GB2561993A

GB2561993A - Air conditioning device

Info

Publication number: GB2561993A
Application number: GB1810610.4A
Authority: GB
Inventors: Shinoda Ippei; kawai Kazuhiko
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2016-02-10
Filing date: 2016-02-10
Publication date: 2018-10-31
Also published as: JPWO2017138110A1; WO2017138110A1; GB201810610D0

Abstract

An air conditioning device comprises: a first circulation circuit in which a first condenser and a first evaporator are connected via piping and in which refrigerant is transported by natural circulation of the refrigerant; a second circulation circuit that is configured to be independent of the first circulation circuit and in which a compressor, a second condenser, a throttling device, and a second evaporator are connected via piping; a shared fan that supplies air to the first evaporator and the second evaporator; and a hollow box case that comprises an intake face provided with an inlet to draw in air, and a blowout face downstream of the inlet and provided with an outlet to blow air, and that forms a main air channel to connect the inlet and the outlet. The first evaporator and the second evaporator are disposed inside the case so that the first evaporator is positioned upstream of the second evaporator. The case further has formed therein a bypass inlet that draws in air separately from the inlet, and a bypass air channel that connects the bypass inlet and the outlet and that merges with the main air channel between the first evaporator and the second evaporator.

Description

(54) Title of the Invention: Air conditioning device Abstract Title: Air conditioning device (57) An air conditioning device comprises: a first circulation circuit in which a first condenser and a first evaporator are connected via piping and in which refrigerant is transported by natural circulation of the refrigerant; a second circulation circuit that is configured to be independent of the first circulation circuit and in which a compressor, a second condenser, a throttling device, and a second evaporator are connected via piping; a shared fan that supplies air to the first evaporator and the second evaporator; and a hollow box case that comprises an intake face provided with an inlet to draw in air, and a blowout face downstream of the inlet and provided with an outlet to blow air, and that forms a main air channel to connect the inlet and the outlet. The first evaporator and the second evaporator are disposed inside the case so that the first evaporator is positioned upstream of the second evaporator. The case further has formed therein a bypass inlet that draws in air separately from the inlet, and a bypass air channel that connects the bypass inlet and the outlet and that merges with the main air channel between the first evaporator and the second evaporator.

[02]

/4

FIG. 1

2/4

FIG. 2

40e

FIG. 3

40e

40d

3/4

FIG. 4

Γ Sib, 51 1 \

L 51a czz>

40e

FIG. 5

40e

4/4

FIG. 6

fig. 1

DESCRIPTION

Title of Invention

AIR-CONDITIONING APPARATUS

Technical Field [0001]

The present invention relates to an air-conditioning apparatus.

Background Art [0002]

Hitherto, there has been proposed an air-conditioning apparatus configured to convey refrigerant in a circuit through natural circulation using a temperature difference between an indoor temperature and an outdoor air temperature and a height difference between an indoor unit and an outdoor unit (see Patent Literature

1). The air-conditioning apparatus using the natural circulation is mainly used in a place where cooling is required throughout the year. The air-conditioning apparatus is installed in, for example, a communication base station or a server room so as to eliminate heat released from an internal electronic device. Further, particularly under a condition that there is a large temperature difference between indoor and outdoor spaces, cooling can be performed through ventilation so that power of a compressor is not needed. Thus, annual power consumption can be significantly reduced as compared to that of an air-conditioning apparatus using the compressor or other devices.

[0003]

Further, in those technologies, in view of an installation space, there has been proposed a configuration in which a sharable fan is used for an evaporator in a natural-circulation circuit and an evaporator in a forced-circulation circuit that uses a compressor or other devices (see Patent Literatures 1 and 2). In the abovementioned air-conditioning apparatus including the sharable fan, the evaporator in the natural-circulation circuit is arranged on an upstream side of an airflow, and the evaporator in the forced-circulation circuit is arranged on a downstream side thereof. Accordingly, air that is to pass through the evaporator in the forced-circulation circuit can be cooled in advance by the evaporator in the natural-circulation circuit. As a result, power of the compressor in the forced-circulation circuit can be lowered. Citation List

Patent Literature [0004]

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2001-99446

Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2014-202463 Summary of Invention Technical Problem [0005]

In the natural-circulation circuit having no forcible power, under a condition that the temperature difference between the indoor and outdoor spaces cannot be secured, the refrigerant does not naturally circulate, with the result that cooling cannot be performed. In this case, in the air-conditioning apparatus having such a configuration that the sharable fan sends the air to the evaporator in the naturalcirculation circuit and to the evaporator in the forced-circulation circuit, the evaporator in the natural-circulation circuit does not contribute to cooling of the air, and is merely air passage resistance. There is a problem in that an air-sending load of a fan motor is increased instead as compared to a case where a fan is provided for each of the evaporators.

