[esp-r] Re: phase change materials

Mon Sep 15 17:15:06 BST 2014

Hi Arianna,

it is not clear to me how you assume the PCM model (53) in ESP-r can take any kind of PCM degeneration or the like into account. The melting and solidification temperatures given in the PCM definition are fixed!

If you are looking at surface temperatures, there may, of course, be a slight offset to the PCM temperatures in the middle node of the layer.

PCMFAC is defined as a real variable and calculated as a fraction (see the code). Therefore, at a first glance, I find it strange that this fraction should always be an integer value.

The time steps should suffice  ;o)

Have you cross checked on your expected latent heat capacity (SHCtot or SHCarea)? Does that tally with what you think you entered for the PCM description?

Best
Achim

On Sep 15, 2014, at 2:07 PM, Arianna Sdei <A.Sdei at brighton.ac.uk> wrote:

> Hi Achim,
>  
> the plot of surface temperature against PCMFAC shows that the melting temperature is at 26.4 C and the solidification is 25.4 C. That is not exactly what I set up but it is to be expected in PCM because over a number of days the capacity to regain its original properties will be compromised. What do you mean when you say that it seems strange to get only 1 and 2 as outputs? Isn’t 1 for solid and 2 for liquid? What else should I expect? I am using 60 time steps per hour, with no hourly integration. Thank you,
>  
> regards.
> Arianna     
>  
> From: esp-r-bounces at lists.strath.ac.uk [mailto:esp-r-bounces at lists.strath.ac.uk] On Behalf Of Achim Geissler
> Sent: 14 September 2014 10:46
> To: esp-r at lists.strath.ac.uk Club
> Subject: [esp-r] Re: phase change materials
>  
> Hi Arianna,
>  
> the variable AppCon is "apparent conductivity", the values 0.4 and 0.8 should be found in your input data (conductivity "consol" 0.4 when solid, "conliq" 0.8 when liquid, probably). If you plot the surface/node temperature over time and also the "PCMFAC" in the same plot, the switch between values should happen when the temperature crosses the "melting" and "solidification" temperatures you are using. 
>  
> Maybe taking a look at the code (esrubld/spmatl.f, lines 2424 ff.) can help understand some of the variables. The main calculation algorithm is between lines 2532 and 2580 (factf being PCMFAC in the output). It seems strange that you only get the two integer values 1 and 2 as output.
>  
> The input for actual PCM properties is according to lines 2497 ff.:
>  
> C Melting and solidification temperatures (degC).
>       tmelt=spmdat(ispmnod,1)
>       tsoli=spmdat(ispmnod,2)
>  
> C Conductivity in solid and liquid phase (W/m.degC).
>       consol=spmdat(ispmnod,3)
>       conliq=spmdat(ispmnod,4)
>  
> C Specific heat capacity (J/kg.degC).
>       shtsol=spmdat(ispmnod,5)
>  
> C Latent heat coefficients (J/kg.degC^2 & J/kg.degC respectively).
>       shtliqa=spmdat(ispmnod,6)
>       shtliqb=spmdat(ispmnod,7)
>  
> Description of the other h3k variables you mention are (lines 2750 ff.)
>  
>          strspm(ispmnod,2)='/SHCtot'
>          unitspm(ispmnod,2)='(J/kg)'
>          txtspm(ispmnod,2)='Total heat stored in PCM'
>  
>          strspm(ispmnod,3)='/SHCarea'
>          unitspm(ispmnod,3)='(J/m^2)'
>          txtspm(ispmnod,3)='Heat stored per PCM area'
>  
> What number of time steps per hour are you using (see comment by Alaa)?
>  
> Good luck.
> Best
> Achim
>  
>  
> On Sep 14, 2014, at 12:12 AM, Arianna Sdei <A.Sdei at brighton.ac.uk> wrote:
> 
> 
> Hi Achim,
>  
> thank you. I tried to simulate 2 days in July and see what happens to the temperature of two surfaces. The difference if very minimal, in the order of 0.1k. I could find h3k output and “PCMFAC” variable. In the output I can see that PCMFAC is either a factor of 1 or 2. I can see that the index switches from 1 to 2 at different times for different surfaces. There are other variables such as AppCON which has often an index of 0.4 when PCMFAC is 1 and of 0.8 when PCMFAC is 2, what does that mean? There are other variables like SHCarea, SHCtot, what are they?  Let me know, thank you again.
>  
> Best,
>  
> Arianna
