Heat exchange unit and refrigeration system

Abstract

Suppress the decrease in the air volume of the centrifugal fan due to the water absorption state of the shroud. 【Solution means】In the indoor unit (3), the inner diameter of the fan suction port (66) of the resin shroud (62) of the centrifugal fan (50) arranged on the downstream side of the air flow from the utilization side heat exchanger (23) is φD [m], the inner diameter of the vent hole (83) of the bell mouth (80) is φd [m], the air volume of the air passing through the suction port is Q [m 3 / min], the static pressure at the gap (Gs) between the peripheral part of the fan suction port and the cylindrical part (82) of the bell mouth is ΔPs [Pa], and the density of the air is ρ [kg / m 3 . When ], the radial dimensional change rate Rs [%] due to water absorption of the shroud is (Q - (π × ((φD × (1 + Rs / 100)) 2 - φd 2 ) × (2 × ΔPs / ρ) 1 / 2 × 15)) / (Q - (π × (φD 2 - φd 2 ) × (2 × ΔPs / ρ) 1 / 2 × 15)) ≥ 19 / 20 is satisfied.

Description

[Technical Field]

[0001] This disclosure relates to a heat exchange unit and a refrigeration system. [Background technology]

[0002] The indoor unit of an air conditioning system comprises a heat exchanger and a fan. A centrifugal fan is a well-known type of fan. A centrifugal fan comprises an impeller and a fan motor. The impeller has a base plate attached to the fan motor, a shroud spaced apart from the base plate in the axial direction along the axis of rotation, and a plurality of blades provided between the base plate and the shroud. The plurality of blades are spaced apart from each other in the circumferential direction around the axis of rotation of the centrifugal fan.

[0003] In a centrifugal fan, the impeller rotates due to the drive of the fan motor. As the impeller rotates, air is drawn in through the fan intake formed in the center of the shroud, and air is blown out from between each blade towards the outer periphery. In centrifugal fans, it has been proposed that the base plate, shroud, and multiple blades be made of resin, and that the impeller be integrally molded by injection molding. An example of a centrifugal fan having such a resin impeller is disclosed in Patent Document 1. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-102003 [Overview of the project] [Problems that the invention aims to solve]

[0005] When a centrifugal fan, such as the one disclosed in Patent Document 1, is used in an indoor unit, if the centrifugal fan is positioned downstream of the heat exchanger in the airflow path within the casing, moisture in the air may adhere to the impeller during operation of the indoor unit. When moisture adheres to a resin impeller, the impeller expands due to water absorption, causing a change in dimensions. This leads to a problem of reduced airflow from the centrifugal fan.

[0006] To explain in more detail, a bell mouth is positioned on the intake side of a centrifugal fan. The cylindrical part of the bell mouth, which forms the ventilation opening, is inserted into the fan intake port of the impeller. A gap is provided between the periphery of the fan intake port of the impeller and the cylindrical part of the bell mouth. This gap is necessary to avoid interference with the bell mouth and to allow the impeller to rotate smoothly. However, due to the pressure difference between the intake and discharge sides of the impeller, some of the air discharged from the impeller passes through the gap between the periphery of the fan intake port of the impeller and the cylindrical part of the bell mouth, creating a circulating flow (leakage flow) of air that re-enters the impeller.

[0007] When the indoor unit is in operation, if the impeller shroud expands due to water absorption, the inner diameter of the fan intake port increases. As a result, the gap between the periphery of the impeller's fan intake port and the cylindrical part of the bell mouth widens, and the amount of air leaking into the impeller through this gap due to the aforementioned circulating flow increases. Consequently, the airflow of the centrifugal fan decreases. If the airflow of the centrifugal fan decreases significantly due to water absorption by the shroud, the quality of the indoor unit is compromised.

[0008] The purpose of this disclosure is to suppress the decrease in airflow of the centrifugal fan caused by water absorption by the shroud. [Means for solving the problem]

[0009] A first aspect of this disclosure relates to a heat exchange unit (3). The heat exchange unit (3) comprises a casing (21) in which an air passage (AP) is formed, a heat exchanger (23) disposed in the air passage (AP), and a centrifugal fan (50) disposed downstream of the heat exchanger (23) in the air passage (AP). The centrifugal fan (50) has an impeller (60) and a bell mouth (80) disposed on the intake side of the impeller (60). The impeller (60) has a base plate (61) that rotates around a predetermined axis of rotation (Ac), a shroud (62) provided at an axial distance from the base plate (61) along the axis of rotation (Ac), and a plurality of blades (63) provided between the base plate (61) and the shroud (62) at intervals from each other in the circumferential direction about the axis of rotation (Ac). The shroud (62) is made of resin and has a fan intake port (66) that draws air into the impeller (60). The bell mouth (80) has a cylindrical portion (82) that forms a vent (83) and is inserted into the fan intake port (66) with a predetermined gap (Gs) between it and the peripheral edge of the fan intake port (66). The inner diameter of the fan intake port (66) is φD [m], the inner diameter of the vent (83) is φd [m], and the airflow rate of the air passing through the fan intake port (66) is Q [m³]. 3 [ / min], the static pressure in the gap (Gs) is ΔPs [Pa], and the density of air is ρ [kg / m³]. 3 In this case, the radial dimensional change rate Rs[%] of the shroud (62) due to water absorption is (Q-(π×((φD×(1+Rs / 100)) 2 -φd 2 ) × (2 × ΔPs / ρ) 1 / 2 ×15)) / (Q-(π×(φD 2 -φd 2 ) × (2 × ΔPs / ρ) 1 / 2 (x15)) ≥ 19 / 20

[0010] In the first embodiment, the radial dimensional change rate Rs due to water absorption of the shroud (62) satisfies the above relation. According to this, the airflow of the centrifugal fan (50) when the shroud (62) undergoes a dimensional change due to water absorption is maintained at 95% or more for each impeller (60) compared to the airflow of the centrifugal fan (50) when the shroud (62) is dry. In other words, the increase in the amount of air leakage during operation of the centrifugal fan (50) is limited to 5% or less for each impeller (60) when the shroud (62) is dry compared to when it is wet. Therefore, the decrease in the airflow of the centrifugal fan (50) due to water absorption by the shroud (62) can be suppressed.

[0011] A second aspect of this disclosure is a heat exchange unit (3) of the first aspect, wherein the radial dimensional change rate Rs due to water absorption of the shroud (62) is 1% or less.

[0012] In the second embodiment, the radial dimensional change rate Rs due to water absorption of the shroud (62) is relatively low, at 1% or less. When the radial dimensional change rate due to water absorption of the shroud (62) is low in this way, it is possible to suppress the increase in the inner diameter of the fan intake port (66) when the shroud (62) expands due to water absorption. This is advantageous in suppressing the increase in the amount of air leakage from the centrifugal fan (50) due to water absorption by the shroud (62).

[0013] A third aspect of the present disclosure is a heat exchange unit (3) according to the first or second aspect, wherein the resin is polyphenylene ether (PPE), polyphenylene sulfide (PPS), or polypropylene glycol (PPG).

[0014] In the third embodiment, polyphenylene ether (PPE), polyphenylene sulfide (PPS), or polypropylene glycol (PPG) is used as the resin forming the shroud (62). These resins have a relatively low rate of dimensional change due to water absorption, which is advantageous in satisfying the above relation and suppressing the increase in air leakage from the centrifugal fan due to water absorption by the shroud (62).

[0015] According to a fourth aspect of the present disclosure, in the heat exchange unit (3) according to any one of the first to third aspects, the base plate (61), the shroud (62), and the plurality of blades (63) are integrally formed of the resin, and the heat exchange unit is a heat exchange unit (3).

[0016] In the fourth aspect, the impeller (60) is configured as a resin integrally molded product. The centrifugal fan (50) using such an impeller (60) is suitable for mass production because it can omit the process of assembling parts compared to a centrifugal fan using an assembled impeller in which the base plate (61), the shroud (62), and the plurality of blades (63), which are separate parts, are integrated. Further, the centrifugal fan (50) can reduce the weight of the centrifugal fan (50) and suppress vibration during rotation of the centrifugal fan (50) compared to the case where a metal part is adopted for at least one of the base plate (61), the shroud (62), and the plurality of blades (63).

[0017] According to a fifth aspect of the present disclosure, in the heat exchange unit (3) according to any one of the first to fourth aspects, the centrifugal fan (50) includes, as the impeller (60), a first impeller (60A) in which the fan suction port (66) opens toward one side in the axial direction, and a second impeller (60B) in which the fan suction port (66) opens toward the other side in the axial direction. The first impeller (60A) and the second impeller (60B) are connected to a drive shaft (53b) of the same fan motor (53) to form a double-suction centrifugal fan that sucks air from both sides in the axial direction.

[0018] In the fifth aspect, the first impeller (60A) and the second impeller (60B) constitute a double-suction centrifugal fan. The double-suction centrifugal fan has the advantage that it can efficiently suck in air when the air volume increases. However, if the air volume of the centrifugal fan (50) decreases due to dimensional changes caused by water absorption of the shroud (62), the advantages of such a double-suction centrifugal fan will also be impaired. On the contrary, the technology of the present disclosure can suppress the decrease in the air volume of the centrifugal fan (50) due to water absorption of the shroud (62), so it is particularly effective in a double-suction centrifugal fan.

