What is the minimum flow rate through a McQuay air cooled chiller?
The catalog refers to the minimum flow at full capacity but it would be more reasonable to assume that an engineer wants to know the minimum flow rate at a reduced capacity. Here is the answer from Tom Nichols, Applications Engineer from McQuay International. We have to be careful of the velocity in the evaporator tubes, if it gets to low we can freeze the evaporator. They don’t give us that velocity but the go no lower than number is 3.0 FPS. This equals to about 60% of the published full capacity minimum flow assuming the chiller is operating at 25%. Example; AGZ120B has a published minimum flow rate of 180 GPM so the real minimum we should tell the engineer is 108 GPM, with a rate of change no greater than 10%/minute.
