AIR-CONDITIONING APPARATUS

Abstract

An air-conditioning apparatus according to the present disclosure includes: a refrigerant cycle circuit in which a compressor, a heat-source-side heat exchanger, an expansion device, and a refrigerant-side flow passage of an inter-heat-medium heat exchanger are connected by refrigerant pipes, and refrigerant is circulated; and a heat-medium cycle circuit in which a pump, a use-side heat exchanger, and a heat-medium-side flow passage of the inter-heat-medium heat exchanger are connected by heat-medium conveying pipes, and the heat medium is circulated. An inside diameter D of each of the heat-medium conveying pipes is determined based on a capacity Q of the use-side heat exchanger connected to the heat-medium conveying pipes and a length L of at least part of each of the heat-medium conveying pipes included in the heat-medium cycle circuit, and is set to satisfy the following formula (1):

Description

TECHNICAL FIELD

The present disclosure relates to an air-conditioning apparatus in which a heat medium subjected to heat exchange with refrigerant is circulated to perform air conditioning, and in particular, to a pipe structure in which the heat medium is circulated.

BACKGROUND

An existing air-conditioning apparatus used as, for example, a variable refrigerant flow (VRF) system, includes an outdoor unit that is a heat source unit installed outdoors, an indoor unit or units installed indoors, and a relay unit that is interposed between the outdoor unit and the indoor units to connect the outdoor unit and the indoor units. The relay unit includes inter-heat-medium heat exchangers that cause heat exchange to be performed between refrigerant from the heat source unit and a heat medium to be supplied to the indoor units. The inter-heat-medium heat exchangers are connected to use-side heat exchangers in the indoor units by heat-medium conveying pipes. In the air-conditioning apparatus, the heat medium is circulated between the relay unit and the indoor units to supply cooling energy or heating energy to the use-side heat exchangers, and at the use-side heat exchangers, heat exchange is performed between the heat medium and air in an indoor space that is an air-conditioning target space, thereby performing air conditioning. The relay unit and the indoor units are connected by the heat-medium conveying pipes, and the heat medium is circulated between the relay unit and the indoor units.

Such an air-conditioning apparatus as described above includes a relay unit provided with a plurality of inter-heat-medium heat exchangers and is also capable of performing a cooling and heating mixed operation in which heating energy is supplied to one or some of a plurality of indoor units and cooling energy is supplied to the other or others of the indoor units. In such an air-conditioning apparatus, when the flow velocity of a heat medium in heat-medium conveying pipes is high, an oxide layer on an inner surface of a pipe may be separated, and when the flow velocity of the heat medium in the heat-medium conveying pipes is low, corrosion products may accumulate in the pipe. Therefore, the inside diameter of each of the heat-medium conveying pipes of the air-conditioning apparatus is set such that an appropriate flow velocity of the heat medium in the pipe can be ensured (see, for example, Patent Literature 1).

PATENT LITERATURE

• • Patent Literature 1: Japanese Patent No. 5972397

However, in such an air-conditioning apparatus as described above, in the case where heat-medium conveying pipes which connect inter-heat-medium heat exchangers and use-side heat exchangers are long, it takes long time before a heat medium reaches the use-side heat exchangers at the time of starting the operation of the air-conditioning apparatus, and the comfortability of an indoor space is impaired. In addition, in the air-conditioning apparatus, in the case where the lengths of heat-medium conveying pipes are increased and a pressure loss is thus increased, the output of a pump that circulates the heat medium between a relay unit and indoor units needs to be increased, and the operation efficiency of the air-conditioning apparatus is reduced.

SUMMARY

The present disclosure is applied to solve such problems as described above and relates to an air-conditioning apparatus which improves the comfortability of an air-conditioning target space and whose operation efficiency is improved.

An air-conditioning apparatus according to an embodiment of the present disclosure includes: a refrigerant cycle circuit in which a compressor, a heat-source-side heat exchanger, an expansion device, and a refrigerant-side flow passage of an inter-heat-medium heat exchanger are connected by refrigerant pipes, and refrigerant is circulated, the inter-heat-medium heat exchanger being configured to cause heat exchange to be performed between the refrigerant and a heat medium; and a heat-medium cycle circuit in which a pump, a use-side heat exchanger, and a heat-medium-side flow passage of the inter-heat-medium heat exchanger are connected by heat-medium conveying pipes, and the heat medium is circulated. An inside diameter D of each of the heat-medium conveying pipes is determined based on a capacity Q of the use-side heat exchanger connected to the heat-medium conveying pipes and a length L of at least one of the heat-medium conveying pipes included in the heat-medium cycle circuit, and is set to satisfy the following formula (1):

$\begin{array}{cc}3{\left({\mathrm{LQ}}^2\right)}^{0.2}<D<104{\left(Q/L\right)}^{0.5}.& \left(1\right)\end{array}$

According to the embodiment of the present disclosure, the inside diameter of each of the heat-medium conveying pipes is set to be in an appropriate range based on the formula (1). Therefore, it is possible to reduce the amount of the heat medium and the pressure loss in the heat-medium conveying pipes, thus improving the comfortability of an air-conditioning target space and the operation efficiency of the air-conditioning apparatus regardless of the length of each of the heat-medium conveying pipes.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a circuit diagram of an air-conditioning apparatus 100A according to Embodiment 1.

FIG. 2 indicates a set range of an inside diameter D of each of heat-medium conveying pipes 5 of an air-conditioning apparatus 100 according to Embodiment 1.

FIG. 3 indicates a set range of the inside diameter D of each of the heat-medium conveying pipes 5 of the air-conditioning apparatus 100 according to Embodiment 1.

FIG. 4 is a circuit diagram of an air-conditioning apparatus 100B according to Embodiment 2.

FIG. 5 is a circuit diagram of an air-conditioning apparatus 100C that is a modification of the air-conditioning apparatus 100B according to Embodiment 2.

FIG. 6 is a circuit diagram of an air-conditioning apparatus 100D that is another modification of the air-conditioning apparatus 100B according to Embodiment 2.

FIG. 7 is a circuit diagram of an air-conditioning apparatus 100E that is still another modification of the air-conditioning apparatus 100B according to Embodiment 2.

FIG. 8 is a circuit diagram of an air-conditioning apparatus 100F that is a further modification of the air-conditioning apparatus 100B according to Embodiment 2.

FIG. 9 is a circuit diagram of an air-conditioning apparatus 100G according to Embodiment 3.

FIG. 10 is a circuit diagram of an air-conditioning apparatus 100H that is a modification of the air-conditioning apparatus 100G according to Embodiment 3.