[0019] The sixth aspect of the present disclosure is a heat exchange unit (3) in any one of the first to fifth aspects, wherein the casing (21) is a floor-standing type placed on the floor surface (FL).

[0020] In the sixth aspect, the casing (21) is placed on the floor surface (FL). In such a floor-standing heat exchange unit (3), the decrease in the air volume of the centrifugal fan (50) due to water absorption of the shroud (62) can be suppressed, so the quality can be improved.

[0021] The seventh aspect of the present disclosure is a heat exchange unit (3) in the heat exchange unit (3) of the sixth aspect, wherein the base plate (61), the shroud (62), and the plurality of blades (63) are integrally formed by the resin. And the centrifugal fan (50) is disposed in the upper half inside the casing (21).

[0022] In the seventh embodiment, the centrifugal fan (50) is positioned in the upper half of the interior of the casing (21). If the centrifugal fan (50) includes metal parts, its weight tends to increase vibration during rotation. When such a centrifugal fan (50) is positioned in the upper half of the interior of the casing (21), the center of gravity of the entire heat exchange unit (3) is positioned higher and further away from the floor surface (FL) on which the casing (21) is installed, compared to when the centrifugal fan (50) is positioned in the lower half of the interior of the casing (21). As a result, the heat exchange unit (3) becomes more susceptible to vibration in conjunction with the vibration of the centrifugal fan (50) during rotation. In contrast, if the centrifugal fan (50) is a single-piece molded resin product, vibration of the centrifugal fan (50) during rotation, and consequently vibration of the heat exchange unit (3), can be suppressed.

[0023] An eighth aspect of the present disclosure is a heat exchange unit (3) having a duct connection portion (21j) to which a duct (102) extending from a target space is connected, in any one of the first to fifth aspects of the present disclosure.

[0024] In the eighth aspect, the heat exchange unit (3) has a duct connection (21j). A duct (102) extending from the target space is connected to the duct connection (21j). Such a heat exchange unit (3) can constitute a duct-connected air conditioning system (1). In a duct-connected air conditioning system (1), air transported by the drive of a centrifugal fan (50) is supplied to the target space through the duct (102), resulting in pressure loss within the duct (102). As a result, a decrease in the airflow of the centrifugal fan (50) has a significant impact on product performance. The technology of this disclosure is advantageous in a duct-connected air conditioning system (1) because it can suppress the decrease in airflow of the centrifugal fan (50) due to water absorption by the shroud (62).

[0025] A ninth aspect of this disclosure relates to a refrigeration system (1). The refrigeration system (1) comprises one of the heat exchange units (3,8) of the first to eighth aspects.

[0026] In the ninth embodiment, the heat exchange unit (3,8) described above is provided. The heat exchange unit (3,8) can suppress the decrease in airflow of the centrifugal fan (50) due to water absorption by the shroud (62). This contributes to improving the energy efficiency of the refrigeration device (1). [Brief explanation of the drawing]

[0027] [Figure 1] Figure 1 is a refrigerant circuit diagram illustrating the configuration of an air conditioning system according to an embodiment. [Figure 2] Figure 2 is a perspective view showing the exterior of the indoor unit. [Figure 3] Figure 3 shows the interior of the indoor unit as seen from the front. [Figure 4] Figure 4 shows the inside of the indoor unit as viewed from the right side. [Figure 5] Figure 5 is a perspective view illustrating the configuration of a user-side fan. [Figure 6] Figure 6 is a cross-sectional view of the first centrifugal fan along the line VI-VI in Figure 5. [Figure 7] Figure 7 is an exploded perspective view illustrating the main components of the first centrifugal fan. [Figure 8] Figure 8 is a perspective view illustrating the configuration of an impeller. [Figure 9] Figure 9 is a plan view illustrating the configuration of an impeller. [Figure 10A] Figure 10A is a cross-sectional view showing the main part of the impeller of the first centrifugal fan, enclosed by X in Figure 6, when it is in a dry state. [Figure 10B] Figure 10B is a cross-sectional view showing the main part of the first centrifugal fan impeller, enclosed by X in Figure 6, when it is in the water intake state. [Figure 11] Figure 11 is a schematic diagram illustrating the configuration of a modified air conditioning system. [Figure 12] Figure 12 is a perspective view partially illustrating the interior of a modified air conditioning unit. [Figure 13]Figure 13 is a side view of the modified air conditioning unit, seen from the right side with the right-side panel removed. For convenience, Figure 13 shows the internal configuration through the first fan casing. [Modes for carrying out the invention]

[0028] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the following embodiments, the example will be that the heat exchange unit according to this disclosure is applied to the indoor unit of a separate-type air conditioning system. The drawings are intended to conceptually illustrate the technology of this disclosure. Therefore, in order to facilitate understanding of the technology of this disclosure, dimensions, ratios, or numbers may be exaggerated or simplified in the drawings.

[0029] 《Embodiment》 In this embodiment, a floor-standing indoor unit (3) is described as the heat exchange unit according to the present disclosure. The indoor unit (3) is used in a refrigeration system. The refrigeration system in this embodiment is an air conditioning system (1). The air conditioning system (1) is a device that provides air conditioning to a large indoor space, such as a computer room where multiple servers or other computers are located, or a factory or warehouse; it is a so-called commercial air conditioner.

[0030] (1) Overall configuration of the air conditioning system As shown in Figure 1, the air conditioning system (1) is a paired air conditioning system comprising an outdoor unit (2) and an indoor unit (3). The outdoor unit (2) is installed outdoors. The indoor unit (3) is installed indoors. The outdoor unit (2) and the indoor unit (3) are connected to each other via a liquid connection pipe (4) and a gas connection pipe (5). This connection constitutes a refrigerant circuit (6).

[0031] The refrigerant circuit (6) is filled with refrigerant. The refrigerant circuit (6) mainly includes a compressor (22), a heat source side heat exchanger (11), an expansion valve (25), a four-way switching valve (26), and a utilization side heat exchanger (23). The compressor (22), heat source side heat exchanger (11), expansion valve (25), four-way switching valve (26), and utilization side heat exchanger (23) are connected by piping. The refrigerant circuit (6) performs a refrigeration cycle by circulating the refrigerant.

[0032] The compressor (22), the heat exchanger on the utilization side (23), the expansion valve (25), and the four-way switching valve (26) are included in the indoor unit (3). The compressor (22) draws in low-pressure gaseous refrigerant, compresses it, and discharges the compressed refrigerant. The refrigerant filled in the refrigerant circuit (6) circulates due to the operation of the compressor (22). The expansion valve (25) reduces the pressure of the refrigerant. The four-way switching valve (26) switches the direction of circulation of the refrigerant in the refrigerant circuit (6).

[0033] The four-way directional valve (26) is in the first state (shown by the solid line in Figure 1) during cooling operation. When the four-way directional valve (26) is in the first state, the refrigerant flows through the refrigerant circuit (6) in the direction indicated by the solid arrow. The four-way directional valve (26) is in the second state (shown by the dashed line in Figure 1) during heating operation. When the four-way directional valve (26) is in the second state, the refrigerant flows through the refrigerant circuit (6) in the direction indicated by the dashed arrow.

[0034] The indoor unit (3) further includes a user-side fan (48). The user-side fan (48) rotates under the drive of a first fan motor (53) and transports indoor air so that it passes through the user-side heat exchanger (23). In this embodiment, the user-side fan (48) is composed of two centrifugal fans (50). The user-side heat exchanger (23) exchanges heat between the air transported by the user-side fan (48) and the refrigerant flowing inside it.

[0035] The heat source side heat exchanger (11) is included in the outdoor unit (2). The outdoor unit (2) further includes a heat source side fan (12). The heat source side fan (12) rotates driven by a second fan motor (13) and transports outdoor air so that it passes through the heat source side heat exchanger (11). The heat source side heat exchanger (11) exchanges heat between the air transported by the heat source side fan (12) and the refrigerant flowing inside.

[0036] The air conditioning unit (1) provides air conditioning to the target space, which is the indoor space (IS). The air conditioning unit (1) performs both cooling and heating operations.

[0037] Cooling operation is the operation to cool the air in the indoor space (IS). In cooling operation, with the four-way switching valve (26) in the first state, the heat source side fan (12), compressor (22), and user side fan (48) are operated, the heat source side heat exchanger (11) functions as a heat radiator, and the user side heat exchanger (23) functions as an evaporator. The air transported by the user side fan (48) is cooled by the user side heat exchanger (23) and supplied to the indoor space (IS).

[0038] Heating operation is the operation of heating the air in the indoor space (IS). In heating operation, the four-way switching valve (26) is set to the second state, and the heat source side fan (12), compressor (22), and user side fan (48) are operated, with the heat source side heat exchanger (11) functioning as an evaporator and the user side heat exchanger (23) functioning as a heat radiator. The air transported by the user side fan (48) is heated in the user side heat exchanger (23) and supplied to the indoor space (IS).

[0039] (2) Indoor unit The indoor unit (3) will be explained with reference to Figures 2 to 4. In the following explanation, terms such as "up," "down," "front," "back," "left," and "right" refer to the directions of the arrows shown in Figures 2 to 4. In Figures 3 and 4, the airflow in the indoor unit (3) is indicated by dashed white arrows.