[0006]

Further, along with increase in air-sending load of the fan motor, heat generation of the fan motor is also increased. Thus, the air-conditioning apparatus including the motor arranged in the indoor unit has a problem in that a cooling capacity is reduced.

[0007]

The present invention has been made to solve the above-mentioned problems, and has an object to obtain an air-conditioning apparatus that enhances a cooling capacity and reduces power consumption through reduction of air passage resistance.

Solution to Problem [0008]

According to one embodiment of the present invention, there is provided an airconditioning apparatus, including: a first circuit, which is configured to convey refrigerant through refrigerant natural circulation, and includes a first condenser and a first evaporator connected together through a pipe; a second circuit, which is formed independently of the first circuit and includes a compressor, a second condenser, an expansion device, and a second evaporator connected together through a pipe; a sharable fan, which is configured to supply air to the first evaporator and the second evaporator; and a case, which has a hollow box shape and includes a suction surface with an air inlet that allows the air to be sucked therethrough, a blow-out surface with an air outlet that is formed downstream of the air inlet and allows the air to be blown out therethrough, and a main air passage formed so as to establish communication between the air inlet and the air outlet, in which the first evaporator and the second evaporator are arranged inside the case so that the first evaporator is positioned upstream of the second evaporator, in which the case further includes a bypass air inlet, which is formed in addition to the air inlet and allows the air to be sucked therethrough, and a bypass air passage, which is formed so as to establish communication between the bypass air inlet and the air outlet and allows the air to join the air along the main air passage from between the first evaporator and the second evaporator.

Advantageous Effects of Invention [0009]

According to one embodiment of the present invention, the air-conditioning apparatus includes the bypass air passage that is formed to allow the air to bypass the first evaporator arranged on the upstream side of the air flow with respect to the second evaporator. Accordingly, even in a case where the air is supplied to both the evaporators by one fan, when the natural-circulation circuit does not function, the air passage involving less air passage resistance can be used. Thus, a load on the sharable fan is reduced so that the indoor space can be cooled efficiently considering power consumption.

Brief Description of Drawings [0010] [Fig. 1] Fig. 1 is a configuration diagram for illustrating an air-conditioning apparatus according to Embodiment 1 to Embodiment 5 of the present invention.

[Fig. 2] Fig. 2 is a schematic side view for illustrating a configuration of an indoor unit (of a front suction type) according to Embodiment 1 of the present invention.

[Fig. 3] Fig. 3 is a schematic side view for illustrating a configuration of the indoor unit (of a duct suction type) according to Embodiment 1 of the present invention.

[Fig. 4] Fig. 4 is a schematic view for illustrating a vicinity of an evaporator in a first circuit according to Embodiment 2 to Embodiment 5 of the present invention (a state in which an openable and closable door is opened).

[Fig. 5] Fig. 5 is a schematic view for illustrating a vicinity of the evaporator in the first circuit according to Embodiment 2 to Embodiment 5 of the present invention (a state in which the openable and closable door is closed).

[Fig. 6] Fig. 6 is a perspective view for illustrating a vicinity of the evaporator in the first circuit according to Embodiment 2 to Embodiment 5 of the present invention (a state in which the openable and closable door is opened).

[Fig. 7] Fig. 7 is a flow chart for illustrating control on an openable and closable louver according to Embodiment 4 of the present invention.

Description of Embodiments [0011]

Now, embodiments of the present invention are described with reference to the drawings. In the following description, a case where an air-conditioning apparatus performs a cooling operation is described as an example. Further, an indoor space to be air-conditioned refers to, for example, a space in a warehouse, a data center, a server room, or a house.

[0012]

Embodiment 1.

