Patent Publication Number: US-2022221228-A1

Title: Chilling unit

Description:
TECHNICAL FIELD 
     The present disclosure relates to a chilling unit that forms, for example, an air-conditioning apparatus, a heat-pump water heater, or a refrigeration apparatus. 
     BACKGROUND ART 
     In the past, chilling units have been proposed each of which includes a heat exchange unit that houses an air heat exchanger and a fan and a machine room that houses a compressor and a heat exchanger (see, for example, Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent No. 5760049 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the case of performing maintenance on a chilling unit having an elongated shape, a worker enters a heat exchange portion of the chilling unit from an end face thereof that corresponds to a front side of the chilling unit in a longitudinal direction thereof. However, the chilling unit described in Patent Literature 1 has an L-shaped bent portion at its end portion in the longitudinal direction, and heat transfer tubes of a pair of air heat exchangers disposed in the lateral direction extend on the front side of the chilling unit. Therefore, in the chilling unit described in Patent Literature 1, two systems of header pipes or distributors associated with a pair of air heat exchangers are disposed at part of the chilling unit through which the worker enters the front side of the chilling unit. Thus, the worker does not easily enter or leave the heat exchange portion, and thus does not easily perform maintenance on the chilling unit. 
     The present disclosure is applied to solve the above problem, and relates to a chilling unit that allows a worker to easily enter and exit a space defined by air heat exchangers, whereby the ease of maintenance of a heat exchange portion of the chilling unit is improved. 
     Solution to Problem 
     A chilling unit according to an embodiment of the present disclosure includes: a plurality of air heat exchangers each including a plurality of heat transfer tubes and a plurality of fins; and a machine room unit which is formed in the shape of an elongated box and on which the plurality of air heat exchangers are provided. The plurality of air heat exchangers each have a long-side portion that extends in a longitudinal direction of the machine room unit. The plurality of air heat exchangers include two pairs of air heat exchangers, the pairs of air heat exchangers are arranged side by side in the longitudinal direction, and the air heat exchangers of each of the pairs of air heat exchangers are opposite to each other in a lateral direction of the machine room unit. The air heat exchangers of each pair are inclined such that a spacing between upper end portions of the air heat exchangers that are located far from the machine room unit is greater than a spacing between lower end portions of the air heat exchangers that are located close to the machine room unit. In each pair, the long-side portion of at least one of the air heat exchangers has a heat-exchanger end portion that is located at one of unit end portions of the machine room unit in the longitudinal direction, and from the heat-exchanger end portion of the long-side portion of the at least one of the air heat exchangers, heat transfer tubes that protrude from an outermost one of the plurality of fins in a direction in which the plurality of fins are arranged and that extend linearly in the lateral direction do not extend. 
     Advantageous Effects of Invention 
     According to an embodiment of the present disclosure, in the chilling unit, the heat-exchanger end portion of the long-side portion of at least one air heat exchanger of a pair of air heat exchangers is provided at one of the unit end portions of the machine room unit in the longitudinal direction (X-axis direction). From the heat-exchanger end portion, heat transfer tubes that protrude from an outermost one of the fins in the direction where the fins are arranged and that extend linearly in the lateral direction (Y-axis direction) do not extend. Therefore, in the chilling unit, the heat transfer tubes of at least one of a pair of air heat exchangers provided in the lateral direction do not extend to cover the front side of the chilling unit. Thus, in the chilling unit, not both two systems of header pipes or not both distributors at a pair of air heat exchangers are disposed on the front side of the chilling unit where the worker enters the chilling unit. It is therefore possible to provide a sufficient space for the worker to enter the chilling unit on the front side of the chilling unit. The worker is thus able to easily enter and exit a space defined by air exchangers and corresponding to the heat exchange part of the chilling unit. The ease of maintenance of the chilling unit is improved. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a chilling unit according to Embodiment 1. 
         FIG. 2  is a side view of the chilling unit according to Embodiment 1. 
         FIG. 3  is a front view of the chilling unit according to Embodiment 1. 
         FIG. 4  is a conceptual diagram schematically illustrating a configuration of a machine room unit as illustrated in  FIG. 1 . 
         FIG. 5  is a plan view schematically illustrating an internal configuration of the machine room unit as illustrated in  FIG. 1 . 
         FIG. 6  is a schematic view illustrating the shapes and positions of air heat exchangers in the chilling unit according to Embodiment 1. 
         FIG. 7  is a schematic view illustrating a modification of the chilling unit according to Embodiment 1. 
         FIG. 8  is a schematic view illustrating the shapes and positions of air heat exchangers in a chilling unit according to a comparative example. 
         FIG. 9  is a schematic view illustrating the shapes and positions of air heat exchangers in a chilling unit according to Embodiment 2. 
         FIG. 10  is a schematic view illustrating a modification of the chilling unit according to Embodiment 2. 
         FIG. 11  is a schematic view illustrating the shapes and positions of air heat exchangers in a chilling unit according to Embodiment 3. 
         FIG. 12  is a schematic view illustrating a modification of the chilling unit according to Embodiment 3. 
         FIG. 13  is a schematic view illustrating the shapes and positions of air heat exchangers in a chilling unit according to Embodiment 4. 
         FIG. 14  is a schematic view illustrating a modification of the chilling unit according to Embodiment 4. 
         FIG. 15  is an enlarged view of an end portion of an air heat exchanger in a chilling unit according to Embodiment 5. 
