EP3249320A1

EP3249320A1 - Regenerative air conditioner

Info

Publication number: EP3249320A1
Application number: EP15872261.1A
Authority: EP
Inventors: Shuuji Fujimoto; Kouichi Yasuo; Kebi Chen; Takuya Nakao
Original assignee: Daikin Industries Ltd
Current assignee: Daikin Industries Ltd
Priority date: 2014-12-26
Filing date: 2015-12-22
Publication date: 2017-11-29
Anticipated expiration: 2035-12-22
Also published as: ES2833435T3; EP3249320B1; JP6020550B2; WO2016103690A1; JP2016125736A; EP3249320A4

Abstract

A refrigerant circuit (11) performs a cooling and cold thermal energy storage cycle in which a discharge end of a compressor (21) is connected to a gas end of an outdoor heat exchanger (22), a suction end of the compressor (21) is connected to a gas refrigerant channel (13), the outdoor heat exchanger (22) serves as a condenser, and an indoor heat exchanger (27) and a thermal storage heat exchanger (43) serve as evaporators. A pressure regulating mechanism (44) is configured to regulate the pressure of a refrigerant flowing between the thermal storage heat exchanger (43) and the gas refrigerant channel (13).

Description

TECHNICAL FIELD

The present disclosure relates to a thermal storage air conditioner.

BACKGROUND ART

A thermal storage air conditioner which cools the air in a room using a thermal storage medium as a cold thermal energy source has been known as disclosed by Patent Document 1. According to Patent Document 1, a thermal storage heat exchanger having a channel through which a refrigerant flows is arranged in a thermal storage tank storing a thermal storage medium. The refrigerant cools the thermal storage medium. A thermal storage material in which clathrate hydrates are generated if cooled (e.g., a tetra-n-butyl ammonium bromide aqueous solution) is adopted as the thermal storage medium. The thermal storage air conditioner of Patent Document 1 performs a cooling and cold thermal energy storage operation to cool the room while storing cold thermal energy.

CITATION LIST

PATENT DOCUMENT

Patent Document 1: Japanese Unexamined Patent Publication No. 2007-17089

SUMMARY OF THE INVENTION

TECHNICAL PROBLEM

Regarding the thermal storage air conditioner disclosed by Patent Document 1, it may be possible to arrange the thermal storage heat exchanger outside the thermal storage tank (thermal storage vessel) to form a thermal storage circuit through which the thermal storage medium circulates between the thermal storage heat exchanger and the thermal storage tank. If a cooling and cold thermal energy storage operation is performed in this configuration, the thermal storage medium that has flowed from the thermal storage tank into the thermal storage heat exchanger gives heat to the refrigerant flowing through the thermal storage heat exchanger while passing through the thermal storage heating exchanger, and is cooled.
Further, in the above-described configuration, the suction pressure of a compressor may be reduced to lower the evaporating pressure of the refrigerant in an indoor heat exchanger to ensure the cooling capacity of the indoor heat exchanger (i.e., capacity to cool the air in the room) during the cooling and cold thermal energy storage operation. For example, if there is a large pressure loss between a gas end of the indoor heat exchanger and a suction end of the compressor (more specifically, if the gas end of the indoor heat exchanger and the suction end of the compressor are connected via a long pipe, or there is a large difference in height between the gas end of the indoor heat exchanger and the suction end of the compressor), the suction pressure of the compressor is set to be low such that the evaporating pressure of the refrigerant in the indoor heat exchanger is set to a certain level required for ensuring the cooling capacity. Further, if a cooling load in the room increases to decrease the cooling capacity to an insufficient level, the suction pressure of the compressor is lowered to reduce the evaporating pressure of the refrigerant in the indoor heat exchanger.
However, if the suction pressure of the compressor is lowered to reduce the evaporating pressure of the refrigerant in the indoor heat exchanger, the evaporating pressure of the refrigerant in the thermal storage heat exchanger also decreases with the decrease in the suction pressure of the compressor, thereby lowering the evaporating temperature of the refrigerant. Thus, the thermal storage medium in the thermal storage heat exchanger may possibly be cooled too much to generate a large amount of clathrate hydrates (solid component). As a result, the circulation efficiency of the thermal storage medium in the thermal storage circuit may possibly decrease.
In view of the foregoing background, it is therefore an object of the present disclosure to provide a thermal storage air conditioner which may substantially prevent the decrease in circulation efficiency of the thermal storage medium while ensuring the cooling capacity during the cooling and cold thermal energy storage operation.

SOLUTION TO THE PROBLEM

A first aspect of the present disclosure is directed to a thermal storage air conditioner including: a refrigerant circuit (11) including a compressor (21), an outdoor heat exchanger (22), an indoor heat exchanger (27), a liquid refrigerant channel (12) connecting a liquid end of the outdoor heat exchanger (22) and a liquid end of the indoor heat exchanger (27), a gas refrigerant channel (13) connected to a gas end of the indoor heat exchanger (27), and a bypass channel (14) having one end connected to the liquid refrigerant channel (12) and the other end connected to the gas refrigerant channel (13); a thermal storage circuit (31) which allows a thermal storage medium, which would generate a solid component if cooled, to flow therein; a thermal storage heat exchanger (43) which is connected to the bypass channel (14) and the thermal storage circuit (31), and allows a refrigerant flowing through the bypass channel (14) and the thermal storage medium flowing through the thermal storage circuit (31) to exchange heat; and a pressure regulating mechanism (44) provided in the bypass channel (14) between the thermal storage heat exchanger (43) and the gas refrigerant channel (13), wherein the refrigerant circuit (11) performs a cooling and cold thermal energy storage cycle in which a discharge end of the compressor (21) is connected to a gas end of the outdoor heat exchanger (22), a suction end of the compressor (21) is connected to the gas refrigerant channel (13), the outdoor heat exchanger (22) serves as a condenser, and the indoor heat exchanger (27) and the thermal storage heat exchanger (43) serve as evaporators, and the pressure regulating mechanism (44) is configured to regulate a pressure of the refrigerant flowing between the thermal storage heat exchanger (43) and the gas refrigerant channel (13).
According to the first aspect, provision of the pressure regulating mechanism (44) allows the evaporating pressure of the refrigerant in the thermal storage heat exchanger (43) to be regulated such that the evaporating pressure becomes higher than the suction pressure of the compressor (21) during the cooling and cold thermal energy storage operation (i.e., when the refrigerant circuit (11) performs the cooling and cold thermal energy storage cycle). This may substantially prevent the decrease in the evaporating pressure of the refrigerant in the thermal storage heat exchanger (43) with the decrease in the suction pressure of the compressor (21), thereby substantially preventing the evaporating temperature of the refrigerant in the thermal storage heat exchanger (43) from decreasing too much. Thus, the excessive cooling of the thermal storage medium in the thermal storage heat exchanger (43) may be prevented.
A second aspect of the present disclosure is an embodiment of the first aspect described above. According to the second aspect, the thermal storage air conditioner further includes an operation control section (100) which instructs the refrigerant circuit (11) to perform the cooling and cold thermal energy storage cycle, and adjusts the amount of pressure reduction by the pressure regulating mechanism (44) such that an evaporating temperature of the refrigerant in the thermal storage heat exchanger (43) does not fall below a predetermined lower limit evaporating temperature.
According to the second aspect, the evaporating pressure of the refrigerant in the thermal storage heat exchanger (43) may suitably be determined. Thus, the thermal storage medium can suitably be cooled in the thermal storage heating exchanger (43).
A third aspect of the present disclosure is an embodiment of the first or second aspect described above. According to the third aspect, the bypass channel (14) includes a first channel portion (14d) which connects the thermal storage heat exchanger (43) and the gas refrigerant channel (13), and the pressure regulating mechanism (44) includes a pressure regulating valve (45) which is provided in the first channel portion (14d) and has an adjustable degree of opening.
According to the third aspect, the amount of pressure reduction by the pressure regulating mechanism (44) may be adjusted by regulating the degree of opening of the pressure regulating valve (45). As a result, the evaporating pressure of the refrigerant in the thermal storage heat exchanger (43) may be regulated such that the evaporating pressure is higher than the suction pressure of the compressor (21), which may prevent the excessive cooling of the thermal storage medium in the thermal storage heat exchanger (43).
A fourth aspect of the present disclosure is an embodiment of the third aspect described above. According to the fourth aspect, the bypass channel (14) further includes a second channel portion (14e) which is provided in parallel with the first channel portion (14d), and connects the thermal storage heat exchanger (43) and the gas refrigerant channel (13), and the pressure regulating mechanism (44) further includes an open/close valve (46) which is provided in the second channel portion (14e) and configured to be switchable between an open state and a closed state.
According to the fourth aspect, the open/close valve (46) may be opened, while the pressure regulating valve (45) may be fully closed. Thus, the refrigerant is allowed to flow between the thermal storage heat exchanger (43) and the gas refrigerant channel (13) via the open/close valve (46). A pressure loss in the open/close valve (46) is smaller than a pressure loss in the pressure regulating valve (45). Thus, the pressure loss in the pressure regulating mechanism (44) may be reduced as compared with the case where the refrigerant is allowed to flow between the thermal storage heat exchanger (43) and the gas refrigerant channel (13) via the pressure regulating valve (45). As a result, during other operations than the cooling and cold thermal energy storage operation, the pressure loss in the pressure regulating mechanism (44) may be reduced.

