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[EnergyPlus_Support] Re: Multiple chillers
Dear All,
I¡¯d like to explain more about the questions.
For example, PlantLoopCoolingDemand:HVAC, namely the Total Water
Cooling Coil Energy of all zones, is 2272.7kw, but all the 4 chillers
operated at the same Chiller Part Load Ratio 0.425, and Chiller Evap
Heat Trans Rate for every chiller is 586.3kw, the full load chiller
capacity for every chiller is 1512 kw in this model. According to the
reality, only two chillers can provide the system cooling demand
2272.7kw, why the 4 chillers operate together? The sum of the Chiller
Evap Heat Trans Rate of the 4 chillers (2345.6 kw) are not equal to
the system cooling demand 2272.7kw. What make the difference? The Load
Distribution Scheme is set as Sequential.
According to the report variable for Chiller Evap Heat Trans Rate and
Chiller Part Load Ratio, the value of Chiller Evap Heat Trans Rate
over Chiller Part Load Ratio is not equal to the maximum chiller
capacity, why this happened? Chiller Evap Heat Trans Rate is the
chiller capacity? Why the Chiller Evap Water Outlet Temp[C] is not 7¡æ
as expected?
In addition, CHILLED WATER LOOP CHILLED WATER LOOP:Plant Loop Cooling
Demand is 7730.5kw, CHILLED WATER LOOP CHILLED WATER LOOP:Plant Loop
Unmet Demand is 175.3kw. Why the Plant Loop Unmet Demand is not zero?
The Minimum Unloading Ratio is set as 0.25. What¡¯s the relationship
between the Plant Loop Cooling Deman and the Total Water Cooling Coil
Energy of all zones?
I appreciate your help!
Young
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "beyangj" <beyangj@...> wrote:
>
> Dear all,
>
> I have some questions about the model of multiple chillers. There are
> four water-cooled centrifugal chillers in the model, and their
> capacity are the same. The chillers are controlled as SEQUENTIAL.
>
> The first question is what's the relationship between Plant Loop
> Cooling Demand [W] and Chiller Evap Heat Trans Rate [W]? When I change
> the reference capacity in Chiller:Electric:EIR, the Plant Loop Cooling
> Demand[W] also changed, why this happened?
>
>
> The second question is that the Reference Leaving Chilled Water
> Temperature is set as 7¡æ, and Leaving Chilled Water Lower Temperature
> Limit is set as 5¡æ. But in the outputs, the Chiller Evap Water Outlet
> Temp[C] is 5¡æ in all outdoor conditions, why the Chiller Evap Water
> Outlet Temp[C] is not 7¡æ as expected?
>
> When the cooling capacity of three chillers satisfied the cooling
> demand, but all the 4 chillers operated, and all the chiller operated
> on low part load ratio, even all less than 0.3, and Chiller Evap Heat
> Trans Rate [W] of the first three chillers are the same, why no
> chillers can operate at full load capacity? And why the fourth chiller
> operates even there is no need for it to operate? If three chillers
> can provide enough cooling capacity, they can operate at even load
> sharing without operating the 4th chiller?
>
>
> Thanks in advance.
>
>
> Young
>
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