         FIG. 16  is an enlarged view of an end portion of another air heat exchanger in the chilling unit according to Embodiment 5. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A chilling unit  100  according to each of embodiments will be described with reference to the drawings or other illustrations. In figures including  FIG. 1  that will be referred to below, the relative dimensions, shapes, and other features of various components may differ from actual ones. In each of the figures, components that are the same as or equivalent to a previous figure or previous figures are denoted by the same reference sings, and the same is true of the entire text of the specification. With respect to the embodiments, in order that they be easily understood, terms related to directions (such as “upper”, “lower”, “right”, “left”, front”, and “rear”) are used as appropriate. However, these terms are used only for explanation, that is, they do not limit the locations or orientations of devices or components. 
     Embodiment 1 
     [Chilling Unit  100 ] 
       FIG. 1  is a perspective view of the chilling unit  100  according to Embodiment 1.  FIG. 2  is a side view of the chilling unit  100  according to Embodiment 1.  FIG. 3  is a front view of the chilling unit  100  according to Embodiment 1. It should be noted that  FIG. 3  is a front view of the chilling unit  100  as seen in a direction indicated by an outlined in  FIG. 1 . An overview of the chilling unit  100  will be described with reference to  FIGS. 1 to 3 . In the figures including  FIG. 1 , the X-axis represents a longitudinal direction of the chilling unit  100 , the Y-axis represents a width direction or a lateral direction of the chilling unit  100 , and the Z-axis represents a height direction of the chilling unit  100 . The positional relationship between individual components (for example, their positional relationship in the height direction) described in the following description is basically a positional relationship between the components that is established when the chilling unit  100  is installed in a usable state. 
     The chilling unit  100  is used as a heat source apparatus of a chiller. The chilling unit  100  is supplied with a heat transfer fluid, such as water or antifreeze, from a load-side unit (not illustrated). The heat transfer fluid is cooled or heated in the chilling unit  100  and then supplied to the load-side unit. The chilling unit  100  causes the heat transfer fluid to circulate as described above, thereby supplying cooling energy or heating energy to the load-side unit. 
     The chilling unit  100  has an elongated shape. The chilling unit  100  includes an air heat exchanger  1 , a fan  5 , and a machine room unit  4  that form a heat-source-side refrigeration cycle circuit. 
     (Air Heat Exchanger  1 ) 
     The air heat exchanger  1  causes heat exchange to be performed between outside air and refrigerant that flows in the air heat exchanger  1 , and operates as an evaporator or a condenser. The air heat exchanger  1  includes a plurality of heat transfer tubes  7  and a plurality of fins  8 . The air heat exchanger  1  is, for example, a parallel-flow heat exchanger, and includes a pair of headers (not illustrated), the heat transfer tubes  7 , and the fins  8 . The heat transfer tubes  7  are, for example, aluminum flat tubes. The fins  8  are, for example, corrugated fins. The air heat exchanger  1  is not limited to a parallel-flow heat exchanger. The air heat exchanger  1  may be, for example, a fin-and-tube heat exchanger in which fins  8  each formed in the shape of a plate are arranged in parallel, and heat transfer tubes  7  penetrate the fins  8 . The air heat exchanger  1  includes four air heat exchangers  1  that are an air heat exchanger  1 A, an air heat exchanger  1 B, an air heat exchanger  1 C, and an air heat exchanger  1 D. The air heat exchanger  1 A corresponds to a first air heat exchanger the air heat exchanger  1 B corresponds to a second air heat exchanger; the air heat exchanger  1 C corresponds to a third air heat exchanger; and the air heat exchanger  1 D corresponds to a fourth air heat exchanger. 
     In the lateral direction (Y-axis direction) of the machine room unit  4 , the air heat exchanger  1 A and the air heat exchanger  1 B are provided opposite to each other. The air heat exchanger  1 A and the air heat exchanger  1 B are provided as a pair of air heat exchangers  1  and inclined such that an upper spacing SP 1 , which is the spacing between upper end portions  11   a  of the air heat exchangers  1 A and  1 B that are located far from the machine room unit  4 , is greater than a lower spacing SP 2 , which is the spacing between lower end portions  11   b  of the air heat exchangers  1 A and  1 B that are located close to the machine room unit  4 . That is, the air heat exchangers  1 A and  1 B are inclined such that the air heat exchangers  1 A and  1 B are V-shaped as illustrated in  FIG. 3  that is a front view, that is, as viewed in a direction toward the front of the chilling unit  100 . Similarly, in the lateral direction (Y-axis direction) of the machine room unit  4 , the air heat exchanger  1 C and the air heat exchanger  1 D are provided opposite to each other and inclined such that the air heat exchangers  1 C and  1 D are V-shaped. In Embodiment 1, the air heat exchanger  1 A is inclined at an inclination angle α of, for example, 65 to 80 degrees. Similarly, the air heat exchanger  1 B, the air heat exchanger  1 C, and the air heat exchanger  1 D, as well as the air heat exchanger  1 A, are each inclined at an inclination angle of 65 to 80 degrees. 
     A top frame  60  is provided above the air heat exchanger  1 A, the air heat exchanger  1 B, the air heat exchanger  1 C, and the air heat exchanger  1 D. The top frame  60  forms an upper wall of the chilling unit  100 . The top frame  60  is fixed to the machine room unit  4  by support posts  70 . The support posts  70  are disposed at opposite end portions of the chilling unit  100  in the longitudinal direction (X-axis direction). To be more specific, at each of the end portions of the chilling unit  100  in the longitudinal direction (X-axis direction), two support posts  70  are provided. The two support posts  70  are provided to extend in the vertical direction, and spaced apart from each other in the lateral direction (Y-axis direction). An upper end portion of each of the support posts  70  is fixed to the top frame  60 , and a lower end portion of each support post  70  is fixed to the machine room unit  4 . 