Embodiment 1 is described with reference to Fig. 1 to Fig. 3. Fig. 1 is a configuration diagram for illustrating an air-conditioning apparatus according to Embodiment 1 to Embodiment 5 of the present invention. As illustrated in Fig. 1, an air-conditioning apparatus 1 includes a first circuit 10 configured to convey refrigerant through refrigerant natural circulation, and a second circuit 20, which is formed independently of the first circuit 10 and is powered to forcibly convey the refrigerant. The first circuit 10 is a refrigeration cycle obtained by connecting a first condenser 11 and a first evaporator 12 together through a pipe. In place of the refrigerant, a heat medium such as water may be filled in the first circuit 10. Further, the second circuit 20 is a refrigeration cycle obtained by connecting a compressor 21, a second condenser 22, an expansion device 23, and a second evaporator 24 together through a pipe.

[0013]

In the first circuit 10, the first condenser 11 is installed in a first outdoor unit 3.

In the second circuit 20, the compressor 21, the second condenser 22, and the expansion device 23 are connected in series and installed in a second outdoor unit 4. Meanwhile, the first evaporator 12, the second evaporator 24, and a sharable fan 31 are installed in an indoor unit 2.

[0014]

The compressor 21 sucks the refrigerant, and compresses the refrigerant into a high-temperature and high-pressure state. The compressor 21 may be constructed by, for example, a scroll type that is controlled in rotation speed and capacity by an inverter. The first condenser 11, the second condenser 22, the first evaporator 12, and the second evaporator 24 are each constructed by, for example, a heat exchanger of a fin tube type, and exchange heat between air and the refrigerant. An outdoor fan configured to supply the air is additionally provided to each of the first condenser 11 and the second condenser 22. The outdoor fan is constructed by, for example, a propeller fan. Each evaporator exchanges heat between the refrigerant and the air supplied by the outdoor fan, to thereby condense and liquify the refrigerant. Each evaporator exchanges heat between the refrigerant and the air supplied by the sharable fan 31, to thereby evaporate and gasify the refrigerant. [0015]

A case 40, which serves as a casing of the indoor unit 2, includes a first case 40a configured to accommodate the first evaporator 12 therein, and a second case 40b configured to accommodate the second evaporator 24 and the sharable fan 31 therein. The first case 40a and the second case 40b are coupled to each other, and share an air inlet 40c through which the air is sucked from an indoor space 5 to be cooled, and an air outlet 40d through which the cooled air is blown into the indoor space 5. The second evaporator 24 is installed on a downstream side of an air flow with respect to the first evaporator 12. Further, the sharable fan 31 is a sharable fan configured to supply the air to the first circuit 10 and the second circuit 20.

[0016]

In the first circuit 10, the refrigerant in the first evaporator 12 is evaporated through heat exchange with the air to become gas refrigerant, and the gas refrigerant flows into the first condenser 11 through the pipe. In the first condenser 11, the gas refrigerant is condensed through heat exchange with outdoor air supplied by the outdoor fan to become liquid refrigerant. The liquid refrigerant is returned to the first evaporator 12 through the pipe through natural circulation caused by a density difference between the gas refrigerant and the liquid refrigerant.

[0017]

In the second circuit 20, the refrigerant is compressed by the compressor 21 into the high-temperature and high-pressure state. The high-temperature and highpressure refrigerant is discharged from the compressor 21, and flows into the second condenser 22. The refrigerant having flowed into the second condenser 22 is condensed and liquefied through heat exchange with the air supplied by the outdoor fan. The condensed and liquefied refrigerant flows into an expansion valve of the indoor unit 2 through the pipe. The refrigerant having flowed into the indoor expansion valve is decompressed and expanded, to thereby be changed into twophase gas-liquid refrigerant having a low temperature and a low pressure. The twophase gas-liquid refrigerant flows into the second evaporator 24. The two-phase gas-liquid refrigerant having flowed into the second evaporator 24 is evaporated and gasified through heat exchange with the air supplied by the sharable fan 31. The evaporated and gasified refrigerant flows out of the second evaporator 24, and then flows into the expansion device 23 of the second outdoor unit 4 through the pipe.

The refrigerant having flowed into the expansion device 23 is decompressed, and is sucked again into the compressor 21.