FIG. 11 is a circuit diagram of an air-conditioning apparatus 100I that is another modification of the air-conditioning apparatus 100G according to Embodiment 3.

FIG. 12 is a circuit diagram of an air-conditioning apparatus 100J that is still another modification of the air-conditioning apparatus 100G according to Embodiment 3.

DETAILED DESCRIPTION

Embodiment 1

FIG. 1 is a circuit diagram of an air-conditioning apparatus 100A according to Embodiment 1. An air-conditioning apparatus 100 will be described with reference to FIG. 1. The air-conditioning apparatus 100 as illustrated in FIG. 1 is, for example, a variable refrigerant flow (VRF) system and circulates a heat medium between a heat source unit 10 installed outdoors and an indoor unit 20 installed indoors. The heat source unit 10 includes a refrigerant cycle circuit (not illustrated) in which a compressor (not illustrated), a heat-source-side heat exchanger (not illustrated), an expansion device (not illustrated), and an inter-heat-medium heat exchanger 1 are connected by refrigerant pipes (not illustrated). In the refrigerant cycle circuit, refrigerant is circulated. The inter-heat-medium heat exchanger 1 includes a refrigerant-side flow passage connected to the refrigerant cycle circuit and a heat-medium-side flow passage connected to heat-medium conveying pipes 5. The inter-heat-medium heat exchanger 1 causes heat exchange to be performed between refrigerant and a heat medium, and causes a heat medium such as water to be heated or cooled by the refrigerant.

The inter-heat-medium heat exchanger 1 is connected to a use-side heat exchanger 3 provided in the indoor unit 20 by the heat-medium conveying pipes 5. The heat medium heated or cooled by heat exchange with the refrigerant in the inter-heat-medium heat exchanger 1 flows out from the inter-heat-medium heat exchanger 1, flows in a heat-medium conveying pipe 5a, and flows into the use-side heat exchanger 3 provided in the indoor unit 20. In the use-side heat exchanger 3, the heat medium exchanges heat with air in an air-conditioning target space. The heat medium then flows out from the use-side heat exchanger 3, flows into a heat-medium conveying pipe 5b, passes through a pump 2 connected to the heat-medium conveying pipe 5b, and flows into the inter-heat-medium heat exchanger 1 in the heat source unit 10. The circuit in which the heat medium is circulated will be referred to as a heat-medium cycle circuit 50. The heat medium is circulated in the heat-medium cycle circuit 50 by the pump 2.

In Embodiment 1, the heat-medium conveying pipe 5a connects an outlet 11 of the heat source unit 10 and an inlet 21 of the indoor unit 20. On the other hand, the heat-medium conveying pipe 5b connects an outlet 22 of the indoor unit 20 and the suction side of the pump 2. A discharge side of the pump 2 is connected to an inlet 12 of the heat source unit 10 by a pipe. An internal pipe 7a is installed between the inter-heat-medium heat exchanger 1 and the outlet 11 of the heat source unit 10. An internal pipe 7b is installed between the inter-heat-medium heat exchanger 1 and the inlet 12 of the heat source unit 10. The heat-medium conveying pipes 5 are connected to the respective internal pipes 7a and 7b at the outlet 11 and the inlet 12. On the other hand, an internal pipe 24a is installed between the use-side heat exchanger 3 and the inlet 21 of the indoor unit 20, and an internal pipe 24b is installed between the use-side heat exchanger 3 and the outlet 22 of the indoor unit 20. The heat-medium conveying pipes 5 are connected to the respective internal pipes 24a and 24b at the inlet 21 and the outlet 22.

Referring to FIG. 1, at outer surfaces of the heat source unit 10 and the indoor unit 20, the heat-medium conveying pipes 5 are connected to the heat source unit 10 and the indoor unit 20; however, in the inside of a housing 19 of the heat source unit 10 and the inside of a housing 29 of the indoor unit 20, the heat-medium conveying pipes 5 may be connected to the heat source unit 10 and the indoor unit 20. Alternatively, at the outside of the housing 19 and the outside of the housing 29, the heat-medium conveying pipes 5 may be connected to the heat source unit 10 and the indoor unit 20. In addition, in the heat-medium cycle circuit 50, the pump 2 may be provided at another position, and for example, may be provided in the heat source unit 10.

Heat-Medium Conveying Pipe 5

The air-conditioning apparatus 100 is, for example, a variable refrigerant flow (VRF) system, the heat source unit 10 is installed outdoors, and the indoor unit 20 is installed indoors. Thus, the lengths of the heat-medium conveying pipes 5 are appropriately set depending on the position where the indoor unit 20 is installed. That is, the lengths of the heat-medium conveying pipes 5 are appropriately changed depending on the structure of a building and the installation positions of the heat source unit 10 and the indoor unit 20. In this case, in the case where the inside diameter of each of the heat-medium conveying pipes 5 is small, a pressure loss is increased during circulation of a heat medium, thus reducing the flow rate of the heat medium in the heat-medium conveying pipe 5.

By contrast, in the case where the inside diameter of the heat-medium conveying pipe 5 is set large, the volume of the inside of the heat-medium conveying pipe 5 is large, and the amount of a heat medium in the heat-medium cycle circuit 50 is thus increased. Therefore, it takes time before a heat medium having heating energy or cooling energy generated in the inter-heat-medium heat exchanger 1 of the heat source unit 10 is supplied to the use-side heat exchanger 3 of the indoor unit 20. Therefore, desired heat exchange is not performed in the use-side heat exchanger 3, and it takes time before appropriate air conditioning is performed in an indoor space that is an air-conditioning target space. Inevitably, it is not possible to perform appropriate air conditioning in the indoor space.

In order to solve the above problem, the inside diameter of the heat-medium conveying pipes 5 of the air-conditioning apparatus 100 is set to satisfy the following formula.

$\begin{array}{cc}3{\left({\mathrm{LQ}}^2\right)}^{0.2}<D<104{\left(Q/L\right)}^{0.5}& \left(1\right)\end{array}$

where D is the inside diameter [mm] of the heat-medium conveying pipe 5, L is the length [m] of the heat-medium conveying pipe 5, and Q is the total capacity [kW] of the use-side heat exchangers 3.

