[TRNSYS-users] COP curve inconsistency WW-HP

[David BRADLEY]

Vitor,

   Check to make sure that the values you have specified as parameters 
for things like the number of source temperatures - cooling match the 
number of values that are actually in the data file. I have seen this 
happen when I had specified (for example) that there were 10 source 
temperatures in the data file when in fact there were only eight.

kind regards,

  David



On 08/18/2019 14:26, Vitor Leite via TRNSYS-users wrote:
> Sorry all for the spam, but forgot to add attach the files
> ------------------------------------------------------------------------
> *From:* Vitor Leite <vitorleite95 at hotmail.com>
> *Sent:* Sunday, August 18, 2019 4:23 PM
> *To:* TRNSYS users mailing list at OneBuilding.org 
> <trnsys-users at lists.onebuilding.org>
> *Subject:* Re: [TRNSYS-users] COP curve inconsistency WW-HP
> Hello Jeff,
>
> First,thanks for the answer.
>
> I isolated the heat pump into a new project, created 2 equation 
> components representing source and load side flow and inlet 
> temperatures but the heat pump is still having quite strange COP 
> results, and I have no idea why.
>
> Here is basically what I did:
>
> Timestep: 0.1h
>
> Type 927 (parameters 15 to 18):
> rated heating capacity 177kW
> rated power: 46kW
> rated load/souce flowrate: 9.5 l/s
>
> I attached my expected performance curve according to the performance 
> data from TESS library for type 927, and the results from some of the 
> tests I performed.
>
> The main thing that I don't understand is why, even on the test 
> project, there are so many scenarios that is in direct conflict with 
> the performance data sheet.
>
> By reducing the load-side flowrate and increasing the EWT for the 
> load-side, the heating COP went to above 5, when according to the 
> performance curve, both scenarios should decrease COP.
> By having load-side EWT of 20 degrees C and flowrate equal to the 
> rated value (9.5 l/s), the COP was near 3. By decreasing only the 
> flowrate, COP increased to almost 4 (again, against performance curve).
> And last, by decreasing source-side EWT, COP increased as well, when 
> it should decrease.
>
> Am I misunderstanding the system? Or I made a mistake even on the test 
> project, as well?
>
> On my main project I have a storage tank added and there are no errors 
> during the simulation. I think my only problem is understanding this 
> COP curve.
>
> Thank you again,
>
> Vitor L.
>
> ------------------------------------------------------------------------
> *From:* Jeff Thornton <thornton at tess-inc.com>
> *Sent:* Monday, August 5, 2019 11:20 AM
> *To:* TRNSYS users mailing list at OneBuilding.org 
> <trnsys-users at lists.onebuilding.org>
> *Cc:* Vitor Leite <vitorleite95 at hotmail.com>
> *Subject:* Re: [TRNSYS-users] COP curve inconsistency WW-HP
> Victor,
>
> The best thing you can do to start  is to isolate the heat pump in a 
> separate project and drive it with various inlet temperature and flow 
> rates to make sure the performance of the machine matches the map. 
>  When you’re sure it’s working correctly that’ll help you track down 
> what’s happening with the rest of your project.
>
> Jeff
>
> Sent from my iPhone
>
> On Aug 1, 2019, at 10:24 AM, Vitor Leite via TRNSYS-users 
> <trnsys-users at lists.onebuilding.org 
> <mailto:trnsys-users at lists.onebuilding.org>> wrote:
>
>> Hello everyone,
>>
>> I got the results from a simulation and I think I am getting 
>> inconsistent results when comparing the heat pump COP and comparing 
>> it normalized performance data sample included with the component, 
>> which is the one I am currently using (type 927).
>>
>> The system is basically two identical heat pumps (50RT) being 
>> controlled by a multi-stage differential controller. (which is also 
>> controlling the flow rate for both source side and load side pumps). 
>> So for the load side (connected to a vertical heat exchanger) there 
>> is only really small changes in temperature and the flow-rate goes 
>> from 0 to 0.5 to 1 following the number of H.Ps on.
>> Load side flow-rate also goes from 0 to 0.5 to 1 but there are bigger 
>> temperature changes according to the demand.
>>
>> But, according to the performance data, during heating mode, the load 
>> side flow-rate should no change normalized capacity and if the load 
>> side temperature increases, normalized capacity should decrease. 
>> Which was not what happened with my results.
>>
>> Can someone with a better understanding about H.Ps take a quick look 
>> and see if this graph is reasonable compared to the performance curve?
>>
>> Thanks in advance
>>
>> <COP.jpg>
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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

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

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