Re: [TRNSYS-users] TRNSYS Type 534 doubt cross sectional area and temperature-dependent properties

Dear Oriol,

I am using the same type for the same reason and i have a lot of doubts on coil hx's geometry, i suppose that cross section area is: coil height*coil diameter, even if i am not sure that is right, the tank works. I list all my hypothesis below, to compare with yours:

Coil pitch= the distance center to center between two tubes;

Coil diameter= i choose the diameter of the tank, because i don't have information about coil diameter;

Number of tubes= one single tube coiled;

Length= number of circumferences*pi*coil diameter;

where the number of circumferences=heat transfer surface (from data sheet of tank) / (pi*coil_diameter*pi*tube_diameter)

coil height=number of circumferences*coil pitch + tube diameter;

For miscellaneous flows i set zero, because i ve only auxiliary heaters.... i think your hypothesis is right.

Do you agree with me?

if you have any other suggestion, please tell me.

Best regards,

Francesca lorusso

2017-03-03 11:19 GMT+01:00 Oriol Casal via TRNSYS-users <trnsys-users@lists.onebuilding.org>:

Dear all,

I am currently working on a hot sanitary water system with a solar collector and a storage tank, and I have chosen Type 534 for the tank because it seemed to be able to cover all my modeling needs.

However I have not found much information on a couple of topics: If I use the version without the plug-in I cannot choose Propylene Glycol as a fluid and instead I have to input a single value for the physical properties. Is there a way to not use the plug-in and be able to have time-dependent properties?

Furthermore, I have struggled a lot to try to grasp what "HX cross-sectional area" is, I have finally decided that for the coil HX case it must be pi*(CoilPipeOuterRadius-CoilPipeInnerRadius)^2, however the default value from TRNSYS is quite higher (two orders of magnitude higher), is my interpretation correct? I have also found other default values to be far away from the ones that I am using, such as the HX wall conductivity, which is two orders of magnitude lower than I would expect, does this mean I should not be using TRNSYS default values for those parameters I have no information on? (such as heat transfer phenomena inside the coil).

Finally, I have set miscellanous flows to zero, despite not being entirely sure of what they are, I suppossed they would only be used in case of external energy flows, but instead, in order to do that I am using the auxiliary gains.

Kind regards,

O.C.

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FRANCESCA LORUSSO