[TRNSYS-users] Causes of Pump mass balance warning?

[Fred Betz]

David,

There is a slight imbalance probably based on the changing flow due to the controller output. 

The imbalance is less than 5 kg/hr out of a total flow of 2.5 million kg/hr. 

I tried changing the component order in the control cards, but that doesn't solve it. The best I can do is 91 warnings over 1680 time steps. 

I am going to ignore it for now unless anyone else has a thought. 

Fred


FRED BETZ  PhD., LEED AP 
SUSTAINABLE SYSTEMS ANALYST
 
AEI | AFFILIATED ENGINEERS, INC.  
5802 Research Park Blvd. | Madison, WI  53719

P: 608.236.1175 | F: 608.238.2614  
fbetz at aeieng.com  |  www.aeieng.com  



-----Original Message-----
From: David Bradley [mailto:bradley at tess-inc.com] 
Sent: Tuesday, April 20, 2010 1:47 PM
To: Fred Betz
Cc: trnsys-users at cae.wisc.edu
Subject: Re: [TRNSYS-users] Causes of Pump mass balance warning?

Fred,
 Fundamentally, the only thing that can cause a pump mass imbalance is 
if it is not getting the same flow in as it is putting out. I'd 
recommend putting an online plot into your sim and plotting the flow 
rate coming out of every component in your closed loop. It should be 
pretty easy to spot where the flow is going.
Best,
David

Fred Betz wrote:
>
> I have two closed loop systems, one heating, one cooling and I am 
> getting several mass balance warnings.
>
>  
>
> What I am doing is using a proportional controller to control a 
> variable speed pump based on the return temperature of a load.
>
>  
>
> All the flow connections have been double checked.
>
>  
>
> Any thoughts on what might be causing this?
>
>  
>
> Fred
>
>  
>
> *Fred Betz**  *PhD., LEED AP
> Sustainable Systems Analyst
>
> 	
>
>  
>
> 	
>
> *AEI* | AFFILIATED ENGINEERS, INC.  
> 5802 Research Park Blvd. | Madison, WI  53719
>
> P: 608.236.1175 | F: 608.238.2614  
> fbetz at aeieng.com <mailto:fbetz at aeieng.com>  |  *www.aeieng.com 
> <http://www.aeieng.com/>*  
>
>  
>
>  
>
> ------------------------------------------------------------------------
>
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