ReplyKlove, where did you get the info on turbulence and flow on the condensor tubes? I am trying to get a better understanding of system operation under HX conditions and cold startups.
Regards to all, Controlnut[/QUOTE]
It's just one of those things you put together after speaking with a lot of equipment and system engineers, and seeing the reaction of equipment on countless startups and commissioning jobs. One of the great things about working with folks who were in research and development is that they had unlimited access to test facilities and they could give you minute details about what things do under certain conditions (even though they don't normally know how the overall system operates, that's our job). After awhile, you can start putting the pieces of the puzzle together out of sheer repetition, having seen how stuff reacts in a given situation.HHMMMMMM?
What I was speaking of in this case was pressure gradients on the refrigerant side of the condenser being caused by extreme temp differentials from inlet to outlet. Also, in a throttling situation, you almost always fall well below minimum flow rates on the HX. If your valve is on the outlet, your flow is very stable through the HX, but you also get a type of laminar flow due to greatly reduced water velocities. Some of this only comes into play after extended periods of operation under conditions outside the eqpt's design parameters, but not being there to actually see things, I've found it better over the years to throw it in and let you cull through what you don't need. In your case, with the valve on the inlet, you're creating turbulence before it hits the barrel, which aids in the water distribution through the tubes, regardless of how far below minimum recommended flow rate you may be. That's always a plus.
p.s. I also took what "triggerhappy" said about control guys not knowing what NPSH stood for as a compliment to you (I know guys who've been doing eqpt commissioning for years that don't know a pump curve from a shotgun). Many a truth has been spoken in jest.
Still Learning
Thank you for the additional information though, it is always appreciated. Peace triggerhappy, I actually did take it as a complement, and did not mean my reply as a comeback. It was just a statement. I did get my start in commercial, and then environmental controls. It still amazes me that control techs aren't taught more about system fundamentals before they are turned loose to control the world. Anyway, I wasn't offended, and thanks for your input as well. I don't have many postings, but I read on this board a lot, and have found the answers to many questions by searching previous postings. This is one of the few times that I actually needed to post in order to get more information. This is a great site. I have a little more confidence in what the engineer is requesting now. I guess his placing the tower too low for proper head on the spec'd condensor pump made me a little skeptical about his corrections to the system. 