Capacity control

[hendry]

Hello I was asked a question on a mock exam paper,and I am unsure of the correct answer.

The question was Capacity control of a screw compressor is generally accomplished by:

(a) Hot gas bypass

(b) throttling the suction vapour

(c) Cylinder unloading

(d) sliding valve

I did not get this correct,and i am unsure still.

I think it might be (a) though.

sparrow

since it was an exam Q, i feel the educator is looking for answer D.

however, in real life all the above is applicable in capacity ctrl.

it has to do with the engineer's design concept & his/her selection of equipment.

sometimes, the lowest capacity after unloading the compressor is still too high cap for the job, you have to introduce something else to stabilize the system.

i feel, for exam, we have to answer smartly to fits the needs and not so much to our expertise.