[0040] The indoor unit (3) is a floor-standing indoor unit and is installed on the floor (FL) of the indoor space (IS). The indoor unit (3) comprises a casing (21), a user-side heat exchanger (23), a drain pan (40), an electrical component box (45), a compressor (22), an expansion valve (25), a four-way switching valve (26), and a user-side fan (48). In Figures 3 and 4, the expansion valve (25) and the four-way switching valve (26) are not shown.

[0041] (2-1) Casing The casing (21) is formed in a generally rectangular box shape. The casing (21) houses the user-side heat exchanger (23), drain pan (40), electrical equipment box (45), compressor (22), and user-side fan (48). The casing (21) is placed on the floor (FL) and fixed to the floor by fasteners via fittings (not shown). The casing (21) is constructed by combining metal or resin plates. The casing (21) has a top plate (21a), a bottom plate (21b), a front plate (21c), a rear plate (21d), a left side plate (21e), and a right side plate (21f).

[0042] The top plate (21a) and bottom plate (21b), the front plate (21c) and rear plate (21d), and the left side plate (21e) and right side plate (21f) are opposite each other. The top plate (21a) forms the upper surface of the casing (21). The bottom plate (21b) forms the lower surface of the casing (21). The front plate (21c) forms the front surface of the casing (21). The rear plate (21d) forms the rear surface of the casing (21). The left side plate (21e) forms the left side of the casing (21). The right side plate (21f) forms the right side of the casing (21).

[0043] The front plate (21c) is divided into three sections vertically. The front plate (21c) consists of an upper plate (21g), an intermediate plate (21h), and a lower plate (21i). The upper plate (21g), intermediate plate (21h), and lower plate (21i) are arranged in this order from the top to the bottom of the front plate (21c), and are each detachable from the casing body (CB). The casing body (CB) is the part of the casing (21) excluding the front plate (21c). An operation panel (30) for operating the air conditioning unit (1) is provided on the intermediate plate (21h).

[0044] The casing (21) has an intake port (31) and an outlet port (32). The intake port (31) is an opening for drawing air from the indoor space (IS) into the casing (21). Multiple intake ports (31) are provided on the intermediate plate (21h) of the front plate (21c), avoiding the control panel (30). Each intake port (31) is made up of, for example, a slit extending in the left-right direction. Multiple intake ports (31) are arranged parallel to each other with a gap between them in the vertical direction.

[0045] The air outlets (32) are openings for blowing out air that has undergone heat exchange within the casing (21) into the interior space (IS). Two air outlets (32) are provided on the top plate (21a). The two air outlets (32) are the first air outlet (32a) and the second air outlet (32b). The first air outlet (32a) and the second air outlet (32b) open with a gap between them in the left-right direction. The first air outlet (32a) and the second air outlet (32b) are each composed of, for example, rectangular openings.

[0046] A frame-like section (35) is provided on the upper surface of the top plate (21a). The frame-like section (35) surrounds the two air outlets (32) and forms a connection port (36) that protrudes upward from the top plate (21a). The frame-like section (35) is constructed by combining multiple metal fittings, such as L-shaped long angles. A duct (100) is connected to the connection port (36) made up of this frame-like section (35) to transport the air blown out from each air outlet (32) to various locations in the interior space (IS).

[0047] Furthermore, a first opening (37) and a second opening (38) are formed in the left panel (21e) and the right panel (21f), respectively. The first opening (37) is located at the top of the casing (21) and is used when performing maintenance on the user-side fan (48). The second opening (38) is located at the bottom of the casing (21) and is used when performing maintenance on the electrical component box (45) and the compressor (22). The first opening (37) and the second opening (38) are normally covered by a cover (39), and the cover (39) is removed and the openings are opened during maintenance.

[0048] An air passage (AP) is formed inside the casing (21). The air passage (AP) is a passage that extends from multiple intake ports (31) to the first outlet (32a) and the second outlet (32b). The air passage (AP) has a right-side passage (Pa) and a left-side passage (Pb). The right-side passage (Pa) is a passage that is drawn into the first centrifugal fan (50A) and reaches the first outlet (32a), and is located on the right side inside the casing (21). The left-side passage (Pb) is a passage that is drawn into the second centrifugal fan (50B) and reaches the second outlet (32b), and is located on the left side inside the casing (21).

[0049] (2-2) User-side heat exchanger The user-side heat exchanger (23) is positioned in the air passage (AP) within the casing (21). The user-side heat exchanger (23) is fixed to the casing (21) so that substantially all of the air flowing through the air passage (AP) passes through it. In this example, the user-side heat exchanger (23) is positioned vertically behind the intermediate plate (21h) and is installed in a forward-tilting position so that it protrudes forward as it goes upward. The lower part of the user-side heat exchanger (23) is located at the rear of the casing (21) and is fixed to a bracket (24) attached to the rear plate (21d). The user-side heat exchanger (23) is a fin-and-tube type air heat exchanger.

[0050] (2-3) Drain pan The drain pan (40) consists of a first drain pan (40a) and a second drain pan (40b).

[0051] The first drain pan (40a) is fixed to the bracket (24) together with the utilization-side heat exchanger (23) and is positioned below the bottom of the utilization-side heat exchanger (23). The first drain pan (40a) receives water (condensation) that condenses on the surface and around the utilization-side heat exchanger (23). A discharge pipe (41) is provided at one end of the first drain pan (40a) in the left-right direction (the left end in the example shown in Figure 3). The discharge pipe (41) extends downward from the bottom of the first drain pan (40a) and drains the water in the first drain pan (40a) downward.

[0052] The second drain pan (40b) is located in the lower part of the casing (21). The second drain pan (40b) faces almost the entire surface of the bottom plate (21b) of the casing (21), and is installed in a forward-sloping position such that its front edge is slightly above its rear edge. Although not shown in the figures, a drain channel (42) is formed at the rear of the second drain pan (40b) so as to extend in the left-right direction. The water collected in the first drain pan (40a) and the second drain pan (40b) is collected in the drain channel (42) and discharged outside or elsewhere via a drain hose.

[0053] (2-4) Electrical component box The electrical component box (45) is located on the right side of the lower part of the casing (21). The electrical component box (45) is fixed to a stand member (46) attached to the casing (21) and is positioned above the second drain pan (40b). The electrical component box (45) is a box that is generally rectangular in shape and houses predetermined electrical components. These electrical components include a control board that controls equipment such as the user-side fan (48) and compressor (22) and receives signals from various sensors.

[0054] (2-5) Compressor The compressor (22) is installed on the second drain pan (40b) in a position that does not overlap with the electrical component box (45) when viewed from the front. The compressor (22) is located on the left side in the lower part of the casing (21). The compressor (22) is a variable displacement compressor. The compressor (22) is configured to have a variable rotation speed via inverter control by a control board in the electrical component box (45), and to be able to change the volume of refrigerant being compressed.

[0055] (2-6) User-side fan The two centrifugal fans (50) that make up the user-side fan (48) are a first centrifugal fan (50A) and a second centrifugal fan (50B). Both the first centrifugal fan (50A) and the second centrifugal fan (50B) are turbo fans and are located in the upper half of the interior of the casing (21). In this embodiment, the first centrifugal fan (50A) and the second centrifugal fan (50B) are attached to the top plate (21a) of the casing (21) and are located above the user-side heat exchanger (23), and are positioned downstream of the user-side heat exchanger (23) in the airflow.

[0056] The first centrifugal fan (50A) is located on the right side of the upper part of the casing (21). The second centrifugal fan (50B) is located on the left side of the upper part of the casing (21). A first fan motor (53) is located between the first centrifugal fan (50A) and the second centrifugal fan (50B). The first fan motor (53) is a double-shaft motor in which the drive shaft (53b) extends from the motor body (53a) to both the left and right sides. The first fan motor (53) is shared by both the first centrifugal fan (50A) and the second centrifugal fan (50B).

[0057] The first centrifugal fan (50A) is connected to a drive shaft (53b) extending to the right of the first fan motor (53). The second centrifugal fan (50B) is connected to a drive shaft (53b) extending to the left of the first fan motor (53). Both the first centrifugal fan (50A) and the second centrifugal fan (50B) are rotated by the drive of the first fan motor (53). The axis of the drive shaft (53b) coincides with the rotation axes (Ac) of the first centrifugal fan (50A) and the second centrifugal fan (50B). The rotation axes (Ac) of the first centrifugal fan (50A) and the second centrifugal fan (50B) extend in the left-right direction. That is, the left-right direction in this embodiment corresponds to the axial direction along the rotation axis (Ac).

[0058] (2-6-1) First centrifugal fan The first centrifugal fan (50A) is a double-suction centrifugal fan. As shown in Figures 5 and 6, the first centrifugal fan (50A) includes a first impeller (60A), a second impeller (60B), a first fan casing (54), a first bell mouth (80A), and a second bell mouth (80B). The first impeller (60A) and the second impeller (60B) are connected to the drive shaft (53b) of the first fan motor (53) via a first connecting component (70), and are arranged in this order from the side closest to the first fan motor (53) toward the side away from it. That is, the first impeller (60A) is located on the left side and the second impeller (60B) is located on the right side.

[0059] The first impeller (60A) and the second impeller (60B) have essentially the same components. The first impeller (60A) and the second impeller (60B) each include a base plate (61), a shroud (62), and a number of blades (63). The first impeller (60A) is provided such that the fan intake port (66) formed in the shroud (62) opens to one side in the axial direction, in this example to the left. The second impeller (60B) is provided such that the fan intake port (66) formed in the shroud (62) opens to the other side in the axial direction, in this example to the right.

