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I'm trying to compare the energy outputs of cooling air using a 100% Outdoor AHU connected to an air cooled chiller. I'm trying to compare a simplistic enthlpy calculation where i use the dry bulb RH and set-point to get the enthalpy difference and than divide it by the COP which is assumed to be at constant value of 3.1.

I found a 20% difference from the EnergyPlus output where my calculation is lower. In both models i assumed a set-point of 18C, constant CFM and use the same weather file (mainly dry ball temp and RH values)

I can also tell that the enthalpy calculation is more sensitive to change at high temperatures and is less accurate there.I'm trying to think where is this change in results is coming from, maybe from using a constant cop? but 20% is a lot i would expect less. anyway any insights will be welcomed

I'm adding an HTML of the graph compering both models

I'm trying to compare the energy outputs of cooling air using a 100% Outdoor AHU connected to an air cooled chiller. I'm trying to compare a simplistic enthlpy calculation where i use the dry bulb RH and set-point to get the enthalpy difference and than divide it by the COP which is assumed to be at constant value of 3.1.

I found a 20% difference from the EnergyPlus output where my calculation is lower. In both models i assumed a set-point of 18C, constant CFM and use the same weather file (mainly dry ball temp and RH values)

I can also tell that the enthalpy calculation is more sensitive to change at high temperatures and is less accurate there.I'm trying to think where is this change in results is coming from, maybe from using a constant cop? but 20% is a lot i would expect less. anyway any insights will be welcomed

I'm adding an HTML of the graph compering both models

I'm trying to compare the energy outputs of cooling air using a 100% Outdoor AHU connected to an air cooled chiller. I'm trying to compare a simplistic enthlpy calculation where i use the dry bulb RH and set-point to get the enthalpy difference and than divide it by the COP which is assumed to be at constant value of 3.1.

I found a 20% difference from the EnergyPlus output where my calculation is lower. In both models i assumed a set-point of 18C, constant CFM and use the same weather file (mainly dry ball temp and RH values)

I can also tell that the enthalpy calculation is more sensitive to change at high temperatures and is less accurate there.I'm trying to think where is this change in results is coming from, maybe from using a constant cop? but 20% is a lot i would expect less. anyway any insights will be welcomed

I'm adding an HTML of the graph compering both models

I'm trying to compare the energy outputs of cooling air using in a 100% Outdoor AHU connected to an air cooled chiller. chiller without reheat. I'm trying to compare a simplistic enthlpy calculation where i use the dry bulb RH and set-point to get the enthalpy difference and than divide it by the COP which is assumed to be at constant value of 3.1.

I found a 20% difference from the EnergyPlus output when loking at the yearly consumption in kwh, where my calculation is lower. In both models i assumed a set-point of 18C, constant CFM and use the same weather file (mainly dry ball temp and RH values)

I can also tell that the enthalpy calculation is more sensitive to change at high temperatures and is less accurate there.I'm there. and that in low temperatures i get a result I'm trying to think where is this change in results is coming from, maybe from using a constant cop? but 20% is a lot i would expect less. less for a yearly consumption

. anyway any insights will be welcomed

I'm adding an HTML of the graph some pictures compering both models

HTMLthe models, this is a general yearly view.

this one shows behavior in high temperatures:

and this one is for low temperatures

I'm trying to compare the energy outputs of cooling air in a 100% Outdoor AHU connected to an air cooled chiller without reheat. I'm trying to compare a simplistic enthlpy calculation where i use the dry bulb RH and set-point to get the enthalpy difference and than divide it by the COP which is assumed to be at constant value of 3.1.

I found a 20% difference from the EnergyPlus output when loking at the yearly consumption in kwh, where my calculation is lower. In both models i assumed a set-point of 18C, constant CFM and use the same weather file (mainly dry ball temp and RH values)

I can also tell that the enthalpy calculation is more sensitive to change at high temperatures and is less accurate there. and that in low temperatures i get a result I'm trying to think where is this change in results is coming from, maybe from using a constant cop? but 20% is a lot i would expect less for a yearly consumption

. anyway any insights will be welcomed

I'm adding some pictures compering the models, this is a general yearly view.

this one shows behavior in high temperatures:

and this one is for low temperatures