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Re: [TRNSYS-users] Negative value of Radiation in TRNSYS 16



Wang,
 As it says in all of the"More" button comments for the Type9 "Interpolate or not" parameter and also in the mathematical description of Type9, you should NOT use Type9 to interpolate solar radiation data. Type9 interpolates linearly, which is a poor assumption for the way in which solar radiation behaves over an hour. Furthermore, the point of Type16 (solar radiation processor) is to carry out an interpolation of solar radiation for timesteps smaller than an hour.

I would highly recommend that you run a simulation with ONLY Type9 and Type65. Plot out all of the values that you are reading from your file and make sure that they are all being treated correctly. It can be somewhat tricky to set the "average or instantaneous value" parameter and the "interpolate or not" parameters. Only after you have verified the data is being read in properly should you then adda Type16 to the project to make sure that solar radiation is being processed correctly; again, there are some parameters that can be challenging to set correctly.
Regards,
 David


On 10/29/2012 05:17, 王洋 wrote:
dear all,

I would like to ask you a question about solar radiation. I met an error as follows. I used Type 9e to import our own solar radiation data whose unit is W/m2, meantime, I also used an Equation to transfer its unit to kJ/hm2 (i.e. xx*3.6) and used ABS to ensure its value as Positive connected with Type 16a (Radiation processors). But it still appears the error as follows. Please tell me how could I solve this problem? E.g. use which Type I should use more easily and correctly and what are the detailed processes to import our own solar radiation to connect with Type 56?

*** Fatal Error at time   :      3820.800000
    Generated by Unit     :    56
    Generated by Type     :    56
    Message               : Negative value of solar radiation for   5orientation encountered


Many thanks in advance!
Br.
wang


2012/10/26 王洋 <wanghongyang1767@gmail.com>
dear all,

I would like to ask you a question about solar radiation. I met an error as follows. I used Type 9e to import our own solar radiation data whose unit is W/m2, meantime, I also used an Equation to transfer its unit to kJ/hm2 (i.e. xx*3.6) and used ABS to ensure its value as Positive. But it still appears the error as follows. Please tell me how could I solve this problem? E.g. use which Type I should use more easily and what are the detailed processes to import our own solar radiation to connect with Type 56?

*** Fatal Error at time   :      3820.800000
    Generated by Unit     :    56
    Generated by Type     :    56
    Message               : Negative value of solar radiation for   5orientation encountered


Many thanks in advance!
Br.
wang

2012/10/26 <trnsys-users-request@cae.wisc.edu>
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Today's Topics:

   1. Max. time points of Type 14 in TRNSYS 16 (??)


---------- 已转发邮件 ----------
From: 王洋 <wanghongyang1767@gmail.com>
To: trnsys-users@cae.wisc.edu
Cc: 
Date: Fri, 26 Oct 2012 11:27:38 +0200
Subject: [TRNSYS-users] Max. time points of Type 14 in TRNSYS 16
Dear all,

I'd like to ask you whether or not max. time points of Type 14 is only 20 in TRNSYS 16?
If I need more than 20 points, how could I solve this problem?

Many thanks in advance!

Br

wang

2012/10/26 <trnsys-users-request@cae.wisc.edu>
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Today's Topics:

   1. Re: Type energy balance (David BRADLEY)
   2. Re: Type energy balance (Micha?l Kummert)


---------- 已转发邮件 ----------
From: David BRADLEY <d.bradley@tess-inc.com>
To: PARTENAY Vincent <vincent.partenay@cstb.fr>
Cc: "trnsys-users@cae.wisc.edu" <trnsys-users@cae.wisc.edu>
Date: Thu, 25 Oct 2012 16:34:28 -0500
Subject: Re: [TRNSYS-users] Type energy balance
Vincent,
  When you perform an energy balance on a tank, you need to take into account its change in temperature between the beginning and the end of the simulation (output 7 of your Type4). If the tank ends up hotter at the end of the simulation than it was at the beginning, it has stored some energy. If it ends up colder, then it has given up some energy. I would imagine that with 10 nodes, there is some stratification developing in the tank that is not modeled when you have a fully mixed tank (1 node)
Best,
 David


On 10/25/2012 09:40, PARTENAY Vincent wrote:

Dear all,

 

Typ4a (Storage tank) allows to model a stratified tank with several temperature nodes. The problem I noticed is that the energy balance of both sides on the tank can vary depending on the chosen timestep :

 

In the attached file, a simplified example, the tank is coupled to an energy production and energy consumption model (very simple in an equation). Thermal losses of the tank is set to zero.

When I run a simulation with one node (1m height for 0.5m3) for the tank and a timestep of 0.1hr, I get the same energy on both side (see plotter “”Power&NRJ”, Esource = 2659kWh and Eload = 2666kWh), slight difference maybe explained by initial charging period to setpoint temperature.

When I run it in the same conditions but with 10 nodes (each 0.1m), these two energy are different ! While I still have 2666kWh for Eload I have 3146kWh !

When I run it again reducing the timestep from 0.1hr to 0.001 hr, still with 10 nodes, I get 2666kWh, the energy balance is ok…

 

So, my question is : is it necessary to check before every bigger simulation (that can include lots of tank models) the energy balance of this model for one defined timestep and boundary conditions to the model or is there some rules to predefine adapted discretisation for one given timestep ?

