Chapter hvac engineering Fundamentals: Part 1 Introduction

9.3.3
Helical rotary compressors
Helical rotary or screw compressors are made in single-screw and
twin-screw types. The single-screw compressor (Fig. 9.7) consists of a
helical main rotor with two star wheels. The enclosure of the main
rotor has two slots through which the star wheel teeth pass; these
teeth, together with the rotor and its enclosure, provide the bounda-
ries of the compression chambers. The twin-screw compressor (Fig.
9.8) has two meshing helical gears and works much as a gear pump,
with the helical shape forcing the gas to move in a direction parallel
to the rotor shaft. These machines typically are direct-driven at 3600
r / min and are usually oil-flooded for lubrication and to seal leakage
paths. Capacity control is obtained by means of a sliding or rotating
slotted valve.
Equipment: Part 1
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