[0018]

Owing to action of the sharable fan 31, the air in the indoor space 5 flows into the indoor unit 2 through the air inlet 40c formed in the case 40 of the indoor unit 2. When the refrigerant naturally expands in the first circuit 10 and the first evaporator 12 exerts a cooling capacity, first, the air having flowed into the indoor unit 2 is primarily cooled by the first evaporator 12 arranged on a primary side (upstream side of the air flow). The primarily cooled air is cooled by the second evaporator 24 arranged on a secondary side (downstream side of the airflow), and then is released into the indoor space 5 through the air outlet 40d formed in the case 40. In this manner, the air-conditioning apparatus 1 circulates and cools the air in the indoor space 5. The sharable fan 31 is arranged on the downstream side with respect to the first evaporator 12.

[0019]

Further, the indoor unit 2 includes a controller 60 constructed by, for example, a microcomputer. The controller 60 controls, for example, an opening degree of the indoor expansion valve and rotation speed of the sharable fan 31 based on operation information (a temperature of the air to be air-conditioned, a temperature of the outdoor air, a set temperature, a temperature of a refrigerant pipe, and other parameters).

Further, the first outdoor unit 3 and the second outdoor unit 4 each include an outdoor controller. Each outdoor controller is connected to the controller 60 of the indoor unit 2 by, for example, a transmission line, and is configured to send and receive information. The outdoor controller obtains the operation information from, for example, the controller 60, and performs preset control on the compressor 21 and the outdoor fan based on the obtained operation information. In this manner, the outdoor controller changes rotation speed of the compressor 21 and rotation speed of the outdoor fan.

[0020]

The air-conditioning apparatus 1 further includes an indoor sensor 62 configured to measure a temperature of the air in the indoor space 5, and an outdoor sensor 61 configured to measure a temperature of the outdoor air. Those temperature sensors are connected to the controller 60, and are configured to send the measurement information.

[0021]

Fig. 2 is a schematic side view for illustrating a configuration of the indoor unit (of a front suction type) according to Embodiment 1 of the present invention. In Fig. 2, in the case 40 of the indoor unit 2, the air inlet 40c is formed in a suction surface on the upper side of the drawing sheet of Fig. 2, and the air outlet 40d is formed in a blow-out surface on the lower side of the drawing sheet of Fig. 2. Further, the case 40 has a hollow box shape. Inside the case 40, the first evaporator 12 is arranged on the primary side close to the air inlet 40c, and the second evaporator 24 is arranged on the secondary side that is the downstream side with respect to the first evaporator 12. The sharable fan 31 is arranged downstream of those evaporators, and is configured to send the air to both the evaporators.

[0022]

Under a condition that the first circuit 10 does not function, the first evaporator 12 contributes little to cooling of the air. Accordingly, as illustrated in Fig. 2, in the configuration in which the two evaporators share the air inlet 40c and the air outlet 40d, the first evaporator 12 is merely a resistance object for the air that flows into the case 40 toward the second evaporator 24. That is, the air does not need to pass through the first evaporator 12.

[0023]

In Fig. 2, a main air passage 45a establishing communication between the air inlet 40c and the air outlet 40d is indicated by the arrow. When the refrigerant in the first circuit 10 circulates and the first evaporator 12 has the cooling capacity, the air that is primarily cooled by the first evaporator 12 in the first circuit 10 including no power source is sent to the second evaporator 24. At this time, as illustrated in Fig.

2, the air taken into the case 40 is sent along the main air passage 45a.

[0024]

Further, in addition to the air inlet 40c, a bypass air inlet 40e is formed in the case 40. The air is sucked through the bypass air inlet 40e. The bypass air inlet 40e is formed in a wall surface of the case 40 between the first evaporator 12 and the second evaporator 24. The air having flowed into the case 40 through the bypass air inlet 40e flows along a bypass air passage 45b, and joins the air flowing along the main air passage 45a. Then, the air passes through the second evaporator 24, and is blown out of the case 40 through the air outlet 40d. The bypass air passage 45b is indicated by the arrow in Fig. 2.

[0025]

Fig. 3 is a schematic side view for illustrating a configuration of the indoor unit (of a duct suction type) according to Embodiment 1 of the present invention. Fig. 3 is an illustration of a mode in which the first evaporator 12 is installed inside a duct, and in which the duct is connected to the primary side of the air inlet 40c of the case 40. When the air inlet 40c is directly connected to the duct, the suction surface of the case 40 is enlarged, and the bypass air inlet 40e is formed in an enlarged portion of the case 40 side by side with the air inlet 40c. Accordingly, similarly to the mode illustrated in Fig. 2, the air having flowed into the case 40 through the bypass air inlet 40e can bypass the first evaporator 12 and flow along the bypass air passage 45b without passing through the first evaporator 12.

