of "tee-flow through" for a length of 100m and resulted in a 0.13psi difference in pressure loss (with all inputted data to be the same for both calculations made: 11275GPM, 100m of 24" schedule 40pipe).

Question #1: If the branch line is closed and no flow goes to the branch line (as shown in figure A), is it just the same as the flow through a straight pipe (as shown in "Figure B" in terms of total friction loss? Or, expressing my question in another way, do we expect to have the same pressure at point 2 for both Figures A and B?

Question #2: If the pressure at point 2 in Figure A is different in Figure B, what causes this difference, considering the assumptions stated above, if we are only considering the flow from point 1 to point 2? (The online calculation showed this difference)

In addition to the investigation made on the online calculation, I also noticed that in some hydraulic calculation software (that we are using), there are several options for a tee: tee-through (or run), tee-branch. It seems that different considerations are made in the k-factor depending on the flow in the tee. I am not sure if it would really matter I specify straight pipe instead of specifying "tee-flow through".

Your point-of-view on this will be appreciated. Thank you very much.

**Edited by E-Tantoy, 19 August 2012 - 08:34 PM.**