[0060] As shown in Figure 7, the first impeller (60A) and the second impeller (60B) are integrated in a back-to-back configuration with their base plates (61) facing each other via a first connecting component (70). The first connecting component (70) connects the first impeller (60A) and the second impeller (60B) and also receives the drive shaft (53b). The first connecting component (70) has a boss portion (71) and a flange portion (72). The boss portion (71) is a cylindrical portion through which the insertion hole (73) passes. The flange portion (72) is formed in an annular shape that protrudes outward from the boss portion (71).

[0061] The boss portion (71) is inserted through the shaft hole (64) of the second impeller (60B). The flange portion (72) is sandwiched between the base plate (61) of the first impeller (60A) and the base plate (61) of the second impeller (60B). Both base plates (61) are fastened together to the flange portion (72) with bolts (75) and nuts (76). A pin hole (74) is also formed in the boss portion (71). The pin hole (74) penetrates the boss portion (71) radially. The drive shaft (53b) is inserted through the insertion hole (73) of the boss portion (71). A retaining pin (77) is inserted into the drive shaft (53b) through the pin hole (74). In this way, the drive shaft (53b) is fixed to the first connecting component (70).

[0062] The first impeller (60A) and the second impeller (60B) are integrated via the first connecting component (70) and have a mirror-symmetric structure or shape relative to each other. The blades (63) of the first impeller (60A) and the blades (63) of the second impeller (60B) are positioned with a half-pitch offset from each other in the circumferential direction of the impeller (60). When the first centrifugal fan (50A) is viewed from the axial direction, the blades (63) of the second impeller (60B) correspond to the adjacent blades (63) of the first impeller (60A), and the blades (63) of the first impeller (60A) correspond to the adjacent blades (63) of the second impeller (60B).

[0063] The first impeller (60A) and the second impeller (60B) use the same impeller (60) except that the orientation of the blades (63) is different. The configuration of this impeller (60) is shown in Figures 8 and 9, using the first impeller (60A) as an example. The impeller (60) is a single-piece molded resin part. The base plate (61), shroud (62), and multiple blades (63) of the impeller (60) are integrally molded from resin.

[0064] The base plate (61) is formed in a disc shape. The base plate (61) is the hub of the impeller (60) and is positioned substantially coaxially with the drive shaft (53b) of the first fan motor (53). An axle hole (64) is formed in the central part of the base plate (61). In addition, a plurality of fastening holes (65) (three fastening holes (65) in the example shown in Figure 8, etc.) are formed around the axle hole (64) of the base plate (61). The plurality of fastening holes (65) are holes through which bolts (75) are inserted and are provided at equal intervals in the circumferential direction of the axle hole (64). The central axis of the base plate (61) coincides with the rotation axis (Ac) of the impeller (60).

[0065] The shroud (62) is formed in an annular shape. The shroud (62) is positioned opposite the base plate (61) at a distance from the base plate (61) in the axial direction (left-right in this example) along the axis of rotation (Ac). The shroud (62) is also positioned substantially coaxially with the base plate (61). The shroud (62) has a fan intake port (66). The fan intake port (66) is an opening that draws air into the interior of the first impeller (60A). The inner peripheral edge of the shroud (62) protrudes away from the base plate (61), forming the fan intake port (66).

[0066] Multiple blades (63) are provided between the base plate (61) and the shroud (62). The multiple blades (63) are spaced apart from each other in the circumferential direction around the axis of rotation (Ac), that is, in the direction of rotation of the impeller (60). In this example, the impeller (60) has 6 blades (63). There may be 5 or fewer blades (63), or 7 or more blades. Each of the multiple blades (63) is located in a region near the outer edge of the base plate (61). Each blade (63) is provided upright in a direction in which the base plate (61) and the shroud (62) face each other.

[0067] Each blade (63) has an inner edge (63a) and an outer edge (63b). The inner edge (63a) is the edge located on the inner circumference side of the blade (63). The inner edge (63a) is located on the front side in the direction of rotation of the impeller (60) and corresponds to the inner circumference of the fan intake (66) in a plan view of the impeller (60). The outer edge (63b) is the edge located on the outer circumference side of the blade (63). The outer edge (63b) is located on the rear side in the direction of rotation of the impeller (60) and corresponds to the outer circumference edge of the shroud (62) in a plan view of the impeller (60). Each blade (63) has a cross-sectional shape that curves from the inner circumference side to the outer circumference side in a cross section perpendicular to the axis of rotation (Ac).

[0068] Each blade (63) further has a positive pressure surface (63p) and a negative pressure surface (63s). The positive pressure surface (63p) is the surface that becomes the positive pressure side due to the airflow being conveyed when the impeller (60) rotates. The positive pressure surface (63p) faces the outside of the curvature of the blade (63) between the inner edge (63a) and the outer edge (63b), and constitutes the surface facing the outer circumference of the impeller (60). The negative pressure surface (63s) is the surface that becomes the negative pressure side due to the airflow being conveyed when the impeller (60) rotates. The negative pressure surface (63s) faces the inside of the curvature of the blade (63) between the inner edge (63a) and the outer edge (63b), and constitutes the surface facing the rotation axis (Ac) side of the impeller (60).

[0069] A fan outlet (67) is formed between the outer edge of the base plate (61) and the outer edge of the shroud (62). The fan outlet (67) is an opening that blows air out from the impeller (60) to the outside. In the impeller (60), the portion of the space between the base plate (61) and the shroud (62) where the blades (63) are arranged constitutes a fan flow path (Pf). The fan flow path (Pf) is an annular flow path that is continuous with the fan outlet (67) and is partitioned by multiple blades (63). The fan flow path (Pf) between adjacent blades (63) widens from the rotation axis (Ac) side of the impeller (60) toward the outer edge.

[0070] As the impeller (60) rotates, air is drawn in through the fan intake (66) and blown out through the fan outlet (67). The air passing through the impeller (60) flows from the inside to the outside in the radial direction of the fan flow path (Pf). Each blade (63) increases the air pressure due to the change in the rotational velocity of the airflow between the inner edge (63a) and the outer edge (63b), and the difference in peripheral velocities between the inner edge (63a) and the outer edge (63b). As a result, the impeller (60) pressurizes the air drawn in through the fan intake (66) and blows it out through the fan outlet (67).

[0071] The first impeller (60A) is configured as a clockwise rotating impeller (60). In the first impeller (60A), the inner edge (63a) of each blade (63) is located clockwise forward of the outer edge (63b) of the blade (63). The second impeller (60B) is configured as a counterclockwise rotating impeller (60). In the second impeller (60B), the inner edge of each blade (63) is located counterclockwise forward of the outer edge (63b) of the blade (63). The first impeller (60A) and the second impeller (60B) are connected to the drive shaft (53b) of the same first fan motor (53) via a first connecting component (70) to form a double-suction centrifugal fan.

[0072] As shown in Figures 5 and 6, the first fan casing (54) houses the first impeller (60A) and the second impeller (60B). The first fan casing (54) is formed in a box shape with an open top. The first fan casing (54) has a first upper opening (55) that is open upward. A first mounting piece (56) is provided on the periphery of the first upper opening (55) of the first fan casing (54), protruding outwards. The first mounting piece (56) is attached to the top plate (21a) of the casing (21). The first fan casing (54) is fixed to the top plate (21a) of the casing (21) with the first upper opening (55) corresponding to the first air outlet (32a).

[0073] A first side opening (57) is formed on the left side wall (54a) of the first fan casing (54). A second side opening (58) is formed on the right side wall (54b) of the first fan casing (54). The first side opening (57) and the second side opening (58) are formed, for example, in a circular shape. The first side opening (57) corresponds to the fan intake port (66) of the first impeller (60A). The inner diameter of the first side opening (57) is larger than the inner diameter of the fan intake port (66) of the first impeller (60A). On the other hand, the second side opening (58) corresponds to the fan intake port (66) of the second impeller (60B). The inner diameter of the second side opening (58) is larger than the inner diameter of the fan intake port (66) of the second impeller (60B).

[0074] The first bell mouth (80A) is fitted into the first side opening (57) of the first fan casing (54). The first bell mouth (80A) is located on the intake side of the first impeller (60A) and is a component that guides air from outside the first centrifugal fan (50A) to the first impeller (60A). The second bell mouth (80B) is fitted into the second side opening (58) of the first fan casing (54). The second bell mouth (80B) is located on the intake side of the second impeller (60B) and is a component that guides air from outside the first centrifugal fan (50A) to the second impeller (60B).

[0075] The same bell mouth (80) is used for both the first bell mouth (80A) and the second bell mouth (80B). The bell mouth (80) is a metal component and has a rim portion (81) and a cylindrical portion (82). The rim portion (81) is formed in the shape of an annular plate. The rim portion (81) of the first bell mouth (80A) is fixed to the periphery of the first side opening (57) on the left side wall (54a) of the first fan casing (54). The rim portion (81) of the second bell mouth (80B) is fixed to the periphery of the second side opening (58) on the right side wall (54b) of the first fan casing (54).

