Re: [TRNSYS-users] I: TYPE 56 - chilled ceiling

["hotline" <hotline@transsolar.com>]

Title: Nachricht

Bettina,

a.) the Type 56 building model so far is not a geometric model thus geometric distribution of radiation exchange between walls is by surface area weightening only.

b.) you cannot define the emissivity

 

c./d.) thank you for finding this bug in the TRNBuild Interface, we will correct this for the next update.

In the "Properties" table the correct expressions must be:

 

constant chilled ceiling, if   (Tsurfceiling-Tairceiling)  <  0         3.888

exponent chilled ceiling, if   (Tsurfceiling-Tairceiling)  <  0        0.31

 

and

 

constant heated ceiling, if   (Tsurfceiling-Tairceiling)  > 0         7.2

exponent heated ceiling, if   (Tsurfceiling-Tairceiling)  > 0        0.31

 

The unit of the resulting alfa_conv is kJ/(h*m^2*K). So of course the constant has to have another unit which however includes K to the power of the exponent. What we wanted to make clear is that the constant has to be a value which includes the capacity given in TRNSYS units (kJ/h)  We will have t think of how to explain this better in TRNBuild.

 

e.) yes

 

f.) the sign of Qcomo and Qcomi is giving the direction of the heat flow:

QCOMI combined heat flux to inside (going into zone+; going into wall -)

QCOMO combined heat flux to outside (going to outside-; going into wall +)

 

I hope this can help.

 

Monika

 

 

 

-----Ursprüngliche Nachricht-----
Von: Bettina Nocke [mailto:bettina@dream.unipa.it]   
Gesendet: Donnerstag, 14. Juni 2007 10:41
An: trnsys-users@engr.wisc.edu
Betreff: [TRNSYS-users] I: TYPE 56 - chilled ceiling

 

 

---

Da: Bettina Nocke [mailto:bettina@dream.unipa.it]
Inviato: mercoledì 13 giugno 2007 20.08
A: 'trnsys-users@engr.wisc.edu'
Oggetto: TYPE 56 - chilled ceiling

 

Dear TRNSYS User’s,

 

 

using the Integrated Model for Chilled Ceiling Panels I’m not able to resolve some problems. My questions are:

 

a) if I define only internal walls (test room for cooling panels), how let I know the model the geometrics of the room (perpendicular walls etc.)?

 

b) can I define the emissivity of the internal surfaces? (prEN 14240 stipulates an emission rate at least 0.9)

 

c) the coefficients const and exp (Properties) are done for the condition Tsurfceiling ? Tairceiling < 0. but so I have to apply the exponent for a negative value. It means only the amount, without sign? ?

 

d) For calculate α_conv with equation 6.3.2-157, the constant is done in KJ/m^2K, but multiplying with delta T, remains KJ/m^2. I’m not sure if I understand rightly the units, so I have a problem to change the default values (for achieve in the simulatione the same results as the test of radiant panels).

 

e) is the same model suited to be used for a heating ceiling? The results of my simulation seems a little bit strange…

 

I want to add another question at the mail of yesterday:

In the energy balance output, in the cooling case, gains (SQCSURF) AND energy flows to other surfaces (QCOMO, QCOMI) have a negative value. This is a little bit confusing for me, for understand the convective and the radiative part of energy changes (setting identical all boundary temperatures).

 

 

Can anybody help me? Thanks very much.

 

Bettina