FIELD OF THE INVENTION
The present disclosure relates to the field of air conditioning, and in
particular to an air conditioning system and a control method thereof.
BACKGROUND OF THE INVENTION
5 At present, more and more large-scale scenes with refrigeration
requirements in commercial applications are using carbon dioxide type air
conditioning systems with injectors. On one hand, natural refrigerants including
carbon dioxide have better environmental friendliness. On the other hand,
injecting air conditioning systems typically have a simple structure and a small
10 volume, and can be applied to a large-temperature-difference environment. In
addition, multiple sets of parallel injectors can be used to obtain better partial-load
regulation and operating efficiency. Of course, for such an air conditioning system
with injectors, how to further improve its system performance and improve energy
efficiency has become the research and application objects.
15 SUMMARY OF THE INVENTION
In view of this, an air conditioning system and a control method thereof
are provided by the present disclosure, thereby effectively solving or at least
alleviating one or more of the above problems in the prior art and in other aspects.
In order to achieve at least one object of the present disclosure, an air
20 conditioning system is provided according to an aspect of the present disclosure,
which includes a main circuit and a first subcooling circuit, wherein the main
circuit has: a main compressor and an injector; a gas cooler connected between an
exhaust port of the main compressor and a primary flow inlet of the injector; a
gas-liquid separator connected between a suction port of the main compressor and
25 an outlet of the injector; and a main throttling element and an evaporator
connected between a liquid outlet of the gas-liquid separator and a secondary flow
inlet of the injector; and wherein the first subcooling circuit has: a first subcooling
compressor, a first condenser, a first subcooling throttling element and a first
3
subcooler connected in sequence; wherein the first subcooler is further disposed in
a flow path between the outlet of the injector and the gas-liquid separator in the
main circuit.
Optionally, the first subcooling circuit further includes a second subcooler
5 which is connected in parallel with the first subcooler; wherein the second
subcooler is further disposed between the primary flow inlet of the injector and
the gas cooler in the main circuit.
Optionally, the air conditioning system further includes a second throttling
element, wherein the second throttle element and the second subcooler are
10 connected in parallel with the first throttling element and the first subcooler.
Optionally, the air conditioning system further includes a back pressure
valve connected in parallel with the first subcooler and disposed between the
second subcooler and an exhaust port of the first subcooling compressor.
Optionally, the first subcooling circuit further includes a second subcooler
15 connected in series with the first subcooler; wherein the second subcooler is
further disposed between the primary flow inlet of the injector and the gas cooler
in the main circuit.
Optionally, the air conditioning system further includes a second
subcooling circuit having a second subcooling compressor, a second condenser, a
20 second subcooling throttling element, and a second subcooler connected in
sequence; wherein the second subcooler is further disposed between the primary
flow inlet of the injector in the main circuit and the gas cooler.
Optionally, the air conditioning system further includes a suction line heat
exchanger disposed in a flow path between the gas cooler and the primary flow
25 inlet of the injector; wherein a refrigerant flowing out of a gas outlet of the gasliquid separator flows into the suction port of the main compressor via the suction
line heat exchanger.
4
Optionally, the air conditioning system further includes a liquid pump
disposed in a flow path between the liquid outlet of the gas-liquid separator and
the secondary flow inlet of the injector.
Optionally, the liquid pump is disposed between the liquid outlet of the
5 gas-liquid separator and the main throttling element.
Optionally, the refrigerant participating in the operation in the main circuit
is a carbon dioxide refrigerant.
Optionally, the refrigerant participating in the operation in the first
subcooling circuit or the second subcooling circuit is a propane refrigerant.
10 Optionally, the air conditioning system includes a cooling system, a heat
pump system, or a refrigeration/freezing system.
In order to achieve at least one object of the present disclosure, according
to another aspect of the present disclosure, a control method for an air
conditioning system is further provided, which is used for the air conditioning
15 system described above, wherein the control method includes: starting the first
subcooling circuit when the main circuit is in operation.
Optionally, when the air conditioning system has a second subcooling
circuit, the control method further includes: starting the second subcooling circuit
when the main circuit is in operation.