[0076] The cylindrical portion (82) of the bell mouth (80) is formed in a cylindrical shape that protrudes into the interior of the first fan casing (54) from the inner peripheral edge of the rim portion (81). The cylindrical portion (82) constitutes an air vent (83) through which air flows. The tip of the cylindrical portion (82) of the first bell mouth (80A) is inserted into the fan intake port (66) of the first impeller (60A) with a predetermined gap (Gs) between it and the peripheral edge of the fan intake port (66). The tip of the cylindrical portion (82) of the second bell mouth (80B) is inserted into the fan intake port (66) of the second impeller (60B) with a predetermined gap (Gs) between it and the peripheral edge of the fan intake port (66).

[0077] In the first centrifugal fan (50A), when the first fan motor (53) is driven, the first impeller (60A) and the second impeller (60B) rotate together, drawing in air from the vents (83) of the first bell mouth (80A) and the second bell mouth (80B) located on both sides of the first fan casing (54). The air drawn in from the vents (83) of the first bell mouth (80A) passes through the first impeller (60A), and the air drawn in from the vents (83) of the second bell mouth (80B) passes through the second impeller (60B). The air that has passed through the first impeller (60A) and the second impeller (60B) is blown out from the first upper opening (55) to the first outlet (32a).

[0078] (2-6-2) Second centrifugal fan The second centrifugal fan (50B) is a single-inlet centrifugal fan. As shown in Figure 5, the second centrifugal fan (50B) includes a third impeller (60C), a second fan casing (84), and a third bell mouth (80C). The same impeller (60) as the first impeller (60A) is used for the third impeller (60C). The third impeller (60C) is provided such that the fan intake port (66) formed in the shroud (62) opens to one side in the axial direction, in this example, to the left. The third impeller (60C) is connected to the drive shaft (53b) of the first fan motor (53) via a second connecting component (not shown). The second connecting component is similar to the first connecting component (70).

[0079] The second fan casing (84) houses the third impeller (60C). The second fan casing (84) is formed in a box shape with an open top. The second fan casing (84) has a second upper opening (85) that is open upward. A second mounting piece (86) is provided on the periphery of the second upper opening (85) of the second fan casing (84), protruding outwards. The second mounting piece (86) is attached to the top plate (21a) of the casing (21). The second fan casing (84) is fixed to the top plate (21a) of the casing (21) with the second upper opening (85) aligned with the second air outlet (32b).

[0080] A third side opening (not shown) is formed in the left side wall (84a) of the second fan casing (84). The third side opening is formed, for example, in a circular shape. The third side opening corresponds to the fan intake port (66) of the third impeller (60C). The inner diameter of the third side opening is larger than the inner diameter of the fan intake port (66) of the third impeller (60C). The third bell mouth (80C) is fitted into the third side opening of the second fan casing (84). The third bell mouth (80C) is positioned on the intake side of the third impeller (60C) and is a component that guides air from outside the second centrifugal fan (50B) to the third impeller (60C). Although not shown, a hole is formed in the right side wall (84b) of the second fan casing (84) through which the drive shaft (53b) is inserted.

[0081] The third bell mouth (80C) uses the same metal bell mouth (80) as the first bell mouth (80A) and the second bell mouth (80B). The rim portion (81) of the third bell mouth (80C) is fixed to the periphery of the third side opening on the left side wall (84a) of the second fan casing (84). The cylindrical portion (82) of the third bell mouth (80C) protrudes into the interior of the second fan casing (84). The tip of the cylindrical portion (82) is inserted into the fan intake port (66) of the third impeller (60C) with a predetermined gap (Gs) between it and the periphery of the fan intake port (66).

[0082] In the second centrifugal fan (50B), when the first fan motor (53) is driven, the third impeller (60C) rotates and draws air in through the vent (83) of the third bell mouth (80C) located on the left side of the second fan casing (84). The air drawn in through the vent (83) of the third bell mouth (80C) passes through the third impeller (60C) and is blown out through the second upper opening (85) to the second outlet (32b). The air blown out from the second outlet (32b) flows through the duct (100) together with the air blown out from the first outlet (32a) and is transported to various locations in the interior space (IS).

[0083] (3) Configuration relating to the gap between the impeller and the bell mouth In the following explanation, when the first centrifugal fan (50A) and the second centrifugal fan (50B) are not distinguished, they will simply be referred to as the centrifugal fan (50); when the first impeller (60A), the second impeller (60B), and the third impeller (60C) are not distinguished, they will simply be referred to as the impeller (60); and when the first bell mouth (80A), the second bell mouth (80B), and the third bell mouth (80C) are not distinguished, they will simply be referred to as the bell mouth (80). Furthermore, the explanation of the relationship between the impeller (60) and the bell mouth (80) will explain the relationship between the first impeller (60A) and the first bell mouth (80A), the second impeller (60B) and the second bell mouth (80B), and the third impeller (60C) and the third bell mouth (80C).

[0084] As shown in Figure 10A, when the user-side fan (48) is operating, the pressure difference between the intake and discharge sides of the impeller (60) causes a portion of the air blown out from the impeller (60) to pass through the gap (Gs) between the periphery of the fan intake port (66) of the impeller (60) and the cylindrical part (82) of the bell mouth (80), creating a circulating flow (leakage flow) of air that re-enters the impeller (60). The amount of air leaking into the impeller (60) due to this circulating flow changes as the impeller (60) expands due to water absorption and undergoes a dimensional change.

[0085] For example, when the air conditioning unit (1) is in cooling operation, moisture in the air cooled by the heat exchanger (23) on the user side may adhere to the impeller (60). When moisture adheres to the impeller (60), as shown in Figure 10B, the shroud (62) absorbs the water and expands, which increases the inner diameter of the fan intake (66). This widens the gap (Gs) between the periphery of the fan intake (66) of the impeller (60) and the cylindrical part (82) of the bell mouth (80), increasing the amount of air that leaks into the interior of the impeller (60) through this gap (Gs).

[0086] Thus, if the gap (Gs) between the first impeller (60A) and the first bell mouth (80A), or the gap (Gs) between the second impeller (60B) and the second bell mouth (80B), increases, the airflow of the first centrifugal fan (50A) decreases. Also, if the gap (Gs) between the third impeller (60C) and the third bell mouth (80C) increases, the airflow of the second centrifugal fan (50B) decreases. As a result, during cooling operation of the air conditioner (1), this leads to a decrease in the airflow of the user-side fan (48).

[0087] Therefore, in the indoor unit (3), in order to suppress the reduction in the air volume of the utilization-side fan (48) during the cooling operation of the air conditioner (1), the configuration related to the gap (Gs) between the impeller (60) and the bellmouth (80) is devised. In the present embodiment, the radial dimensional change rate Rs due to water absorption of the shroud (62) is defined so that the increase in the air leakage amount during the operation of the utilization-side fan (48) when the impeller (60) is in the dry state and when it is in the water absorption state is suppressed to 5% or less for each impeller (60).

[0088] Specifically, the inner diameter of the fan inlet (66) is φD [m], the inner diameter of the vent (83) is φd [m], the air volume passing through the fan inlet (66) is Q [m 3 / min], the static pressure at the gap (Gs) between the peripheral part of the fan inlet (66) of the impeller (60) and the cylindrical part (82) of the bellmouth (80) is ΔPs [Pa], and the density of air is ρ [kg / m 3 . When this is the case, the radial dimensional change rate Rs [%] due to water absorption of the shroud (62) satisfies the relationship shown in the following formula 1. (Q - (π × ((φD × (1 + Rs / 100)) 2 - φd 2 ) × (2 × ΔPs / ρ) 1 / 2 × 15)) / (Q - (π × (φD 2 - φd 2 ) × (2 × ΔPs / ρ) 1 / 2 × 15)) ≥ 19 / 20 ····· (Formula 1)

[0089] The inner diameter φD of the fan inlet (66) is the inner diameter of the fan inlet (66) when the impeller (60) is in the dry state. The "dry state" of the impeller (60) here means the state of the impeller (60) in a standard environment of normal temperature and normal humidity, specifically, the state of the impeller (60) when it is left standing for 24 hours in an environment of temperature 23°C (±2°C) and relative humidity 50% (±5%). The inner diameter φDe [m] of the fan inlet (66) when the impeller (60) is in the water absorption state where it expands due to water absorption is represented by the following formula 2. φDe = φD × (1 + Rs / 100) ····· (Formula 2)

[0090] The shape of the gap (Gs) between the peripheral edge of the fan intake port (66) of the impeller (60) and the cylindrical part (82) of the bell mouth (80) is annular. The area A1 [m²] of the gap (Gs) when the impeller (60) is dry. 2 ] is expressed by the following equation 3. Also, the area A2[m²] of the gap (Gs) when the impeller (60) is in a water-absorbing state. 2 ] is expressed by the following equation 4. Here, φd is the inner diameter [m] of the vent (83) as described above. A1 = π / 4 × (φD 2 -φd 2 )...(Formula 3) A2 = π / 4 × (φDe 2 -φd 2 )...(Formula 4)

[0091] The amount of air leaking through the gap (Gs) between the peripheral edge of the fan intake port (66) of the impeller (60) and the cylindrical part (82) of the bell mouth (80) during the operation of the centrifugal fan (50) increases as the area of ​​the gap (Gs) increases. The area of ​​the gap (Gs) is larger when the impeller (60) is wet than when it is dry, by the amount that the gap (Gs) widens.