     In the lateral direction (Y-axis direction) of the chilling unit  100 , a side panel  50  is provided on one side of the chilling unit  100  such that the side panel  50  covers a space between the air heat exchanger  1 A and the air heat exchanger  1 C. The side panel  50  is a plate-like panel formed in a substantially rectangular shape. The side panel  50  extends in the vertical direction (Z-axis direction) and the longitudinal direction (X-axis direction). The side panel  50  is provided along the inclination of each air heat exchanger  1  described above. In the lateral direction (Y-axis direction) of the chilling unit  100 , another side panel  50  is provided on the other side of the chilling unit  100  such that the side panel  50  covers a space between the air heat exchanger  1 B and the air heat exchanger  1 D. 
     In the longitudinal direction (X-axis direction) of the chilling unit  100 , a side panel  51  is provided on the one side of the chilling unit  100  such that a side panel  51  covers the space between the air heat exchanger  1 A and the air heat exchanger  1 B. The side panel  51  is a plate-like panel formed in a substantially trapezoidal shape. The side panel  51  is formed such that an upper edge portion  51   a  of the side panel  51  is longer than a lower edge portion  51   b  of the side panel  51 . The side panel  51  extends in the vertical direction (Z-axis direction) and the lateral direction (Y-axis direction). The side panel  51  is provided such that in the longitudinal direction (X-axis direction) of the chilling unit  100 , the side panel  51  partially covers the end portions of the air heat exchanger  1 A and the air heat exchanger  1 B. In the longitudinal direction (X-axis direction) of the chilling unit  100 , another side panel  51  is also provided on the other side of the chilling unit  100  such that the side panel  51  covers the space between the air heat exchanger  1 C and the air heat exchanger  1 D. The side panel  51  is provided such that in the longitudinal direction (X-axis direction) of the chilling unit  100 , the side panel  51  partially covers the end portions of the air heat exchanger  1 C and the air heat exchanger  1 D. The shapes and positions of the air heat exchangers  1 , which are included in the features of the chilling unit  100  according to Embodiment 1, will be described later. 
     (Fan  5 ) 
     The top frame  60  is provided with the fan  5  described above. The fan  5  produces a flow of air that will pass through each of the air heat exchangers  1  and be discharged from an air outlet  14  of, for example, a bell mouth  6 A described later. The fan  5  is an air-sending unit provided with an axial fan. The fan  5  produces a flow of air for efficient heat exchange at each air heat exchanger  1 . The fan  5  includes four fans  5  that are a fan  5 A, a fan  5 B, a fan  5 C, and a fan  5 D. 
     At the top frame  60 , a bell mouth  6 A, a bell mouth  6 B, a bell mouth  6 C, and a bell mouth  6 D are provided. The fan  5 A, the fan  5 B, the fan  5 C, and the fan  5 D are provided inward of the bell mouth  6 A, the bell mouth  6 B, the bell mouth  6 C, and the bell mouth  6 D, respectively. 
     In upper end portions of the bell mouth  6 A, the bell mouth  6 B, the bell mouth  6 C, and the bell mouth  6 D, respective air outlets  14  are provided. The chilling unit  100  is a “top-flow type” chilling unit in which the blowing side of each fan  5  faces upward. At the air outlets  14  of the bell mouth  6 A, the bell mouth  6 B, the bell mouth  6 C, and the bell mouth  6 D, respective fan guards  17  are provided. The fan  5 A, the fan  5 B, the fan  5 C, and the fan  5 D are covered by the respective fan guards  17 . 
       FIG. 4  is a conceptual diagram schematically illustrating a configuration of the machine room unit  4  as illustrated in  FIG. 1 . In  FIGS. 1 and 4 , the space occupied by the machine room unit  4  is indicated by dotted lines. The configuration of the machine room unit  4  will be described with reference to  FIGS. 1 and 4 . The machine room unit  4  is formed in the shape of an elongated box, and is cuboid. The machine room unit  4  includes a cuboid frame  40  and side walls  45  that cover respective spaces between adjacent ones of frame elements included in the frame  40 . 
     The frame  40  includes the following frame elements: an underframe  41 , gateposts  42 , intermediate posts  43 , and a top beam  44 . The gateposts  42  include four gateposts  42  that are a gatepost  42 A, a gatepost  42 B, a gatepost  42 C, and a gatepost  42 D. The intermediate posts  43  include four intermediate posts  43  that are an intermediate post  43 A, an intermediate post  43 B, an intermediate post  43 C, and an intermediate post  43 D. The underframe  41  is rectangular as viewed in plan view, and forms bottom part of the frame  40 . 
     The gatepost  42 A, the gatepost  42 B, the gatepost  42 C, and the gatepost  42 D are provided at respective corners of the underframe  41  and extend in a direction orthogonal to the underframe  41 . The intermediate post  43 A and the intermediate post  43 B are provided between the gatepost  42 A and the gatepost  42 C and spaced from each other in the longitudinal direction (X-axis direction) of the underframe  41 . The intermediate post  43 C and the intermediate post  43 D are provided between the gatepost  42 B and the gatepost  42 D and spaced from each other in the longitudinal direction (X-axis direction) of the underframe  41 . The intermediate post  43 A, the intermediate post  43 B, the intermediate post  43 C, and the intermediate post  43 D extend in the direction orthogonal to the underframe  41 . The top beams  44  are provided above the gatepost  42 A, the gatepost  42 B, the gatepost  42 C, and the gatepost  42 D, as well as the intermediate post  43 A, the intermediate post  43 B, the intermediate post  43 C, and the intermediate post  43 D. The above configuration of the frame  40  is described above by way of example. The configuration of the above frame  40  is not limited to the above configuration, and the frame  40  may have any configuration as long as the machine room unit  4  is formed to have a cuboid shape. 
