chiller surging?
chiller surging?
(OP)
hi,
what is centrifugal chiller surging?How to avoid it if it is due to low cooling load?
thanks.
what is centrifugal chiller surging?How to avoid it if it is due to low cooling load?
thanks.
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RE: chiller surging?
RE: chiller surging?
One common solution is to use ''hotgas bypass''.Hot gas bypass means to dischrage the hot compressed gas back into the suction line.This would raise the flow through the compressor and bring to the safe operating region on its performance curve. During surging the compressor tries to do the same thing as hot gas bypass by itself by sending the gas back to its suction chamber but with disasterous results !I am not sure whether ''Hot gas bypass'' can be done on an existing installation on site.The manufacturer would be the best person to advise.Another option used to overcome surging is to use a variable speed drive unit.But this agian is not an easy solution as the control circuitry and motor needs to be designed for it.
For the above reason one needs to be careful about specifying the capacity of a centrifugal compressor.If you are not sure about your load,it is better to go for multiple centrifugal compressors.Some manufacturers have two compressors on board the machine each sized for 50% capacity to overcome this problem.
In my opinion centrifugal compressors should not operate below 30% of their capacity
RE: chiller surging?
If you know that the chiller will run on part loads, ask the manufacturer to select and furnish part load information of the chiller down to 20% or 30% (this will depend on how low the chiller will load down to) at CONSTANT condenser entering water temperature. If the machine is stable at these conditions at Constant condenser entering water temperatures, chances of surging are very slim. The flip side, though is a slightly expensive equipment, due to probably a bigger evaporator and/or condenser, but has the advantage of better power consumption.
One needs to know their load pattern before taking this decision.
HVAC68