Refrigeration – Automatic control – Diverse – cascade or compound refrigeration-producing system
Reexamination Certificate
2003-03-04
2004-10-26
Tanner, Harry B. (Department: 3744)
Refrigeration
Automatic control
Diverse, cascade or compound refrigeration-producing system
C062S231000, C236S0010EA
Reexamination Certificate
active
06807816
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an air conditioning system with two compressors and a method for operating the same, and more particularly to an air conditioning system with two compressors, so as to shorten standby time for re-operating a stopped compressor, and a method for operating the air conditioning system.
2. Description of the Related Art
Generally, an air conditioner comprises a compressor for compressing a gaseous refrigerant in a low-temperature and low-pressure state so as to convert it into a high-temperature and high-pressure state, a condenser for condensing the gaseous refrigerant in the high-temperature and high-pressure state compressed by the compressor so as to convert it into a liquid refrigerant in a high-temperature and high-pressure state, and an evaporator for evaporating the liquid refrigerant in the high-temperature and high-pressure state condensed by the condenser so as to convert it into a gaseous refrigerant in a low-temperature and low-pressure state. A heat pump air conditioner, additionally having a heating function, further comprises a four-way valve for converting a flow direction of the refrigerant according to cooling and heating modes.
In such a heat pump air conditioner, an indoor heat exchanger and an outdoor heat exchanger have different functions according to their cooling and heating modes. That is, the indoor heat exchanger serves as the condenser and the outdoor heat exchanger serves as the evaporator in the heating mode, thereby forming a heating cycle. On the other hand, the indoor heat exchanger serves as the evaporator and the outdoor heat exchanger serves as the condenser in the cooling mode, thereby forming a cooling cycle. Therefore, the heat pump air conditioner is unlimitedly applicable in all seasons.
Hereinafter, the air conditioner for forming the cooling cycle and the heat pump air conditioner for forming the cooling and heating cycles are generally referred to as an air conditioner.
Recent, air conditioners employ a plurality of compressors having different capacities, thereby variably changing a compression capacity of the refrigerant and optimizing cooling and heating efficiencies.
FIG. 1
is a block diagram illustrating a flow of a refrigerant of a conventional air conditioner in a cooling mode, and
FIG. 2
is a graph illustrating operating states of compressors in the conventional air conditioner. With reference to
FIGS. 1 and 2
, a method for operating the conventional air conditioner is described, as follows.
FIG. 1
is a block diagram illustrating the flow of the refrigerant of the conventional air conditioner in the cooling mode. The conventional air conditioner comprises a plurality of compressors
10
for compressing a gaseous refrigerant in a low-temperature and low-pressure state so as to convert it into a high-temperature and high-pressure state. The compressors
10
includes first and second compressors
11
and
12
, having different compression capacities of the refrigerant.
Each of the first and second compressors
11
and
12
has a designated compression capacity of the refrigerant, so as to compress a specific percentage of the total capacity (100%) of the refrigerant. The compression capacities of the refrigerant of the first and second compressors
11
and
12
are set by a manufacturer. Herein, the first compressor
11
has a 60% compression capacity of the refrigerant, and the second compressor
12
has a 40% compression capacity of the refrigerant.
Therefore, the total compression capacity of the refrigerant in the air conditioner is variably changed by selectively or simultaneously operating the first compressor
11
and the second compressor
12
according to a cooling load.
The conventional air conditioner further comprises check valves
13
and
14
, a four-way valve
20
, an outdoor heat exchanger
30
, an expansion valve
40
, an indoor heat exchanger
50
, and an accumulator
60
, thereby forming a cooling cycle via a flow of the refrigerant. The check valves
13
and
14
respectively prevent the reverse-flow of the refrigerant compressed by the first and second compressors
11
and
12
. The four-way valve
20
converts the flow direction of the refrigerant passing through the first and second compressors
11
and
12
, thereby reversing functions of the outdoor and indoor heat exchangers
30
and
50
. The outdoor heat exchanger
30
exchanges heat between external air and the refrigerant, thereby condensing the gaseous refrigerant in the high-temperature and high-pressure state, so as to convert it into a liquid refrigerant in a mid-temperature and high-pressure state. The expansion valve
40
decompresses the liquid refrigerant passing through the outdoor heat exchanger
30
, so as to convert it into a low-temperature and low-pressure state. The indoor heat exchanger
50
exchanges heat between the indoor air and the refrigerant passing through the expansion valve
40
so as to convert it into a two-phase refrigerant in liquid and gaseous phases. The accumulator
60
separates the liquid phase from the two-phase refrigerant passing through the indoor heat exchanger
50
, and then supplies only the gaseous phase to the first and second compressors
11
and
12
.
When the cooling or heating load is relatively light, only the second compressor
12
of the air conditioner is operated. Herein, the first compressor
11
is stopped, and the check valve
13
of the first compressor
11
is closed.
Therefore, the gaseous refrigerant compressed in the high-pressure state, which is discharged from an outlet
11
b
of the first compressor
11
and then supplied to the check valve
13
, is cut off, and then high pressure at the outlet
11
b
of the first compressor
11
is maintained. Since the gaseous refrigerant at an inlet
11
a
of the first compressor
11
is not yet compressed, low pressure at an inlet
11
a
of the first compressor
11
is maintained. Therefore, a pressure difference between the inlet
11
a
and the outlet
11
b
of the compressor
11
is generated.
When the pressures at the inlet
11
a
and the outlet
11
b
of the compressor
11
are equalized so as to remove the pressure difference, the stopped compressor
11
is re-operated. Standby time for re-operating the stopped compressor
11
is the same as the time taken to equalize the pressures at the inlet
11
a
and the outlet
11
b
of the compressor
11
.
When the high-pressure refrigerant around the outlet
11
b
moves toward the inlet
11
a
during the pressure equilibrium time, so as to equalize the pressures at the inlet
11
a
and the outlet
11
b
of the compressor
11
, oil used to operate the first compressor
11
leaks via gaps formed through the first compressor
11
and is accumulated in a pipe (P
1
) connected to the inlet
11
a
. When the first compressor
11
is re-operated and the refrigerant flows into the first compressor
11
via the inlet
11
a
, the leaking oil accumulated in the pipe (P
1
) flows into the first compressor
11
, together with the refrigerant.
However, when the first compressor
11
is stopped for a long time, the leaking oil accumulated in the pipe (P
1
) is solidified and an inner surface of the pipe (P
1
) becomes uneven. The uneven inner surface of the pipe (P
1
) with the solidified oil obstructs the flow of the refrigerant to re-operate the first compressor
11
, thereby extending the standby time for re-operating the stopped compressor
11
. Further, when the standby time is extended, the air conditioner cannot rapidly cope with the variation of the cooling load, thereby not satisfying users' comfort requirement within a room.
With reference to
FIG. 2
, the operating states of the compressors of the conventional air conditioner is described as follows.
When a cooling order is inputted to the air conditioner and the compressors are operated, the second compressor having the 40% compression capacity of the refrigerant is first operated, and later the first compressor having the 60% compression capacity of the refrige
Choi Chang Min
Huh Deok
Hwang Yoon Jei
Kim Cheol Min
Lee Won Hee
Greenblum & Bernstein P.L.C.
LG Electronics Inc.
Tanner Harry B.
LandOfFree
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