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MEP 2013: Duct Flow = Multiple Values l/s

40 REPLIES 40
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Message 1 of 41
Schmit01
3669 Views, 40 Replies

MEP 2013: Duct Flow = Multiple Values l/s

Ok so the new air flow breakdown of a single duct is a nice update when when checking my Flow and velocities. But besides having to place a damper and measure its flow at a point, how am I suppose to tag a duct now indicating its flow without getting "Multiple Valuel/s"?

 

Ryan 

South Africa

MEP 2013

40 REPLIES 40
Message 21 of 41
dave.short
in reply to: Martin__Schmid

Martin , we need to be able to size individual duct branches and at least see the actual cfm at each piece of ductwork in the properties REVIT MEP 2013 software does not allow us to do this.  The multiple values to me is an error.  Am I missing something?   

Message 22 of 41
asommer
in reply to: dave.short

You are not missing anything, but it is not an error.

 

If you have a single diffuser placed at the end of a branch (not tapped into the side of a branch), the values are absolute.  However, if you tap into the middle of a duct run, that duct run has different values (a value for up-stream of the tap, a different value down-stream of the tap), hence the "Multiple Values" issue.  If you create a new plan view of duct, apply a color fill to the duct, set up the color fill legend for static pressure or velocity.  You can then see what Revit is trying to do.  I understand why, but it did change the way we look at the duct systems (we used schedules with conditional formatting on the Static Pressure and Velocities).  We are now using the color fill to check Static Pressures and Velocities.

 

I would definitely agree that a "Maximum Value" could be applied to the instance properties of Duct and Piping.

Message 23 of 41

Fellow Designers and Autodesk consultants,

 

In our company, here in Brasil, we do use the flow parameter in the tags and the schedules for use them in sheets and project documents. I think this is an backwards evolution for the software. If there exists multiple values for flow and friction parameters, the software must show all of them to the user and not an general information like "multiple values". We do like the software for the presentation and others features like the mechanical and electrical functions and for this we stay use the software. Autodesk can not simply accommodate itself while other softwares evolve. I hope to read an consultant answer like "We will work to develop an upgrade to this version to fix this problem." and not an aswer like "Unfortunately the software does not give that information anymore". Give us the min Flow and the max flow in the sections, for the love of god.

 

I hope.

 

Diego Perez

Executive Officer

Arquimedes Engineering LTDA

 

 

Message 24 of 41

Diego-- how do you use flow in a schedule... what does it help you accomplish?

 

As I read through the thread here, there seem to actually be three separate concerns:

 

1.  I would like to be able to tag the flow/velocity/reynolds number/friction (etc.) at any point on a tapped duct/pipe, and get the value at that location, so I can properly document the computed values


2.  I would like to be able to easily find any cases of duct/pipes that exceed a velocity or pressure drop per length, because I need to be able to quickly find issues in my project


3.  I want to be able to select and easily see the flows in a tapped duct/pipe, so I have an idea of what design constraints I may have if I need to make a modification 

 

There are all logged for consideration for future development,.



Martin Schmid
Product Line Manager
Mechanical Detailing and Electrical Design
Architecture, Engineering, and Construction
Autodesk, Inc.

Message 25 of 41

Thanks for your time Martin. I really hope this problem does not exist anymore in the next version. But I'd really like to see this resolution in an Upgrade for Revit 2013. Is it not possible?

 

Diego Perez

Message 26 of 41

Question: Diego-- how do you use flow in a schedule... what does it help you accomplish?
Answer: Most of our clients like to check this parameters with their Engeneering Department in a quick way. We put these informations (like tags and schedules) in the sheets and we have an excelent return from our clients about which is the best presentation way in our projects and this is one of our diferentials here in our country. And I tell you that one of the points that made us to choose to buy the Revit was this one, because the software speeds up the presentation process.

 

Thanks for your concern.

 

Diego Perez

Message 27 of 41

How does having a list of ducts with their flows help a client's engineering department?  What is it that they are checking? 



Martin Schmid
Product Line Manager
Mechanical Detailing and Electrical Design
Architecture, Engineering, and Construction
Autodesk, Inc.

Message 28 of 41

Unfortunately, for reasons both technical and non-technical, it is not possible to upgrade wihtin a version. 



Martin Schmid
Product Line Manager
Mechanical Detailing and Electrical Design
Architecture, Engineering, and Construction
Autodesk, Inc.

Message 29 of 41
al.armiger
in reply to: dave.short

...and the list of groups that have developed workflows around these parameters grows.

 

Whether they be used by internal or external clients and to what purpose is immatetial, there is (as seen by the ever growing thread) a value to this information being available.