ADVANTAGES OF THE INVENTION

According to the first and third aspects, the excessive cooling of the thermal storage medium in the thermal storage heat exchanger (43) may be prevented. This may substantially prevent the circulation efficiency of the thermal storage medium in the thermal storage circuit (31) from decreasing, while ensuring the cooling capacity (i.e., capacity to cool the room) of the indoor heat exchanger during the cooling and cold thermal energy storage operation.
According to the second aspect, the thermal storage medium can suitably be cooled in the thermal storage heating exchanger (43), and thus, the cold thermal energy may suitably be stored during the cooling and cold thermal energy storage operation.
According to the fourth aspect, during other operations than the cooling and cold thermal energy storage operation, the pressure loss in the pressure regulating mechanism (44) may be reduced, which allows the other operations to be suitably performed.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] FIG. 1 illustrates a configuration of a thermal storage air conditioner.
[FIG. 2] FIG. 2 shows the flow of a refrigerant during a simple cooling operation.
[FIG. 3] FIG. 3 shows the flow of a refrigerant during a simple heating operation.
[FIG. 4] FIG. 4 shows the flow of a refrigerant and the flow of a thermal storage medium during a cold thermal energy storage operation.
[FIG. 5] FIG. 5 shows the flow of a refrigerant and the flow of a thermal storage medium during a utilization cooling operation.
[FIG. 6] FIG. 6 shows the flow of a refrigerant and the flow of a thermal storage medium during a cooling and cold thermal energy storage operation.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will now be described in detail with reference to the drawings. Note that like reference characters designate identical or corresponding components in the drawings, and description of components designated by like reference characters will not be repeated.

(Thermal Storage Air Conditioner)

FIG. 1 illustrates an exemplary configuration of a thermal storage air conditioner (10) according to an embodiment. The thermal storage air conditioner (10) is comprised of an outdoor unit (20a), an indoor unit (20b), and a thermal storage unit (30), and includes a refrigerant circuit (11), a thermal storage circuit (31), a preheating heat exchanger (41), a thermal storage expansion valve (42), a thermal storage heat exchanger (43), a pressure regulating mechanism (44), and a controller (100).

[Refrigerant Circuit]

The refrigerant circuit (11) is filled with a refrigerant. The refrigerant circulates in the refrigerant circuit (11) so that a refrigeration cycle is performed. The refrigerant circuit (11) includes a compressor (21), an outdoor heat exchanger (22), an outdoor expansion valve (23), an outdoor subcooling heat exchanger (24), a thermal storage subcooling heat exchanger (25), an indoor expansion valve (26), an indoor heat exchanger (27), and a four-way switching valve (28). The refrigerant circuit (11) further includes a liquid refrigerant channel (12), a gas refrigerant channel (13), a bypass channel (14), and a branch channel (15).
The outdoor unit (20a) is placed outside the room. The outdoor unit (20a) includes the compressor (21), the outdoor heat exchanger (22), the outdoor expansion valve (23), the outdoor subcooling heat exchanger (24), and the four-way switching valve (28). The outdoor unit (20a) further includes an outdoor fan (22a) which transfers the air to the outdoor heat exchanger (22).
The indoor unit (20b) is placed inside the room. The indoor unit (20b) includes the indoor expansion valve (26) and the indoor heat exchanger (27). The indoor unit (20b) further includes an indoor fan (27a) which transfers the air to the indoor heat exchanger (27).
The thermal storage unit (30) is connected between the outdoor and indoor units (20a, 20b) to be adjacent to the outdoor unit (20a). The thermal storage unit (30) includes the thermal storage subcooling heat exchanger (25), the thermal storage circuit (31), the preheating heat exchanger (41), the thermal storage expansion valve (42), the thermal storage heat exchanger (43), and the pressure regulating mechanism (44).

The compressor (21) has a discharge end connected to a first port of the four-way switching valve (28), and a suction end connected to a second port of the four-way switching valve (28). The compressor (21) compresses a refrigerant sucked therein, and discharges the refrigerant thus compressed. The compressor (21) has a variable capacity (rotational speed). For example, the compressor (21) is a variable capacity compressor, the rotational speed (i.e., the operating frequency) of which is varied by an inverter circuit (not shown).

The outdoor heat exchanger (22) has a gas end connected to a third port of the four-way switching valve (28) via a first refrigerant pipe (11a), and a liquid end connected to one end of the refrigerant channel (12) via a second refrigerant pipe (11b). The outdoor expansion valve (23) and the outdoor subcooling heat exchanger (24) are sequentially arranged in the second refrigerant pipe (11b) in the direction from a liquid end of the outdoor heat exchanger (22) to the one end of the liquid refrigerant channel (12). Specifically, the liquid end of the outdoor heat exchanger (22) is connected to the liquid refrigerant channel (12) via the outdoor expansion valve (23) and the outdoor subcooling heat exchanger (24) arranged in this order. The outdoor heat exchanger (22) allows the refrigerant and the outdoor air transferred by the outdoor fan (22a) to exchange heat. The outdoor heat exchanger (22) is, for example, a cross-fm-and-tube heat exchanger.

The outdoor expansion valve (23) has an adjustable degree of opening, adjustment of which regulates the pressure and flow rate of the refrigerant. The outdoor expansion valve (23) is configured, for example, as an electronic expansion valve (motor-operated valve).

The outdoor subcooling heat exchanger (24) includes a high-pressure passage (24a) and a low-pressure passage (24b). The high-pressure passage (24a) is inserted in (connected to) the second refrigerant pipe (11b) in series. The low-pressure passage (24b) is inserted in an auxiliary pipe (24d) in series. The auxiliary pipe (24d) has one end connected to the second refrigerant pipe (11b) between the outdoor expansion valve (23) and the outdoor subcooling heat exchanger (24), and the other end connected to the suction end of the compressor (21). The outdoor subcooling heat exchanger (24) is configured to allow the refrigerant flowing through the high-pressure passage (24a) and the refrigerant flowing through the low-pressure passage (24b) to exchange heat so as to subcool the refrigerant flowing through the high-pressure passage (24a). The auxiliary pipe (24d) is provided with an outdoor subcooling expansion valve (24c) which regulates the flow rate of the refrigerant flowing through the low-pressure passage (24b).

The thermal storage subcooling heat exchanger (25) is provided in the liquid refrigerant channel (12). The thermal storage subcooling heat exchanger (25) is provided adjacent to the other end of the liquid refrigerant channel (12). The thermal storage subcooling heat exchanger (25) has a high-pressure passage (25a) and a low-pressure passage (25b). The high-pressure passage (25a) is inserted in the liquid refrigerant channel (12) in series. The low-pressure passage (25b) is inserted in an auxiliary pipe (25d) in series. The auxiliary pipe (25d) has one end connected to some midpoint of the liquid refrigerant channel (12) between the one end of the liquid refrigerant channel (12) and the thermal storage subcooling heat exchanger (25), and the other end connected to the gas refrigerant channel (13). The thermal storage subcooling heat exchanger (25) is configured to allow the refrigerant flowing through the high-pressure passage (25a) and the refrigerant flowing through the low-pressure passage (25b) to exchange heat so as to subcool the refrigerant flowing through the high-pressure passage (25a). The auxiliary pipe (25d) is provided with a thermal storage subcooling expansion valve (25c) which regulates the flow rate of the refrigerant flowing through the low-pressure passage (25b).

