VRF performance curve

12 posts / 0 new
Last post

Dear All,
I worked on a couple of projects in equest? using the VRF performance curves from Daikin and LG. The methodology i followed is as below:
1) Modelled packaged VAV with minimum flow ratio 1.
2) Created systems based on number of ODU's and assigned multiple zones to the respective ODU. (Just like modelling a AHU)
3) Inputted the ODU Cooling capacity and supply flow4) Fans will be constant volume.5) Since it is a cooling only system, i assigned only the "Cool EIR - fEWB-OAT", "Cool-EIR-fPLR" and "Cool cap-fEWB&OAT" curves. Rest were all default DX unit curves.
?PVAV system is used as PSZ system cannot handle multiple zones well thus causing unmet hours.
I did 2 trials, one with default DX curves and the other with performance curves from LG and Daikin. The results showed a decrease in cooling energy consumption by more than 30% thus impacting the overall energy consumption by more than 10%.

Is the simulation methodology and results appropriate? I feel the savings is on a higher side.
Please advise.

Regards,Rathnashree

Rathna Shree's picture
Offline
Joined: 2011-10-02
Reputation: 0

When I have modeled VRF systems I have always used the PVVT system type in eQUEST as recommended in this presentation: http://energytrust.org/library/bsug-files/modeling_real_performance_of_vrf_systems_kc-05.15.13.pdf

Using the efficiencies and the curves for the VRF system will get you pretty close, but if you want to account for heat-recovery within the system (one terminal unit in cooling while another is in heating), you will have to do some post-processing calculations.

Nathan Miller, PE, LEED AP BD+C ? Mechanical Engineer/Senior Energy Analyst
RUSHING | D 206-788-4577 | O 206-285-7100
www.rushingco.com

Nathan Miller's picture
Offline
Joined: 2011-09-30
Reputation: 200

I would either use a WSHP or a chilled water system with 0 pumping energy.

Cory Duggin, PE, LEED AP BD+C
Associate/Energy Engineer
TLC Engineering for Architecture
direct:

615-346-1939

crduggin's picture
Offline
Joined: 2013-04-16
Reputation: 0

Hi Rathna,
LG has a plug-in that works good with eQuest, I tried it and I noticed the % of energy saving will be on the region of 20% when compared to PTAC (Not compared to the App G. Baseline).
Thanks;
Sherif Farag
Technical Director
Integrated Environmental Services (IES) Ltd.
Abu Dhabi - UAE

Sherif Farag's picture
Offline
Joined: 2012-12-25
Reputation: 0

Hi Rathna,

What software are you using ? You might want to go through the attached modelling protocol attached from LG as Sherif mentions .

Harris

Harris Qureshi, B.E(Mech), MSc. Energy, LEED AP Homes
Mechanical Engineer
Stantec
Dubai Investment Park, PO Box 52764 Dubai UAE
Phone: +971-4-812-5947
Cell: +971-50-189-9924
Harris.Qureshi at stantec.com

[http://www.stantec.com/content/dam/stantec/images/esignature/stantec.png]

The content of this email is the confidential property of Stantec and should not be copied, modified, retransmitted, or used for any purpose except with Stantec's written authorization. If you are not the intended recipient, please delete all copies and notify us immediately.

? Please consider the environment before printing this email.

Qureshi, Harris's picture
Offline
Joined: 2015-05-22
Reputation: 0

When I have modeled VRF systems I have always used the PVVT system type in eQUEST as recommended in this presentation: http://energytrust.org/library/bsug-files/modeling_real_performance_of_vrf_systems_kc-05.15.13.pdf

Using the efficiencies and the curves for the VRF system will get you pretty close, but if you want to account for heat-recovery within the system (one terminal unit in cooling while another is in heating), you will have to do some post-processing calculations.

Nathan Miller, PE, LEED AP BD+C ? Mechanical Engineer/Senior Energy Analyst
RUSHING | D 206-788-4577 | O 206-285-7100
www.rushingco.com

Nathan Miller's picture
Offline
Joined: 2011-09-30
Reputation: 200

Hi Rathna,
LG has a plug-in that works good with eQuest, I tried it and I noticed the % of energy saving will be on the region of 20% when compared to PTAC (Not compared to the App G. Baseline).
Thanks;
Sherif Farag
Technical Director
Integrated Environmental Services (IES) Ltd.
Abu Dhabi - UAE

Sherif Farag's picture
Offline
Joined: 2012-12-25
Reputation: 0

As Cory noted, WSHP works well for water source VRF systems. Up here in the north, these systems typically have a boiler and fluid cooler for maintaining the refrigerant loop temperature along with a circulating pump. The WSHP system captures the effects of ?moving? energy from one side of the building to the other without post processing. Two of the three Daikin curves can be implemented in the HP units and show additional savings.