[0026]

As described above, in Embodiment 1, the air-conditioning apparatus 1 includes: the first circuit 10, which is configured to convey the refrigerant through the refrigerant natural circulation and includes the first condenser 11 and the first evaporator 12 connected together through the pipe; the second circuit 20, which is formed independently of the first circuit 10 and includes the compressor 21, the second condenser 22, the expansion device 23, and the second evaporator 24 connected together through the pipe; the sharable fan 31, which is configured to supply the air to the first evaporator 12 and the second evaporator 24; and the case 40, which has a hollow box shape and includes the suction surface with the air inlet 40c that allows the air to be sucked therethrough, the blow-out surface with the air outlet 40d that is formed downstream of the air inlet 40c and allows the air to be blown out therethrough, and the main air passage 45a formed so as to establish communication between the air inlet 40c and the air outlet 40d. The first evaporator 12 and the second evaporator 24 are arranged inside the case 40 so that the first evaporator 12 is positioned upstream of the second evaporator 24. The case 40 further includes the bypass air inlet 40e, which is formed in addition to the air inlet 40c and allows the air to be sucked therethrough, and the bypass air passage 45b, which is formed so as to establish communication between the bypass air inlet 40e and the air outlet 40d and allows the air to join the air along the main air passage 45a from between the first evaporator 12 and the second evaporator 24.

[0027]

With this configuration, the air-conditioning apparatus 1 includes the bypass air passage 45b that is formed to allow the air to bypass the first evaporator 12 arranged on the upstream side of the air flow with respect to the second evaporator 24. Accordingly, even in a case where the air is supplied to both the evaporators by one fan, when the natural-circulation circuit does not function, the air passage involving less air passage resistance can be used. Thus, a load on the sharable fan is reduced so that the indoor space can be cooled efficiently considering power consumption.

[0028]

Further, in the air-conditioning apparatus 1, the bypass air inlet 40e may be formed in the case 40 at a position between the first evaporator 12 and the second evaporator 24. Accordingly, the bypass air passage 45b can be formed irrespective of suction types. Thus, the air passage resistance is reduced so that efficient cooling can be performed.

[0029]

Further, in the air-conditioning apparatus 1, the bypass air inlet 40e may be formed in the suction surface side by side with the air inlet 40c. Accordingly, the bypass air passage 45b can be formed irrespective of suction types. Thus, the air passage resistance is reduced so that efficient cooling can be performed.

[0030]

Embodiment 2.

Fig. 4 is a schematic view for illustrating a vicinity of an evaporator in a first circuit according to Embodiment 2 to Embodiment 5 of the present invention (a state in which an openable and closable door is opened). In Embodiment 2, an openable and closable door 51 configured to open and close the bypass air inlet 40e is provided on the case 40. Description of the same components as those of Embodiment 1 is omitted, and only different components are described. Description is made below of a case where the openable and closable door 51 is formed of an openable and closable louver and mounted to the bypass air inlet 40e. The openable and closable louver includes a plurality of plate-like slats 51a. Both ends of louver shafts 51b are pivotally supported on bearing portions recessed in the bypass air inlet 40e so that the slats 51a are each pivoted about a longitudinal direction thereof in an up-and-down direction.

[0031]

Fig. 5 is a schematic view for illustrating a vicinity of the evaporator in the first circuit according to Embodiment 2 to Embodiment 5 of the present invention (a state in which the openable and closable door is closed). When the refrigerant in the first circuit 10 circulates, the bypass air inlet 40e can be closed by pivoting the openable and closable louver into a closed state. When the openable and closable door 51 is brought into the closed state, all the air is taken into the indoor unit 2 through the air inlet 40c. Thus, the air flows via the main air passage 45a in the case 40, and heat is exchanged in the first evaporator 12. Further, when the refrigerant in the first circuit 10 does not circulate, the openable and closable louver is pivoted into an opened state so that the air is sucked through the bypass air inlet 40e. In this manner, the air can be caused to flow via the bypass air passage 45b.

