Pipesys (In Hysys) Cannot Comprehend Pressure & Velocity

[Iomcube]

I am having a problem comprehending HYSYS simulation results. Its a basic PIPESYS case involving three pipe segments of various lengths & at different elevations (graphs included). The outcome of two scenarios where only pipe DIA are changed is collectively shown in the PDFs..

I have created two PDFs one for 4in & the other 3in (each Schedule 40). Each file contain Inlet, Outlet, Composition & Overall Summary from pages 1-3 ...then from page 4-7 there are graphs only with visible values for viewers

http://files.engineering.com/getfil...7f95&file=Export_Pages_HYSYS-Print_4inSCH.pdf

http://files.engineering.com/getfil...974f&file=Export_Pages_HYSYS-Print_3inSCH.pdf

What I fail to understand are the results produced by the last scenario (3in Sch.40). The velocity profile & the pressure profile are but bizarre, when compared with first scenario? The stream in question is total Gas.

I am attaching the case file as well if someone want to reproduce results

https://www.mediafire.com/file/lem1hm1gmw3hm32/uk_2.hsc

 

[Latexman]

Bizarre? No. At 4", the effects of elevation on pressure are more pronounced than the lower pressure drop/length. At 3", the higher pressure drop/length are more pronounced than the effects of elevation on pressure. The velocity is just resulting from what is calculated from T, P and flow area. And, the scale on velocity of the 3" is 4.4X higher resolution so the changes seem more pronounced. Ditto on 3" flowing pressure but not as obvious (2X higher).

Good luck,
Latexman

To a ChE, the glass is always full - 1/2 air and 1/2 water.