     A base  10  is provided on the top beam  44  of the machine room unit  4 . The base  10  is supported by the gateposts  42  and the intermediate posts  43 . The air heat exchanger  1 A, the air heat exchanger  1 B, the air heat exchanger  1 C, and the air heat exchanger  1 D as described above are provided on the base  10 . That is, the air heat exchangers  1  are provided on the top of the machine room unit  4 . Also, a drain pan  55  is provided on the top of the machine room unit  4 . The drain pan  55  receives droplets of water discharged from the air heat exchangers  1 . The drain pan  55  is provided below the air heat exchangers  1  to receive droplets of water that drips down from the air heat exchangers  1 . The drain pan  55  extends in the longitudinal direction (X-axis direction) of the machine room unit  4 . The drain pan  55  collects and guides the droplets of water that naturally drips down under gravity from the air heat exchangers  1 , as drain water, to a drain outlet (not illustrated). 
     The side walls  45  includes first side walls  45   a  provided at respective end portions of the machine room unit  4  that are located opposite to each other in the longitudinal direction (X-axis direction) and second side walls  45   b  provided at respective end portions of the machine room unit  4  that are located opposite to each other in the lateral direction (Y-axis direction). The first side walls  45   a  are plate-like side walls that extend in the vertical direction (Z-axis direction) and the lateral direction (Y-axis direction). One of the first side walls  45   a  is located to cover a space located between the gatepost  42 A and the gatepost  42 B, and the other first side wall  45   a  is located to cover a space located between the gatepost  42 C and the gatepost  42 D. The second side walls  45   b  are plate-like side walls that extend in the vertical direction (Z-axis direction) and the longitudinal direction (X-axis direction). Of the second side walls  45   b , second wide walls  45   b  located on one side cover a space located between the gatepost  42 A and the intermediate post  43 A, a space located between the intermediate post  43 A and the intermediate post  43 B, and a space located between the intermediate post  43 B and the gatepost  42 C, and second side walls  45   b  located on the other side cover a space located between the gatepost  42 B and the intermediate post  43 C, a space located between the intermediate post  43 C and the intermediate post  43 D, and a space located between the intermediate post  43 D and the gatepost  42 D. 
       FIG. 5  is a plan view schematically illustrating an internal configuration of the machine room unit  4  as illustrated in  FIG. 1 . The machine room unit  4  houses a compressor  31 , a flow switching device  33 , a heat exchanger  3 , and a pressure reducing device (not illustrated). The compressor  31 , the flow switching device  33 , the heat exchanger  3 , the pressure reducing device, and the air heat exchangers  1  are connected in series by refrigerant pipes to form a refrigerant circuit. A plurality of chilling units  100  include respective heat exchangers  3  that are connected in parallel by a water pipe, and a heat transfer fluid in the water pipe is circulated by a pump unit (not illustrated) to flow to a load-side unit (not illustrated) through the heat exchangers  3 . A plurality of devices installed in the machine room unit  4  include respective control boxes  32 . 
     The compressor  31  sucks low-temperature and low-pressure refrigerant, compresses the sucked low-temperature and low-pressure refrigerant into high-temperature and high-pressure refrigerant, and discharges the high-temperature and high-pressure refrigerant. The flow switching device  33  is, for example, a four-way valve, and switches, under control by a controller (not illustrated), the flows of refrigerant. The heat exchanger  3  causes heat exchange to be performed between refrigerant and a heat transfer fluid such as water or antifreeze. The pressure reducing device is, for example, an expansion valve, and reduces the pressure of refrigerant. The control box  32  houses, for example, a control board that controls the flow switching device  33 , a control board that controls the opening degree of the pressure reducing device or other conditions, an inverter board that controls the rotation speed of the compressor  31  or other conditions, etc. 
     The machine room unit  4  may include a heater  57 . In the case where the chilling unit  100  is operated in a cold area, it may present a question how to handle ice that remains on the drain pan  55 . However, in the case where the heater  57  is provided in the chilling unit  100 , when the chilling unit  100  is operated in the cold area, the heater  57  can melt ice that forms on the drain pan  55 , or prevent icing of drain water. Also, in the case where the machine room unit  4  includes the heater  57 , the heater  57  is provided close to one or some the air heat exchangers  1 . For example, the heater  57  is provided above the drain pan  55  in such a manner as to extend along the lower end portion  11   b  of one or some of the air heat exchangers  1  in the longitudinal direction (X-axis direction) of the machine room unit  4 . 
     [Shape and Position of Air Heat Exchanger  1 ] 
       FIG. 6  is a schematic view illustrating illustrates the shapes and positions of the air heat exchangers  1  in the chilling unit  100  according to Embodiment 1.  FIG. 6  is a top view of the chilling unit  100 , and schematically illustrates the shapes and positions of the air heat exchangers  1  as viewed in a direction from the top frame  60  toward the machine room unit  4 , with illustration of some components of the chilling unit  100  omitted. Arrows in  FIG. 6  indicate directions in which a worker enters the chilling unit  100 . 