[0032]

Fig. 6 is a perspective view for illustrating a vicinity of the evaporator in the first circuit according to Embodiment 2 to Embodiment 5 of the present invention (a state in which the openable and closable door is opened). Fig. 6 is an illustration of the first case 40a from which a filter is removed. The filter covers each of the air inlet 40c and the bypass air inlet 40e so as to catch dust and dirt. The air in the indoor space 5 to be air-conditioned is taken into the case 40 not only through the air inlet 40c but also through the bypass air inlet 40e.

[0033]

As described above, in Embodiment 2, the air-conditioning apparatus 1 further includes the openable and closable door 51 configured to open and close the bypass air inlet 40e. Accordingly, when the refrigerant in the first circuit 10 does not circulate, the bypass air passage 45b, along which the air bypasses the first evaporator 12 without passing through the first evaporator 12, can be formed by opening the openable and closable louver. Further, when the refrigerant in the first circuit 10 circulates, the main air passage 45a, along which the air passes through the first evaporator 12, can be formed by closing the openable and closable louver.

Thus, in accordance with operation conditions, there can be used cooling that puts a priority on reducing power in the second circuit 20 by performing primary cooling in the first circuit 10, or on reducing an air passage loss of the air passing an inside of the case 40. Therefore, power consumption can be reduced.

[0034]

Embodiment 3.

In Embodiment 3, the air-conditioning apparatus 1 according to Embodiment 2 further includes an opening and closing drive unit 52 configured to open and close the openable and closable louver by pivoting the openable and closable louver in accordance with an electric signal. The opening and closing drive unit 52 is constructed by, for example, a motor. The motor is mounted at a vicinity of the louver, and opens and closes the openable and closable louver by pivoting the coupled louver shafts 51 b. A control line of the motor is connected to a control board of the indoor unit 2 so as to allow signal transmission between the controller 60 of the indoor unit 2 and the motor.

[0035]

The air-conditioning apparatus 1 includes a remote controller for the indoor unit 2, through which a user inputs an operation instruction. Further, a light receiver configured to receive an infrared signal is provided on a surface of the indoor unit 2. The light receiver is connected to the controller 60 through a signal line. With this configuration, when an instruction is issued through the remote controller to open or close the openable and closable door 51, the light receiver mounted to the indoor unit 2 receives a signal, and sends the instruction to the controller 60. Further, the controller 60 sends the opening or closing instruction to the opening and closing drive unit 52. In accordance with the instruction, the opening and closing drive unit 52 brings the openable and closable door 51 into the opened state or the closed state. [0036]

As described above, in Embodiment 3, the air-conditioning apparatus 1 further includes the opening and closing drive unit 52 configured to open and close the openable and closable door 51 in accordance with the electric signal. Accordingly, it is not necessary to manually pivot the openable and closable louver, and the openable and closable louver can be operated through the remote controller form the indoor unit 2. Thus, usability for a user is improved. Further, even in a case of the large-sized indoor unit 2 or the ceiling-hung indoor unit 2 in which the openable and closable door 51 is out of reach and manual switching is difficult, operation is easily performed.

[0037]

Embodiment 4.

In Embodiment 4, the openable and closable louver of the air-conditioning apparatus 1 of Embodiment 3 is automatically opened and closed. Fig. 7 is a flow chart for illustrating control on the openable and closable louver according to Embodiment 4 of the present invention. Based on outdoor and indoor temperatures detected by the outdoor sensor 61 and the indoor sensor 62, the controller 60 determines timings of opening and closing the openable and closable louver.

[0038]

The controller 60 always obtains temperature information from the outdoor sensor 61 mounted in an air inlet of the first outdoor unit 3, and from the indoor sensor 62 mounted at a vicinity of the air inlet 40c of the indoor unit 2. Based on the obtained temperature information, the controller 60 works out a temperature difference between the indoor temperature and the outdoor air temperature by calculation. Next, the controller 60 determines whether or not there is satisfied a condition that the calculated temperature difference is smaller than a specified temperature difference (S101). When the condition is satisfied, the controller 60 determines that it is necessary to open the openable and closable louver because the refrigerant in the first circuit 10 does not circulate (S102). Meanwhile, when it is determined in S101 that the calculated temperature difference is not smaller than the set value, the controller 60 determines whether or not there is satisfied a condition that the calculated temperature difference is equal to or larger than the set value and is smaller than a second set value (S103). When the condition is satisfied, the controller 60 keeps the opened or closed state of the openable and closable louver just prior to determination (S104). Meanwhile, when the condition is not satisfied in S103, the refrigerant in the first circuit 10 circulates because the temperature difference between the indoor temperature and the outdoor temperature is large. Thus, it is determined that it is necessary to close the openable and closable louver (S105). Then, the controller 60 sends, to the opening and closing drive unit 52, a signal corresponding to the determination result. The opening and closing drive unit 52 drives the openable and closable louver in accordance with the signal received from the controller 60 so as to open or close the openable and closable louver.