Christopher Jones, P.Eng.
Tel: 416.644.4226 ? Toll Free: 1.888.425.7255 x 527

Chris Jones

crollinjones's picture
Offline
Joined: 2013-12-12
Reputation: 0

Hi Rathna,

What software are you using ? You might want to go through the attached modelling protocol attached from LG as Sherif mentions .

Harris

Harris Qureshi, B.E(Mech), MSc. Energy, LEED AP Homes
Mechanical Engineer
Stantec
Dubai Investment Park, PO Box 52764 Dubai UAE
Phone: +971-4-812-5947
Cell: +971-50-189-9924
Harris.Qureshi at stantec.com

[http://www.stantec.com/content/dam/stantec/images/esignature/stantec.png]

The content of this email is the confidential property of Stantec and should not be copied, modified, retransmitted, or used for any purpose except with Stantec's written authorization. If you are not the intended recipient, please delete all copies and notify us immediately.

? Please consider the environment before printing this email.

Qureshi, Harris's picture
Offline
Joined: 2015-05-22
Reputation: 0

Interesting post and thanks for the info - I find VRF a bit of a 'black
box' when it comes to modelling. Part of the issue is the huge variety of
indoor/ outdoor unit combinations.

I have no doubt that the better VRF systems are a superb technology.
However, I do believe some of the performance claims are audacious (I can
only speak of the European market). For example, heat recovery VRF with
seasonal average heating COP (kW/kW) > 8.0 and seasonal Cooling EER > 6 is
competing with centrifugal chillers - the most advanced VRF compressor
technology I know of is scroll.

I guess part of my beef is not trusting the Euro test standards for VRF!

Bye for now

Chris

Chris Yates2's picture
Offline
Joined: 2011-10-02
Reputation: 0

Dear All,
Thanks a lot for all the responses. I followed the procedure outlined in the LG guide. The overall savings are up by 13%, savings on cooling alone is up by 35% when compared to the default DX curves. Of course there is unmet hour issue as i have considered PSZ system.
Also i tried a few trials to understand which particular curve is responsible for the higher savings and found that "f(t entering wet bulb, t enter condenser) curve gives higher savings. And then changing the cooling capacity curve provides additional savings. The least impact is from the PLR curve.
Now the question is whether the savings achieved is justifiable. Has anyone else come across the same issue?.
I am concerned about the savings because, in a core and shell project, with DX curves the project is achieving 5% savings and once i input the VRF curves, the savings shoots to more than 15%. Meeting LEED mandatory is dependent on the VRF curves.?
I am working on Equest software.?
Regards,Rathnashree

Interesting post and thanks for the info - I find VRF a bit of a 'black box' when it comes to modelling. Part of the issue is the huge variety of indoor/ outdoor unit combinations.
I have no doubt that the better VRF systems are a superb technology. However, I do believe some of the performance claims are audacious (I can only speak of the European market). For example, heat recovery VRF with seasonal average heating COP (kW/kW)? > 8.0 and?seasonal Cooling EER > 6 is competing with centrifugal chillers - the most advanced VRF compressor technology I know of is scroll.
I guess part of my beef is not trusting the Euro test standards for VRF!
Bye for now
Chris

Rathna Shree's picture
Offline
Joined: 2011-10-02
Reputation: 0

Dear All,
Thanks a lot for all the responses. I followed the procedure outlined in the LG guide. The overall savings are up by 13%, savings on cooling alone is up by 35% when compared to the default DX curves. Of course there is unmet hour issue as i have considered PSZ system.
Also i tried a few trials to understand which particular curve is responsible for the higher savings and found that "f(t entering wet bulb, t enter condenser) curve gives higher savings. And then changing the cooling capacity curve provides additional savings. The least impact is from the PLR curve.
Now the question is whether the savings achieved is justifiable. Has anyone else come across the same issue?.
I am concerned about the savings because, in a core and shell project, with DX curves the project is achieving 5% savings and once i input the VRF curves, the savings shoots to more than 15%. Meeting LEED mandatory is dependent on the VRF curves.?
I am working on Equest software.?
Regards,Rathnashree

Interesting post and thanks for the info - I find VRF a bit of a 'black box' when it comes to modelling. Part of the issue is the huge variety of indoor/ outdoor unit combinations.
I have no doubt that the better VRF systems are a superb technology. However, I do believe some of the performance claims are audacious (I can only speak of the European market). For example, heat recovery VRF with seasonal average heating COP (kW/kW)? > 8.0 and?seasonal Cooling EER > 6 is competing with centrifugal chillers - the most advanced VRF compressor technology I know of is scroll.
I guess part of my beef is not trusting the Euro test standards for VRF!
Bye for now
Chris

Rathna Shree's picture
Offline
Joined: 2011-10-02
Reputation: 0