     As illustrated in  FIG. 6 , as viewed in the direction orthogonal to the heat transfer tubes  7 , the air heat exchanger  1 A, the air heat exchanger  1 B, the air heat exchanger  1 C, and the air heat exchanger  1 D are each bent at 90 degrees at a location between a middle portion and one end portion of each heat transfer tube  7  in the extending direction thereof. That is, the air heat exchanger  1 A, the air heat exchanger  1 B, the air heat exchanger  1 C, and the air heat exchanger  1 D are each L-shaped as viewed in the direction from the top frame  60  toward the machine room unit  4 . 
     (Air Heat Exchanger  1 A) 
     The air heat exchanger  1 A has a long-side portion  1 AL, a corner portion  1 AE, and a short-side portion  1 AS. The long-side portion  1 AL is a portion of the air heat exchanger  1 A that is longer than the short-side portion  1 AS in flow passages in associated heat transfer tubes  7 . A heat-exchanger end portion  1 AT is an end portion of the long-side portion  1 AL and is also an end portion of the air heat exchanger  1 A in the longitudinal direction (X-axis direction) of the machine room unit  4 . The corner portion  1 AE is an L-shaped portion of the air heat exchanger  1 A. The corner portion  1 AE is a first corner portion located between the long-side portion  1 AL and the short-side portion  1 AS. The short-side portion  1 AS is a portion of the air heat exchanger  1 A that is shorter than the long-side portion  1 AL in the direction in which the heat transfer tubes  7  extend. 
     The above heat transfer tubes  7  protrude from an end portion of the short-side portion  1 AS of the air heat exchanger  1 A. The heat transfer tubes  7  protruding from the end portion of the short-side portion  1 AS do not penetrate the fins  8  and are exposed to the outside. The heat transfer tubes  7  protruding from the end portion of the short-side portion  1 AS are linearly formed. Regarding the heat transfer tubes  7  protruding from the end portion of the short-side portion  1 AS, an end portion of one of the heat transfer tubes  7  that is an end portion corresponding to the inlet for refrigerant is connected with a header pipe  12 , and an end portion of another one of heat transfer tubes  7  that is an end portion corresponding to the outlet for refrigerant is connected with a header pipe  13 . One of the header pipe  12  and the header pipe  13  may not be a header pipe but may be a distributor. 
     (Air Heat Exchanger  1 B) 
     The air heat exchanger  1 B has a long-side portion  1 BL, a corner portion  1 BE, and a short-side portion  1 BS. The long-side portion  1 BL is a portion of the air heat exchanger  1 B that is longer than the short-side portion  1 BS in the direction in which associated heat transfer tubes  7  extend. A heat-exchanger end portion  1 BT is an end portion of the long-side portion  1 BL and is also an end portion of the air heat exchanger  1 B in the longitudinal direction (X-axis direction) of the machine room unit  4 . The corner portion  1 BE is an L-shaped portion of the air heat exchanger  1 B. The corner portion  1 BE is a second corner portion located between the long-side portion  1 BL and the short-side portion  1 BS. The short-side portion  1 BS is a portion of the air heat exchanger  1 B that is shorter than the long-side portion  1 BL in the direction in which the heat transfer tubes  7  extend. 
     The above heat transfer tubes  7  protrude from an end portion of the short-side portion  1 BS of the air heat exchanger  1 B. The heat transfer tubes  7  protruding from the end portion of the short-side portion  1 BS do not penetrate the fins  8  and are exposed to the outside. The heat transfer tubes  7  protruding from the end portion of the short-side portion  1 BS are linearly formed. Regarding the heat transfer tubes  7  protruding from an end portion of the short-side portion  1 BS, an end portion of one of the heat transfer tubes  7  that is an end portion corresponding to the inlet for refrigerant is connected with the header pipe  12 , and an end portion of another one of the heat transfer tubes  7  that is an end portion corresponding to the outlet for refrigerant is connected with the header pipe  13 . One of the header pipe  12  and the header pipe  13  may not be a header pipe but may be a distributor. 
     (Air Heat Exchanger  1 C) 
     The air heat exchanger  1 C has a long-side portion  1 CL, a corner portion  1 CE, and a short-side portion  1 CS. The long-side portion  1 CL is a portion of the air heat exchanger  1 C that is longer than the short-side portion  1 CS in the direction in which the heat transfer tubes  7  extend. A heat-exchanger end portion  1 CT is an end portion of the long-side portion  1 CL and is also an end portion of the air heat exchanger  1 C in the longitudinal direction (X-axis direction) of the machine room unit  4 . The corner portion  1 CE is an L-shaped portion of the air heat exchanger  1 C. The corner portion  1 CE is a third corner portion located between the long-side portion  1 CL and the short-side portion  1 CS. The short-side portion  1 CS is a portion of the air heat exchanger  1 C that is shorter than the long-side portion  1 CL in the direction in which the heat transfer tubes  7  extend. 
     The above heat transfer tubes  7  protrude from an end portion of the short-side portion  1 CS of the air heat exchanger  1 C. The heat transfer tubes  7  protruding from the end portion of the short-side portion  1 CS do not penetrate the fins  8  and are exposed to the outside. The heat transfer tubes  7  protruding from the end portion of the short-side portion  1 CS are linearly formed. Regarding the heat transfer tubes  7  protruding from the end portion of the short-side portion  1 CS, an end portion of one of the heat transfer tubes  7  that is an end portion corresponding to the inlet for refrigerant is connected with the header pipe  12 , and an end portion of another one of the heat transfer tubes  7  that is an end portion corresponding to the outlet for refrigerant is connected with the header pipe  13 . One of the header pipe  12  and the header pipe  13  may not be a header pipe but may be a distributor. 