[0039]

When control is performed on an opening or closing operation of the louver based on the temperature difference, it is preferred to set an operation differential (differential) to a threshold of the temperature difference (10 degrees in this case) at which the opening or closing operation is switched. With this, even when ON-OFF control is performed on the operation between two positions, the controller 60 can be prevented from frequently sending, to the opening and closing drive unit 52, a signal for switching the louver between the opened state and the closed state. Further, an influence caused by noise or chattering can be reduced. Thus, the air-conditioning apparatus 1 can avoid waste of control, and perform stable cooling operation.

[0040]

As described above, in Embodiment 4, the air-conditioning apparatus 1 further includes the outdoor sensor 61 configured to detect the outdoor temperature, the indoor sensor 62 configured to detect the indoor temperature, and the controller 60 configured to determine, based on the results detected by the outdoor sensor 61 and the indoor sensor 62, whether or not it is necessary to open or close the openable and closable door 51, thereby controlling the opening and closing drive unit 52 in accordance with the determination result.

[0041]

With this configuration, a user does not need to judge whether or not the refrigerant naturally circulates, and automation is possible. Accordingly, the air passage can be switched at an appropriate timing. Further, the controller 60 performs determination based on the information obtained from the indoor sensor 62 and the outdoor sensor 61. Thus, the controller 60 can perform control while preventing the louver from being frequently switched between the opened state and the closed state by a slight change in the temperature difference or by the noise. [0042]

Embodiment 5.

In Embodiment 5, before and after the openable and closable louver is switched between the opened state and the closed state, a change in airflow rate is suppressed. When inverter control is performed on a fan motor of the sharable fan of the indoor unit 2, an opened or closed condition of the openable and closable louver is detected, and an inverter frequency of the fan motor is changed. In Fig. 1, an inverter 63 is installed in the indoor unit 2, and is connected to the controller 60 through a signal line.

[0043]

First, the controller 60 obtains information from the opening and closing drive unit 52, and detects the opened or closed state of the openable and closable door 51. The opening and closing drive unit 52 may inform the controller 60 of the opened or closed state at a timing of changing the opened or closed state of the opening and closing drive unit 52 manually or by the remote controller.

[0044]

The controller 60 controls rotation speed of the sharable fan 31 based on operation information. When the rotation speed of the sharable fan 31 is the same both in the opened state and the closed state of the openable and closable louver, an air passage pressure loss differs depending on the formed air passage so that an airflow rate also differs. For example, in a case where the inverter frequency is 45 Hz in the closed state, when the same frequency is set and the air-conditioning apparatus is brought into operation in the opened state, the airflow rate is increased. Accordingly, when detecting the opened state, the controller 60 lowers the inverter frequency to 43 Hz, and controls the rotation speed of the sharable fan 31 so as to prevent the airflow rate from changing before and after the openable and closable louver is switched between the opened state and the closed state.

[0045]

It is only necessary that the controller 60 store inverter frequencies of the inverter 63 that are capable of attaining the same airflow rate in both the opened state and the closed state of the openable and closable door 51. Specifically, with respect to an inverter frequency in the closed state, an inverter frequency in the opened state capable of attaining substantially the same airflow rate is determined in advance by experiment or other methods, and a relationship between the inverter frequency in the opened state and the inverter frequency in the closed state is stored in the controller

60. When detecting the opened or closed state, the controller 60 performs calculation to work out an inverter frequency capable of attaining a constant airflow rate before and after the opening or closing operation. The controller 60 sets the calculated frequency to the inverter 63, thereby controlling the rotation speed of the sharable fan 31.