The indoor expansion valve (26) is provided for a third refrigerant pipe (11c) connecting the other end of the liquid refrigerant channel (12) and the liquid end of the indoor heat exchanger (27). The indoor expansion valve (26) has an adjustable degree of opening, adjustment of which regulates the pressure and flow rate of the refrigerant. The indoor expansion valve (26) is configured, for example, as an electronic expansion valve (motor-operated valve).

The indoor heat exchanger (27) has a liquid end connected the other end of the liquid refrigerant channel (12) via the third refrigerant pipe (11c), and has a gas end connected to one end of the gas refrigerant channel (13) via a fourth refrigerant pipe (11d). Specifically, the liquid end of the indoor heat exchanger (27) is connected to the liquid refrigerant channel (12) via the indoor expansion valve (26). The indoor heat exchanger (27) allows the refrigerant and indoor air transferred by the indoor fan (27a) to exchange heat. The indoor air that has exchanged heat in the indoor heat exchanger (27) is fed into the room again. The indoor heat exchanger (27) is, for example, a cross-fin-and-tube heat exchanger.

<Four-Way Switching Valve>

The four-way switching valve (28) switches the connection state of the first to fourth ports between a first state (the state indicated by the solid curves in FIG. 1) and a second state (the state indicated by broken curves in FIG. 1) according to the operational mode of the thermal storage air conditioner (10). The fourth port of the four-way switching valve (28) is connected to the other end of the gas refrigerant channel (13) via a fifth refrigerant pipe (11e).

The bypass channel (14) has one end connected to the liquid refrigerant channel (12), and the other end connected to the gas refrigerant channel (13). The preheating heat exchanger (41), the thermal storage expansion valve (42), the thermal storage heat exchanger (43), and the pressure regulating mechanism (44) are sequentially arranged on the bypass channel (14) in the direction from the one end to other of the bypass channel (14), i.e., from the liquid refrigerant channel (12) to the gas refrigerant channel (13).
A junction (a first junction (P1)) of the bypass channel (14) and the liquid refrigerant channel (12) is closer to the one end of the liquid refrigerant channel (12), i.e., the second refrigerant pipe (11b), than a junction (a second junction (P2)) of the auxiliary pipe (25d) of the thermal storage subcooling heat exchanger (25) and the liquid refrigerant channel (12) is. In this example, the bypass channel (14) includes a first primary pipe (14a), a second primary pipe (14b), a third primary pipe (14c), a first branch pipe (14d), and a second branch pipe (14e). The first primary pipe (14a) connects the preheating heat exchanger (41) to some midpoint of the liquid refrigerant channel (12). The second primary pipe (14b) connects the preheating heat exchanger (14) and the thermal storage heat exchanger (43). The third primary pipe (14c) has one end connected to the thermal storage heat exchanger (43). The first branch pipe (14d) connects the other end of the third primary pipe (14c) and the gas refrigerant channel (13). The second branch pipe (14e) is arranged in parallel with the first branch pipe (14d), and connects the third primary pipe (14c) and the gas refrigerant channel (13). Specifically, the first branch pipe (14d) constitutes a pipe (first channel portion) connecting the thermal storage heat exchanger (43) and the gas refrigerant channel (13). The second branch pipe (14e) constitutes a pipe (second channel portion) which is arranged in parallel with the first branch pipe (14d) and connects the thermal storage heat exchanger (43) and the gas refrigerant channel (13).

The branch channel (15) has one end connected to some midpoint of the bypass channel (14) between the thermal storage heat exchanger (43) and the pressure regulating mechanism (44), and the other end connected to some midpoint of the liquid refrigerant channel (12) between the first and second junctions (PI, P2). Specifically, a junction (a third junction (P3)) of the branch channel (15) and the liquid refrigerant channel (12) is located between the first and second junctions (P1, P2) on the liquid refrigerant channel (12).

The refrigerant circuit (11) further includes a first open/close valve (51), a second open/close valve (52), a third open/close valve (53), a first check valve (51a), a second check valve (52a), and a third check valve (53a). For example, the first, second and third open/close valves (51, 52, 53) are configured as solenoid valves.
The first open/close valve (51) is provided between the first and second junctions (P1, P2) on the liquid refrigerant channel (12). The first check valve (51a) is connected in parallel with the first open/close valve (51). Further, the first check valve (51a) is configured to allow the refrigerant to flow from the thermal storage subcooling heat exchanger (25) to the outdoor subcooling heat exchanger (24) during a simple heating operation to be described later.
The second open/close valve (52) is connected in parallel with the thermal storage expansion valve (42). The second check valve (52a) is connected to the second open/close valve (52) in series, and is parallel to the thermal storage expansion valve (42). The second check valve (52a) allows the refrigerant to flow only from the preheating heat exchanger (41) toward the thermal storage heat exchanger (43).
The third open/close valve (53) is provided in the branch channel (15). The third check valve (53a) is provided for the branch channel (15), and allows the refrigerant to flow only from the bypass channel (14) toward the liquid refrigerant channel (12).

[Preheating Heat Exchanger]

The preheating heat exchanger (41) is connected to the bypass channel (14) of the refrigerant circuit (11) and the thermal storage circuit (31), and allows the refrigerant flowing through the bypass channel (14) to exchange heat with the thermal storage medium flowing through the thermal storage circuit (31). Specifically, the preheating heat exchanger (41) includes a refrigerant passage (41a) and a thermal storage medium passage (41b). The refrigerant passage (41a) is inserted in the bypass channel (14) in series. In this example, the refrigerant passage (41a) is connected to the bypass channel (14) between the first and second primary pipes (14a, 14b). The thermal storage medium passage (41b) is inserted in the thermal storage circuit (31) in series. The preheating heat exchanger (41) allows the refrigerant flowing through the refrigerant passage (41a) and the thermal storage medium flowing through the thermal storage medium passage (41b) to exchange heat.

The thermal storage expansion valve (42) is provided on the bypass channel (14) between the preheating heat exchanger (41) and the thermal storage heat exchanger (43). In this example, the thermal storage expansion valve (42) is provided in the second primary pipe (14b) of the bypass channel (14). The thermal storage expansion valve (42) has an adjustable degree of opening, adjustment of which regulates the pressure and flow rate of the refrigerant. The thermal storage expansion valve (42) is configured, for example, as an electronic expansion valve (motor-operated valve).
A pressure release valve (42a) is connected in parallel to the thermal storage expansion valve (42). The pressure release valve (42a) releases the pressure of the thermal storage heat exchanger (43) side if it exceeds an allowable value while the thermal storage air conditioner (10) is being suspended, for example.

[Thermal Storage Heat Exchanger]

The thermal storage heat exchanger (43) is connected to the bypass channel (14) of the refrigerant circuit (11) and the thermal storage circuit (31), and allows the refrigerant flowing through the bypass channel (14) to exchange heat with the thermal storage medium flowing through the thermal storage circuit (31). Specifically, the thermal storage heat exchanger (43) includes a refrigerant passage (43a) and a thermal storage medium passage (43b). The refrigerant passage (43a) is inserted in the bypass channel (14) in series. In this example, the refrigerant passage (43a) is connected to the bypass channel (14) between the second and third primary pipes (14b, 14c). The thermal storage medium passage (43b) is inserted in the thermal storage circuit (31) in series. The thermal storage heat exchanger (43) allows the refrigerant flowing through the refrigerant passage (43a) and the thermal storage medium flowing through the thermal storage medium passage (43b) to exchange heat.