20 According to the air conditioning system of the present disclosure and the
control method thereof, a two-phase flow of refrigerant flowing out of the outlet
of the injector of the main circuit is further cooled by the first subcooling circuit
disposed downstream of the injector, so that part of the gas-phase refrigerant is
further condensed into a liquid-phase refrigerant; as a result, the proportion of the
25 liquid-phase refrigerant that subsequently enters the evaporator to participate in
heat exchange is increased, thereby effectively improving the system performance
and energy efficiency thereof.
5
BRIEF DESCRIPTION OF THE DRAWINGS
The technical solutions of the present disclosure will be further described
in detail below with reference to the accompanying drawings and embodiments,
but it should be understood that the drawings are only provided for the purpose of
5 explanation, and should not be considered as limiting the scope of the present
disclosure. In addition, unless otherwise specified, the drawings are only intended
to conceptually illustrate the structures and constructions described herein, and are
not necessarily drawn to scale.
FIG. 1 is a schematic diagram of an embodiment of an air conditioning
10 system according to the present disclosure;
FIG. 2 is a schematic diagram of another embodiment of an air
conditioning system according to the present disclosure; and
FIG. 3 is a schematic diagram of further another embodiment of an air
conditioning system according to the present disclosure.
15 DETAILED DESCRIPTION OF THE EMBODIMENT(S) OF THE
INVENTION
The present disclosure will be described in detail below with reference to
the exemplary embodiments in the drawings. However, it should be understood
that the present disclosure may be embodied in a variety of different forms and
20 should not be construed as being limited to the embodiments set forth herein. The
embodiments are provided to make the disclosure of the present disclosure more
complete and thorough, and to fully convey the concept of the present disclosure
to those skilled in the art.
It should also be understood by those skilled in the art that the air
25 conditioning system proposed by the present disclosure does not narrowly refer to
an air conditioner in the industry which is used in a building and equipped with an
outdoor cooling/heating unit and an indoor heat exchange unit. Rather, it should
6
be considered as a kind of thermodynamic system with air conditioning function,
which is driven by various types of power sources (for example, electric power) to
exchange heat with the air at a position to be conditioned, by means of a phase
change of the refrigerant in the system. For example, when the air conditioning
5 system is used in a Heating Ventilating & Air Conditioning (HVAC) system in a
building, it may be a cooling system with a cooling-only function or a heat pump
system with both cooling and heating functions. As another example, when the air
conditioning system is used in the field of cold chain, it may be a transport
cooling system or a refrigeration/freezing system. However, regardless of which
10 form the air conditioning system is in, an injector should be present so as to be
suitable for the concept of the present disclosure.
Referring to FIG. 1, an embodiment of an air conditioning system is
illustrated. The air conditioning system 100 includes a main circuit 110 and a first
subcooling circuit 120. The main circuit 110 of the air conditioning system 100
15 includes a main compressor 111 for compressing gas and an injector 112 for
initially compressing a refrigerant fluid before the refrigerant fluid enters the main
compressor 111, thereby increasing a suction pressure of the fluid entering the
main compressor 111. The main circuit further includes a gas cooler 113
connected between an exhaust port of the main compressor 111 and a primary
20 flow inlet of the injector 112, a gas-liquid separator 114 connected between a
suction port of the main compressor 111 and an outlet of the injector 112, and a
main throttling element 115 and an evaporator 116 connected between a liquid
outlet of the gas-liquid separator 114 and a secondary flow inlet of the injector
112.
25 In addition, the first subcooling circuit 120 of the air conditioning system
100 includes a first subcooling compressor 121, a first condenser 122, a first
subcooling throttling element 123, and a first subcooler 124 that are connected in
sequence to form a closed loop. The first subcooler 124 mentioned herein is also
disposed in a flow path between the outlet of the injector 112 and the gas-liquid
30 separator 114 in the main circuit 110, thereby providing space for the heat
7
exchange between the refrigerant in the main circuit and the refrigerant in the first
subcooling circuit.
