COP comparison under ARI condition

[MartinHsu111]

Hi All,
I met an owner of a building and he has a question about two brands water cooled machines(applied products): Per ARI standard rating conditions, we shall set condenser water entering temp 85F and flow rate 3.0gpm/ton, leaving evaporator temp 44F and flow 2.4gpm/ton.
If cooling capacity desired 300tons and we set flow rate and temp per ARI ,then one machine delivers 290tons and the other 298tons(this could be happen such as most screw chillers capacity ranges steply ), obviously their entering evaporator temp and leaving condenser water temp will be different. The owner said both the capacities is acceptable but he can not tell which one is better in energy saving.Could any one give some advise on this? I think if we set entering/leaving temp for both evap and cond will be better for efficiency comparison than ARI rating settings.

[wambat]

The ARI specs are for standerd 10 degree heat exchangers however you always have the latatude of of adjusting the flow rates to get the best efficiency. You can always make adjustments and check the effects on power use or KW/ton