25 - Applications -
OPERATIONAL LIMITATIONS
GP refrigerant pumps are suitable for operation with all refrigerants.
GP 52 can be operated with ammonia up to 1450 RPM.
GP 52 is only permitted for operation with higher density refrigerants (ρ > 800 kg/m³)
below 1200 RPM!
5.2 DETERMINATION OF THE DELIVERY HEAD
The required delivery head is the resistance the pump needs to overcome to supply the evap-
orator with the high-est pressure loss with sufficient liquid refrigerant (in most cases this will
be the furthest distant evaporator).
The delivery head is depending from:
Height difference between pumps and evaporators
Resistance of pipe work and evaporators
Pressure losses of valves and fittings in the delivery line
Density of the refrigerant
The max. allowable delivery head should never be exceeded, because otherwise the pump is
operated outside the permitted range and will see internal damages (see chap. 6.5)
5.3 DETERMINATION OF THE REQUIRED FLOW
The evaporators have to be supplied with sufficient liquid refrigerant, so that
The surface of the evaporators is fully used
Supply to several evaporators with ifferent duties is as even as possible.
The re-circulation rate is calculated as follows:
Recirculation rate
mass flow pump
evaporated refrigerant
pump
Q0
A re-circulation factor of 4 means that 3 parts refrigerant are returned as liquid and 1 part is
evaporated.
The recirculation rate depends on the type of evaporator equipment and operation conditions.
The larger the duty, loading rate, the greater the recommended recirculation factor.
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