 

We await a potential return of the parameters in 2014.

 

Al

 

Message 30 of 41
Martin__Schmid
in reply to: al.armiger

Hi Al,

 

I understand where you're comming from, and if I were you, I'd probably be quite tired of me asking 'why' as well.

 

However, the propose to how someone uses a proposed functionality is very important, and asking why helps identify how to best solve the workflow, or workflows, that someone is hoping to achieve.

 

If we take the scheduling case, for example, we could solve the problem by simply putting the multiple values in the schedule cell as a concatenated list of values... for example: "300; 400; 500".  However, if someone is exporting this data from the schedule to a 3rd party software, having concatenated values like this may be less useful than if we were to come up with a better way to provide the data.  Someone may be interested in the 'minimum' flow for ensuring particulate matter doesn't settle in the air or fluid stream... whereas someone else may be interested in the 'maximum' flow to avoid excessive pressure drop or noise.  Or, the client may be using the raw schedule data as input to a hydraulic analysis software that if we partnered with directly, could potentially have a much better workflow of sharing the data.

 

We're not asking question to suggest that we don't understand there is value in having this information avaialble.  We're simply asking to make sure that we have all the cases covered in the three I listed previously, or if there might be a 4th, 5th, or 6th usage of the data that hasn't been surfaced as of yet.



Martin Schmid
Product Line Manager
Mechanical Detailing and Electrical Design
Architecture, Engineering, and Construction
Autodesk, Inc.

Message 31 of 41

Question: How does having a list of ducts with their flows help a client's engineering department?  What is it that they are checking?

 

Answer: Here in Brazil, we have certain technical standards for flow and noise that are verified by these engineering departments and our business customers like to check these parameters. If any flow is outside the norm can cause liability lawsuits against the company. So in my company we maintain this standard to let the customers satisfied. We pay dearly for Revit and so I make it clear that it was a setback for us.

Message 32 of 41
al.armiger
in reply to: dave.short

Don't we all love a good robust discussion!!

 

I understand there needs to be justification for bringing these back too and in what form.

 

From the current thread i would say that the users would like to be able to:

 

  1. New functionality: Tag the flow/pressure at a given point on a duct: The data exists as the colourised flow views use this data.  (rather than a concatanated list)
  2. Return of old functionality: Schedule the Min and Max values. The data exists only within the conenctors (i believe) atm.

Al

Message 33 of 41
stromhawk
in reply to: Martin__Schmid

"The only way that you could populate a 'maximum flow' parameter on a duct element would be to use code (via the API) to dynamically ... update such a parameter by extracting the values from each connector, and finding the largest."

Martin,

Could you give us a few details about how this could be done, or at least point us to some tutorials so that we can learn how to add that 'maximum flow' parameter using the API?

I work for an MEP consultant firm, and we recently began our first 2013 project.  Like others here, I too was greatly annoyed to discover this 'multiple values' issue in duct segments with taps connected.  I understand why this was done, but it doesn't seem like Autodesk thought through the implications of this change.  Regardless of whatever functionality was added, the fact remains that in 2012 I was able to select a duct with taps and see it's total flow, and with 2013 I can't.

 

I want to learn how to add this duct parameer using the API, and if I'm successful, I'll post the solution here.



Message 34 of 41
%4seasons%
in reply to: Martin__Schmid

Hi Martin,

 

In my case I use these values in schematic diagram.

 

Version 2014 was already released but the issue is still there. When do you think we can have a solution to this? In the meantime, can you give us a "link" on how to extract this values.

Message 35 of 41
Martin__Schmid
in reply to: %4seasons%

Unfortunately, I can't comment on when I think this functionality will be improved, however, here is a sample code snippet that will look at all connectors on the duct, and find the maximum flow.... you can run this in the macro editor to verify.  There are samples in the RevitSDK.exe (on your install dvd/image) for how to create parameters... so with that, and this example, one could concivably come up with a tool to automate the process of populating the duct with a parameter/value.

 

         public void MaxFlow()
        {
            UIDocument uidoc = this.ActiveUIDocument;
    
            SelElementSet sel = uidoc.Selection.Elements;
            foreach (Element e in sel) 
            {
                Autodesk.Revit.DB.Mechanical.Duct d = (Autodesk.Revit.DB.Mechanical.Duct)e;
                double flow = 0;
                foreach(Connector c in d.ConnectorManager.Connectors)
                {
                    if(c.Flow>flow)
                        flow = c.Flow;                    
                }
                
                Units u = uidoc.Document.GetUnits();
                string result = UnitFormatUtils.FormatValueToString(u, UnitType.UT_HVAC_Airflow, flow, falsefalse);
            }
        }



Martin Schmid
Product Line Manager
Mechanical Detailing and Electrical Design
Architecture, Engineering, and Construction
Autodesk, Inc.