FIG. 2 indicates the set range of the inside diameter D of each of the heat-medium conveying pipes 5 of the air-conditioning apparatus 100 according to Embodiment 1. In a graph in FIG. 2, the vertical axis represents the inside diameter D of the heat-medium conveying pipe 5, and the horizontal axis represents the capacity Q of the use-side heat exchanger connected to the heat-medium conveying pipe 5. In the case where the number of use-side heat exchangers connected to the heat-medium conveying pipes 5 is two or more, the horizontal axis represents the total capacity Q of the use-side heat exchangers 3. FIG. 2 indicates a possible set range of the inside diameter D in the case where the length L of each of the heat-medium conveying pipes 5 is set to 50 m. In FIG. 2, the inside diameter D is set to fall within the range between the maximum pipe diameter indicated by a curved line M and the minimum pipe diameter indicated by a curved line m.

In the air-conditioning apparatus 100A as illustrated in FIG. 1, it is assumed that the length of part of the heat-medium conveying pipe 5a that is located from the outlet 11 of the heat source unit 10 to the inlet 21 of the indoor unit 20 is the length L of the heat-medium conveying pipe 5, and the capacity (power) of the use-side heat exchanger 3 of the indoor unit 20 is the capacity Q.

For example, referring to FIG. 1, when the capacity of the use-side heat exchanger 3 is 10 KW, the inside diameter D of the heat-medium conveying pipe 5a is set to a value that is greater than 16.5 mm and smaller than 46.5 mm. As a result, it is possible to reduce the pressure loss in the heat-medium conveying pipe 5a and time that is required until the use-side heat exchanger 3 starts appropriate heat exchange.

Specifically, when the length L of the heat-medium conveying pipe 5a in the air-conditioning apparatus 100A as illustrated in FIG. 1 is 50 m, as illustrated in FIG. 2, the inside diameter D of the heat-medium conveying pipe 5a is set to a value that is greater than 6.6 mm and smaller than 14.7 mm. In addition, for example, the inside diameter of the heat-medium conveying pipe 5b extending from the outlet 22 of the indoor unit 20 to the pump 2 is also set to the inside diameter D corresponding to that of the heat-medium conveying pipe 5a. In this case also, where L is the length of the heat-medium conveying pipe 5 extending from the outlet 22 to the pump 2, and Q is the total capacity of the use-side heat exchangers 3, it is necessary that the inside diameter D of the heat-medium conveying pipe 5b is set to fall within the range satisfying the formula (1). By virtue of such a configuration, the air-conditioning apparatus 100A can reduce the pressure loss in each of the heat-medium conveying pipes 5a and 5b, which correspond to large part of the heat-medium cycle circuit 50, in an appropriate range, and reduce the volume of each of the heat-medium conveying pipes 5a and 5b to a value which falls into an appropriate range. Thus, the air-conditioning apparatus 100A is capable of reducing the time required until the use-side heat exchanger 3 starts appropriate heat exchange, for example, when the air-conditioning apparatus 100A starts its operation or the operating conditions are changed. The air-conditioning apparatus 100A is thus capable of improving the comfortability of the air-conditioning target space. In addition, the operation efficiency of the air-conditioning apparatus 100A is improved because it is not necessary to increase the output of the pump 2.

Of the heat-medium cycle circuit 50 of the air-conditioning apparatus 100A, the internal pipes 7 of the heat source unit 10, the internal pipes 24 of the indoor unit 20, and the pipe extending from the discharge side of the pump 2 to the inlet 12 of the heat source unit 10 may be set to have the same inside diameter D as the heat-medium conveying pipes 5a and 5b. Where L is the length of each of the internal pipes 7 of the heat source unit 10, the internal pipes 24 of the indoor unit 20, and the pipe extending from the discharge side of the pump 2 to the inlet 12 of the heat source unit 10, and Q is the capacity of the use-side heat exchanger 3, the inside diameter D of each of the above pipes falls within the range indicated by the formula (1).

FIG. 3 indicates the set range of the inside diameter D of the heat-medium conveying pipes 5 of the air-conditioning apparatus 100 according to Embodiment 1. In a graph in FIG. 3, the vertical axis represents the inside diameter D of each of the heat-medium conveying pipes 5, and the horizontal axis represents the length of the heat-medium conveying pipe 5. To be more specific, FIG. 3 illustrates a possible set range of the inside diameter D of each of the heat-medium conveying pipe 5 in the case the capacity Q of the use-side heat exchanger 3 is fixed at 1 KW and the length L of the heat-medium conveying pipe 5 is varied. According to FIG. 3, the greater the length L of the pipe, the smaller the possible set range of the inside diameter D of the pipe. Therefore, in the air-conditioning apparatus 100A as illustrated in FIG. 1, to the inside diameter D of a heat-medium conveying pipe 5a that is the longest in the heat-medium cycle circuit 50, the inside diameters of the other pipes are added, whereby the inside diameter of each of the internal pipes 7 of the heat source unit 10, the internal pipes 24 of the indoor unit 20, and a pipe 9 located at the discharge side of the pump 2, that is, the internal pipes 7, the internal pipes 24, and the pipe 9 which are included in the heat-medium cycle circuit 50, falls within the range indicated by the formula (1).

Embodiment 2

The air-conditioning apparatus 100 according to Embodiment 2 differs from the air-conditioning apparatus 100 according to Embodiment 1 in the number of indoor units 20 installed. Embodiment 2 will be described mainly regarding the differences between Embodiments 1 and 2. Regarding the air-conditioning apparatus 100 according to Embodiment 2, in each of figures, components that have the same functions as those in a previous figure or previous figures are denoted by the same reference signs.

FIG. 4 is a circuit diagram of an air-conditioning apparatus 100B according to Embodiment 2. It should be noted that the air-conditioning apparatus 100A according to Embodiment 1 includes a single indoor unit 20. By contrast, the air-conditioning apparatus 100B according to Embodiment 2 includes two indoor units 20a and 20b. Thus, in the heat-medium cycle circuit 50, a branch portion 51 is provided on the way from the heat source unit 10 toward the indoor units 20, and a joining portion 52 is provided on the way from the indoor units 20 toward the heat source unit 10.

The indoor unit 20a includes a use-side heat exchanger 3a and a flow-rate control valve 4a, and the indoor unit 20b includes a use-side heat exchanger 3b and a flow-rate control valve 4b. The flow-rate control valves 4a and 4b control the respective flow rates of heat mediums that flow into the use-side heat exchangers 3a and 3b of the heat-medium cycle circuit 50. For example, when the flow-rate control valve 4a as illustrated in FIG. 4 is closed and the flow-rate control valve 4b as illustrated in FIG. 4 is opened, in the air-conditioning apparatus 100B, the heat medium circulates only in part of the heat-medium cycle circuit 50 that is located between the heat source unit 10 and an associated one of the indoor units 20b, and the heat-medium cycle circuit 50 thus serves as a heat-medium cycle circuit similar to the heat-medium cycle circuit of the air-conditioning apparatus 100A according to Embodiment 1. It should be noted that use-side heat exchanger 3a may be referred to as a first use-side heat exchanger 3a, and the use-side heat exchanger 3b may be referred to as a second use-side heat exchanger 3b.

