[TRNSYS-users] Questions about Type941 source code

David BRADLEY d.bradley at tess-inc.com
Mon Apr 22 12:25:49 PDT 2013
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Dear Zhe,
   It would help me to answer you more clearly if you could send me the 
data file from which you are working. Please send it directly to me 
(instead of replying to this message, which will go to everyone 
subscribed to the trnsys-user list.)
Kind regards,
  David


On 4/22/2013 12:18, Zhe Li wrote:
>
> Dear David,
>
> Thanks very much for your prompt answer.
>
> I understand your first point. For the circumstance I am working with, 
> the relative humidity is actually not necessary. Hence for 
> calculations concern, I don't have to have it.
>
> For the second point, What I am trying to ask is what will happen if 
> the inlet temperature is 4.7oC and inlet water temperature is 27.5oC. 
> The file contains the fraction of capacity and power: 0.759 0.787 at 
> T_air=2.2oC and T_water_in = 25oC, and 1.048 0.938 at T_air= 7.2oC and 
> T-water_in=30oC. The required value is actually half of the value in 
> the data. How would the interpolation routine deal with it or similar 
> circumstance?
>
> Thank you very much for your help.
>
> Zhe Li
>
> *From:*David BRADLEY [mailto:d.bradley at tess-inc.com]
> *Sent:* 22 April 2013 16:12
> *To:* Zhe Li
> *Cc:* trnsys-users at cae.wisc.edu
> *Subject:* Re: Questions about Type941 source code
>
> Dear Zhe,
>   I have seen air(source)-to-water heat pumps used in two kinds of 
> applications. In one, the air side is outside the conditioned space 
> and you are correct that in this circumstance, the RH of the outlet 
> air is probably not going to be used for anything. In the other type 
> of application, however, the air side is in a conditioned space (for 
> example there are devices called heat pump water heaters that sit on 
> top of a water tank; they keep the water tank hot but in the process 
> they cool (and dehumidify) the air near the tank. In this case it is 
> important to know what happens on the air side.
>
>   You are correct that the data cannot be extrapolated beyond the 
> range given in the file. If you give the heat pump entering conditions 
> that are below the range, the model will get the capacity and power of 
> the closest point (ie the bottom of the range). The case is similar 
> for the top of the range; the interpolation routine will find the 
> closest available point. If you want to be more rigorous about your 
> calculations, you can put additional data points into the file that 
> show a 0 capacity and 0 power draw for the device if it gets very cold 
> or very hot inlet conditions.
> Kind regards,
>  David
>
>
>
> On 4/22/2013 09:19, Zhe Li wrote:
>
>     Dear David,
>
>     Thank you very much for your previous reply.
>
>     I am hoping you can clarify some of my confusions with this source
>     code(Type941). I have studied this Type941 source code carefully.
>     From my understanding is the outlet fluid temperature is not
>     calculated from the amount of heat contained in the air. The
>     Capacity and Power is worked out completely depending on the Rated
>     Catalog Performance using the hourly ambient temperature and
>     temperature of the fluid. So why does the relative humidity
>     require at all? Is it only used to calculate the inlet and the
>     outlet air properties which is not going to affect the fluid
>     temperature in any way?
>
>     As I understand from previous questions, the interpolation Rated
>     Catalog Performance data could not be extrapolated from beyond the
>     range provided? However, what would be the calculation (selection)
>     if the inlet ambient temperature is 5oC and inlet water
>     temperature is 27.5oC, how would the fraction capacity and power
>     calculated out (decided)?
>
>     Thank you very much for your kind answer.
>
>     Zhe Li
>
>     *From:*David BRADLEY [mailto:d.bradley at tess-inc.com]
>     *Sent:* 19 April 2013 18:04
>     *To:* TRNSYS users mailing list at the Solar Energy Lab, UW-Madison
>     *Cc:* Zhe Li
>     *Subject:* Re: [TRNSYS-users] Question about a line in Type941
>     source code
>
>     Zhe,
>       lps_air is the volumetric flow rate of the air (in liters per
>     second) and rho_air_dry_in is the density (in kg/m3) of the dry
>     air at the heat pump inlet temperature.
>     Best,
>      David
>
>
>     On 4/19/2013 11:11, Zhe Li wrote:
>
>         Dear All,
>
>         Thank you for your time.
>
>         I am trying to understand how TRNSYS calculates power output
>         from this air-water heat pumps (Type941).
>
>         I am stuck in a line which I don't know what the two terms are
>         standing for?
>
>         ! Determine the dry air mass flow rate
>
>         Flow_air = lps_air*3.6*rho_air_dry_in
>
>         Could somebody let me know what are the *lps_air* and
>         *rho_air_dry_in *standing for?
>
>         I hope I did not break TRNSYS source code rule by asking this
>         question.
>
>         Thank you for your help in advance.
>
>         Zhe Li
>
>
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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 at tess-inc.com  <mailto:d.bradley at tess-inc.com>
>
>       
>
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>
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>
>     Tá an teachtaireacht seo scanta ó thaobh ábhar agus víreas ag
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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 at tess-inc.com  <mailto:d.bradley at tess-inc.com>
>   
> http://www.tess-inc.com
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>
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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 at tess-inc.com

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

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