[Pressure Regulating Mechanism]

The pressure regulating mechanism (44) is provided in the bypass channel (14) between the thermal storage heat exchanger (43) and the gas refrigerant channel (13). The pressure regulating mechanism (44) is configured to regulate the pressure of the refrigerant flowing between the thermal storage heat exchanger (43) and the gas refrigerant channel (13).
In this example, the pressure regulating mechanism (44) includes a pressure regulating valve (45) and a channel open/close valve (46). The pressure regulating valve (45) is provided in the first branch pipe (14d) of the bypass channel (14). The degree of opening of the pressure regulating valve (45) is adjustable. The pressure regulating valve (45) is configured, for example, as a motor-operated valve. The channel open/close valve (46) is provided in the second branch pipe (14e) of the bypass channel (14). The channel open/close valve (46) is configured to be switchable between an open state and a closed state. The channel open/close valve (46) is configured, for example, as a solenoid valve.

[Thermal Storage Circuit]

The thermal storage circuit (31) is filled with a thermal storage medium. The thermal storage circuit (31) performs a circulation operation by circulating the thermal storage medium. The thermal storage circuit (31) includes a thermal storage tank (32) and a circulation pump (33).

[Thermal Storage Tank]

The thermal storage tank (32) is a hollow vessel in which the thermal storage medium is stored. For example, the thermal storage tank (32) has a cylindrical shape with both ends being closed, and is arranged such that its axial direction extends vertically. The thermal storage tank (32) has an outlet and an inlet. For example, the outlet is located above the inlet.

The circulation pump (33) circulates the thermal storage medium among the thermal storage tank (32), the preheating heat exchanger (41) and the thermal storage heat exchanger (43) in the thermal storage circuit (31). The thermal storage medium circulates as described below. Specifically, the thermal storage medium that has flowed out of the thermal storage tank (32) passes through the thermal storage medium passage (41b) of the preheating heat exchanger (41) and the circulation pump (33), and then flows through the thermal storage medium passage (43b) of the thermal storage heat exchanger (43) into the thermal storage tank (32). The controller (100) controls the on/off operations of the circulation pump (33) and the flow rate of the thermal storage medium transferred by the circulation pump (33).

[Thermal Storage Medium]

The thermal storage medium will now be described. The thermal storage medium can be a medium in which a solid component is generated when cooled (more specifically, a medium in which a solid component is generated when cooled to a temperature higher than 0°C and lower than 20°C). The solid component is a component which has experienced phase transition (i.e., latent heat change) from a liquid phase at its melting point, and generating heat. Examples of the solid component may include clathrate hydrates.
An exemplary example will be described below. In this example, a thermal storage material in which clathrate hydrates are generated when cooled (i.e., a thermal storage material having flowability) is adopted as the thermal storage medium. Examples of such a thermal storage medium may include: a tetra-n-butyl ammonium bromide aqueous solution containing tetra-n-butyl ammonium bromide (TBAB); a trimethylolethane (TME) aqueous solution; and paraffin-based slurry. For example, the tetra-n-butyl ammonium bromide aqueous solution maintains the aqueous solution state even if it is stably cooled and turns into a subcooled state in which the temperature of the aqueous solution is lower than a hydrate formation temperature. However, once some trigger is given in this subcooled state, the subcooled solution transitions to a solution containing clathrate hydrates (i.e., transitions to slurry). That is, the subcooled state of the tetra-n-butyl ammonium bromide aqueous solution is changed to the state of slurry with relatively high viscosity due to the generation of clathrate hydrates (hydrate crystals) made of tetra-n-butyl ammonium bromide and water molecules. The subcooled state as used herein refers to a state in which clathrate hydrates are not generated and the state of solution is maintained even if the thermal storage medium reaches a temperature lower than or equal to the hydrate formation temperature. On the other hand, the clathrate hydrates melt if the temperature of the tetra-n-butyl ammonium bromide aqueous solution becomes higher, by heating, than the hydrate formation temperature. Then, the tetra-n-butyl ammonium bromide aqueous solution in the state of slurry turns to liquid (i.e., a solution) with relatively high flowability.
In the present embodiment, a tetra-n-butyl ammonium bromide aqueous solution containing tetra-n-butyl ammonium bromide is adopted as the thermal storage medium. In particular, it is recommended that the thermal storage medium has a concentration close to a congruent concentration. The congruent concentration refers to a concentration of an aqueous solution which does not change before and after the generation of the clathrate hydrates. In the present embodiment, the congruent concentration is set to about 40%. In this case, the hydrate formation temperature of the tetra-n-butyl ammonium bromide aqueous solution is about 12°C.
Note that the hydrate formation temperature of the tetra-n-butyl ammonium bromide aqueous solution varies depending on the concentration of the thermal storage medium. For example, if the thermal storage medium has a concentration of about 20%, the hydrate formation temperature is about 8.5°C.

[Refrigerant Temperature Sensor]

The thermal storage air conditioner (10) is provided with various sensors, such as a first refrigerant temperature sensor (61) and a second refrigerant temperature sensor (62).
The first refrigerant temperature sensor (61) detects the temperature of the refrigerant (first refrigerant temperature) adjacent to one end side (the gas refrigerant channel (13) side) of the thermal storage heat exchanger (43). In this example, the first refrigerant temperature sensor (61) is arranged adjacent to one end of the refrigerant passage (43a) of the thermal storage heat exchanger (43), and detects the temperature of the refrigerant at this position as a first refrigerant temperature.
The second refrigerant temperature sensor (62) detects the temperature of the refrigerant (second refrigerant temperature) adjacent to the other end side (the liquid refrigerant channel (12) side) of the thermal storage heat exchanger (43). In this example, the second refrigerant temperature sensor (62) is arranged adjacent to the other end of the refrigerant passage (43a) of the thermal storage heat exchanger (43), and detects the temperature of the refrigerant at this position as a second refrigerant temperature.

[Controller (Operation Control Section)]

The controller (100) controls the components of the thermal storage air conditioner (10) to control the operation of the thermal storage air conditioner (10) based on the values detected by various sensors. This thermal storage air conditioner (10) performs a simple cooling operation, a simple heating operation, a cold thermal energy storage operation, a utilization cooling operation, and a cooling and cold thermal energy storage operation.

[Simple Cooling Operation]

The simple cooling operation will be described below with reference to FIG. 2. The simple cooling operation is performed to cool the room using only the cold thermal energy obtained through a refrigeration cycle of the refrigerant circuit (11).
The refrigerant circuit (11) performs a refrigeration cycle (simple cooling cycle) in which the outdoor heat exchanger (22) serves as a condenser and the indoor heat exchanger (27) serves as an evaporator. The thermal storage medium in the thermal storage circuit (31) does not circulate.
Specifically, the four-way switching valve (28) is set to the first state. As a result, the discharge end of the compressor (21) is connected to the gas end of the outdoor heat exchanger (22), and the suction end of the compressor (21) is connected to the gas refrigerant channel (13). Further, the first open/close valve (51) is opened, and the second and third open/close valves (52, 53) are closed. The outdoor expansion valve (23) is fully opened, the degree of opening of the indoor expansion valve (26) is adjusted to a predetermined degree (a degree of opening which allows the refrigerant at the exit of the indoor heat exchanger (27) to have a target degree of superheat), and the thermal storage expansion valve (42) is fully closed. The degree of opening of the outdoor subcooling expansion valve (24c) is adjusted to a predetermined degree, and the thermal storage expansion valve (25c) is fully closed. The pressure regulating valve (45) is fully closed, and the channel open/close valve (46) is opened. Then, the compressor (21), the outdoor fan (22a), and the indoor fan (27a) are driven, while the circulation pump (33) is stopped. The setting and regulation described above are performed in response to the control by the controller (100). The same will be applied to the following description.
The refrigerant discharged from the compressor (21) flows into the outdoor heat exchanger (22), and is condensed through heat dissipation into the outdoor air in the outdoor heat exchanger (22). The refrigerant that has flowed from the outdoor heat exchanger (22) passes through the outdoor expansion valve (23) which is fully opened, flows into the outdoor subcooling heat exchanger (24), and is cooled in the outdoor subcooling heat exchanger (24). The refrigerant that has flowed from the outdoor subcooling heat exchanger (24) sequentially passes through the opened first open/close valve (51) and the thermal storage subcooling heat exchanger (25) in the liquid refrigerant channel (12) to flow into the indoor expansion valve (26), and has its pressure reduced by the indoor expansion valve (26). The refrigerant that has passed through the indoor expansion valve (26) flows into the indoor heat exchanger (27), and absorbs heat from the indoor air in the indoor heat exchanger (27) to evaporate. The indoor air is cooled in this manner. The refrigerant that has flowed from the indoor heat exchanger (27) is sucked into the compressor (21) through the gas refrigerant channel (13), and is compressed again.
Since the channel open/close valve (46) of the pressure regulating mechanism (44) is opened, the refrigerant may be prevented from accumulating in the refrigerant passage (43a) of the thermal storage heat exchanger (43).