In this arrangement, a two-phase flow of refrigerant flowing out of the
outlet of the injector 112 of the main circuit 110 in the air conditioning system
5 100 is further cooled by the first subcooling circuit 120 disposed downstream of
the injector 112, so that part of the gas-phase refrigerant is further condensed into
a liquid-phase refrigerant; as a result, the proportion of the liquid-phase refrigerant
that enters the evaporator 116 to participate in heat exchange is increased, thereby
effectively improving the air conditioning system performance and energy
10 efficiency thereof.
Regarding the embodiment of the above air conditioning system, the
refrigerant participating in the operation of the main circuit 110 may be a carbon
dioxide refrigerant, which has good environmental friendliness, stable chemical
property, non-toxicity, non-combustibility, and good latent heat of vaporization.
15 In addition, the refrigerant participating in the operation of the first subcooling
circuit 120 may be a propane refrigerant, which has a better compression ratio and
is used to effectively improve system performance when providing supercooling
for the main circuit. Moreover, the system in which the propane refrigerant is
applied can be arranged in a machine room or outdoors, and a coolant is used to
20 transfer cold to the first subcooler 124 so that the system reliability can also be
improved with no need for the refrigerant to flow directly through the application
site (for example, a supermarket, etc.) where the evaporator is arranged.
In addition, in order to further improve the energy efficiency or reliability
of the system, some additional components may be added, as will be exemplified
25 below.
For example, a suction line heat exchanger 117 may be disposed in a flow
path between the gas cooler 113 and the primary flow inlet of the injector 112 in
the air conditioning system, and the refrigerant flowing out of the gas outlet of the
gas-liquid separator 114 flows into the suction port of the main compressor 111
8
after flowing through the suction line heat exchanger 117. Under this arrangement,
the gas-phase refrigerant flowing out of the gas outlet of the gas-liquid separator
114 first absorbs a part of the heat from a supercritical-state or the liquid-state
refrigerant downstream of the gas cooler 113 before entering the main compressor
5 111. On one hand, this causes the aforementioned refrigerant to recover a part of
the cold, thereby contributing to the improvement of energy efficiency, and on the
other hand, the temperature of the aforementioned gas-phase refrigerant is further
raised, thereby facilitating evaporation of a small amount of liquid-phase droplets
mixed in the aforementioned gas-phase refrigerant, and preventing them from
10 entering the main compressor to cause liquid hammering.
In another example, a liquid pump 118 may be disposed in the flow path
between the liquid outlet of the gas-liquid separator 114 and the secondary flow
inlet of the injector 112. More specifically, the liquid pump 118 is disposed
between the liquid outlet of the gas-liquid separator 114 and the main throttling
15 element 115 to provide a driving force to the liquid-phase refrigerant flowing out
of the liquid outlet of the gas-liquid separator 114 when the driving force provided
by the injector is insufficient, so that the liquid-phase refrigerant enters the
evaporator 116 for heat exchange; and if the injector has sufficient driving force,
the liquid pump may not participate in operation.
20 Referring to FIG. 2, another embodiment of an air conditioning system is
shown. In this case, the first subcooling circuit of the air conditioning system has
two parallel subcooling branches, one of which is provided with a first subcooler
124 that is still disposed in the flow path between the outlet of the injector 112
and the gas-liquid separator 114 in the main circuit 110, and the other of which is
25 provided with a second subcooler 126 that is also disposed between the primary
flow inlet of the injector 112 and the gas cooler 113 in the main circuit 110 and
further cools the refrigerant entering the injector 112, thus reducing the refrigerant
enthalpy at the primary flow inlet of the injector 112. On one hand, this increases
a primary flow rate of the refrigerant passing through a nozzle of the injector, and
9
on the other hand, the proportion of liquid-phase refrigerant at the injector outlet
will also be increased to help increase the cooling capacity and efficiency.
In this arrangement, on one hand, a two-phase flow of refrigerant flowing
out of the outlet of the injector 112 of the main circuit 110 in the air conditioning
5 system 100 is further cooled by the first subcooler 124 disposed downstream of
the injector 112, so that part of the gas-phase refrigerant is further condensed into
a liquid-phase refrigerant; as a result, the proportion of the liquid-phase refrigerant
that subsequently enters the evaporator 116 to participate in heat exchange is
increased, thereby effectively improving the air conditioning system performance
10 and energy efficiency thereof; and on the other hand, by disposing the second
subcooler 126 upstream of the injector 112 of the main circuit 110, the refrigerant
flowing out of the gas cooler 113 further absorbs the cold, which contributes to
additionally improving the energy efficiency of the system.