In the heat-medium cycle circuit 50 of the air-conditioning apparatus 100B according to Embodiment 2, a heat-medium conveying pipe 6a is connected to the outlet 11 of the heat source unit 10, and branches into two heat-medium conveying pipes 5a and 5c at the branch portion 51. The heat-medium conveying pipe 5a is connected to the indoor unit 20a, and the heat-medium conveying pipe 5c is connected to the indoor unit 20b. In addition, a heat-medium conveying pipe 5b connected to an outlet 22a of the indoor unit 20a and a heat-medium conveying pipe 5d connected to an outlet 22b of the indoor unit 20b join each other at the joining portion 52 and are connected to a heat-medium conveying pipe 6b. The heat-medium conveying pipe 6b connects the joining portion 52 and the suction side of the pump 2. The discharge side of the pump 2 is connected to the inlet 12 of the heat source unit 10.

The heat-medium conveying pipes 5a and 5c extending from the branch portion 51 to the respective indoor units 20 and the heat-medium conveying pipes 5b and 5d extending from the respective indoor units 20 to the joining portion 52 may be referred to as use-side pipes. In addition, the heat-medium conveying pipe 6a extending from the heat source unit 10 to the branch portion 51 and the heat-medium conveying pipe 6b extending from the joining portion 52 to the pump 2 may be referred to as heat-source-side pipes. Each of the use-side pipes is connected to an associated one of the use-side heat exchangers.

Heat-Source-Side Pipe

An inside diameter Da of the heat-medium conveying pipe 6a, which is a heat-source-side pipe, is set to fall within a range which satisfies the formula (1) when a length La from the outlet 11 of the heat source unit 10 to the branch portion 51 is substituted for the length L and a total capacity Qa of the use-side heat exchangers 3a and 3b connected to the heat-medium conveying pipes 5a and 5c, respectively, which are use-side pipes, is substituted for the capacity Q. That is, where Q1 is the capacity of the use-side heat exchanger 3a, and Q2 is the capacity of the use-side heat exchanger 3b, the set range of the inside diameter D which is obtained when Q1+Q2 is substituted for Q of the formula (1) and the pipe length La from the outlet 11 to the branch portion 51 is substituted for L of the formula (1) is a possible set range of the inside diameter Da of the heat-medium conveying pipe 6a, which is a heat-source-side pipe.

The inside diameter Da of the heat-medium conveying pipe 6b, which is the heat-source-side pipe located on the return side of the heat medium, may be set to correspond to the inside diameter Da of the heat-medium conveying pipe 6a. It should be noted that referring to FIG. 4, the heat-medium conveying pipe 6a is longer than the heat-medium conveying pipe 6b. Thus, as illustrated in FIG. 3, the heat-medium conveying pipe 6b is set to have an appropriate inside diameter when the inside diameter of the heat-medium conveying pipe 6b is set to correspond to the inside diameter Da of the heat-medium conveying pipe 6a.

Use-Side Pipe

An inside diameter D1 of the heat-medium conveying pipe 5a, which is a use-side pipe, is set to fall within a range that satisfies the formula (1) when the capacity Q1 of the use-side heat exchanger 3a connected to the heat-medium conveying pipe 5a is substituted for the capacity Q and a length L1 of the heat-medium conveying pipe 5a from the branch portion 51 to the indoor unit 20a is substituted for the length L. It should be noted that the heat-medium conveying pipe 5a connected to the first use-side heat exchanger 3a may be referred to as a first use-side pipe.

The inside diameter D1 of the heat-medium conveying pipe 5b, which is the use-side pipe located on the return side of the heat medium, may be set to correspond to the inside diameter D1 of the heat-medium conveying pipe 5a. It should be noted that referring to FIG. 4, of the use-side pipes, the heat-medium conveying pipe 5a has a length smaller than or equal to that of the heat-medium conveying pipe 5b. Thus, the inside diameter D1 of the heat-medium conveying pipe 5b is set to fall within an appropriate range when being set to be equal to the inside diameter D1 of the heat-medium conveying pipe 5a.

In addition, the inside diameter D2 of the heat-medium conveying pipe 5c, which is a use-side pipe, is set to fall within the range satisfying the formula (1) when the capacity Q2 of the use-side heat exchanger 3b connected to the heat-medium conveying pipe 5c is substituted for the capacity Q and a length L2 of the heat-medium conveying pipe 5c from the branch portion 51 to the indoor unit 20b is substituted for the length L. The heat-medium conveying pipe 5c connected to the second use-side heat exchanger 3b may be referred to as a second use-side pipe.

An inside diameter D2 of the heat-medium conveying pipe 5d, which is the use-side pipe located on the return side of the heat medium, may be set to correspond to the inside diameter D2 of the heat-medium conveying pipe 5c. Referring to FIG. 4, of the use-side pipes, the heat-medium conveying pipe 5d has a length smaller than or equal to that of the heat-medium conveying pipe 5c. Thus, the inside diameter D2 of the heat-medium conveying pipe 5d is set to fall within an appropriate range when being set equal to the inside diameter D2 of the heat-medium conveying pipe 5c.

In the air-conditioning apparatus 100B according to Embodiment 2, the heat-medium conveying pipes 5a, 5c, and 6a located on a feed side from the heat source unit 10 to the indoor units 20 are longer than the heat-medium conveying pipes 5b, 5d, and 6b, respectively, located on a return side, but this is not limiting. In the case where the heat-medium conveying pipes 5b, 5d, and 6b located on the return side are longer than the heat-medium conveying pipes 5a, 5c, and 6a located on the feed side, it suffices that the inside diameter D of each of the heat-medium conveying pipes 5 and 6 is set to fall within the range of D obtained by substituting the length of an associated one of the heat-medium conveying pipes 5b, 5d, and 6b located on the return side for the length L of the formula (1).