[Simple Heating Operation]

The simple heating operation will be described below with reference to FIG. 3. The simple heating operation is performed to heat the room using only the warm thermal energy obtained through a refrigeration cycle of the refrigerant circuit (11).
The refrigerant circuit (11) performs a refrigeration cycle (simple heating cycle) in which the indoor heat exchanger (27) serves as a condenser and the outdoor heat exchanger (22) serves as an evaporator. The thermal storage medium in the thermal storage circuit (31) does not circulate.
Specifically, the four-way switching valve (28) is set to the second state. As a result, the discharge end of the compressor (21) is connected to the gas refrigerant channel (13), and the suction end of the compressor (21) is connected to the gas end of the outdoor heat exchanger (22). Further, the first, second, and third open/close valves (51, 52, 53) are closed. The degree of opening of the outdoor expansion valve (23) is adjusted to a predetermined degree (a degree of opening which allows the refrigerant at the exit of the outdoor heat exchanger (22) to have a target degree of superheat). The degree of opening of the indoor expansion valve (26) is adjusted to a predetermined degree (a degree of opening which allows the refrigerant at the exit of the indoor heat exchanger (27) to have a target degree of subcooling), and the thermal storage expansion valve (42) is fully closed. The outdoor subcooling expansion valve (24c), and the thermal storage subcooling expansion valve (25c) are fully closed. The pressure regulating valve (45) is fully closed, and the channel open/close valve (46) is closed. The compressor (21), the outdoor fan (22a), and the indoor fan (27a) are driven, and the circulation pump (33) is stopped.
The refrigerant discharged from the compressor (21) flows through the gas refrigerant channel (13) into the indoor heat exchanger (27), and is condensed through heat dissipation into the indoor air in the indoor heat exchanger (27). The indoor air is cooled in this manner. The refrigerant that has flowed from the indoor heat exchanger (27) sequentially passes through the indoor expansion valve (26), and the thermal storage subcooling heat exchanger (25), the third junction (P3), the first check valve (51a), and the first junction (PI) in the liquid refrigerant channel (12), flows through the outdoor subcooling heat exchanger (24), and has its pressure reduced by the outdoor expansion valve (23). The refrigerant that has passed through the outdoor expansion valve (23) flows into the outdoor heat exchanger (22), and absorbs heat from the outdoor air in the outdoor heat exchanger (22) to evaporate. The refrigerant that has flowed from the outdoor heat exchanger (22) is sucked into the compressor (21), and is compressed again.

[Cold Thermal Energy Storage Operation]

The cold thermal energy storage operation will be described below with reference to FIG. 4. The cold thermal energy storage operation is performed to store, in the thermal storage tank (32) of the thermal storage circuit (31), the cold thermal energy obtained through the refrigeration cycle of the refrigerant circuit (11).
The refrigerant circuit (11) performs a refrigeration cycle (cold thermal energy storage cycle) in which the outdoor heat exchanger (22) serves as a condenser, the preheating heat exchanger (41) serves as a subcooler, and the thermal storage heat exchanger (43) serves as an evaporator. The thermal storage circuit (31) performs a circulation operation (of circulating the thermal storage medium).
Specifically, the four-way switching valve (28) is set to the first state. As a result, the discharge end of the compressor (21) is connected to the gas end of the outdoor heat exchanger (22), and the suction end of the compressor (21) is connected to the gas refrigerant channel (13). Further, the first open/close valve (51) is opened, and the second and third open/close valves (52, 53) are closed. The outdoor expansion valve (23) is fully opened, the indoor expansion valve (26) is fully closed, and the degree of opening of the thermal storage expansion valve (42) is adjusted to a predetermined degree (a degree of opening which allows the refrigerant at the exit of the thermal storage heat exchanger to have a target evaporating temperature). The outdoor subcooling expansion valve (24c), and the thermal storage subcooling expansion valve (25c) are fully closed. The pressure regulating valve (45) is fully closed, and the channel open/close valve (46) is opened. The compressor (21) and the outdoor fan (22a) are driven, the indoor fan (27a) is stopped, and the circulation pump (33) is driven. The compressor (21) is actuated at a generally constant rotational speed.
The refrigerant discharged from the compressor (21) flows into the outdoor heat exchanger (22), and is condensed through heat dissipation into the outdoor air in the outdoor heat exchanger (22). The refrigerant that has flowed from the outdoor heat exchanger (22) sequentially passes through the outdoor expansion valve (23) being fully opened and the outdoor subcooling heat exchanger (24), and flows into the liquid refrigerant channel (12). The refrigerant that has flowed into the liquid refrigerant channel (12) passes through the first junction (PI) and flows into the bypass channel (14). The refrigerant that has flowed into the bypass channel (14) flows into the refrigerant passage (41a) of the preheating heat exchanger (41), and is cooled through heat dissipation into the thermal storage medium flowing through the thermal storage medium passage (41b) while passing through the refrigerant passage (41a) of the preheating heat exchanger (41). The refrigerant that has flowed from the refrigerant passage (41a) of the preheating heat exchanger (41) has its pressure reduced by the thermal storage expansion valve (42), flows into the refrigerant passage (43a) of the thermal storage heat exchanger (43), and absorbs heat from the thermal storage medium flowing through the thermal storage medium passage (43b) to evaporate while passing through the refrigerant passage (43a) of the thermal storage heat exchanger (43). The refrigerant that has flowed from the refrigerant passage (43a) of the thermal storage heat exchanger (43) sequentially passes through the opened channel open/close valve (46) of the pressure regulating mechanism (44) and the gas refrigerant channel (13), and is sucked into the compressor (21) to be compressed again.
Since the first open/close valve (51) is opened, the liquid refrigerant accumulates in the pipe (liquid pipe) of the bypass channel (14) between the first junction (P1) and the indoor expansion valve (26). Thus, the state of the refrigerant in this pipe is the same as that during the simple cooling operation. This may prevent the generation of a surplus refrigerant.
In the thermal storage circuit (31), the thermal storage medium that has flowed from the thermal storage tank (32) flows into the thermal storage medium passage (41b) of the preheating heat exchanger (41), and is heated by the refrigerant flowing through the refrigerant passage (41a) while passing through the thermal storage medium passage (41b) of the preheating heat exchanger (41). The thermal storage medium that has flowed from the thermal storage medium passage (41b) of the preheating heat exchanger (41) flows through the circulation pump (33) into the thermal storage medium passage (43b) of the thermal storage heat exchanger (43), and is cooled by the refrigerant flowing through the refrigerant passage (43a) while passing through the thermal storage medium passage (43b) of the thermal storage heat exchanger (43). The thermal storage medium that has flowed from the thermal storage medium passage (43b) of the thermal storage heat exchanger (43) flows into the thermal storage tank (32). The cold thermal energy is stored in the thermal storage tank (32) in this manner.

