SIM List,
I need to model a scroll chiller (. Does anyone have an
opinion on which eQUEST chiller is a reasonable choice for this? I was
thinking that centrifugal would be the closest but this is simply based
on mechanical operation. I would like to choose the closest model based
on performance.
Eric Youngson
Not having looked too closely at the options, I would suggest not centrifugal.
Centrifugals are almost always water cooled, have modulating capabilites from10% to 100% capacity, and generally dont go below 200 tons capacity. They are positive displacment compressors and will follow the "fan laws", meaning there is a cubic relationship between energy used and cooling capacity (tons). Similar to a centrifugal pump and fan.
Scrolls are (until the very near future) air cooled and on/off control. They are staged. You wont see them over about 150 tons total chiller size. Part load capacity is pretty constant, in terms of kW/ton. There are usually multiple stages. At 50% load, half the compressors (therefore power requirement) is used.
Generally speaking, scroll IPLVs run about 1.1 kW/ton
water cooled centrifguals operate at around .50 kW/ton. But cooling towers need to be added, as well as condenser water pumps.
Lots of variables to consider.
Hope this was helpful.
W. Peter Anderson, P.E
The eQuest library contains a curve set for an air-cooled scroll chiller. There is no indication if this represents multiple compressors or not, but if you compare the EIR-fPLR curve outputs w/other chillers you might be able to tell. These curves would be selected from the custom curves list in the chiller window / performance curve tab in eQuest, then from each drop down, "library" -> "chiller," after which the curve appears.
Otherwise the multiple-compressor "reciprocating" chiller curves might provide a reasonable representation of typical scroll chillers, at least w/o the effort of making custom curves. These are selected by eQuest automatically when the user selects the "type" & compressors/ckt from the main chiller window. Check the default minimum cycling and hot gas bypass ratios.