On this basis, a second throttling element 125 may also be disposed in
15 another branch connected in parallel with the first subcooler and provides
different throttling degrees for the first subcooler 124 and the second subcooler
126 as needed. Similarly, a back pressure valve 127 may be disposed between the
second subcooler 126 in another branch connected in parallel with the first
subcooler and the suction port of the first subcooling compressor 121 to control
20 the passage of this branch or keep its pressure constant.
Further, referring again to FIG. 3, another embodiment of an air
conditioning system is further provided herein. In this embodiment, the air
conditioning system has the first subcooling circuit of the previous embodiment,
and the first subcooler 124 and the second subcooler 126 are disposed in series in
25 the first subcooling circuit. The second subcooler is also disposed between the
primary flow inlet of the injector and the gas cooler in the main circuit. Since the
evaporation temperature of the second subcooler 126 disposed upstream of the
injector is generally higher than the evaporation temperature of the first subcooler
disposed downstream of the injector, it is also possible for the refrigerant flowing
10
out of the gas cooler to further absorb cold, which is helpful for additionally
increasing energy efficiency of the system. In the parallel arrangement of the
subcoolers in the previous embodiment, it is easier to control the allocation of the
cold, but a back pressure valve should be typically equipped to balance the
5 pressures in the two parallel flow paths; whereas in the series arrangement, there
is a higher requirement on the allocation of the cold, but the need for a back
pressure valve is eliminated.
Similarly, further another embodiment of an air conditioning system not
shown in the drawings is also provided herein. In this embodiment, the air
10 conditioning system also has the first subcooling circuit including at least the first
subcooler in the previous embodiments, and it further has a second subcooling
circuit. The second subcooling circuit includes a second subcooling compressor, a
second condenser, a second subcooling throttling element, and a second subcooler
that are connected in sequence. The second subcooler is also disposed between the
15 primary flow inlet of the injector and the gas cooler in the main circuit, and it is
also possible for the refrigerant flowing out of the gas cooler to further absorb
cold, which is helpful for additionally increasing energy efficiency of the system.
Regarding the embodiments of the above air conditioning system, the
refrigerant participating in the operation of the main circuit 110 may be a carbon
20 dioxide refrigerant, which has good environmental friendliness, stable chemical
property, non-toxicity, non-combustibility, and good latent heat of vaporization.
In addition, the refrigerant participating in the operation of the second subcooling
circuit may be a propane refrigerant, which has a better compression ratio and is
used to effectively improve system performance when providing supercooling for
25 the main circuit. Moreover, the system in which the propane refrigerant is applied
can be arranged in a machine room or outdoors, so that the system reliability can
also be improved with no need for the refrigerant to flow directly through the
application site (for example, a supermarket, etc.) where the evaporator is
arranged.