[0046]

As described above, in Embodiment 5, the air-conditioning apparatus 1 further includes the inverter 63 configured to control operation of the sharable fan 31. The controller 60 detects the opened or closed state of the openable and closable door 51, and changes the frequency of the inverter 63 in accordance with the detection result.

[0047]

In this manner, the constant airflow rate is maintained, and operation can be continued at an airflow rate intended by a user even when the opened or closed condition of the openable and closable louver changes. The air-conditioning apparatus 1 can suppress a sharp change in air-conditioning, and exert a stable cooling capacity. Further, even when the refrigerant in the first circuit 10 does not circulate, the air passage resistance is reduced owing to the bypass air passage 45b, and the controller 60 performs control so as to maintain the constant airflow rate so that power of the sharable fan 31 can be lowered. Accordingly, power consumption of the motor configured to drive the sharable fan 31 can be reduced. Further, power of the sharable fan 31 can be lowered, and heat generation of the motor is suppressed at the same time. Thus, the indoor space 5 is not warmed by the heat generation. That is, reduction in cooling capacity can be prevented. In addition, the airflow rate is constant so that an operation condition is not changed except that the power of the sharable fan 31 is lowered. Accordingly, there is suppressed an influence on operation involved in switching the openable and closable door 51 between the opened state and the closed state, and other kinds of control are easily performed on the cooling operation.

Reference Signs List [0048] air-conditioning apparatus 2 indoor unit 3 first outdoor unit 4 second outdoor unit 5 indoor space 10 first circuit 11 first condenser first evaporator 20 second circuit 21 compressor 22 second condenser 23 expansion device 24 second evaporator 31 sharable fan 40 case 40a first case 40b second case 40c air inlet

40d air outlet

40e bypass air inlet openable and closable door closing drive unit 60 controller inverter

45a main air passage 45b bypass air passage51 51a slat 51b louver shaft 52 opening and 61 outdoor sensor indoor sensor 63

Claims

CLAIMS [Claim 1]

An air-conditioning apparatus, comprising:

a first circuit, which is configured to convey refrigerant through refrigerant natural circulation, and includes a first condenser and a first evaporator connected together through a pipe;

a second circuit, which is formed independently of the first circuit, and includes a compressor, a second condenser, an expansion device, and a second evaporator connected together through a pipe;

a sharable fan, which is configured to supply air to the first evaporator and the second evaporator; and a case, which has a hollow box shape and includes a suction surface with an air inlet that allows the air to be sucked therethrough, a blow-out surface with an air outlet that is formed downstream of the air inlet and allows the air to be blown out therethrough, and a main air passage formed so as to establish communication between the air inlet and the air outlet, wherein the first evaporator and the second evaporator are arranged inside the case so that the first evaporator is positioned upstream of the second evaporator, and wherein the case further includes a bypass air inlet, which is formed in addition to the air inlet and allows the air to be sucked therethrough, and a bypass air passage, which is formed so as to establish communication between the bypass air inlet and the air outlet and allows the air to join the air along the main air passage from between the first evaporator and the second evaporator.
[Claim 2]

The air-conditioning apparatus of claim 1, further comprising an openable and closable door configured to open and close the bypass air inlet.
[Claim 3]

The air-conditioning apparatus of claim 2, further comprising an opening and closing drive unit configured to open and close the openable and closable door in accordance with an electric signal.
[Claim 4]

The air-conditioning apparatus of claim 3, further comprising: an outdoor sensor configured to detect an outdoor temperature; an indoor sensor configured to detect an indoor temperature; and

5 a controller configured to determine, based on results detected by the outdoor sensor and the indoor sensor, whether or not it is necessary to open or close the openable and closable door, thereby controlling the opening and closing drive unit in accordance with the determination result.
[Claim 5]

10 The air-conditioning apparatus of claim 4, further comprising an inverter configured to control operation of the sharable fan, wherein the controller detects whether the openable and closable door is in an opened state or a closed state, and changes a frequency of the inverter in accordance with the detection result.

15 [Claim 6]

The air-conditioning apparatus of any one of claims 1 to 5, wherein the bypass air inlet is formed in the case at a position between the first evaporator and the second evaporator.

[Claim 7]

20 The air-conditioning apparatus of any one of claims 1 to 5, wherein the bypass air inlet is formed in the suction surface side by side with the air inlet.