[Utilization Cooling Operation]

The utilization cooling operation will be described below with reference to FIG. 5. The utilization cooling operation is performed to cool the room using the cold thermal energy stored in the thermal storage tank (32) and the cold thermal energy obtained through the refrigeration cycle of the refrigerant circuit (11).
The refrigerant circuit (11) performs a refrigeration cycle (utilization cooling cycle) in which the outdoor heat exchanger (22) serves as a condenser, the preheating heat exchanger (41) and the thermal storage heat exchanger (43) serve as subcoolers, and the indoor heat exchanger (27) serves as an evaporator. The thermal storage circuit (31) performs a circulation operation.
Specifically, the four-way switching valve (28) is set to the first state. As a result, the discharge end of the compressor (21) is connected to the gas end of the outdoor heat exchanger (22), and the suction end of the compressor (21) is connected to the gas refrigerant channel (13). Further, the first open/close valve (51) is closed, and the second and third open/close valves (52, 53) are opened. The outdoor expansion valve (23) is fully opened, the degree of opening of the indoor expansion valve (26) is adjusted to a predetermined degree (a degree of opening which allows the refrigerant at the exit of the indoor heat exchanger to have a target degree of superheat), and the thermal storage expansion valve (42) is fully opened. The outdoor subcooling expansion valve (24c) is fully closed, and the degree of opening of the thermal storage subcooling expansion valve (25c) is adjusted to a predetermined degree. The pressure regulating valve (45) is fully closed, and the channel open/close valve (46) is closed. The compressor (21), the outdoor fan (22a), the indoor fan (27a), and the circulation pump (33) are all driven.
The refrigerant discharged from the compressor (21) flows into the outdoor heat exchanger (22), and is condensed through heat dissipation into the outdoor air in the outdoor heat exchanger (22). The refrigerant that has flowed from the outdoor heat exchanger (22) sequentially passes through the outdoor expansion valve (23) being fully opened and the outdoor subcooling heat exchanger (24), and flows into the liquid refrigerant channel (12). The refrigerant that has flowed into the liquid refrigerant channel (12) passes through the first junction (PI) and flows into the bypass channel (14). The refrigerant that has flowed into the bypass channel (14) flows into the refrigerant passage (41a) of the preheating heat exchanger (41), and is cooled through heat dissipation into the thermal storage medium flowing through the thermal storage medium passage (41b) while passing through the refrigerant passage (41a) of the preheating heat exchanger (41). The refrigerant that has flowed from the refrigerant passage (41a) of the preheating heat exchanger (41) flows through the fully opened thermal storage expansion valve (42) and the opened second open/close valve (52) into the refrigerant passage (43a) of the thermal storage heat exchanger (43), and is cooled through heat dissipation into the thermal storage medium flowing through the thermal storage medium passage (43b) while passing through the refrigerant passage (43a) of the thermal storage heat exchanger (43). The refrigerant that has flowed from the refrigerant passage (43a) of the thermal storage heat exchanger (43) sequentially passes through the opened third open/close valve (53) and the third check valve (53a) to flow into the liquid refrigerant channel (12), sequentially passes through the third and second junctions (P3, P2) in the liquid refrigerant channel (12) to flow into the thermal storage subcooling heat exchanger (25), and is cooled in the thermal storage subcooling heat exchanger (25). The refrigerant that has passed through the thermal storage subcooling heat exchanger (25) has its pressure reduced by the indoor expansion valve (26), flows into the indoor heat exchanger (27), and absorbs heat from the indoor air in the indoor heat exchanger (27) to evaporate. The indoor air is cooled in this manner. The refrigerant that has flowed from the indoor heat exchanger (27) is sucked into the compressor (21) through the gas refrigerant channel (13), and is compressed again.
In the thermal storage circuit (31), the thermal storage medium that has flowed from the thermal storage tank (32) flows into the thermal storage medium passage (41b) of the preheating heat exchanger (41), and absorbs heat from the refrigerant flowing through the refrigerant passage (41a) while passing through the thermal storage medium passage (41b) of the preheating heat exchanger (41). The thermal storage medium that has flowed from the thermal storage medium passage (41b) of the preheating heat exchanger (41) flows through the circulation pump (33) into the thermal storage medium passage (43b) of the thermal storage heat exchanger (43), and absorbs heat from the refrigerant flowing through the refrigerant passage (43a) while passing through the thermal storage medium passage (43b) of the thermal storage heat exchanger (43). The thermal storage medium that has flowed from the thermal storage medium passage (43b) of the thermal storage heat exchanger (43) flows into the thermal storage tank (32). The cold thermal energy is given to the refrigerant from the thermal storage medium in this manner.

[Cooling and Cold Thermal Energy Storage Operation]

The cooling and cold thermal energy storage operation will be described below with reference to FIG. 6. The cooling and cold thermal energy storage operation is performed to cool the room using part of the cold thermal energy obtained through the refrigeration cycle of the refrigerant circuit (11), while storing the rest of the cold thermal energy in the thermal storage tank. That is, during the cooling and cold thermal energy storage operation, storing the cold thermal energy and cooling the room are simultaneously performed.
The refrigerant circuit (11) performs a refrigeration cycle (cooling and cold thermal energy storage cycle) in which the outdoor heat exchanger (22) serves as a condenser, the preheating heat exchanger (41) serves as a subcooler, and the indoor heat exchanger (27) and the thermal storage heat exchanger (43) serve as evaporators. The thermal storage circuit (31) performs a circulation operation.
Specifically, the four-way switching valve (28) is set to the first state. As a result, the discharge end of the compressor (21) is connected to the gas end of the outdoor heat exchanger (22), and the suction end of the compressor (21) is connected to the gas refrigerant channel (13). Further, the first open/close valve (51) is opened, and the second and third open/close valves (52, 53) are closed. The outdoor expansion valve (23) is fully opened, the degree of opening of the indoor expansion valve (26) is adjusted to a predetermined degree (a degree of opening which allows the refrigerant at the exit of the indoor heat exchanger to have a target degree of superheat), and the degree of opening of the thermal storage expansion valve (42) is adjusted to a predetermined degree (a degree of opening which allows the refrigerant at the exit of the thermal storage heat exchanger (43) to have a target degree of superheat). The outdoor subcooling expansion valve (24c) is fully closed, and the degree of opening of the thermal storage subcooling expansion valve (25c) is adjusted to a predetermined degree. The degree of opening of the pressure regulating valve (45) is adjusted to a predetermined degree, and the channel open/close valve (46) is closed. The compressor (21), the outdoor fan (22a), the indoor fan (27a), and the circulation pump (33) are all driven.
The refrigerant discharged from the compressor (21) flows into the outdoor heat exchanger (22), and is condensed through heat dissipation into the outdoor air in the outdoor heat exchanger (22). The refrigerant that has flowed from the outdoor heat exchanger (22) sequentially passes through the fully opened outdoor expansion valve (23) and the outdoor subcooling heat exchanger (24), and flows into the liquid refrigerant channel (12). Part of the refrigerant that has flowed into the liquid refrigerant channel (12) and passed through the first junction (P1) flows into the opened first open/close valve (51), and the rest of the refrigerant flows into the bypass channel (14). The refrigerant that has passed through the first open/close valve (51) flows into, and is cooled in, the thermal storage subcooling heat exchanger (25). The refrigerant that has passed through the thermal storage subcooling heat exchanger (25) has its pressure reduced by the indoor expansion valve (26), flows into the indoor heat exchanger (27), and absorbs heat from the indoor air in the indoor heat exchanger (27) to evaporate. The indoor air is cooled in this manner. The refrigerant that has flowed from the indoor heat exchanger (27) flows into the gas refrigerant channel (13). On the other hand, the refrigerant that has flowed into the bypass channel (14) flows into the refrigerant passage (41a) of the preheating heat exchanger (41), and is cooled through heat dissipation into the thermal storage medium flowing through the thermal storage medium passage (41b) while passing through the refrigerant passage (41a) of the preheating heat exchanger (41). The refrigerant that has flowed from the refrigerant passage (41a) of the preheating heat exchanger (41) has its pressure reduced by the thermal storage expansion valve (42), flows into the refrigerant passage (43a) of the thermal storage heat exchanger (43), and absorbs heat from the thermal storage medium flowing through the thermal storage medium passage (43b) to evaporate while passing through the refrigerant passage (43a) of the thermal storage heat exchanger (43). The refrigerant that has flowed from the refrigerant passage (43a) of the thermal storage heat exchanger (43) has its pressure reduced by the pressure regulating valve (45) of the pressure regulating mechanism (44), and flows into the gas refrigerant channel (13). In the gas refrigerant channel (13), the refrigerant that has passed through the indoor heat exchanger (27) merges with the refrigerant that has passed through the pressure regulating valve (45) of the pressure regulating mechanism (44), and is sucked into the compressor (21) to be compressed again.
In the thermal storage circuit (31), the thermal storage medium that has flowed from the thermal storage tank (32) flows into the thermal storage medium passage (41b) of the preheating heat exchanger (41), and is heated by the refrigerant flowing through the refrigerant passage (41a) while passing through the thermal storage medium passage (41b) of the preheating heat exchanger (41). The thermal storage medium that has flowed from the thermal storage medium passage (41b) of the preheating heat exchanger (41) flows through the circulation pump (33) into the thermal storage medium passage (43b) of the thermal storage heat exchanger (43), and is cooled by the refrigerant flowing through the refrigerant passage (43a) while passing through the thermal storage medium passage (43b) of the thermal storage heat exchanger (43). The thermal storage medium that has flowed from the thermal storage medium passage (43b) of the thermal storage heat exchanger (43) flows into the thermal storage tank (32). The cold thermal energy is stored in the thermal storage tank (32) in this manner.
Thus, the refrigerant flowing through the refrigerant passage (41a) of the preheating heat exchanger (41) heats the thermal storage medium flowing through the thermal storage medium passage (41b). As a result, the clathrate hydrates contained in the thermal storage medium flowed from the thermal storage tank (32) melt. This may prevent the circulation efficiency of the thermal storage medium from decreasing due to mass generation of the clathrate hydrates in the thermal storage circuit (31). More specifically, in the pipe through which the thermal storage medium that has flowed from the preheating heat exchanger (41) flows (including the thermal storage medium passage (43b) of the thermal storage heat exchanger (43)), the mass generation of the clathrate hydrates in the thermal storage medium, and the resulting clogging of the pipe forming the thermal storage circuit (31) may be prevented.

