ENGLISH
16
Heat exchanger of two-stage centrifugal chiller is composed of two shell type for easy separation into evaporator and
condenser. The tubes are arranged so as to maximize the heat exchanging ability. It is also designed so that the re-
frigerant can be spread evenly on all tubes for the sake of surge prevention and the COP decrease in part load opera-
tion. Efficiency increasing purpose sub cooler is adopted for the subcool of the condensed refrigerant.
A relief valve for an abnormal situation is at the upper part of the heat exchanger.
Heat exchanger
Expansion device is composed of butterfly valve and fixed orifice. At 100% load, the pressure loss of orifice is lower
than the level of refrigerant in condenser. Thus the subcooled refrigerant passes through the orifice while the maxi-
mum refrigerant flows through the evaporator. If the load decreases gradually, the circulation of the refrigerant also
decreases resulting in decreasing of refrigerant level in the condenser. If the refrigerant liquid level decreases, more
gas generated in the orifice and the resistance increased, which becomes to control the flow rate.
The condensed refrigerant liquid passed the 1st orifice
enters the economizer which divides into refrigerant gas
and liquid. The refrigerant gas is mixed with mid-temper-
ature, mid-pressure gas compressed in the 1st impeller.
The refrigerant liquid goes through 2nd orifice to be
taken into evaporator. The mid-temperature and mid-
pressured gas between the 1st and the 2nd impeller be-
come cool by mixing with the cool refrigerant gas
supplied from economizer before sucked in to the 2nd
impeller.
As such, when the 2nd impeller discharge gas tempera-
ture is decreased by decreasing 1st impeller discharge
gas, the power required by the compressor is decreased
-increasing the cycle efficiency. The efficiency increase
much higher than by the 1 Stage compressing method.
Expansion device and economizer
Relief valve
Body
Refrigerant
distributor
Refrigerant outlet
Tubes
Baffle
Accumulator
Tubes
Relief valve
Waterbox
Body
Waterbox
Refrigerant outlet
Refrigerant inlet
Figure 6. Evaporator
Figure 7. Condenser
Figure 8. Economizer