[0092] The amount of air leakage q1 into the impeller (60) from the gap (Gs) when the impeller (60) is dry is expressed by the following equation 5. Furthermore, the amount of air leakage q2 into the impeller (60) from the gap (Gs) when the impeller (60) is wet is expressed by the following equation 6. Here, as mentioned above, ρ is the density of air [kg / m³]. 3 ], where ΔPs is the static pressure [Pa] at the gap (Gs). The static pressure ΔPs at this gap (Gs) is the pressure difference between the upstream side (outside the impeller (60)) and the downstream side (inside the impeller (60)) of the gap (Gs). q1 = A1 × (2 × ΔPs / ρ) 1 / 2 ×60 (Formula 5) q² = A² × (2 × ΔPs / ρ) 1 / 2 ×60 (Formula 6)

[0093] The amount of air Q1 blown out from the impeller (60) when the impeller (60) is dry is expressed by the following equation 7, taking into account the amount of air leakage q1 through the gap (Gs). Also, the amount of air Q2 blown out from the impeller (60) when the impeller (60) is wet is expressed by the following equation 8, taking into account the amount of air leakage q2 through the gap (Gs). Here, Q is the airflow rate [m³] of the air passing through the fan intake (66), as described above. 3 It is [ / min]. Q1=Q-q1 (Formula 7) Q2 = Q - q2 ·····(Equation 8)

[0094] Furthermore, in order to ensure that the airflow of the centrifugal fan (50) when the impeller (60) undergoes a dimensional change due to water absorption is at least 95% of the airflow of the centrifugal fan (50) when the impeller (60) is dry, the following relationship in Equation 9 must be satisfied. By substituting Equations 1 to 8 above into Equation 9, Equation 1 above can be obtained. (Q2 / Q1)×100≧95 (Formula 9)

[0095] The radial dimensional change rate Rs of the shroud (62) due to water absorption is preferably 1% or less. The dimensional change rate Rs of the shroud (62) varies depending on the type of resin forming the impeller (60), the inner and outer diameters of the shroud (62), and the thickness of the shroud (62). The resin forming the impeller (60) is, for example, polyphenylene ether (PPE), polyphenylene sulfide (PPS), or polypropylene glycol (PPG). From the viewpoint of lowering the dimensional change rate Rs of the shroud (62), polyphenylene ether (PPE) is preferred as the resin forming the impeller (60).

[0096] The radial dimensional change rate Rs of the shroud (62) due to water absorption is obtained by measuring the dimensional change when the impeller (60) is subjected to saturated water absorption from a dry state. Specifically, first, the impeller (60) is placed in a moisture-proof bag and stored for 24 hours in an environment of 23°C (±2°C) and 50% (±5%) relative humidity to dry it out. Then, the inner diameter φD of the fan intake port (66) of the dry impeller (60) is measured. Next, the impeller (60) is immersed in 80°C hot water until it reaches a state of water absorption saturation (weight equilibrium). After that, the inner diameter φDe of the fan intake port (66) of the water-absorbed impeller (60) is measured.

[0097] Based on the inner diameter φD of the fan inlet (66) of the impeller (60) in a dry state and the inner diameter φDe of the fan inlet (66) of the impeller (60) in a water-absorbed state, the radial dimensional change rate Rs of the shroud (62) due to water absorption can be determined from the following equation 10. Rs=((φDe-φD) / φD)×100 (Formula 10) Furthermore, the dimensional change rate Rs may be measured by other methods, such as by preparing a resin plate used in the impeller (60), determining the dimensional change rate in the thickness direction of the plate by measuring the dimensional change from the dry state to saturated with water as described above, and then calculating the rate based on the dimensional change rate in the thickness direction of the plate.

[0098] (4) Features of the Embodiment In the indoor unit (3) of this embodiment, the radial dimensional change rate Rs due to water absorption by the shroud (62) satisfies the relationship in Equation 1 above. According to this, when the shroud (62) undergoes a dimensional change due to water absorption, the airflow of the centrifugal fan (50) is maintained at 95% or more for each impeller (60) compared to the airflow of the centrifugal fan (50) when the shroud (62) is dry. In other words, the increase in the amount of air leakage during operation of the first centrifugal fan (50A) is suppressed to 10% or less when the shroud (62) is dry compared to when it is absorbed with water. Also, the increase in the amount of air leakage during operation of the second centrifugal fan (50B) is suppressed to 5% or less. Therefore, it is possible to suppress the decrease in the airflow of the user-side fan (48) due to water absorption by the shroud (62).

[0099] In the indoor unit (3) of this embodiment, the radial dimensional change rate Rs due to water absorption of the shroud (62) is relatively low, at 1% or less. When the radial dimensional change rate Rs due to water absorption of the shroud (62) is low in this way, it is possible to suppress the increase in the inner diameter of the fan intake port (66) when the shroud (62) expands due to water absorption. This is advantageous in suppressing the increase in the amount of air leakage from the centrifugal fan (50) due to water absorption by the shroud (62).

[0100] In the indoor unit (3) of this embodiment, polyphenylene ether (PPE), polyphenylene sulfide (PPS), or polypropylene glycol (PPG) is used as the resin forming the shroud (62). These resins have a relatively low rate of dimensional change Rs due to water absorption, which is advantageous in satisfying the relationship in Equation 1 above and suppressing the increase in the amount of air leakage from the centrifugal fan (50) due to water absorption by the shroud (62).

[0101] In the indoor unit (3) of this embodiment, the impeller (60) is constructed as a single-piece molded resin part. Compared to centrifugal fans (50) that use such an impeller (60), which are assembled from separate parts such as a base plate (61), a shroud (62), and multiple blades (63), the centrifugal fan (50) is suitable for mass production because it eliminates the process of assembling parts. Furthermore, compared to cases where at least one of the base plate (61), shroud (62), and multiple blades (63) is made of metal, the centrifugal fan (50) can be made lighter and vibrations during rotation of the centrifugal fan (50) can be suppressed.

[0102] In the indoor unit (3) of this embodiment, the first impeller (60A) and the second impeller (60B) configure the first centrifugal fan (50A) as a double-suction centrifugal fan. A double-suction centrifugal fan has the advantage of being able to efficiently draw in air when the airflow is large. However, if the airflow of the first centrifugal fan (50A) decreases due to dimensional changes caused by water absorption by the shroud (62), the advantages of such a double-suction centrifugal fan are also lost. In contrast, the technology of this disclosure can suppress the decrease in airflow of the centrifugal fan (50) due to water absorption by the shroud (62), and is therefore particularly effective in a double-suction centrifugal fan.

[0103] In this embodiment, the indoor unit (3) is placed on the floor (FL). In such a floor-standing indoor unit (3), the reduction in airflow of the centrifugal fan (50) due to water absorption by the shroud (62) can be suppressed, thereby improving quality.

[0104] In this embodiment, the indoor unit (3) is positioned in the upper half of the interior of the casing (21). Centrifugal fans (50) that include metal parts tend to vibrate more easily when rotating due to their weight. When such a centrifugal fan (50) is positioned in the upper half of the interior of the casing (21), the center of gravity of the entire indoor unit (3) is positioned higher and further away from the floor surface (FL) on which the casing (21) is installed, compared to when the centrifugal fan (50) is positioned in the lower half of the interior of the casing (21). As a result, the indoor unit (3) becomes more susceptible to vibration in conjunction with the vibration of the centrifugal fan (50) when it rotates. In contrast, if the centrifugal fan (50) is a single-piece molded resin product, the vibration of the centrifugal fan (50) when it rotates, and consequently the vibration of the indoor unit (3), can be suppressed.

[0105] The air conditioning system (1) of this embodiment includes the indoor unit (3) described above. The indoor unit (3) can suppress the decrease in airflow of the centrifugal fan (50) due to water absorption by the shroud (62). This contributes to improving the energy efficiency of the air conditioning system (1).

[0106] Variant form This modified air conditioning system (1) is a type of air conditioning system known as a rooftop system, installed on the roof of a building. The air conditioning system (1) provides air conditioning to the indoor spaces of buildings such as commercial facilities, shops, factories, warehouses, and office buildings. The building has multiple rooms. Each room is a space that the air conditioning system (1) is responsible for conditioned.

[0107] (1) Overall configuration of the air conditioning system The air conditioning system (1) will be explained with reference to Figures 11 to 13. In the following explanation, terms such as "up," "down," "front," "back," "left," and "right" refer to the directions of the arrows shown in Figures 12 and 13. In Figures 11 and 13, the airflow in the air conditioning system (1) is indicated by dashed white arrows.

[0108] As shown in Figure 11, the air conditioning unit (1) is configured as a ducted system that transports temperature-controlled air through ducts. One return air duct (101) and one supply air duct (102) are connected to the air conditioning unit (1). The return air duct (101) is the duct through which the air sent to the air conditioning unit (1) (return air) flows. The supply air duct (102) is the duct through which the conditioned air (supply air) after heat exchange flows, and it branches out along the way to extend to each room.

[0109] As shown in Figure 12, the air conditioning unit (1) is an integrated unit in which the heat source side unit (7) and the utilization side unit (8) are combined into one. The air conditioning unit (1) has a casing (21). The entire closed-circuit refrigerant circuit (6) is housed inside the casing (21). The refrigerant circuit (6) is composed of a compressor (22), a heat source side heat exchanger (11), an expansion valve (25), a four-way switching valve (26), and a utilization side heat exchanger (23), similar to the embodiment described above.