     (Air Heat Exchanger  1 D) 
     The air heat exchanger  1 D has a long-side portion  1 DL, a corner portion  1 DE, and a short-side portion  1 DS. The long-side portion  1 DL is a portion of the air heat exchanger  1 D that is longer than the short-side portion  1 DS in the direction in which the heat transfer tubes  7  extend. A heat-exchanger end portion  1 DT is an end portion of the long-side portion  1 DL and is also an end portion of the air heat exchanger  1 D in the longitudinal direction (X-axis direction) of the machine room unit  4 . The corner portion  1 DE is an L-shaped portion of the air heat exchanger  1 D. The corner portion  1 DE is a fourth corner portion located between the long-side portion  1 DL and the short-side portion  1 DS. The short-side portion  1 DS is a portion of the air heat exchanger  1 D that is shorter than the long-side portion  1 DL in the direction in which the heat transfer tubes  7  extend. 
     The above heat transfer tubes  7  protrude from an end portion of the short-side portion  1 DS of the air heat exchanger  1 D. The heat transfer tubes  7  protruding from the end portion of the short-side portion  1 DS do not penetrate the fins  8  and are exposed to the outside. The heat transfer tubes  7  protruding from the end portion of the short-side portion  1 DS are linearly formed. Regarding the heat transfer tubes  7  protruding from the end portion of the short-side portion  1 DS, an end portion of one of the heat transfer tubes  7  that is end end portion corresponding to the inlet for refrigerant is connected with the header pipe  12 , and an end portion of another one of the heat transfer tubes  7  that is an end portion corresponding to the outlet for refrigerant is connected with the header pipe  13 . One of the header pipe  12  and the header pipe  13  may not be a header pipe but may be a distributor. 
     (Air Heat Exchanger  1 A and Air Heat Exchanger  1 B) 
     The air heat exchanger  1 A and the air heat exchanger  1 B are opposite to each other in the lateral direction (Y-axis direction) of the machine room unit  4 . More specifically, in the lateral direction (Y-axis direction) of the machine room unit  4 , an end portion of the short-side portion  1 AS of the air heat exchanger  1 A is opposite to an end portion of the long-side portion  1 BL of the air heat exchanger  1 B, and an end portion of the short-side portion  1 BS of the air heat exchanger  1 B is opposite to an end portion of the long-side portion  1 AL of the air heat exchanger  1 A. The air heat exchanger  1 A and the air heat exchanger  1 B are arranged symmetrical with respect to a point. 
     In the longitudinal direction (X-axis direction) of the machine room unit  4 , the end portion of the short-side portion  1 AS of the air heat exchanger  1 A is located close to a unit end portion  4 D of the chilling unit  100 , and the end portion of the short-side portion  1 BS of the air heat exchanger  1 B is located close to a middle portion  4 C of the chilling unit  100 . The header pipe  12  and the header pipe  13  connected to the air heat exchanger  1 A are located close to the unit end portion  4 D of the chilling unit  100 , and the header pipe  12  and the header pipe  13  connected to the air heat exchanger  1 B are located close to the middle portion  4 C of the chilling unit  100 . The longitudinal direction (X-axis direction) of the chilling unit  100  is the same as that of the machine room unit  4 . In the longitudinal direction (X-axis direction), the middle portion  4 C of the chilling unit  100  is located at the same position as a portion of the machine room unit  4  that is included in the middle portion  4 C. Likewise, in the longitudinal direction (X-axis direction), the unit end portion  4 D of the chilling unit  100  is located at the same position as a portion of the machine room unit  4  that is included in the unit end portion  4 D. 
     The long-side portion  1 AL of the air heat exchanger  1 A is parallel to the long-side portion  1 BL of the air heat exchanger  1 B in the longitudinal direction (X-axis direction) of the machine room unit  4 . In the longitudinal direction (X-axis direction) of the machine room unit  4 , the heat-exchanger end portion  1 AT of the long-side portion  1 AL of the air heat exchanger  1 A is located close to the middle portion  4 C of the chilling unit  100 . In the longitudinal direction (X-axis direction) of the machine room unit  4 , the heat-exchanger end portion  1 BT of the long-side portion  1 BL of the air heat exchanger  1 B is located close to the unit end portion  4 D of the chilling unit  100 . 
     The air heat exchanger  1 A and the air heat exchanger  1 B are L-shaped and the orientations of the short-side portion  1 AS and the long-side portion  1 AL of the air heat exchanger  1 A are reverse to those of the short-side portion  1 BS and the long-side portion  1 BL of the air heat exchanger  1 B in the longitudinal direction (X-axis direction) of the machine room unit. Accordingly, the air heat exchanger  1 A and the air heat exchanger  1 B are arranged in the shape of a quadrangle in a horizontal plane. That is, the air heat exchanger  1 A and the air heat exchanger  1 B, which are a pair of air heat exchangers  1 , are arranged in the shape of a quadrangle as viewed in plan view. 
     (Air Heat Exchanger  1 C and Air Heat Exchanger  1 D) 
     The air heat exchanger  1 C and the air heat exchanger  1 D are opposite to each other in the lateral direction (Y-axis direction) of the machine room unit  4 . More specifically, in the lateral direction (Y-axis direction) of the machine room unit  4 , the end portion of the short-side portion  1 CS of the air heat exchanger  1 C is located opposite to the end portion of the long-side portion  1 DL of the air heat exchanger  1 D, and the end portion of the short-side portion  1 DS of the air heat exchanger  1 D is located opposite to the end portion of the long-side portion  1 CL of the air heat exchanger  1 C. The air heat exchanger  1 C and the air heat exchanger  1 D are arranged symmetrical with respect to a point. 
