AE4-1322
© 2002 Copeland Corporation
Issued 4-2002
Printed in U.S.A.
13
5.2 Operation principle
5.2 Operation principle
5.2 Operation principle
5.2 Operation principle
5.2 Operation principle
With screw compressors the compression process
occurs only in one flow direction (see Section 2.2).
This fact enables to locate an additional suction port at
the rotor housing. The position is selected so that the
suction process has already been completed and a
slight pressure increase has taken place. Via this
connection an additional mass flow can be taken in,
which has only a minimal effect on the flow from the
suction side.
The pressure level at the ECO suction point is similar
to the intermediate pressure with 2-stage compres-
sors. This means that an additional sub-cooling circuit
or intermediate pressure receiver for 2-stage expansion
can be integrated into the system. This design
achieves a significantly higher cooling capacity through
additional liquid sub-cooling. At the same time, there is
a relatively low increase in the compressor’s power
input, as the total working process becomes more
efficient – due to the higher suction pressure, among
other things.
5.3 Economizer operation with sub-cooling circuit
5.3 Economizer operation with sub-cooling circuit
5.3 Economizer operation with sub-cooling circuit
5.3 Economizer operation with sub-cooling circuit
5.3 Economizer operation with sub-cooling circuit
With this operation mode a heat exchanger is utilized
as a liquid sub-cooler. A part of the refrigerant mass
flow from the condenser enters the sub-cooler via an
expansion device, and evaporates upon absorbing heat
from the counter-flowing liquid refrigerant (sub-cooling).
The superheated vapor is taken in at the compressor’s
ECO connection, mixed with the mass flow from the
evaporator and compressed to a high pressure.
With this type of operation the sub-cooled liquid is
under condensing pressure. Therefore the piping to the
evaporator does not require any special features –
apart from insulation.The system can be applied
universally.
5.4 ECO operation with intermediate pressure
5.4 ECO operation with intermediate pressure
5.4 ECO operation with intermediate pressure
5.4 ECO operation with intermediate pressure
5.4 ECO operation with intermediate pressure
receiver
receiver
receiver
receiver
receiver
This layout version for 2-stage refrigerant pressure relief
is particularly advantageous in connection with flooded
evaporators and is therefore primarily used in plants
with large cooling capacity.
Figure 12
System with sub-cooling circuit