The inside diameter Da of each of the heat-medium conveying pipes 6a and 6b, which are the heat-source-side pipes, is set larger than the inside diameter D1 or D2 of each of the heat-medium conveying pipes 5a, 5b, 5c, and 5d, which are the use-side pipes. This is because the inside diameters D1 and D2 of the use-side pipes are determined depending on the capacity Q1 of one use-side heat exchanger 3, whereas the inside diameter Da of each of the heat-source-side pipes is determined depending on the total capacity Qa or Qb of the plurality of the use-side heat exchangers 3. In addition, it is appropriate that the inside diameter D of each of the internal pipes 7a, 7b, 24a, 24b, 24c, and 24d is set to correspond to that of an associated one of the heat-medium conveying pipes 5 and 6 connected thereto.

By virtue of the above configuration, in the air-conditioning apparatus 100B according to Embodiment 2 which includes a plurality of indoor units 20 or a plurality of use-side heat exchangers 3, it is possible to reduce the pressure loss in the heat-medium cycle circuit 50 and also reduce the volume of each of the heat-medium conveying pipes 5a and 5b such that the volume falls within an appropriate range. Therefore, the air-conditioning apparatus 100B reduces the time taken until the use-side heat exchangers 3 start appropriate heat exchange, for example, when the air-conditioning apparatus 100B starts its operation or the operating conditions are changed, and the air-conditioning apparatus 100B is thus improved in operation efficiency because the output of the pump 2 does not need to be increased.

Modifications

FIG. 5 is a circuit diagram of an air-conditioning apparatus 100C that is a modification of the air-conditioning apparatus 100B according to Embodiment 2. In the air-conditioning apparatus 100C, the pump 2 of the air-conditioning apparatus 100B is provided in the heat source unit 10. Though the air-conditioning apparatus 100C has such a configuration, the inside diameter D of each of the heat-medium conveying pipes 5 and 6 can be set in the same manner as in the air-conditioning apparatus 100B. Referring to FIG. 5, the heat-medium conveying pipe 6b, which is a heat-source-side pipe, is longer than the heat-medium conveying pipe 6a. Thus, it is appropriate that the inside diameter Da of the heat-medium conveying pipe 6b is set to satisfy the formula (1) when the length La of the heat-medium conveying pipe 6b, that is, the length from the joining portion 52 to the inlet 12, is substituted for the length L of the formula (1) and the total capacity Qa of the use-side heat exchangers 3a and 3b is substituted for the capacity Q of the formula (1).

FIG. 6 is a circuit diagram of an air-conditioning apparatus 100D that is another modification of the air-conditioning apparatus 100B according to Embodiment 2. In the air-conditioning apparatus 100D, the inter-heat-medium heat exchanger 1 is removed from the heat source unit 10 of the air-conditioning apparatus 100C and used as a relay unit 30. Thus, in the air-conditioning apparatus 100D, pipes 91a and 91b included in a refrigerant cycle circuit 90 are extended from the heat source unit 10 and connected to the inter-heat-medium heat exchanger 1 provided in the relay unit 30, whereby the refrigerant cycle circuit 90 is formed.

Also, the heat-medium cycle circuit 50 in the air-conditioning apparatus 100D including the relay unit 30 has a similar configuration to that of the air-conditioning apparatus 100C. That is, the relay unit 30 of the air-conditioning apparatus 100D corresponds to the heat source unit 10 of the air-conditioning apparatus 100C and is configured such that the heat-medium cycle circuit 50 is formed between the relay unit 30 and the indoor units 20. The inside diameter D of each of the heat-medium conveying pipes 5 and 6 included in the heat-medium cycle circuit 50 of the air-conditioning apparatus 100D can be set in a similar manner to that in the air-conditioning apparatus 100C.

FIG. 7 is a circuit diagram of an air-conditioning apparatus 100E that is still another modification of the air-conditioning apparatus 100B according to Embodiment 2. The air-conditioning apparatus 100E differs from the air-conditioning apparatus 100D in the set positions of the flow-rate control valves 4a and 4b. In the air-conditioning apparatus 100E, the flow-rate control valves 4a and 4b are provided at the branch portion 51 and the joining portion 52, respectively, in the heat-medium cycle circuit 50. In addition, in the air-conditioning apparatus 100E, the branch portion 51 and the joining portion 52 of the heat-medium cycle circuit 50 are provided in the relay unit 30.

In the air-conditioning apparatus 100E, the relay unit 30 has outlets 31a and 31b and inlets 32a and 32b. The outlet 31a and the inlet 32a of the relay unit 30 are connected to the indoor unit 20a by the heat-medium conveying pipes 5a and 5b, respectively, and the outlet 31b and the inlet 32b of the relay unit 30 are connected to the indoor unit 20b by the heat-medium conveying pipes 5c and 5d, respectively. The inside diameter D1 of each of the heat-medium conveying pipes 5a and 5b can be set to satisfy the formula (1) when the length L1 of the heat-medium conveying pipe 5a or 5b is substituted for the length L and the capacity Q1 of the use-side heat exchanger 3a is substituted for the capacity Q. In addition, the inside diameter D2 of each of the heat-medium conveying pipes 5c and 5d can also be set on the basis of the length L2 of the heat-medium conveying pipe 5c or 5d and the capacity Q2 of the use-side heat exchanger 3b.

FIG. 8 is a circuit diagram of an air-conditioning apparatus 100F that is a further modification of the air-conditioning apparatus 100B according to Embodiment 2. The air-conditioning apparatus 100F differs from the air-conditioning apparatus 100E in that a plurality of inter-heat-medium heat exchangers 1 are mounted in the relay unit 30. The inter-heat-medium heat exchangers 1 include two inter-heat-medium heat exchangers, that is, a first inter-heat-medium heat exchanger 1a and a second inter-heat-medium heat exchanger 1b. The first inter-heat-medium heat exchanger 1a and the second inter-heat-medium heat exchanger 1b are connected to the respective use-side heat exchangers 3 in such a manner as to enable a heat medium to circulate therebetween.

The relay unit 30 includes internal pipes 7a, 7b, 7c, and 7d. The internal pipes 7a and 7b are connected to the first inter-heat-medium heat exchanger 1a. The internal pipes 7c and 7d are connected to the second inter-heat-medium heat exchanger 1b. The internal pipe 7a connected to the first inter-heat-medium heat exchanger 1a branches into internal pipes 7a1 and 7a2 at a branch portion 51a where the flow-rate control valve 4a is provided. In addition, the internal pipe 7c connected to the second inter-heat-medium heat exchanger 1b branches into internal pipes 7c1 and 7c2 at a branch portion 51b where a flow-rate control valve 4c is provided.

