Re: [TRNSYS-users] Type 107 - description of used values

[David Bradley <bradley@tess-inc.com>]

Timo,
  You are right, that documentation is confusing and I think one of the equations is incorrect...

  To clarify: what the documentation refers to as the "fraction of design load" is the energy that has to be removed from the water stream (ie the current load) divided by the machine's rated  capacity. Essentially it is the part load ratio at which the machine has to operate. However, based on the current entering cooling water and hot water temperatures, the machine's entire rated capacity may not currently be available. So, the calculated fraction of design load and the entering water conditions are sent to the data file and the data file returns what is calls the "fraction of the rated capacity" that is currently available. The value is returned as a fraction, not as a capacity; thus "fraction of rated capacity." So basically, the "fraction of design load" is an input to the data file based on only on rated capacity and current load and the "fraction of rated capacity" is returned, taking into account the current entering water conditions.

  In the source code, the returned fraction of rated capacity that is returned from the data file is multiplied by the machine's full-load capacity to determine nominal capacity. The equation that I think is incorrect in the documentation is Eq. 5.3-95. There should only be one multiplier on Capacity_Rated, not two and that multiplier is the one returned from the data file (whatever you want to call it).
Best,
 David


Timo Sengewald wrote:

Hello!

 

I try to set up a Type 107 absorption chiller by using manufacturer’s data but do not understand the difference between the “Fraction of Design Load” and the “fraction of rated capacity” as described in the mathematical reference. I understand the meaning of the fraction of design load. But what is meant by the “fraction of rated capacity” which is returned by the data file? Both terms mean the same to me.

 

Is somebody able to describe the difference in other words than used in the manual?

 

Best regards

 

Timo

 

 

Mit freundlichen Grüßen

BLS Energieplan GmbH
i. A. Timo Sengewald

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D-12435 Berlin
Tel.: +49 30 53 32 81-0
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