>  
> From: esp-r-bounces at lists.strath.ac.uk [mailto:esp-r-bounces at lists.strath.ac.uk] On Behalf Of Achim Geissler
> Sent: 11 September 2014 19:57
> To: esp-r at lists.strath.ac.uk Club
> Subject: [esp-r] Re: phase change materials
>  
> Hi Arianna,
>  
> so probably you are using type 53 (you can see that in the .spm file, by the way, "Type").
>  
> The PCM should go in the middle node of the innermost layer (or the "plasterboard" layer, in any case). I have no idea what the default parameters in the database are. Did you change the latent heat to meet the actual material you are using? Again, I always found it very informative to have a surface with and without PCM side by side and look at the surface and / or central node temperatures of the layer in question. Did you do that? From these temperatures you can also estimate if you are actually melting / solidifying the PCM as Monika mentioned.
>  
> Are you using h3k output? If not, it may be an additional idea. You should find a variable "PCMFAC" in the dictionary. This, I think, is a factor which is 0 for solid and 1 for liquid (or the other way around) and thus gives direct information on what is happening with the PCM.
>  
> Best
> Achim
>  
>  
> On Sep 11, 2014, at 7:53 PM, Arianna Sdei <A.Sdei at brighton.ac.uk> wrote:
> 
> 
> 
> Hi Achim,
> I am using phase change plasterboard via the active material database and I am using quite a bit of it. I am using it on all internal walls of two rooms in a house. It makes only a tiny difference to the temperature and I think I am not using it in the right way at the moment. I should be able to see a reduction of 1 or 2k but I am not. What can I look at? can the way I am positioning the material make any difference? I am trying to have the pcm exposed. Let me know,
> Thank  you.
> Arianna    
>  
> From: esp-r-bounces at lists.strath.ac.uk [mailto:esp-r-bounces at lists.strath.ac.uk] On Behalf Of Achim Geissler
> Sent: 10 September 2014 18:16
> To: esp-r at lists.strath.ac.uk Club
> Subject: [esp-r] Re: phase change materials
>  
> Hi Arianna,
>  
> you write you can't see "substantial reduction" - but you do see a reduction? You will need quite a bit of PCM for substantial differences (.gt. 1 to 2 K), probably.
>  
> Which PCM model are you using? I think the basic "53" model cannot really take different temperatures for melting/solidification into account.
>  
> A simple approach for testing: If you have two otherwise identical surfaces, put the PCM in one and then look at the temperature profiles for a day for these surfaces (or split one of the PCM surfaces into two and remove the PCM from one of these). This should quickly give you an idea on if something is happening ("something" may be disappointingly small temperature differences).
>  
> Best
> Achim
>  
>  
>  
> Von: esp-r-bounces at lists.strath.ac.uk [mailto:esp-r-bounces at lists.strath.ac.uk] Im Auftrag von Arianna Sdei
> Gesendet: Mittwoch, 10. September 2014 16:59
> An: esp-r at lists.strath.ac.uk Club
> Betreff: [esp-r] phase change materials
>  
> Dear All,
>  
> I am trying to use phase change materials, phase change plasterboard, via the active components. I am using a melting temperature of 26°C and a solidification temperature of 27°C. I am not sure about the solidification temperature and I would like to know if some of you can advise on this. I am trying to have the PCM exposed, so I always position it on the internal layer as I suppose when the software asks for the position it starts counting the existing layers from the exterior.
>  
> However I try, I can’t see any substantial reduction in the indoor temperature during a hot summer month. Can any of you give some advice on how to reduce the indoor temperature further by changing the parameters?
>  
> Thank you in advance,
>  
> Best regards,
>  
> Arianna   
>  
> Arianna Sdei
>  
> Research Fellow IFORE (Innovation For Renewal)
>  
> UNIVERSITY OF BRIGHTON
>  
> Moulsecoomb, Lewes Road, Brighton, BN2 4AT
>  
> mobile: 0044 (0)7981739024
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>  
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