[TRNSYS-users] Type 941(Air to water heat pump)

[David BRADLEY]

Muhammad,

  The compressor power (P_compressor) and the heat pump capacity 
(q_evaporator) are specified as model parameters at a rated inlet 
condition. The rated inlet condition is a particular combination of 
inlet air and inlet water temperatures.

  The actual power and capacity are computed from the rated (parameters) 
values times a multiplier (from the external file). The external file 
basically says how the heat pump power and capacity are affected by 
differences between the actual inlet air and water temperatures and the 
rated inlet air and water temperature.

   For instance, if you look at the third line of the Type941 cooling 
performance data file, you should see something like:

0.943    0.753                                    !Fraction capacity and 
power at T_air =    15.6    deg. C and T_water_in =    12

this means that when the air inlet temperature is 15.6C and the water 
inlet temperature is 12C then the heat pump will have 94.3% of its rated 
capacity and will consume 75.3% of its rated power.

So, to answer your question more directly, q_evaporator and p_compressor 
are known because you specified them as parameters and then they were 
modified according to the external data file. With those two values, 
q_condenser can be computed.

I hope that clarifies,

  kind regards,

  David


On 03/27/2020 09:17, Muhammad Zeeshan wrote:
> Thanks a lot David. Would you please elaborate a bit more about the 
> compressor power how it would be calculated?
> External files contains fractions of compressor power e.g. 0.8,0.9 
> etc. Where as in manual equations are quoted as: q_condensor = 
> q_evporator + p_compressor
> Here, both q_condensor and p_compressor are unknown
> How q_condensor and p_compressor will be calculated.
>
> Thanks
>
> Regards,
> Muhammad Zeeshan
>
> On Fri, Mar 27, 2020, 18:45 David BRADLEY <d.bradley at tess-inc.com 
> <mailto:d.bradley at tess-inc.com>> wrote:
>
>     Muhammad,
>
>       Please refer to the Type941 documentation. It explains how the
>     external files and the parameters relate to each other to compute
>     the overall capacity and power consumption of the heat pump.
>
>       The evaporator does not really need to be designed more than to
>     choose a machine with an appropriate rated capacity. Traditionally
>     that might mean adding a safety factor to the peak cooling load
>     (10% is often used) and then selecting a machine that will meet
>     that capacity. Also bear in mind that Type941 models a single
>     speed (ie single capacity) heat pump that is either on or off.
>     Depending on how variable the load in your building it, you might
>     want to meet that load with multiple smaller heat pumps rather
>     than one big one.
>
>     kind regards,
>
>      David
>
>
>     On 03/27/2020 08:02, Muhammad Zeeshan via TRNSYS-users wrote:
>>     Hello Everyone,
>>                                 I am working on cooling a building
>>     with type 41(air to water source heat pump). The cooling load of
>>     the building is 25 tons. I want to know
>>
>>     1)- how the compressor power will be calculated? as the external
>>     files of type 941 contains fractions of compressor power which
>>     shows no link to the equations provided in manual. How to link
>>     the external file with the provided equations?
>>
>>     2)-As the cooling load of the building is 25 tons, how to design
>>     the evaporator for this building load?
>>
>>     Your help in this regard will be highly appreciated.
>>
>>
>>
>>     Regards,
>>     Muhammad Zeeshan
>>
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>
>     -- 
>     ***************************
>     David BRADLEY
>     Principal
>     Thermal Energy Systems Specialists, LLC
>     3 North Pinckney Street - suite 202
>     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
>     http://www.trnsys.com
>
-- 
***************************
David BRADLEY
Principal
Thermal Energy Systems Specialists, LLC
3 North Pinckney Street - suite 202
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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