Mainly do dust collection - 50 to 100 inlets through branches to one outlet (such as a fan).. If we know the outlet properties, can I get flow rate? Are there any limitations to the amount of inlets/outlets?
Answer:
We believe that this question would relate to the fact that there has to be an equal amount of known and unknown boundary conditions. There is some confusion on whether the amount of inlets vs. outlets has limitation.
If I know the flow rate, does PlantFLOW have the intelligence to tell me how many restrictions I will need in my model geometry?
PlantFLOW can be used to test geometry configurations by running an analysis and calculating the pressure drop in each component. However, it will not tell a user how to model the geometry based on the the needed results and inputs.
If my pipe is outside at something like 100 deg C, can I input insulation, etc to calculate heat loss?
For buried and exposed pipe, the user has the option of using a simple or complex heat transfer model. A complex type takes into account the effect of the pipe material and insulation. The last column in the "Component-Flow Report" seems to represent the calculated value of heat flow.
Fluid library - for sewage disposal, is there any way to input the size and density of the solids that will be floating in fluids?
PlantFLOW does not have the ability to do this. The user has to define the liquid in the pipe and cannot do two-phase flow.
Can PlantFLOW analysis the Vacuum pipe with negative pressure??
From online help:
Static pressure: Enter the absolute static pressure at this point. Negative values are not allowed.
As we know we can insert a heat exchanger in PlantFLOW. Can PlantFLOW analyze heat exchanger performance or recommend the configuration of heat exchanger to meet the requirements.
In PlantFLOW, a heat exchanger is modeled as a component with specific properties.
With regards to analyze heat exchanger performance, perform multiple analysis making changes to the model as required to evaluate the performance of the heat exchanger.
With regards to PlantFLOW recommending the configuration of heat exchanger to meet the requirements, this cannot be done with a simple heat exhanger element.
What are the other two pressures (in Ctrl.pts and Initial ones) and what are relations between them?
The initial flow and pressures are a starting point for nonlinear iterations. These are used for elements which you did not specify input for in the control points. Usually the initial data should be an average expected value for the all elements.
What gives the maximum effect on dynamic pressure shown in output report (gas system)? It seems it is the "Base" one (Standard conditions), why?
The dynamic pressure is based on the actual fluid density and velocity upstream of the element.
Can PlantFLOW model on Newtonian fluids (similar to "Yogurt")?
Bentley apologizes for the inconvenience, however there is no modeling approach in this version of the program (Version 06.02.00.05)
Is it possible for Plantflow to accurately simulate saturated steam flow in a long pipe? Or does any sort of condensation invalidate the whole solution?
Bentley apologizes for the inconvenience, however this version of the program (Version 06.02.00.05) 1) of PlantFlow only handles single phase flow, so if there is a situation where there is a phase change, then the results will no longer be valid. If there is heat transfer, then we can run into this situation, without the heat transfer, we are "probably" ok.
The pressure drops for 2 phase flow are totally different than for single phase. If you have 2 phases, you need to take into account how much space the liquid takes up in the pipe, if it’s not horizontal, you have other issues, etc, etc, etc. PlantFlow doesn’t handle this. There is a part of the help file that says this (I put the stuff in bold as being the most important part):
Phase Change Handling
PlantFLOW solver assumes a single phase system. If phase change was detected, this would automatically invalidate all or part of the solution. PlantFLOW checks for correct phase at input and output as follows:
How to model a piping cross?
The junction cross point should be modeled as 2 Tee’s, separated by a very small distance, because no losses can be calculated for a 'cross' element.
Please see the following PlantFLOW help section for more information: Help > Search> Type in the key words> Cross.
Select topic to display:
Crosses, Example model 4, and Example model 4A.
In the system attached, I know that the flow is 14 gpm inlet for each tank. I also know that pressure at the outlet of the tanks is 14.4 psia. However, the piping downstream cannot handle that much flow as the outlet is at atmospheric pressure and the piping has very little slope. My problem is this, if I take the tanks out and put the known pressures at the piping inlets and outlet, I get a very high flowrate that does not reflect reality (granted this could be due to another error in my model). I am trying to find a way to input the flowrate into the tanks as well as the pressure downstream without overspecifying controls or creating an unstable system.
In this particular users model:
Pressure was specified as atmospheric at outlet I13 and also at DR52 which is upstream. This cannot be the case since there no pressure change to drive the flow.
Also specifying flow rates may be unrealistic for tanks, since the elevation is usually what controls in that case. The consumption may drive flow into the pipe or make the water level rises and so it is not appropriate. The water level is what drives the flow. PlantFLOW does not give you the change in elevation as a function of time, you would have to solve for different levels and evaluate that.
When working with water it is best to work with pressure units of ft of water. You can change that under Tools/Units and change the abs. pressure unit (not pressure drop) to ft.H2O. Atmospheric pressure would be 33 ft.
I computed the elevation head between outlet and the two inlets and then added that to 33 ft to get 55 ft and 61 ft of static pressure (absolute).
In this system, there are one inlet and 48 outlets. They’ve defined both pressure and consumption for Inlet and defined consumption for 47 outlets. The problem is how they properly assign consumption for each outlet. Right now, they define it according to the size of pipe but not sure if it is correct. Do you have any recommendation?
PlantFLOW does not have a better way since this is system dependent. If the pressure is known, it may be better to set pressure instead.
Why is PlantFLOW unable to calculate a simple system with one inlet with two outlets. What they really want is they know both pressure and consumption for inlet, and want Plantflow to calculate pressures and consumption for both outlets. I know our rule is no of K’s = no of Unk’s. Is there a way to explain why we need this? And is there a way to figure out if user doesn’t really know for both outlets? What is the industry standard practice for this case.
Usually you can solve for the two outlets if enough conditions are specified, in your case you need one more condition which could be consumption or pressure at the outlets. For example if they think the flow is split equally, they can enter a consumption at one outlet. One thing we do not have in PlantFLOW is the ability to set two outlets to have same unknown pressure or consumption. But ultimately you need 3 equations or conditions to solve for 3 unknowns and there is no way around that.
when modeling in PlantFLOW, I am unable to connect a loop pipe back onto itself, why?
This is a limitation with the application, you will need to insert a new segment from the last node point before connecting back to the segment essential the added segment will close the pipe loop.
Example: Connecting A21 back to A01
1. Select A01. Modify> Convert Point> Run.
2. Select A21, Insert> Segment> press ok button.
3. Insert> Run> Name of point = A01.
4. Enter data for Tee, press ok
5. Segment will then connect and the loop will be complete.
I’m trying to model a seawater intake chambers with two rectangular pipes. Is there’re any way I can model a square straight pipes and bends (fitting losses) using PlantFLOW?
Yes, select a pipe with the same equivalent hydraulic radius for the square pipe / duct. search Google:
http://www.google.com/search?sourceid=navclient&aq=8&oq=hydraulic+radius&ie=UTF-8&rlz=1T4SKPB_enUS271US271&q=hydraulic+radius+of+a+rectangle
For pipe fittings:
Miller, Internal flow systems, 2nd Ed. includes charts for rectangular ducts. PlantFLOW did not implement these charts. But based on the comments on page 78 and charts on page 211-213, the losses are not much different between rectangular and circular ducts for bends. The user can override any loss by entering a user loss factor.
PlantFLOW uses charts in Miller for circular pipes
The PlantFlow is limited to 900mm pipe diameter only, how to model 1,300mm pipe diameter?
The 900mm is the last standard size any bigger size has to be entered as NS (Non Standard) and the actual value given.
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