     In the longitudinal direction (X-axis direction) of the machine room unit  4 , the end portion of the short-side portion  1 CS of the air heat exchanger  1 C is located close to another unit end portion  4 D of the chilling unit  100 , and the end portion of the short-side portion  1 DS of the air heat exchanger  1 D is located close to the middle portion  4 C of the chilling unit  100 . The header pipe  12  and the header pipe  13  connected to the air heat exchanger  1 C are located close to the above unit end portion  4 D of the chilling unit  100 , and the header pipe  12  and the header pipe  13  connected to the air heat exchanger  1 D are located close to the middle portion  4 C of the chilling unit  100 . 
     The long-side portion  1 CL of the air heat exchanger  1 C is parallel to the long-side portion  1 DL of the air heat exchanger  1 D in the longitudinal direction (X-axis direction) of the machine room unit  4 . In the longitudinal direction (X-axis direction) of the machine room unit  4 , the heat-exchanger end portion  1 CT of the long-side portion  1 CL of the air heat exchanger  1 C is located close to the middle portion  4 C of the chilling unit  100 . In the longitudinal direction (X-axis direction) of the machine room unit  4 , the heat-exchanger end portion  1 DT of the long-side portion  1 DL of the air heat exchanger  1 D is located close to the unit end portion  4 D of the chilling unit  100 . 
     The air heat exchanger  1 C and the air heat exchanger  1 D are L-shaped and the orientations of the short-side portion  1 CS and the long-side portion  1 CL of the air heat exchanger  1 C are reverse to the short-side portion  1 DS and the long-side portion  1 DL of the air heat exchanger  1 D in the longitudinal direction (X-axis direction) of the machine room unit. Thus, the air heat exchanger  1 C and the air heat exchanger  1 D are arranged in the shape of a quadrangle in the horizontal plane. That is, the air heat exchanger  1 C and the air heat exchanger  1 D, which are a pair of air heat exchangers  1 , are arranged in the shape of a quadrangle as viewed in plan view. 
     (Overall Configuration of Air Heat Exchangers  1 ) 
     The air heat exchanger  1 A and the air heat exchanger  1 B, which are a pair of heat exchangers  1 , and the air heat exchanger  1 C and the air heat exchanger  1 D, which are another pair of heat exchangers  1 , are arranged symmetrical with respect to the middle portion of the chilling unit  100  in the longitudinal direction (X-axis direction). The air heat exchanger  1 A and the air heat exchanger  1 C are arranged symmetrical with respect to the middle portion of the chilling unit  100  in the longitudinal direction (X-axis direction). The air heat exchanger  1 B and the air heat exchanger  1 D are arranged symmetrical with respect to the middle portion of the chilling unit  100  in the longitudinal direction (X-axis direction). 
     In the air heat exchanger  1 B, which is at least one air heat exchanger  1  of a pair of air heat exchangers  1  provided in the lateral direction of the machine room unit  4 , the heat-exchanger end portion  1 BT of the long-side portion  1 BL is located at an end portion of the machine room unit  4  in the longitudinal direction. In the air heat exchanger  1 D, which is at least one air heat exchanger  1  of a pair of air heat exchangers  1  provided in the lateral direction of the machine room unit  4 , the heat-exchanger end portion  1 DT of the long-side portion  1 DL is located at another end portion of the machine room unit  4  in the longitudinal direction. The above two pairs of air heat exchangers  1  are arranged side by side in the longitudinal direction (X-axis direction) of the machine room unit  4 . That is, the pair of air heat exchangers  1 A and  1 B and the pair of air heat exchangers  1 C and  1 D are arranged side by side in the longitudinal direction (X-axis direction) of the machine room unit  4 . 
     In the longitudinal direction of the machine room unit  4 , the corner portion  1 AE that is the first corner portion is located close to the unit end portion  4 D that is one end portion of the machine room unit  4 , and the corner portion  1 BE that is the second corner portion is located close to the middle portion  4 C of the machine room unit  4 . The air heat exchanger  1 A and the air heat exchanger  1 B are arranged in the shape of a quadrangle in the horizontal plane. In the longitudinal direction of the machine room unit  4 , the corner portion  1 CE that is the third corner portion is located close to the unit end portion  4 D that is the other end portion of the machine room unit  4 , and the corner portion  1 DE that is the fourth corner portion is located close to the middle portion  4 C of the machine room unit  4 . The air heat exchanger  1 C and the air heat exchanger  1 D are arranged in the shape of a quadrangle in the horizontal plane. From each of the heat-exchanger end portion  1 BT and the heat-exchanger end portion  1 DT, heat transfer tubes  7  do not extend. That is, heat transfer tubes  7  that protrude from a fin  8  corresponding to an outermost one of the fins  8  in a direction where the fins  8  are arranged and that extend linearly in the lateral direction (Y-axis direction) do not extend from each of the heat-exchanger end portions  1 BT and  1 DT. 