[0110] The casing (21) is formed in a generally rectangular box shape. The casing (21) is placed and fixed on the roof floor (RF). The casing (21) has a top plate (21a), a bottom plate (21b), a front plate (21c), a rear plate (21d), a left side plate (21e), and a right side plate (21f). A partition plate (27) is provided inside the casing (21). The partition plate (27) divides the inside of the casing (21) into a heat source side space (HS) and a utilization side space (US), and blocks the flow of air between the heat source side space (HS) and the utilization side space (US).

[0111] (2) Heat source side unit The portion of the air conditioning unit (1) including the heat source side space (HS) constitutes a heat source side unit (7) corresponding to the outdoor unit (2) in the above embodiment. Two circular air outlets (33) are formed on the top plate (21a) that partitions the heat source side space (HS). A mesh fan cover (34) is attached to each air outlet (33). Although not shown, an intake port for drawing air into the heat source side space (HS) is formed on the left side plate (21e) that partitions the heat source side space (HS). The intake port is composed of, for example, a plurality of slits extending parallel to each other.

[0112] The heat source side space (HS) houses a heat source side heat exchanger (11), a compressor (22), an expansion valve (25), a four-way switching valve (26), and two heat source side fans (12). The heat source side heat exchanger (11) is positioned in the air passage within the heat source side space (HS) from the intake to the outlet (33). For example, a fin-and-tube type air heat exchanger is used for the heat source side heat exchanger (11). Each heat source side fan (12) is positioned behind the fan cover (34) to transport air toward the outlet (33). For example, propeller fans are used for the heat source side fans (12).

[0113] The heat source side fan (12) rotates when driven by the second fan motor (13). When the heat source side fan (12) rotates, outdoor air is drawn in from the intake into the heat source side space (HS), flows through the air passage within the heat source side space (HS), and is then blown out from the outlet (33). In this process, as shown by the dashed white arrows in Figure 11, the outdoor air passes through the heat source side heat exchanger (11) and exchanges heat with the refrigerant inside the heat source side heat exchanger (11). The heat source side heat exchanger (11) functions as a radiator when the air conditioning unit (1) is in cooling operation and as an evaporator when it is in heating operation.

[0114] (3) User Unit The portion of the air conditioning unit (1) including the user-side space (US) constitutes a user-side unit (8) corresponding to the indoor unit (3) in the above embodiment. The user-side unit (8) is an example of a heat exchange unit. As shown in Figures 12 and 13, a return air port (28) and an air supply port (29) are formed in the bottom plate (21b) that partitions the user-side space (US). The return air port (28) opens to the rear side of the user-side space (US), and the air supply port (29) opens to the front side of the user-side space (US). A return air duct (101) is connected to the return air port (28). An air supply duct (102) is connected to the air supply port (29).

[0115] A first rib (211) is provided on the periphery of the return air port (28) of the bottom plate (21b), projecting inward into the user-side space (US). The periphery of the return air port (28), including this first rib (211), constitutes a duct connection section (21j) to which the return air duct (101) is connected. A second rib (212) is provided on the periphery of the supply air port (29) of the bottom plate (21b), projecting inward into the user-side space (US). The periphery of the supply air port (29), including this second rib (212), constitutes a duct connection section (21j) to which the supply air duct (102) is connected.

[0116] The user-side space (US) houses a user-side heat exchanger (23), a user-side fan (48), and a furnace heat exchanger (93). The user-side heat exchanger (23) is positioned in the air passage (AP) within the user-side space (US) from the return air inlet (28) to the supply air inlet (29). For example, a fin-and-tube type air heat exchanger is used for the user-side heat exchanger (23). The user-side heat exchanger (23) is supported by a support frame (88) and is installed in a tilted position that extends backward as it goes upward. The user-side heat exchanger (23) is located above the return air inlet (28).

[0117] A support base (89) is provided on the bottom plate (21b) that partitions the user-side space (US). The support base (89) is located in the user-side space (US) from between the return air port (28) and the intake air port (29) to above the supply air port (29). The support base (89) divides the user-side space (US) into an upstream space (S1) located upstream of the air passage (AP) including the user-side fan (48), and a downstream space (S2) located downstream of the user-side fan (48). The portion of the support base (89) located between the return air port (28) and the supply air port (29) is located below the lower part of the user-side heat exchanger (23) and constitutes a drain pan (40).

[0118] The support base (89) has a support plate (89a) that extends horizontally in front of the user-side space (US). The support plate (89a) is located above the air intake (29). A user-side fan (48) and an inverter (90) are provided on the support plate (89a). The user-side fan (48) rotates when driven by a first fan motor (53). The inverter (90) is a control device for the user-side fan (48) and is electrically connected to the first fan motor (53) and capable of transmitting control signals.

[0119] The user-side fan (48) is supported by a support base (89) and is located above the air intake (29). The user-side fan (48) is positioned downstream of the user-side heat exchanger (23) in the airflow path (AP). The user-side fan (48) is composed of a centrifugal fan (50). The centrifugal fan (50) that makes up the user-side fan (48) is a double-suction centrifugal fan similar to the first centrifugal fan (50A) that makes up the user-side fan (48) in the above embodiment, and is composed of a first impeller (60A), a second impeller (60B), a first fan casing (54), a first bell mouth (80A), and a second bell mouth (80B).

[0120] The first fan casing (54) is configured in the same way as the first fan casing (54) of the above embodiment, except that its upper surface is closed while its lower surface is open. The first fan casing (54) has a lower opening (59) that is open downwards. The receiving plate (89a) has a communication port (89h) that connects the upstream space (S1) and the downstream space (S2). The first fan casing (54) is fixed to the receiving plate (89a) of the support base (89) with the lower opening (59) corresponding to the communication port (89h).

[0121] The first fan casing (54) houses the first impeller (60A) and the second impeller (60B). The first fan motor (53) is mounted on the front wall (54c) of the first fan casing (54). The first impeller (60A) and the second impeller (60B) are connected to the drive shaft (53b) of the first fan motor (53) via a first connecting component (70). The first impeller (60A) is located at the front, and the second impeller (60B) is located at the rear. The rotation axis (Ac) of the centrifugal fan (50) in this example extends in the front-rear direction.

[0122] A first side opening (57) is formed in the front side wall (54c) of the first fan casing (54). A second side opening (58) is formed in the rear side wall (54d) of the first fan casing (54). The first bell mouth (80A) is fitted into the first side opening (57) of the first fan casing (54) and positioned on the suction side of the first impeller (60A). The second bell mouth (80B) is fitted into the second side opening (58) of the first fan casing (54) and positioned on the suction side of the second impeller (60B).

[0123] The radial dimensional change rate Rs due to water absorption of each shroud (62) of the first impeller (60A) and the second impeller (60B) satisfies the relationship shown in Equation 1 described in the above embodiment. Preferably, the radial dimensional change rate Rs due to water absorption of the shroud (62) is 1% or less. Polyphenylene ether (PPE) is preferred as the resin forming the first impeller (60A) and the second impeller (60B). The radial dimensional change rate Rs due to water absorption of the shroud (62) is measured by the same method as in the above embodiment.

[0124] A rack (91) is fixed to the lower part of the support plate (89a) of the support base (89). The rack (91) is positioned in the downstream space (S2). The furnace heat exchanger (93) is held in place by the rack (91). The furnace heat exchanger (93) is composed of a bundle of auxiliary heating gas pipes (93a). The furnace heat exchanger (93) constitutes the combustion heater (92) shown in Figure 11. In addition to the furnace heat exchanger (93), the combustion heater (92) has a combustion section (94), an air intake pipe (96), a gas supply pipe (97), and an exhaust pipe (99).

[0125] The combustion section (94) is located at one end of the furnace heat exchanger (93). The air intake pipe (96) and the gas supply pipe (97) are connected to the combustion section (94). The exhaust pipe (99) is connected to the other end of the furnace heat exchanger (93). The air intake pipe (96) is equipped with a furnace fan (not shown). The furnace fan drives air from the air intake pipe (96) to the combustion section (94), which is then transported through the furnace heat exchanger (93) to the exhaust pipe (99). The gas supply pipe (97) is equipped with a gas valve (98). Opening the gas valve (98) allows fuel gas to be sent from the gas supply pipe (97) to the combustion section (94).

[0126] The combustion section (94) has an igniter (95), such as a spark plug. In the combustion section (94), a mixture of air supplied from the air intake pipe (96) and fuel gas supplied from the gas supply pipe (97) is ignited by the igniter (95) and combusted. The combustion gas obtained in the combustion section (94) flows through the gas pipe (93a) and is discharged outdoors through the exhaust pipe (99). Such a combustion heater (92) is driven when the heating capacity is insufficient with only the refrigeration cycle of the refrigerant circuit (6) during heating operation, and heat is heated by exchanging heat between the air flowing in the downstream space (S2) and the combustion gas inside the furnace heat exchanger (93).

[0127] The user-side fan (48) rotates when driven by the first fan motor (53). When the user-side fan (48) rotates, indoor air is drawn into the user-side space (US) through the return air duct (101) and the return air inlet (28), flows through the air passage (AP) within the user-side space (US), and is then blown out into each room through the supply air duct (102) from the supply air inlet (29). As the air drawn into the user-side space (US) flows through the air passage (AP) within it, it passes through the user-side heat exchanger (23), as shown by the dashed white arrow in Figure 11, and exchanges heat with the refrigerant inside the user-side heat exchanger (23). The user-side heat exchanger (23) functions as an evaporator when the air conditioning unit (1) is in cooling operation and as a heat radiator when it is in heating operation.

