York R-134a, Руководство по эксплуатации и обслуживанию, Страница: 7 / 38

JOHNSON CONTROLS
7
FORM 160.76-O1
ISSUE DATE: 05/22/2019
1
The refrigerant vapor, which is produced by the boil-
ing action in the evaporator, flows to the compressor
where the rotating impeller increases its pressure and
temperature and discharges it into the condenser. Wa-
ter flowing through the condenser tubes absorbs heat
from the refrigerant vapor, causing it to condense. The
condenser water is supplied to the chiller from an ex-
ternal source, usually a cooling tower. The condensed
refrigerant drains from the condenser into the liquid
return line, where the variable orifice meters the flow
of liquid refrigerant to the evaporator to complete the
refrigerant circuit.
The major components of a chiller are selected to han-
dle the refrigerant, which would be evaporated at full
load design conditions. However, most systems will
be called upon to deliver full load capacity for only a
relatively small part of the time the unit is in operation.
CAPACITY CONTROL
The major components of a chiller are selected for full
load capacities, therefore capacity must be controlled
to maintain a constant chilled liquid temperature leav-
ing the evaporator. Pre-rotation vanes (PRV), located
at the entrance to the compressor impeller, compensate
for variation in load (See Figure 1 ).
The position of these vanes is automatically controlled
through a lever arm attached to an electric motor lo-
cated outside the compressor housing. The automatic
adjustment of the vane position in effect provides the
performance of many different compressors to match
various load conditions from full load with vanes wide
open to minimum load with vanes completely closed.
SECTION 1 - DESCRIPTION OF SYSTEM AND
FUNDAMENTALS OF OPERATION
SYSTEM OPERATION DESCRIPTION
The YORK Model YK Chiller is commonly applied
to large air conditioning systems, but may be used
on other applications. The chiller consists of an open
motor mounted to a compressor (with integral speed
increasing gears), condenser, evaporator and variable
flow control.
The chiller is controlled by a modern state of the art
Microcomputer Control Center that monitors its opera-
tion. The Control Center is programmed by the opera-
tor to suit job specifications. Automatic timed start-ups
and shutdowns are also programmable to suit night-
time, weekends, and holidays. The operating status,
temperatures, pressures, and other information perti-
nent to operation of the chiller are automatically dis-
played and read on a graphic display. Other displays
can be observed by pressing the keys as labeled on the
Control Center. The chiller with the OptiView Control
Center is compatible with an electro-mechanical start-
er, YORK Solid State Starter (optional), or Variable
Speed Drive (optional).
In operation, a liquid (water or brine to be chilled)
flows through the evaporator, where boiling refrigerant
absorbs heat from the liquid. The chilled liquid is then
piped to fan coil units or other air conditioning terminal
units, where it flows through finned coils, absorbing
heat from the air. The warmed liquid is then returned to
the chiller to complete the chilled liquid circuit.
7619A(D)
FIGURE 1 - COMPRESSOR PRE-ROTATION VANES