Danfoss iSave 21, Руководство пользователя

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User manual iSave 21
15
180R9221 / 521B1174 / DKCFN.PS.003.A1.02
5.7 How does the iSave work?
Figure 5.1 shows a section view of the iSave
The iSave consists of a rotating isobaric pressure exchanger and a positive displacement
pump, also called booster pump. The rotation speed of the pressure exchanger and the
pump is exactly the same, as they are driven by the same electric motor.
Fig. 5.1.
5.7.1 Pressure exchanger function:
The pressure exchanger consists of two port plates, one at the concentrate side and one at
the seawater side. In between there is a rotor with several ducts that connect the concen-
trate side with the seawater side.
The pressure exchanger transfers pressure from the high-pressure (HP) concentrate (HP in)
to the low-pressure (LP) seawater coming from low-pressure feed pump (LP in).
To separate the HP side from the LP side there is a sealing zone on both port plates. A single
duct in the rotor is either on the HP side, or on the LP side or in the sealing zone. A single
duct is never in contact with more than one zone at the time. When the rotor rotates a duct
will go from the LP zone over the first sealing zone into the HP zone, and hereafter from the
HP zone over the second sealing zone and back to the LP zone.
The flow through the HP side of the iSave is forced and controlled by the booster pump.
When the high-pressure concentrate is flowing into the iSave it pressurizes the sea water in
the duct coming from “LP in”. The pressurized seawater is then pumped out of “HP out”. Just
before the HP concentrate in the duct comes to the seawater port plate, the duct goes into
the sealing zone and the flow in the duct stops. When the duct goes into the LP zone the
concentrate water is de-pressurized. The (LP) seawater coming from the LP feed pump (LP
in) forces the LP concentrate out of “LP out”.
This pressure exchange process is repeated for each duct with every rotation of the rotor,
and the ducts are thus continuously filling and discharging. The flow on the HP side and LP
side of the iSave is nearly constant over time.
There is no physical barrier in the ducts between the concentrate and seawater. This means
that there will be a small amount of mixing between the two liquids.
When the iSave is rotating the water always flows respectively from LP-in to HP-out, AND
from HP-in to LP-out. However, if the feed flow into LP-in is higher than the flow into HP-in,
some of the LP feed flow will flow directly to LP-out.
When the iSave is not rotating the seawater can only run directly from LP-in to LP-out.
NB!
HP-in
Concentrate
side
LP-out
LP-in
Seawater side
HP-out