[Control during Cooling and Cold Thermal Energy Storage Operation]

The control (by the controller (100)) during the cooling and cold thermal energy storage operation shown in FIG. 6 will be described below. During the cooling and cold thermal energy storage operation, the controller (100) performs, in parallel, superheat degree control for the indoor unit, superheat degree control for the thermal storage unit, target low pressure control, and evaporating temperature control for the thermal storage unit. The temperature and degree of superheat to be described below can be detected based on the values detected by various sensors (not shown).

During the superheat degree control for the indoor unit, the controller (100) regulates the degree of opening of the indoor expansion valve (26) such that the degree of superheat of the refrigerant at the exit of the indoor heat exchanger (27) (hereinafter will be referred to as the "degree of superheat of the indoor-unit refrigerant") is set to a predetermined target degree of superheat of the indoor-unit refrigerant. Specifically, the controller (100) increases the degree of opening of the indoor expansion valve (26) if the degree of superheat of the indoor-unit refrigerant is higher than the associated target degree of superheat, and reduces the degree of opening of the indoor expansion valve (26) if the degree of superheat of the indoor-unit refrigerant is lower than the associated target degree of superheat. Note that the controller (100) determines the target degree of superheat of the indoor-unit refrigerant such that it decreases with increase in difference between the temperature of the indoor air and a predetermined target cooling temperature (a difference obtained by subtracting the temperature of the indoor air from the target cooling temperature).

During the superheat degree control for the thermal storage unit, the controller (100) regulates the degree of opening of the thermal storage expansion valve (42) such that the degree of superheat of the refrigerant at the exit of the thermal storage heat exchanger (43) (hereinafter will be referred to as the "degree of superheat of the thermal-storage-unit refrigerant") is set to a predetermined target degree of superheat of the thermal-storage-unit refrigerant. Specifically, the controller (100) increases the degree of opening of the thermal storage expansion valve (42) if the degree of superheat of the thermal-storage-unit refrigerant is higher than the associated target degree of superheat, and decreases the degree of opening of the thermal storage expansion valve (42) if the degree of superheat of the thermal-storage-unit refrigerant is lower than the associated target degree of superheat. Note that the degree of superheat of the thermal-storage-unit refrigerant can be calculated based on the values detected by the first and second refrigerant temperature sensors (61, 62).

During the target low pressure control, the controller (100) controls the rotational speed of the compressor (21) such that the low pressure in the refrigerant circuit (11) (the suction pressure of the compressor (21) in this example) reaches the predetermined target low pressure. Specifically, the controller (100) increases the rotational speed of the compressor (21) if the suction pressure of the compressor (21) is higher than the target low pressure, and reduces the rotational speed of the compressor (21) if the suction pressure of the compressor (21) is lower than the target low pressure. Note that the controller (100) determines the target low pressure such that the target low pressure decreases with increase in cooling load (i.e., a difference between the temperature of the indoor air and the target refrigerant temperature).

During the evaporating temperature control for the thermal storage unit, the controller (100) adjusts the amount of pressure reduction by the pressure regulating mechanism (44) such that the evaporating temperature of the refrigerant in the thermal storage heat exchanger (43) (hereinafter will be referred to as the "evaporating temperature of the thermal-storage-unit refrigerant") does not fall below a predetermined lower limit evaporating temperature. Note that the lower limit evaporating temperature is set to be a lower limit temperature in the range of the evaporating temperature of the refrigerant suitable for cooling the thermal storage medium in the thermal storage heat exchanger (43) (hereinafter will be referred to as the "suitable range of the evaporating temperature"). The suitable range of the evaporating temperature can be determined based on the hydrate formation temperature in the thermal storage medium and the size (heat exchange area) of the thermal storage heat exchanger (43). For example, if a tetra-n-butyl ammonium bromide aqueous solution is adopted as the thermal storage medium, the suitable range of the evaporating temperature may be from about 4°C to 7°C. The lower limit evaporating temperature may be set to 4°C.
In this example, the controller (100) regulates the degree of opening of the pressure regulating valve (45) of the pressure regulating mechanism (44) such that the evaporating temperature of the thermal-storage-unit refrigerant reaches a predetermined reference evaporating temperature. Specifically, the controller (100) reduces the degree of opening of the pressure regulating valve (45) if the evaporating temperature of the thermal-storage-unit refrigerant is lower than the reference evaporating temperature, and increases the degree of opening of the pressure regulating valve (45) if the evaporating temperature of the thermal-storage-unit refrigerant is higher than the reference evaporating temperature. The reference evaporating temperature is set to be a temperature obtained by adding a predetermined temperature (e.g., 1°C) to the lower limit evaporating temperature (i.e., a temperature higher than the lower limit evaporating temperature). Note that the reference evaporating temperature is suitably set to be equal to or lower than the upper limit temperature in the suitable range of the evaporating temperature.
Further, in this example, the controller (100) is configured to perform the evaporating temperature control for the thermal storage unit using the value detected by the second refrigerant temperature sensor (62) (i.e., the temperature of the refrigerant at the inlet of the thermal storage heat exchanger (43)) as the evaporating temperature of the thermal-storage-unit refrigerant.

[Specific Examples of Control by Controller]

If the cooling load increases (i.e., if the temperature of the indoor air is higher than the target cooling temperature), the target low pressure decreases. Thus, the suction pressure of the compressor (21) becomes higher than the target low pressure, and then the rotational speed of the compressor (21) increases to lower the suction pressure of the compressor (21). As a result, the evaporating pressure of the refrigerant in the indoor heat exchanger (27) decreases to lower the evaporating temperature of the refrigerant in the indoor heat exchanger (27). In this manner, the cooling capacity (i.e., capacity to cool the room) of the indoor heat exchanger (27) is ensured.
The evaporating pressure of the refrigerant in the thermal storage heat exchanger (43) also decreases with decrease in the suction pressure of the compressor (21). Thus, the evaporating temperature of the refrigerant in the thermal storage heat exchanger (43) decreases to lower the value detected by the second refrigerant temperature sensor (62) (i.e., the temperature of the refrigerant at the inlet of the thermal storage heat exchanger (43)). Then, if the temperature of the refrigerant at the inlet of the thermal storage heat exchanger (43) becomes lower than the reference evaporating temperature, the degree of opening of the pressure regulating valve (45) of the pressure regulating mechanism (44) decreases. Thus, the amount of pressure reduction by the pressure regulating valve (45) increases to raise the evaporating pressure of the refrigerant in the thermal storage heat exchanger (43). As a result, the evaporating temperature of the refrigerant in the thermal storage heat exchanger (43) increases.

