Overriding Hydronic economizer with air cooled gas heatpump in EnergyPlus

asked 2017-04-13 10:17:07 -0600

updated 2017-04-13 16:30:38 -0600

Hi, My system has a cooling tower that provides condenser water to a hydronic economizer. When the outside air temperatures below 17°C the chilled water from the demand side of the hydronic economizer is fed into the chilled water demand loop(cooling coils and radiant slabs). When the outside air temperature exceeds 17°C, the hydronic economizer is shut and an air cooled gas heat pump feeds the chilled water demand loop. The aircooled gas heat pump also feeds the hot water demand loop (heating coils and radiant slabs).

Based on this question, I used a ChillerHeater:Absorption:DirectFired component to model the air-cooled gas heat pump. And based on this question, I tried overriding the non-integrated hydronic economizer with the ChillerHeater component.

As the (air-cooled) ChillerHeater:Absorption:DirectFired component does not have a condenser water loop, the condenser side inlet and outlet were modeled as outdoorair:nodes. For the hydronic economizer (HeatExchanger:FluidToFluid component), I am not sure what node name should be used in the field "Component Override Loop Demand Side Inlet Node Name". This is similar to this question but I do no see an answer there.

Any help is appreciated.

Thank you, Raghu

answered 2017-04-25 14:10:43 -0600

rsunnam

960 ●2 ●9 https://rmi.org/our-wo...

Hello Me from the past,

Since I noticed multiple questions from the past about using hydronic economizer with air cooled plant equipment with no clear answers, I thought I would write about my approach (That seems to work) to see if someone else has any further suggestions.

The HeatExchanger:FluidToFluid component cannot be overridden by air cooled components using the option "CoolingSetpointOnOffwithComponentOverride". The sequence of operation basically wanted the heatpumps to be turned off when the OutsideAir WetBulb temp < 10.7°C. I modelled the hydronic economizer as an “integrated economizer” and placed it on the same branch as the chilled water pump. Further, I created two separate schedules for the “PlantEquipmentOperationSchemes” (for cooling equipment list that comprises of only the air cooled gas heat pumps) and “CondenserEquipmentOperationSchemes” (For the condenser equipment list with the cooling tower). I added these schedules as EMS:Actuators that are updated at every timestep based on the OA WB Temp. This turned the heat pumps only when the OA WB Temp >10.7°C and simultaneously turned the cooling tower off (thereby overriding the economizer). The plant loop and condenser loop are as follows

image description

I checked the ESO file and was able to verify that the air-cooled gas heatpumps were turned off when the economizer was operation and vice-versa. These results seem acceptable to me. If someone else has a better/alternative approach to go about overriding the hydronic economizer with air-cooled plant equipment, I would be very interested to know.

Raghu