Message 36 of 41

Martin,

I've noticed in this thread you have repeatedly asked why.  Please allow me to walk you through a typical scenario I might encounter on a project:

 

I have an air handler feeding 50 terminal units.  I've done the original design and sized my ductwork according to my design standards, but later on in the project something changes and I need to add 5 more terminal units on the job and I need to adjust the airflow of 15 of those initial 50 boxes.  I'm interested to find out how that additional airflow impacts my supply mains.  In 2012 I needed only to click on the section of duct in question and it would tell me all of the characteristics of that duct i wanted to know, and if necessary I could resize.  

 

In 2013, under the same scenario it seems your options are limited.  One would seemingly have to find each terminal unit on the main and add them up manually.  If there are a lot of terminal units downstream of the duct in question, this could be a very tedious process, adding lots of time and possible human error to a process that was instantaneous in 2012.

 

So far, the only work around i've come up with I believe has been suggested in this thread and others (or some variation).  Basically i just need to create a section of ductwork upstream of a tap that does not have any taps associated with it.  If would seem that if a section of ductwork has no taps, it can tell you the total airflow on the duct.  So, if I put an elbow on the duct upstream of the tap, I can take that untapped section of duct to learn the airflow characteristics at that point.  It's an added couple of steps, and might not always be an option but it works in a pinch.

 

Just thought I'd share.

-Eric

Tags (1)
Message 37 of 41
%4seasons%
in reply to: EMill311

For those of you who are desperate to check the duct properties at any point of the duct length, you can add 2 split element in between duct branches or 1 if there is a transition (please see attached screenshot).

Message 38 of 41
Martin__Schmid
in reply to: EMill311

Hi Eric-- thanks for shaing.

 

>> I've noticed in this thread you have repeatedly asked why.

yes, it helps make sure we hit all potential use cases... for example, in your explaination, you said nothing about being able to tag.. but others have in this forum and elsewhere.

 

>> I'm interested to find out how that additional airflow impacts my supply mains.

Is this 'impact' actually directly to the Flow parameter?  Or, is it indirectly in terms of the resulting velocity or friction (loss per length)?



Martin Schmid
Product Line Manager
Mechanical Detailing and Electrical Design
Architecture, Engineering, and Construction
Autodesk, Inc.

Message 39 of 41
EMill311
in reply to: Martin__Schmid

I guess i'm not sure what you mean when you say "is this impact actually directly to the flow parameter? or is it indirectly in terms of the resulting velocity or friction"  so i'll put it this way:

 

Right, wrong or indifferent - when I size my ductwork i try to make sure that at any given point on the system my ductwork does not have a pressure drop per 100' in excess of a certain value - for example, 0.20 inches per 100'.  I understand that while the section of duct in question may only be 10 feet long and thus won't necessarily cause a huge impact on the system, I consider it best practice to not knowingly design my ductwork for a pressure drop above a 0.20 even if it is only for a few feet.  

It's a nice check to be able to select a piece of ductwork at any point on the system and know what kind of airflow, velocity, pressure drop, etc. that I have in the system at that time.  Maybe it's because I want to design for future capacity, maybe it's because I have space constraints and I want to know how severe the conditions will be at that point because I cannot upsize my ductwork or reduce the airflow.  These are all common issues I encounter on projects.   Yes, we do look at the system as a sum of it's parts, in which case the system analyzer is good, but it's also nice to have a convenient way of checking your design at making adjustments while getting instantaneous updated information.

Message 40 of 41
Martin__Schmid
in reply to: EMill311

Hi Eric.. what you've described is exactly what I mean by 'indirect'... you're not really interested in the Flow itself, you're interested in the pressure drop that is computed from the flow.  To help with the workflow you've described, you can use the System Color Scheme to give you immediate visual feedback as you work... for example, configure the Color Scheme to color ducts with friction above 0.20 red, and eveything else green.  This way, you can quickly find friction issues as you work, and not even have to select a duct to see the values.  You specify the criteria, and it helps you meet them, with out having to pick ducts one by one and look over to the correct location in the Properties Palette.  

 

See attached image for example.

 

I understand the desire to see more of the flow related parameters when a duct is selected, however.  We have this  in our backlog for future consideration.  

 

Thanks,
MS



Martin Schmid
Product Line Manager
Mechanical Detailing and Electrical Design
Architecture, Engineering, and Construction
Autodesk, Inc.

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