11
A control method for an air conditioning system, which can be used in the
air conditioning system of any of the foregoing embodiments or combinations
thereof, is continuedly described herein in connection with FIG. 1. Specifically,
the control method includes starting the first subcooling circuit 120 when the main
5 circuit 110 is in operation. At this point, the refrigerant in the main circuit 110 is
compressed by the main compressor 111 and then flows into the gas cooler 113 to
be cooled, and subsequently flows through the suction line heat exchanger 117 to
be further cooled by the gas-phase refrigerant from the separator. Then, it enters
the injector 112 via the primary flow inlet, mixes in the injector 12 with the gas10 phase refrigerant entering the injector 112 from the secondary flow inlet, is
ejected from the outlet of the injector 112 after being initially compressed by the
injector and forming a mixed two-phase flow, and then passes through the first
subcooler 124. At the same time, the propane refrigerant in the first supercooling
circuit 120 is compressed by the supercooling compressor 121 and then flows
15 through the first condenser 122 to be cooled, and subsequently flows through the
first subcooler 124 after passing through the first subcooling throttling element
123 for expansion throttling. The propane refrigerant cools the carbon dioxide
mixed two-phase refrigerant in the first subcooler 124, further condenses part of
the gas-phase refrigerant into a liquid-phase refrigerant, and increases the
20 proportion of the carbon dioxide liquid-phase refrigerant. Then, the propane
refrigerant returns to the first supercooling compressor 121, and a new cycle is
started. The cooled carbon dioxide mixed two-phase refrigerant continues to enter
the gas-liquid separator 114 for gas-liquid separation. The liquid-phase refrigerant
having an increased proportion due to supercooling is throttled by the main
25 throttling element 115 when driven by the liquid pump 118, and flows into the
evaporator 116 to participate in heat exchange. Since the amount of refrigerant
participating in the heat exchange is increased, the heat exchange capacity and
efficiency thereof can also be correspondingly increased. This part of the
refrigerant enters the secondary flow inlet of the injector 112 after completion of
30 heat exchange and participates in the refrigerant mixing and initial compression
process. The gas-phase refrigerant having a decreased proportion due to
12
supercooling flows out of the gas outlet of the gas-liquid separator 114, and passes
through the suction line heat exchanger 117 to further cool the refrigerant flowing
out of the gas cooler 113. After part of the heat is recovered, the gas-phase
refrigerant enters the compressor 111 to participate in a new cycle, and meanwhile
5 liquid hammering is also effectively avoided.
With continued reference to FIG. 2, if the first subcooling circuit in the
system now has another branch, the refrigerant in the main circuit 110 is
compressed by the main compressor 111 and then flows into the gas cooler 113 to
be cooled. Then, it flows through the second subcooler 126. At the same time, the
10 propane refrigerant in the first subcooling circuit 120 is compressed by the
supercooling compressor 121 and then flows through the first condenser 122 to be
cooled, and subsequently flows through the second subcooler 126 after passing
through the second supercooling throttling element 125 for expansion throttling.
The propane refrigerant cools the carbon dioxide refrigerant in the second
15 subcooler 126 to lower its enthalpy, and then flows through the back pressure
valve 127 and returns to the first subcooling compressor 121 to start a new cycle.
The cooled carbon dioxide refrigerant then enters the injector 112 from the
primary flow inlet, mixes in the injector 112 with the gas-phase refrigerant
entering the injector 112 from the secondary flow inlet, is ejected from the outlet
20 of the injector 112 after being initially compressed by the injector and forming a
mixed two-phase flow, and then passes through the first subcooler 124. At the
same time, the propane refrigerant in the first supercooling circuit 120 is
compressed by the supercooling compressor 121 and then flows through the first
condenser 122 to be cooled, and subsequently flows through the first subcooler
25 124 after passing through the first subcooling throttling element 123 for expansion
throttling. The propane refrigerant cools the carbon dioxide mixed two-phase
refrigerant in the first subcooler 124, further condenses part of the gas-phase
refrigerant into a liquid-phase refrigerant, and increases the proportion of the
carbon dioxide liquid-phase refrigerant. Then, the propane refrigerant returns to
30 the first supercooling compressor 121, and a new cycle is started. The cooled
13
carbon dioxide mixed two-phase refrigerant continues to enter the gas-liquid
separator 114 for gas-liquid separation. The liquid-phase refrigerant having an
increased proportion due to supercooling is throttled by the main throttling
element 115 when driven by the liquid pump 118, and flows into the evaporator
5 116 to participate in heat exchange. Since the amount of refrigerant participating
in the heat exchange is increased, the heat exchange capacity and efficiency
thereof can also be correspondingly increased. This part of the refrigerant enters
the secondary flow inlet of the injector 112 after completion of heat exchange and
participates in the refrigerant mixing and initial compression process. The gas10 phase refrigerant having a decreased proportion due to supercooling flows out of
the gas outlet of the gas-liquid separator 114, and enters the compressor 111 to
participate in a new cycle.