In the internal pipe 7a1, the heat medium from the first inter-heat-medium heat exchanger 1a flows, and in the internal pipe 7c1, the heat medium from the second inter-heat-medium heat exchanger 1b flows. The internal pipe 7a1 and the internal pipe 7c1 join each other at a joining portion 53a to cause the heat medium to flow out to the outside of the relay unit 30 through an internal pipe 7ac. On the other hand, in the internal pipe 7a2, the heat medium from the first inter-heat-medium heat exchanger 1a flows, and in the internal pipe 7c2, the heat medium from the second inter-heat-medium heat exchanger 1b flows; and the internal pipe 7a2 and the internal pipe 7c2 join each other at a joining portion 53b to cause the heat medium to flow out to the outside of the relay unit 30 through an internal pipe 7ca. The relay unit 30 has the outlets 31a and 31b which are connected to the heat-medium conveying pipes 5a and 5c, respectively. The heat medium from the relay unit 30 is supplied to the indoor units 20a and 20b through the heat-medium conveying pipes 5a and 5c.

The heat mediums from the indoor units 20a and 20b pass through the inlets 32a and 32b via the heat-medium conveying pipes 5b and 5d and flow into the relay unit 30.

The heat medium that has flowed from the use-side heat exchanger 3a into the relay unit 30 passes through an internal pipe 7bd and branches, at a branch portion 54a, into a heat medium that flows into an internal pipe 7b1 communicating with the first inter-heat-medium heat exchanger 1a and a heat medium that flows into an internal pipe 7d1 communicating with the second inter-heat-medium heat exchanger 1b.

The heat medium that has flowed from the use-side heat exchanger 3b into the relay unit 30 passes through an internal pipe 7db and branches, at a branch portion 54b, into a heat medium that flows into an internal pipe 7b2 communicating with the first inter-heat-medium heat exchanger 1a and a heat medium that flows into an internal pipe 7d2 communicating with the second inter-heat-medium heat exchanger 1b.

In the internal pipe 7b1, the heat medium from the use-side heat exchanger 3a flows, and in the internal pipe 7b2, the heat medium from the use-side heat exchanger 3b flows; the internal pipe 7b1 and the internal pipe 7b2 join each other at a joining portion 52a where the flow-rate control valve 4b is provided; and the heat medium which flows through the internal pipe 7b1 and the heat medium which flows through the internal pipe 7b2 join each other to turn into a single heat medium, and the heat medium passes through a pump 2a via the internal pipe 7b and returns to the first inter-heat-medium heat exchanger 1a.

In the internal pipe 7d1, the heat medium from the use-side heat exchanger 3a flows, and in the internal pipe 7d2, the heat medium from the use-side heat exchanger 3b flows; the internal pipe 7d1 and the internal pipe 7d2 join at a joining portion 52b where a flow-rate control valve 4d is provided; and the heat medium which flows through the internal pipe 7d1 and the heat medium which flows through the internal pipe 7d2 join each other to turn into a single heat medium, and the heat medium passes through a pump 2b via the internal pipe 7d and returns to the second inter-heat-medium heat exchanger 1b.

As described above, the air-conditioning apparatus 100F is configured to cause the heat mediums from the inter-heat-medium heat exchangers 1 to branch off and join each other in the relay unit 30, and can selectively supply the heat mediums from the inter-heat-medium heat exchangers 1 to the use-side heat exchangers 3. Therefore, one or more of the use-side heat exchangers 3 can be used in the heating operation and the other or others of the use-side heat exchangers 3 can be used in the cooling operation.

The inside diameter D1 of each of the heat-medium conveying pipes 5a and 5b of the air-conditioning apparatus 100F can be set to satisfy the formula (1) when the length L1 of the heat-medium conveying pipe 5a or 5b is substituted for the length L and the capacity Q1 of the use-side heat exchanger 3a is substituted for the capacity Q, as in the air-conditioning apparatus 100E. In addition, the inside diameter D2 of each of the heat-medium conveying pipes 5c and 5d of the air-conditioning apparatus 100F can also be set on the basis of the length L2 of the heat-medium conveying pipe 5c or 5d and the capacity Q2 of the use-side heat exchanger 3b.

In addition, it is appropriate that the inside diameter of each of the internal pipes 7a, 7b, 7c, 7d, 7a1, 7a2, 7b1, 7b2, 7c1, 7c2, 7d1, 7d2, 7ac, 7bd, 7ca, and 7db in the relay unit 30 of the air-conditioning apparatus 100F is set to fall within the range of the inside diameter D which is obtained by substituting the length of the internal pipe for L of the formula (1) and substituting the capacity of each of the use-side heat exchangers 3 which is connected to the pipe for Q of the formula (1).

In the air-conditioning apparatuses 100B to 100F according to Embodiment 2, the inside diameter of the internal pipe 7a, 7b, 7c, 7d, 7a1, 7a2, 7b1, 7b2, 7c1, 7c2, 7d1, or 7d2 in the heat source unit 10 or the relay unit 30 may be set to correspond to the inside diameter D of each of the heat-medium conveying pipes 5 or 6 as in Embodiment 1. The heat-medium conveying pipes 5 and 6 and the internal pipes 7 are each set to have an appropriate inside diameter D, whereby the air-conditioning apparatuses 100B to 100E can reduce the output of the pump while reducing the time required until the use-side heat exchangers 3 start appropriate heat exchange, and can improve the efficiency.

Embodiment 3

An air-conditioning apparatus 100 according to Embodiment 3 differs from the air-conditioning apparatuses 100 according to Embodiment 2 in the number of relay units 30 installed. Embodiment 3 will be described mainly regarding the differences between Embodiments 2 and 3. Regarding the air-conditioning apparatus 100 according to Embodiment 3, in each of the figures, components that have the same functions as a previous figure or previous figures relating to each of Embodiments 1 and 2 are denoted by the same reference signs.

FIG. 9 is a circuit diagram of an air-conditioning apparatus 100G according to Embodiment 3. In the air-conditioning apparatus 100G, elements closer to the indoor units 20 are removed from the branch portion 51 and the joining portion 52 of the relay unit 30 of the air-conditioning apparatus 100E as illustrated in FIG. 7 relating to Embodiment 2 and are used in an auxiliary relay unit 330. In such a manner, the relay units are separated from each other. Therefore, the air-conditioning apparatus 100G can be configured such that the relay unit 30 and the auxiliary relay unit 330 are small, and the air-conditioning apparatus 100G can be easily installed.

The relay unit 30 and the auxiliary relay unit 330 of the air-conditioning apparatus 100G are installed apart from each other. Therefore, intermediate pipes 8a and 8b, which are heat-medium conveying pipes set between the relay unit 30 and the auxiliary relay unit 330, may be long. Thus, an inside diameter Db of each of the intermediate pipes 8a and 8b is set on the basis of the formula (1) in the same manner as the inside diameter of each of the heat-medium conveying pipes 5 and 6 described regarding Embodiments 1 and 2.

