Refrigeration – Refrigeration producer – Compressor-condenser-evaporator circuit
Reexamination Certificate
2001-07-16
2002-10-08
Doerrler, William C. (Department: 3744)
Refrigeration
Refrigeration producer
Compressor-condenser-evaporator circuit
C062S510000
Reexamination Certificate
active
06460371
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multistage compression refrigerating machine such as a centrifugal chiller, screw chiller, or the like.
2. Description of the Related Art
Multistage compression refrigerating machines are widely used in air conditioning systems of general buildings, factories, and the like. For example, the two-stage compression refrigerating machine as shown in
FIG. 3
comprises an evaporator
51
, a first-stage compressor
53
and a second-stage compressor
54
which are rotationally driven by an electric motor
52
(abbreviated to the motor
52
, hereinbelow), a condenser
55
, a subcooler
56
, a motor cooler
57
for cooling the motor
52
by using a refrigerant, and a lubricating-oil cooler
58
for cooling lubricating oil by using a refrigerant.
In the evaporator
51
, a liquid refrigerant is heated by cold water
60
having a temperature of 12° C. passing through a tube
59
, so that vaporized refrigerant
61
is generated. In this process, the cold water
60
is cooled to approximately 7° C. thorough the heat exchange in the evaporator
51
, and it is then delivered outside. Therefore, the temperature in the evaporator
51
is maintained to be approximately 5° C.
The vaporized refrigerant
61
generated in the evaporator
51
is supplied to the first-stage compressor
53
and second-stage compressor
54
, and the supplied refrigerant is two-stage-compressed by using impellers which are rotated by the motor
52
, thereby discharging high-temperature and high-pressure vaporized refrigerant
61
a
. Here, vaporized refrigerant
61
b
from the subcooler
56
is also introduced (or supplied) into a path between the first-stage and second-stage compressors
53
and
54
(i.e., the upstream side of the second-stage compressor
54
), and the supplied vaporized refrigerant
61
b
is also compressed together with the vaporized refrigerant
61
from the evaporator
51
.
In the condenser
55
, the high-temperature and high-pressure vaporized refrigerant
61
a
discharged from the second-stage compressor
54
is cooled using cooling water
63
which flows through a tube
62
, thereby condensing the vaporized refrigerant
61
a
into a liquid. In this process, the cooling water
63
is heated through the heat exchange in the condenser
55
and is then discharged outside. The condensed liquid refrigerant
64
is collected at the bottom of the condenser
55
; thus, the temperature inside the condenser
55
is approximately 40° C.
The pressure of the liquid refrigerant
64
a
supplied from the condenser
55
is reduced to an intermediate pressure by using a first-stage expansion valve
65
, so that the refrigerant
64
a
is expanded, and a portion of the expanded refrigerant is output from the subcooler
56
as vaporized refrigerant
61
b
. As explained above, this vaporized refrigerant
61
b
is supplied to an intermediate position between the first-stage compressor
53
and the second-stage compressor
54
. On the other hand, the pressure of the remaining refrigerant
64
a
cooled through the evaporation of the refrigerant
64
a
is further reduced using a second-stage expansion valve
66
and is then supplied to the evaporator
51
.
In addition, a portion
64
b
of the refrigerant
64
, which is collected at the bottom of the condenser
55
, is used for cooling the motor
52
and the lubricating oil. More specifically, the refrigerant
64
b
is first supplied to the lubricating-oil cooler
58
so as to cool the lubricating oil and is then supplied to the motor cooler
57
so as to cool the motor
52
. After that, the refrigerant
64
b
including a vaporized portion is returned to the evaporator
51
.
However, in the conventional multistage compression refrigerating machines, the refrigerant
64
b
(a portion of the liquid refrigerant
64
) collected at the bottom of the condenser
55
having a temperature of approximately 40° C. is used for cooling the motor
52
and the lubricating oil, and the refrigerant
64
b
after the cooling process is returned to the evaporator
51
whose inner temperature is approximately 5° C. Therefore, the liquid refrigerant
64
b
expands due to a pressure difference between the condenser
55
and the evaporator
51
, and as a result, the refrigerant
64
b
evaporates in the evaporator
51
. Accordingly, the amount of the liquid refrigerant to be used to provide or increase the refrigerating capacity is reduced, thereby decreasing the refrigerating capacity.
SUMMARY OF THE INVENTION
In consideration of the above circumstances, an object of the present invention is to provide a multistage compression refrigerating machine for efficiently cooling a rotating machine such as an electric motor and lubricating oil by using a refrigerant and increasing the amount of refrigerant to be used to provide the refrigerating capacity in the evaporator, thereby improving the refrigerating capacity.
Therefore, the present invention provides a multistage compression refrigerating machine comprising:
an evaporator;
a condenser for condensing a refrigerant and supplying the condensed refrigerant to the evaporator via a subcooler:
a multistage compression system having a plurality of compressors which are connected in series, for:
receiving the refrigerant evaporated in the evaporator;
receiving a refrigerant evaporated from the subcooler, from an intermediate position between adjacent compressors in the multistage compression system; and
compressing the received refrigerants together and discharging the compressed refrigerant to the condenser;
a rotating machine for driving the multistage compression system;
a rotating-machine cooler for cooling the rotating machine; and
a lubricating-oil cooler for cooling lubricating oil for lubricating the rotating machine, and wherein:
the refrigerant extracted from the subcooler is supplied to the rotating-machine cooler and the lubricating-oil cooler, and this refrigerant is returned to the evaporator after cooling.
According to the present invention, the rotating machine and the refrigerant can be efficiently cooled, and the amount of the liquid refrigerant (in the evaporator) to be used to provide or increase the refrigerating capacity can be reduced, thereby improving the refrigerating capacity and reducing the running cost.
It is possible that:
one or more subcoolers connected in series are provided for supplying the evaporated refrigerant from each subcooler to each intermediate position between adjacent compressors of the multistage compression system; and
the refrigerant supplied to the lubricating-oil cooler and the rotation-machine cooler is extracted from the subcooler positioned at a position most downstream of the subcoolers connected in series.
In this case, the refrigerant capacity can be further improved and the cost can be further reduced.
Typically, the rotating machine is an electric motor.
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Doerrler William C.
Mitsubishi Heavy Industries Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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