-Advantages of Embodiments-

As can be seen from the foregoing, provision of the pressure regulating mechanism (44) allows the evaporating pressure of the refrigerant in the thermal storage heat exchanger (43) to be regulated such that the evaporating pressure becomes higher than the suction pressure of the compressor (21) during the cooling and cold thermal energy storage operation (i.e., when the refrigerant circuit (11) performs the cooling and cold thermal energy storage cycle). This may substantially prevent the evaporating pressure of the refrigerant in the thermal storage heat exchanger (43) from decreasing with the decrease in the suction pressure of the compressor (21), thereby substantially preventing the evaporating temperature of the refrigerant in the thermal storage heat exchanger (43) from decreasing too much. Therefore, excessive cooling of the thermal storage medium in the thermal storage heat exchanger (43) may be prevented, which may substantially prevent the circulation efficiency of the thermal storage medium in the thermal storage circuit (31) from decreasing. In this example, the thermal storage medium in the thermal storage heat exchanger (43) is not cooled too much. Thus, mass generation of the clathrate hydrates (i.e., solid components) is less likely to occur, which may substantially prevent the circulation efficiency of the thermal storage medium from decreasing (specifically, the pipe forming the thermal storage circuit (31) from being clogged with the clathrate hydrates). In this manner, the excessive cooling of the thermal storage medium in the thermal storage heat exchanger (43) may be prevented. This may substantially prevent the circulation efficiency of the thermal storage medium in the thermal storage circuit (31) from decreasing, while ensuring the cooling capacity (i.e., capacity to cool the room) of the indoor heat exchanger during the cooling and cold thermal energy storage operation.
Further, the amount of pressure reduction by the pressure regulating mechanism (44) (specifically, the degree of opening of the pressure regulating valve (45)) is adjusted such that the evaporating temperature of the refrigerant in the thermal storage heat exchanger (43) does not fall below the lower limit evaporating temperature. Thus, the evaporating temperature of the refrigerant in the thermal storage heat exchanger (43) may suitably be determined. Since the thermal storage medium can suitably be cooled in the thermal storage heating exchanger (43), the cold thermal energy may suitably be stored during the cooling and cold thermal energy storage operation.
Moreover, since the pressure regulating mechanism (44) is comprised of the pressure regulating valve (45), the amount of pressure reduction by the pressure regulating mechanism (44) may be adjusted by regulating the degree of opening of the pressure regulating valve (45). As a result, the evaporating pressure of the refrigerant in the thermal storage heat exchanger (43) may be regulated such that the evaporating pressure is higher than the suction pressure of the compressor (21), which may prevent the excessive cooling of the thermal storage medium in the thermal storage heat exchanger (43).
In addition, since the pressure regulating mechanism (44) is comprised of the pressure regulating valve (45) and the channel open/close valve (46), the channel open/close valve (46) may be opened, while the pressure regulating valve (45) is fully closed. Thus, the refrigerant is allowed to flow between the thermal storage heat exchanger (43) and the gas refrigerant channel (13) via the channel open/close valve (46). A pressure loss in the channel open/close valve (46) is smaller than a pressure loss in the pressure regulating valve (45). Thus, the pressure loss in the pressure regulating mechanism (44) may be reduced as compared with the case where the refrigerant is allowed to flow between the thermal storage heat exchanger (43) and the gas refrigerant channel (13) via the pressure regulating valve (45). As a result, during other operations than the cooling and cold thermal energy storage operation, the pressure loss in the pressure regulating mechanism (44) may be reduced, which allows the other operations to be suitably performed.

(Other Embodiments)

The thermal storage medium may be other thermal storage materials than the tetra-n-butyl ammonium bromide aqueous solution. The concentration of the thermal storage medium is not necessarily 40%.
The above-described embodiments may suitably be combined as needed. Note that the foregoing description of the embodiments is merely beneficial examples in nature, and is not intended to limit the scope, application, or uses of the present disclosure.

INDUSTRIAL APPLICABILITY

As can be seen from the foregoing, the thermal storage air conditioner described above is useful as an air conditioner which is able to store cold thermal energy by using the thermal storage effect of a thermal storage medium.

DESCRIPTION OF REFERENCE CHARACTERS

10: Thermal Storage Air Conditioner
11: Refrigerant Circuit
12: Liquid Refrigerant Channel
13: Gas Refrigerant Channel
14: Bypass Channel
14d: First Branch Channel (First Channel Portion)
14e: Second Branch Channel (Second Channel Portion)
15: Branch Channel
20a: Outdoor Unit
20b: Indoor Unit
21: Compressor
22: Outdoor Heat Exchanger
22a: Outdoor Fan
23: Outdoor Expansion Valve
24: Outdoor Subcooling Heat Exchanger
25: Thermal Storage Subcooling Heat Exchanger
26: Indoor Expansion Valve
27: Indoor Heat Exchanger
27a: Indoor Fan
28: Four-Way Switching Valve
30: Thermal Storage Unit
31: Thermal Storage Circuit
32: Thermal Storage Tank
33: Circulation Pump
41: Preheating Heat Exchanger
42: Thermal Storage Expansion Valve
43: Thermal Storage Heat Exchanger
44: Pressure Regulating Mechanism
45: Pressure Regulating Valve
46: Channel Open/Close Valve (Open/Close Valve)
51: First Open/Close Valve
52: Second Open/Close Valve
53: Third Open/Close Valve
61: First Refrigerant Temperature Sensor
62: Second Refrigerant Temperature Sensor
100: Controller (Operation Control Section)

Claims

A thermal storage air conditioner comprising:
a refrigerant circuit (11) including a compressor (21), an outdoor heat exchanger (22), an indoor heat exchanger (27), a liquid refrigerant channel (12) connecting a liquid end of the outdoor heat exchanger (22) and a liquid end of the indoor heat exchanger (27), a gas refrigerant channel (13) connected to a gas end of the indoor heat exchanger (27), and a bypass channel (14) having one end connected to the liquid refrigerant channel (12) and the other end connected to the gas refrigerant channel (13);

a thermal storage circuit (31) which allows a thermal storage medium, which would generate a solid component if cooled, to flow therein;

a thermal storage heat exchanger (43) which is connected to the bypass channel (14) and the thermal storage circuit (31), and allows a refrigerant flowing through the bypass channel (14) and the thermal storage medium flowing through the thermal storage circuit (31) to exchange heat; and

a pressure regulating mechanism (44) provided in the bypass channel (14) between the thermal storage heat exchanger (43) and the gas refrigerant channel (13), wherein

the refrigerant circuit (11) performs a cooling and cold thermal energy storage cycle in which a discharge end of the compressor (21) is connected to a gas end of the outdoor heat exchanger (22), a suction end of the compressor (21) is connected to the gas refrigerant channel (13), the outdoor heat exchanger (22) serves as a condenser, and the indoor heat exchanger (27) and the thermal storage heat exchanger (43) serve as evaporators, and

the pressure regulating mechanism (44) is configured to regulate a pressure of the refrigerant flowing between the thermal storage heat exchanger (43) and the gas refrigerant channel (13).
The thermal storage air conditioner of claim 1, further comprising:
an operation control section (100) which instructs the refrigerant circuit (11) to perform the cooling and cold thermal energy storage cycle, and adjusts the amount of pressure reduction by the pressure regulating mechanism (44) such that an evaporating temperature of the refrigerant in the thermal storage heat exchanger (43) does not fall below a predetermined lower limit evaporating temperature.
The thermal storage air conditioner of claim 1 or 2, wherein
the bypass channel (14) includes a first channel portion (14d) which connects the thermal storage heat exchanger (43) and the gas refrigerant channel (13), and
the pressure regulating mechanism (44) includes a pressure regulating valve (45) which is provided in the first channel portion (14d) and has an adjustable degree of opening.
The thermal storage air conditioner of claim 3, wherein
the bypass channel (14) further includes a second channel portion (14e) which is provided in parallel with the first channel portion (14d), and connects the thermal storage heat exchanger (43) and the gas refrigerant channel (13), and
the pressure regulating mechanism (44) further includes an open/close valve (46) which is provided in the second channel portion (14e) and configured to be switchable between an open state and a closed state.