[0128] (4) Characteristics of the modified form This modified air conditioning unit (1) has two duct connections (21j). A return air duct (101) extending from the indoor space is connected to one of the duct connections (21j). A supply air duct (102) extending from each room is connected to the other duct connection (21j). In such a duct-connected air conditioning unit (1), the air transported by the user-side fan (48) is drawn in through the return air duct (101) and supplied to each room through the supply air duct (102), resulting in pressure loss within the return air duct (101) and the supply air duct (102). Consequently, a decrease in the airflow of the centrifugal fan (50) that constitutes the user-side fan (48) has a significant impact on product performance. The technology of this disclosure is advantageous in duct-connected air conditioning units (1) because it can suppress the decrease in airflow of the centrifugal fan (50) due to water absorption by the shroud (62).

[0129] Other embodiments The radial dimensional change rate Rs of the shroud (62) due to water absorption satisfies the relationship in Equation 1 above for any one or two of the first impeller (60A), second impeller (60B), and third impeller (60C) (600A). In short, it is sufficient that the dimensional change rate Rs of the shroud (62) satisfies the relationship in Equation 1 above for at least one centrifugal fan (50) included in the indoor unit (3).

[0130] The radial dimensional change rate Rs of the shroud (62) due to water absorption may be greater than 1% as long as the relationship in Equation 1 above is satisfied. The resin forming the impeller (60) is not limited to polyphenylene ether (PPE), polyphenylene sulfide (PPS), or polypropylene glycol (PPG), but may be other resins.

[0131] The impeller (60) only needs to have at least the shroud (62) made of resin. For example, the shroud (62) and the multiple blades (63) of the impeller (60) may be integrally molded from resin, and only the base plate (61) may be made of a metal part.

[0132] The bell mouth (80) may be made of resin instead of metal, provided that the dimensional change of the vent (83) due to water absorption is substantially negligible or minimal.

[0133] In the indoor unit (3) of the above embodiment, both the first centrifugal fan (50A) and the second centrifugal fan (50B) may be double-suction centrifugal fans or single-suction centrifugal fans. The first centrifugal fan (50A) and the second centrifugal fan (50B) may be located in the lower half of the interior of the casing (21). The centrifugal fan (50) forming the user-side fan (48) may be one or three or more.

[0134] The indoor unit (3) may be configured to be wall-mounted. The indoor unit (3) may be positioned on the front side of the ceiling surface and suspended from the ceiling surface. The indoor unit (3) may be positioned on the back side of the ceiling surface and suspended from the ceiling beams. Any installation method can be adopted for the indoor unit (3).

[0135] The air conditioning system (1) does not have to be a pair type having one outdoor unit (2) and one indoor unit (3), but may be an outdoor multi-type having multiple outdoor units (2) or an indoor multi-type having multiple indoor units (3).

[0136] The air conditioning system (1) in the above embodiment does not have to be a separate type having an indoor unit (3) and an outdoor unit (2), but may be an integrated type having only an indoor unit and no outdoor unit (2). In this case, the indoor unit has a heat source side heat exchanger, etc.

[0137] The space to be air-conditioned by the air conditioning system (1) of the above embodiment is not limited to indoor spaces (IS) such as computer rooms, factories, and warehouses. The space to be air-conditioned may also be a space in a shop or building, or an indoor space in a residence.

[0138] In the modified air conditioning system (1) described above, multiple return air ducts (101) and supply air ducts (102) may be connected. Furthermore, the space to be air-conditioned by the modified air conditioning system (1) described above may be the interior space of a house (such as multiple rooms).

[0139] The air conditioning unit (1) does not need to be equipped with a four-way switching valve (26) in the refrigerant circuit (6). In this case, the air conditioning unit (1) may be configured as a heater capable of performing only heating operation. The air conditioning unit (1) may be configured as a cooler capable of performing only cooling operation. Furthermore, the air conditioning unit (1) may be configured to perform dehumidification, ventilation, and humidification operations. Even during these operations, moisture from the air may adhere to the impeller (60) of the indoor unit (3), so the technology of this disclosure is effective.

[0140] In the above modified example, a rooftop type air conditioning system (1) was described, but the duct-connected air conditioning system (1) using the heat exchange unit according to this disclosure may also be a ceiling-mounted type air conditioning system having duct connection parts (21j) to which the return air duct (101) and the supply air duct (102) are connected.

[0141] In the above embodiments and modifications, an air conditioning system (1) was used as an example to describe a refrigeration system in which a heat exchange unit is used, but the system is not limited to this. A refrigeration system in which the heat exchange unit according to this disclosure can be used may also be a water heater, a chiller unit, a cooling device that cools the air inside a storage unit, etc. The cooling device cools the air inside a refrigerator, freezer, container, etc.

[0142] While embodiments and variations have been described above, it will be understood that a variety of modifications to the form and details are possible without departing from the spirit and scope of the claims. Furthermore, these embodiments and variations may be combined or substituted as appropriate, as long as they do not impair the functions covered by this disclosure.

[0143] Furthermore, the designations "First," "Second," etc., in the specification and claims are used to distinguish between the terms to which these designations are attached, and do not limit the number or order of such terms. [Industrial applicability]

[0144] As described above, this disclosure is useful for heat exchange units and refrigeration systems equipped therewith. [Explanation of symbols]

[0145] 1. Air conditioning system (refrigeration system) 3. Indoor unit (heat exchange unit) 8. User-side unit (heat exchange unit) 21 Casing 21j duct connection 23 User-side heat exchanger (heat exchanger) 50 centrifugal fan 53. First fan motor (fan motor) 53b Drive shaft 60 Impeller 60A First Impeller 60B Second Impeller 61 Base plate 62 Shroud 63 feathers 66 Fan intake 80 Bellmouth 82 Cylindrical part 83 Ventilation opening 102 Air supply duct (duct) AC rotation axis AP Airflow Channel Gs gap

Claims

1. A casing (21) in which an air passage (AP) is formed inside, A heat exchanger (23) is arranged in the aforementioned air passage (AP), The air passage (AP) includes a centrifugal fan (50) positioned downstream of the heat exchanger (23) in the airflow path, The centrifugal fan (50) has an impeller (60) and a bell mouth (80) located on the intake side of the impeller (60), The impeller (60) comprises a base plate (61) that rotates around a predetermined axis of rotation (Ac), a shroud (62) provided at an axial distance from the base plate (61) along the axis of rotation (Ac), and a plurality of blades (63) provided between the base plate (61) and the shroud (62) at intervals from each other in the circumferential direction with respect to the axis of rotation (Ac). The shroud (62) is made of resin and has a fan intake port (66) that draws air into the impeller (60). The bell mouth (80) has a cylindrical portion (82) that forms a ventilation opening (83) and is inserted into the fan intake port (66) with a predetermined gap (Gs) between it and the peripheral edge of the fan intake port (66). The inner diameter of the fan intake port (66) is φD [m], the inner diameter of the vent (83) is φd [m], and the airflow rate Q [m³] of the air passing through the fan intake port (66) is φD [m³]. ３ [ / min], static pressure ΔPs [Pa] in the gap (Gs), density of air ρ [kg / m³] ３ The radial dimensional change rate Rs [%] of the shroud (62) due to water absorption is, (Q-(π×((φD×(1+Rs / 100)) ２ -φ$ ２ )×(2×ΔP / / ρ) １／２ ×15)) / (Q-(π×(φD ２ -φ$ ２ )×(2×ΔP / / ρ) １／２ ×15))≧19 / 20 Satisfying Heat exchange unit.

2. In the heat exchange unit according to claim 1, The radial dimensional change rate Rs of the shroud (62) due to water absorption is 1% or less. Heat exchange unit.

3. In the heat exchange unit according to claim 1, The resin is polyphenylene ether, polyphenylene sulfide, or polypropylene glycol. Heat exchange unit.

4. In the heat exchange unit according to claim 1, The base plate (61), the shroud (62), and the plurality of blades (63) are integrally molded from the resin. Heat exchange unit.

5. In the heat exchange unit according to claim 1, The centrifugal fan (50) includes, as the impeller (60), a first impeller (60A) whose fan intake port (66) opens toward one side in the axial direction, and a second impeller (60B) whose fan intake port (66) opens toward the other side in the axial direction. The first impeller (60A) and the second impeller (60B) are connected to the drive shaft (53b) of the same fan motor (53), and constitute a double-suction centrifugal fan that draws in air from both sides in the axial direction. Heat exchange unit.

6. In the heat exchange unit according to claim 1, The casing (21) is a floor-standing type that is placed on the floor surface (FL). Heat exchange unit.

7. In the heat exchange unit according to claim 6, The base plate (61), the shroud (62), and the plurality of blades (63) are integrally molded from the resin. The centrifugal fan (50) is located in the upper half of the interior of the casing (21). Heat exchange unit.

8. In the heat exchange unit according to claim 1, It has a duct connection part (21j) to which a duct (102) extending from the target space is connected. Heat exchange unit.

9. A heat exchange unit (3,8) according to any one of claims 1 to 8 is provided. Refrigeration equipment.

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