 

Kind regards,

 

 

Vincent PARTENAY

Energies Renouvelables - Département ESE

 

Centre Scientifique et Technique du Bâtiment

290 Route des Lucioles BP 209 – F 06904 Sophia Antipolis Cedex

Tél : +33-(0)4-93-95-67-21

Fax : +33-(0)4-93-95-64-31

Évitez d’imprimer vos emails inutilement. Respectez l’environnement

 

 



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TRNSYS-users mailing list
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-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley@tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com


---------- 已转发邮件 ----------
From: "Michaël Kummert" <michael.kummert@gmail.com>
To: <trnsys-users@cae.wisc.edu>
Cc: 
Date: Thu, 25 Oct 2012 18:19:39 -0400
Subject: Re: [TRNSYS-users] Type energy balance

If the energy (de)stored between the initial and final state cannot explain the differences, I think there is another possible cause: Type 4 can have quite large energy balance errors when the nodes are “flushed out” during one time step.

 

Here is my understanding:

If you have 10 nodes and a total volume of 500 L, that means each node holds 50 L of water. Using 0.1 h time steps you cannot have a flowrate through the tank higher than 500 L/h, otherwise you will replace the entire volume of a node within a time step, and the equations used by Type 4 are not valid anymore. This would explain that it works again when you reduce the timestep (with 0.001 h you would need a flowrate of 50000 L/h to “flush” a node out).

 

To my knowledge this problem is specific to Type 4, i.e. it does not affect the Storage tanks in the TESS libraries (Type 534 etc.) – if you have access to them that may be a more practical solution than running 0.001 h timesteps…

 

Michaël Kummert

Polytechnique Montréal

 

From: trnsys-users-bounces@cae.wisc.edu [mailto:trnsys-users-bounces@cae.wisc.edu] On Behalf Of David BRADLEY
Sent: Thursday, October 25, 2012 17:34
To: PARTENAY Vincent
Cc: trnsys-users@cae.wisc.edu
Subject: Re: [TRNSYS-users] Type energy balance

 

Vincent,
  When you perform an energy balance on a tank, you need to take into account its change in temperature between the beginning and the end of the simulation (output 7 of your Type4). If the tank ends up hotter at the end of the simulation than it was at the beginning, it has stored some energy. If it ends up colder, then it has given up some energy. I would imagine that with 10 nodes, there is some stratification developing in the tank that is not modeled when you have a fully mixed tank (1 node)
Best,
 David

On 10/25/2012 09:40, PARTENAY Vincent wrote:

Dear all,

 

Typ4a (Storage tank) allows to model a stratified tank with several temperature nodes. The problem I noticed is that the energy balance of both sides on the tank can vary depending on the chosen timestep :

 

In the attached file, a simplified example, the tank is coupled to an energy production and energy consumption model (very simple in an equation). Thermal losses of the tank is set to zero.

When I run a simulation with one node (1m height for 0.5m3) for the tank and a timestep of 0.1hr, I get the same energy on both side (see plotter “”Power&NRJ”, Esource = 2659kWh and Eload = 2666kWh), slight difference maybe explained by initial charging period to setpoint temperature.

When I run it in the same conditions but with 10 nodes (each 0.1m), these two energy are different ! While I still have 2666kWh for Eload I have 3146kWh !

When I run it again reducing the timestep from 0.1hr to 0.001 hr, still with 10 nodes, I get 2666kWh, the energy balance is ok…

 

So, my question is : is it necessary to check before every bigger simulation (that can include lots of tank models) the energy balance of this model for one defined timestep and boundary conditions to the model or is there some rules to predefine adapted discretisation for one given timestep ?

 

Kind regards,

 

 

Vincent PARTENAY

Energies Renouvelables - Département ESE

 

Centre Scientifique et Technique du Bâtiment

290 Route des Lucioles BP 209 – F 06904 Sophia Antipolis Cedex

Tél : +33-(0)4-93-95-67-21

Fax : +33-(0)4-93-95-64-31

Évitez d’imprimer vos emails inutilement. Respectez l’environnement

 

 




_______________________________________________
TRNSYS-users mailing list
TRNSYS-users@cae.wisc.edu
https://mailman.cae.wisc.edu/listinfo/trnsys-users



-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA
 
P:+1.608.274.2577
F:+1.608.278.1475
d.bradley@tess-inc.com
 
http://www.tess-inc.com
http://www.trnsys.com

_______________________________________________
TRNSYS-users mailing list
TRNSYS-users@cae.wisc.edu
https://mailman.cae.wisc.edu/listinfo/trnsys-users



_______________________________________________
TRNSYS-users mailing list
TRNSYS-users@cae.wisc.edu
https://mailman.cae.wisc.edu/listinfo/trnsys-users





_______________________________________________
TRNSYS-users mailing list
TRNSYS-users@cae.wisc.edu
https://mailman.cae.wisc.edu/listinfo/trnsys-users

-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
22 North Carroll Street - suite 370
Madison, WI  53703 USA

P:+1.608.274.2577
F:+1.608.278.1475
d.bradley@tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com