UNIT 81 REVIEW QUESTIONS ANSWER KEY GO BACK TO INDEX
81-1) Describe the difference between a flooded and a dry (direct expansion) type
cooler.
81-2) What are some advantages and disadvantages to flooded coolers?
81-3) Why are low pressure refrigerants well suited for centrifugal compressor
chillers?
81-4) What is the function of a purge recovery unit?
81-5) What precaution should be taken whenever leak testing a low pressure
chiller?
81-6) What precaution should be taken for coolers that are located outside?
81-7) Why is the cooler shell and suction line insulated on a unit that is located
indoors?
81-8) Explain the operation of lead and lag compressors.
During peak periods, both compressors would be running fully loaded. In
the early evening as the load begins to decrease the chill water temperature
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to decrease, then the lead compressor will begin unloading cylinders.
Eventually when the lead compressor is fully unloaded the hot gas bypass
will open.
81-9) How can the centrifugal compressor speed be higher than the motor speed?
81-10) What is the difference between a single stage and two stage centrifugal
compressor?
81-11) What is the most efficient method of capacity control for a centrifugal
compressor?
81-12) What types of prime movers can be used for centrifugal chillers?
81-13) What type of capacity control is used for a centrifugal compressor that is
driven by a constant speed motor?
81-14) What can be considered an advantage of a screw type chiller as compared
to a centrifugal chiller?
81-15) What is the advantage of a screw compressor that utilizes three screws?
81-16) What is the purpose of a chiller economizer?
81-17) What happens to the flash gas formed in a chiller economizer?
81-18) What is the purpose of an oil return system for a chiller?
81-19) How should refrigerant be transferred from a chiller?
81-20) What could happen if you charge liquid refrigerant into a chiller that is
under a deep vacuum?