As illustrated in FIG. 9, the intermediate pipes 8a and 8b are each connected to both the use-side heat exchangers 3a and 3b. Thus, the set range of the inside diameter D which is obtained when a total capacity Qb (=Q1+Q2) of the use-side heat exchangers 3a and 3b connected to the auxiliary relay unit 330 is substituted for Q of the formula (1) and a pipe length Lb from an outlet 33b to an inlet 33a is substituted for L of the formula (1) is a possible set range of the inside diameter Db of the intermediate pipe 8a. The inside diameter Db of the intermediate pipe 8b located on the return side of a heat medium may also be set on the basis of the formula (1) or may be set to correspond to the inside diameter Da of the intermediate pipe 8a located on the feed side of the heat medium.

As described above, the air-conditioning apparatus 100G includes the auxiliary relay unit 330 and the flexibility in the installation of the air-conditioning apparatus 100G in a building can thus be improved. In addition, in the air-conditioning apparatus 100G, the inside diameter Db of the intermediate pipes 8a and 8b connecting the relay unit 30 and the auxiliary relay unit 330 is set to an appropriate inside diameter on the basis of the formula (1), whereby it is possible to reduce the output of the pump while reducing the time required until the use-side heat exchangers 3 start appropriate heat exchange, and to improve the operation efficiency.

The inside diameter Db of each of the intermediate pipes 8a and 8b is set larger than the inside diameter D1 or D2 of each of the heat-medium conveying pipes 5a, 5b, 5c, and 5d, which are the use-side pipes. This is because the inside diameters D1 and D2 of the use-side pipes are determined depending on the capacity Q1 of one use-side heat exchanger 3, whereas the inside diameter Db of each of the intermediate pipes 8a and 8b is determined depending on the total capacity Qa or Qb of the use-side heat exchangers 3. In addition, the heat-medium conveying pipes 5a, 5b, 5c, and 5d of the air-conditioning apparatus 100G are set to satisfy the formula (1) as in Embodiments 1 and 2.

Modifications

FIG. 10 is a circuit diagram of an air-conditioning apparatus 100H that is a modification of the air-conditioning apparatus 100G according to Embodiment 3. In the air-conditioning apparatus 100H, indoor units 20c and 20d are added to the air-conditioning apparatus 100G described above and are connected to the relay unit 30.

At a branch portion 51a1, the internal pipe 7a connected to the inter-heat-medium heat exchanger 1 branches into the internal pipe 7a1 and the internal pipe 7a2 which extend toward the indoor unit 20d. At a branch portion 51a2, the internal pipe 7a1 branches into an internal pipe 7a11 extending toward the auxiliary relay unit 330 and an internal pipe 7a12 extending toward the indoor unit 20c.

Furthermore, an internal pipe 7b11 through which a heat medium returns from the auxiliary relay unit 330 and an internal pipe 7b12 through which the heat medium returns from the indoor unit 20c to the relay unit 30 join each other at a joining portion 52a2, thereby forming the internal pipe 7b1. In addition, the internal pipe 7b1 and the internal pipe 7b2 through which the heat medium returns from the indoor unit 20d join each other, thereby forming the internal pipe 7b. The heat medium passes through the pump 2 via the internal pipe 7b and returns to the inter-heat-medium heat exchanger 1.

The auxiliary relay unit 330 of the air-conditioning apparatus 100H has a similar configuration to that of the auxiliary relay unit 330 of the air-conditioning apparatus 100G.

In the air-conditioning apparatus 100H, the relay unit 30 and the auxiliary relay unit 330 are connected by the intermediate pipes 8a and 8b as in the air-conditioning apparatus 100G. The inside diameter Db of each of the intermediate pipes 8a and 8b of the air-conditioning apparatus 100H is also set to an appropriate inside diameter using the formula (1).

The heat-medium conveying pipes 5a, 5b, 5c, 5d, 5e, 5f, 5g, and 5h of the air-conditioning apparatus 100H are set to satisfy the formula (1) as in Embodiments 1 and 2.

FIG. 11 is a circuit diagram of an air-conditioning apparatus 100I that is another modification of the air-conditioning apparatus 100G according to Embodiment 3. In the air-conditioning apparatus 100I, a plurality of inter-heat-medium heat exchangers 1 are provided in the relay unit 30 of the air-conditioning apparatus 100G, whereas in the air-conditioning apparatus 100G, only one inter-heat-medium heat exchanger 1 is provided in the relay unit 30. In addition, in the air-conditioning apparatus 100I, elements closer to the indoor units 20a and 20b are removed from the branch portion 51a, the joining portion 52a, the branch portion 51b, and the joining portion 52b of the relay unit 30 of the air-conditioning apparatus 100F according to Embodiment 2 as illustrated in FIG. 8 and are used in the auxiliary relay unit 330.

The relay unit 30 and the auxiliary relay unit 330 of the air-conditioning apparatus 100I are connected by the intermediate pipes 8a, 8b, 8c, and 8d. The inside diameter Db of each of the intermediate pipes 8a, 8b, 8c, and 8d is set to an appropriate inside diameter based on the formula (1) in the same manner as an inside diameter Db of each of the intermediate pipes 8a and 8b of the air-conditioning apparatus 100G.

The intermediate pipes 8a, 8b, 8c, and 8d are each connected to both the use-side heat exchangers 3a and 3b. Thus, the set range of the inside diameter D which is obtained when the total capacity Qb (=Q1+Q2) of the use-side heat exchangers 3a and 3b connected to the auxiliary relay unit 330 is substituted for Q of the formula (1) and the pipe length Lb from the outlet 33b to the inlet 33a is substituted for L of the formula (1) is a possible set range of the inside diameter Db of the intermediate pipe 8a. In addition, the inside diameter of Db of the intermediate pipe 8c, to which a heat medium is sent from the second inter-heat-medium heat exchanger 1b, is also set in the same manner as in the intermediate pipe 8a. Furthermore, the inside diameter Db of each of the intermediate pipes 8b and 8d located on the return side of the heat medium may also be set on the basis of the formula (1) or may be set to correspond to the inside diameter Da of each of the intermediate pipes 8a and 8c located on the feed side of the heat medium.

The heat-medium conveying pipes 5a, 5b, 5c, and 5d of the air-conditioning apparatus 100I are set to satisfy the formula (1) as in Embodiments 1 and 2.