Further, although not shown in the drawings, another control method for
an air conditioning system is provided herein, wherein the air conditioning system
15 100 further has a second subcooling circuit. Specifically, the control method
further includes: starting the second subcooling circuit when the main circuit 110
is in operation. In this case, the second subcooling circuit plays a similar role to
the second branch of the first subcooling circuit in the previous embodiment, and
brings about similar effects. Therefore, a repeated description is omitted herein.
20 In addition, it should be noted that while particular order of steps may
have been shown, disclosed, and claimed in the above particular embodiments, it
is understood that some steps can be carried out, separated or combined in any
order unless it is expressly indicated that they should be executed in the particular
order.
25 The controller described above for performing the aforementioned method
may involve several functional entities that do not necessarily have to correspond
to physically or logically independent entities. These functional entities may also
be implemented in software, or implemented in one or more hardware modules or
14
integrated circuits, or implemented in different processing devices and/or
microcontroller devices.
In the description, examples are used to disclose the present disclosure,
including the best mode, with the purpose of enabling any person skilled in the art
5 to practice the disclosure, including making and using any device or system and
performing any of the methods covered. The scope of protection of the present
disclosure is defined by the claims, and may include other examples that can be
conceived by those skilled in the art. If such other examples have structural
elements that do not differ from the literal language of the claims, or if they
10 include equivalent structural elements that do not substantively differ from the
literal language of the claims, these examples are also intended to be included in
the scope of the claims.

We Claim:
1. An air conditioning system, comprising:
a main circuit having: a main compressor and an injector; a gas cooler
connected between an exhaust port of the main compressor and a primary flow
5 inlet of the injector; a gas-liquid separator connected between a suction port of the
main compressor and an outlet of the injector; and a main throttling element and
an evaporator connected between a liquid outlet of the gas-liquid separator and a
secondary flow inlet of the injector; and
a first subcooling circuit having: a first subcooling compressor, a first
10 condenser, a first subcooling throttling element and a first subcooler connected in
sequence;
wherein the first subcooler is further disposed in a flow path between the
outlet of the injector and the gas-liquid separator in the main circuit.
15 2. The air conditioning system according to claim 1, wherein the first
subcooling circuit further comprises a second subcooler which is connected in
parallel with the first subcooler; and wherein the second subcooler is further
disposed between the primary flow inlet of the injector and the gas cooler in the
main circuit.
20
3. The air conditioning system according to claim 2, further comprising a
second throttling element, wherein the second throttle element and the second
subcooler are connected in parallel with the first throttling element and the first
subcooler.
25
4. The air conditioning system according to claim 2, further comprising a
back pressure valve connected in parallel with the first subcooler and disposed
16
between the second subcooler and an suction port of the first subcooling
compressor.
5. The air conditioning system according to claim 1, wherein the first
5 subcooling circuit further comprises a second subcooler connected in series with
the first subcooler; and wherein the second subcooler is further disposed between
the primary flow inlet of the injector and the gas cooler in the main circuit.
6. The air conditioning system according to claim 1, further comprising a
10 second subcooling circuit having a second subcooling compressor, a second
condenser, a second subcooling throttling element, and a second subcooler
connected in sequence; wherein the second subcooler is further disposed between
the primary flow inlet of the injector and the gas cooler in the main circuit.
15 7. The air conditioning system according to any one of claims 1 to 6,
further comprising a suction line heat exchanger disposed in a flow path between
the gas cooler and the primary flow inlet of the injector; wherein a refrigerant
flowing out of a gas outlet of the gas-liquid separator flows into the suction port of
the main compressor via the suction line heat exchanger.
20
8. The air conditioning system according to any one of claims 1 to 6,
further comprising a liquid pump disposed in a flow path between the liquid outlet
of the gas-liquid separator and the secondary flow inlet of the injector.
25 9. The air conditioning system according to claim 8, wherein the liquid
pump is disposed between the liquid outlet of the gas-liquid separator and the
main throttling element.
17
10. The air conditioning system according to any one of claims 1 to 6,
wherein the refrigerant participating in the operation in the main circuit is a
carbon dioxide refrigerant, and/or the refrigerant participating in the operation in
the first subcooling circuit or the second subcooling circuit is a propane
5 refrigerant.