FIG. 12 is a circuit diagram of an air-conditioning apparatus 100J that is still another modification of the air-conditioning apparatus 100G according to Embodiment 3. In the air-conditioning apparatus 100J, the indoor units 20c and 20d are added to the air-conditioning apparatus 100I described above and are connected to the relay unit 30. In addition, in the air-conditioning apparatus 100J, elements closer to the indoor units 20a and 20b are removed from the branch portion 51a, the joining portion 52a, the branch portion 51b, and the joining portion 52b of the relay unit 30 of the air-conditioning apparatus 100F according to Embodiment 2 as illustrated in FIG. 8 and are used in the auxiliary relay unit 330.

The relay unit 30 and the auxiliary relay unit 330 of the air-conditioning apparatus 100J are connected by the intermediate pipes 8a, 8b, 8c, and 8d as in the air-conditioning apparatus 100I. The inside diameter Db of each of the intermediate pipes 8a, 8b, 8c, and 8d is set to an appropriate inside diameter based on the formula (1) as well as the inside diameter Dd of the intermediate pipes 8a, 8b, 8c, and 8d of the air-conditioning apparatus 100I.

The heat-medium conveying pipes 5a, 5b, 5c, 5d, 5e, 5f, 5g, and 5h of the air-conditioning apparatus 100J are set to satisfy the formula (1) as in Embodiments 1 and 2.

As described above, in the air-conditioning apparatuses 100H to 100J of the modifications, the inside diameter Db of each of the intermediate pipes 8a, 8b, 8c, and 8d which connect the relay unit 30 and the auxiliary relay unit 330 is set to an appropriate inside diameter on the basis of the formula (1), whereby it is possible to reduce the output of the pump while reducing the time required until the use-side heat exchangers 3 start appropriate heat exchange when the air-conditioning apparatuses 100H to 100J start operation or switch operations.

Also, in the air-conditioning apparatuses 100G to 100J according to Embodiment 3, the inside diameter of each of the internal pipes 7 in the relay unit 30 and the auxiliary relay unit 330 may be set to correspond to the inside diameter D of each of the heat-medium conveying pipes 5 or 6 as in Embodiment 1. In addition, each of the internal pipes 7 in the relay unit 30 and the auxiliary relay unit 330 may also be set to have an inside diameter based on the formula (1). The heat-medium conveying pipes 5 and 6 and the internal pipes 7 are each set to have an appropriate inside diameter D, whereby the air-conditioning apparatuses 100G to 100J can reduce the output of the pump while reducing the time required until the use-side heat exchangers 3 start appropriate heat exchange when the air-conditioning apparatuses 100G to 100J start operation or switch operations, and can thus improve the efficiency.

Claims

1. An air-conditioning apparatus comprising: a refrigerant cycle circuit in which a compressor, a heat-source-side heat exchanger, an expansion device, and a refrigerant-side flow passage of an inter-heat-medium heat exchanger are connected by refrigerant pipes, and refrigerant is circulated, the inter-heat-medium heat exchanger being configured to cause heat exchange to be performed between the refrigerant and a heat medium; anda heat-medium cycle circuit in which a pump, a use-side heat exchanger, and a heat-medium-side flow passage of the inter-heat-medium heat exchanger are connected by heat-medium conveying pipes, and the heat medium is circulated,wherein an inside diameter D of each of the heat-medium conveying pipes is determined based on a capacity Q of the use-side heat exchanger connected to the heat-medium conveying pipes and a length L of at least one of the heat-medium conveying pipes included in the heat-medium cycle circuit, and is set to satisfy the following formula (1):

2. The air-conditioning apparatus of claim 1, wherein a plurality of use-side heat exchangers including the use-side heat exchanger are provided,the heat-medium conveying pipes include a plurality of use-side pipes each connected to an associated one of the plurality of use-side heat exchangers, anda heat-source-side pipe connected to the inter-heat-medium heat exchanger, andof the inside diameters D of the heat-medium conveying pipes, an inside diameter Da of the heat-source-side pipe is set to satisfy the formula (1) when a total capacity Qa of the plurality of use-side heat exchangers is substituted for the capacity Q and a length La of the heat-source-side pipe is substituted for the length L.

3. The air-conditioning apparatus of claim 2, wherein the plurality of use-side pipes branch off from the heat-source-side pipe.

4. The air-conditioning apparatus of claim 2, wherein the plurality of use-side heat exchangers include at least a first use-side heat exchanger,the plurality of use-side pipes include a first use-side pipe connected to the first use-side heat exchanger, andof the inside diameters D of the heat-medium conveying pipes, an inside diameter D1 of the first use-side pipe is set to satisfy the formula (1) when a capacity Q1 of the first use-side heat exchanger is substituted for the capacity Q and a length L1 of the first use-side pipe is substituted for the length L.

5. The air-conditioning apparatus of claim 2, wherein the inside diameter Da of the heat-source-side pipe is larger than an inside diameter of each of the plurality of use-side pipes.

6. The air-conditioning apparatus of claim 2, further comprising: a heat source unit including at least the compressor and the heat-source-side heat exchanger; anda relay unit connected to the heat source unit by a pipe, and including at least the inter-heat-medium heat exchanger,wherein the plurality of use-side pipes each connect the relay unit and an associated one of the plurality of use-side heat exchangers.

7. The air-conditioning apparatus of claim 6, further comprising an auxiliary relay unit connected between the relay unit and the plurality of use-side heat exchangers, whereinthe heat-medium conveying pipes further include an intermediate pipe connecting the relay unit and the auxiliary relay unit, andan inside diameter Db of the intermediate pipe is set to satisfy the formula (1) when a total capacity Qb of the plurality of use-side heat exchangers connected to the auxiliary relay unit is substituted for the capacity Q and a length Lb of the intermediate pipe is substituted for the length L.

8. The air-conditioning apparatus of claim 7, wherein the auxiliary relay unit is connected to one or more of the plurality of use-side heat exchangers, the one or more of the plurality of use-side heat exchangers being different from one or more of the plurality of use-side heat exchangers that are connected to the relay unit.

9. The air-conditioning apparatus of claim 6, wherein a plurality of inter-heat-medium heat exchangers including the inter-heat-medium heat exchanger are provided, andeach of the plurality of use-side heat exchangers is connected to an associated one of the plurality of inter-heat-medium heat exchangers.

10. The air-conditioning apparatus of claim 7, wherein the inside diameter Db of the intermediate pipe is larger than an inside diameter of each of the plurality of use-side pipes.