     (Partition Plate  15 ) 
       FIG. 7  is a schematic view illustrating a modification of the chilling unit  100  according to Embodiment 1. The chilling unit  100  according to the modification includes a partition plate  15 . The partition plate  15  forms a wall that isolates the air heat exchangers  1 A and  1 B from the air heat exchangers  1 C and  1 D in the longitudinal direction (X-axis direction) of the chilling unit  100 . That is, the partition plate  15  is provided between two pairs of air heat exchangers  1  arranged side by side in the longitudinal direction (X-axis direction), and defines a wall. The partition plate  15  is located between the air heat exchangers  1 A and  1 B and the air heat exchangers  1 C and  1 D. Also, the partition plate  15  is provided at a center position of each of the machine room unit  4  and the chilling unit  100  in the longitudinal direction (X-axis direction). The “center position” means not only the center position of each of the machine room unit  4  and the chilling unit  100  in the longitudinal direction (X-axis direction) but also a substantially center position close to the center position. 
     As described above, at one end portion of the chilling unit  100  in the longitudinal direction (X-axis direction), one of the side panels  51  is provided to close the space between the air heat exchanger  1 A and the air heat exchanger  1 B. Likewise, at the other end portion of the chilling unit  100  in the longitudinal direction (X-axis direction), the other side panel  51  is provided to close the space between the air heat exchanger  1 C and the air heat exchanger  1 D. Furthermore, one of the side panels  50  is provided to close the space between the air heat exchanger  1 A and the air heat exchanger  1 C. Likewise, the other side panel  50  is provided to close the space between the air heat exchanger  1 B and the air heat exchanger  1 D. The partition plate  15  forms a wall that extends between the above side panels  50 , that is, the side panel  50  provided between the air heat exchanger  1 A and the air heat exchanger  1 C and the side panel  50  provided between the air heat exchanger  1 B and the air heat exchanger  1 D. 
     In the chilling unit  100  of the modification, a first space SA and a second space SB are divided spaces provided by the partition plate  15 . The partition plate  15  isolates the first space SA and the second space SB from each other, and the first space SA being defined by one pair of air heat exchangers  1 , the second space SB being defined by the other pair of air heat exchangers  1 . To be more specific, the first space SA is defined by the air heat exchanger  1 A, the air heat exchanger  1 B, the side panel  50 , the side panel  51 , and the partition plate  15 . The second space SB is defined by the air heat exchanger  1 C, the air heat exchanger  1 D, the side panel  50 , the side panel  51 , and the partition plate  15 . In the chilling unit  100  according to the modification, the first space SA and the second space SB are isolated from each other by the partition plate  15  as described above. As a result, the air heat exchangers  1 A and  1 B provided as the above one pair and the air heat exchangers  1 C and  1 D provided as the above other pair can be operated in different operation modes. 
     [Operation of Chilling Unit  100 ] 
     In the chilling unit  100 , outside air is caused by the fans  5  to pass through the air heat exchangers  1 , whereby the outside air exchanges heat with refrigerant that flows in the air heat exchangers  1 . The air that has exchanged heat with the refrigerant is discharged by the fans  5  from the top of the chilling unit  100 . In the chilling unit  100 , by a switching operation of the flow switching device  33 , the operation is switched between a cooling operation in which one or some of the air heat exchangers  1  operate as condensers and the heat exchanger  3  operates as an evaporator and a heating operation in which the air heat exchangers  1  operate as evaporators and the heat exchanger  3  operates as a condenser. In the cooling operation, a heat transfer fluid cooled at the heat exchanger  3  is provided, and for example, the cooled heat transfer fluid is supplied to the load-side unit (not illustrated) to cool air in a load side (indoor side), thereby cooling the indoor space. In the heating operation, a heat transfer fluid heated at the heat exchanger  3  is provided, and for example, the heated heat transfer fluid is supplied to the load-side unit (not illustrated) to heat air in the load side (indoor side), thereby heating the indoor space. 
     [Advantages of Chilling Unit  100 ] 
     In the chilling unit  100 , the heat-exchanger end portion  1 BT of the long-side portion  1 BL of at least one air heat exchanger  1  of a pair of air heat exchangers  1  and the heat-exchanger end portion  1 DT of the long-side portion  1 DL of at least one air heat exchanger  1  of a pair of air heat exchangers  1  are provided at the respective unit end portions  4 D of the machine room unit  4 , which are located as the end portions thereof in the longitudinal direction. From each of the heat-exchanger end portion  1 BT and the heat-exchanger end portion  1 DT, heat transfer tubes  7  do not extend. That is, heat transfer tubes  7  that protrude from a fin  8  corresponding to the outermost one of the fins  8  in a direction where the fins  8  are arranged and that extend linearly in the lateral direction (Y-axis direction) extend from each of the heat-exchanger end portions  1 BT and  1 DT. Therefore, in the chilling unit  100 , the heat transfer tubes  7  at at least one of a pair of air heat exchangers  1  arranged in the lateral direction do not extend to cover the front side of the chilling unit  100 . Thus, in the chilling unit  100 , not both two systems of header pipes  12  and  13  at a pair of heat exchangers  1  or not both distributors at the pair of air heat exchangers  1  are provided on the front side of the chilling unit where the worker enters the chilling unit. It is therefore possible to provide a sufficient space for the worker to enter the chilling unit  100 , on the front side of the chilling unit  100 . The worker is thus able to easily enter and exit the space defined by the air exchangers. Accordingly, the ease of maintenance of the chilling unit  100  is improved. 
     Furthermore, even in the case where heat transfer tubes  7  are provided to extend from the end portions of the long-side portion  1 BL and the long-side portion  1 DL, in general, the heat transfer tubes  7  are provided to extend to extensions of the long-side portion  1 BL and the long-side portion  1 DL, and header pipes  12  and  13  are provided at the heat transfer tubes  7 . Thus, in the chilling unit  100 , not both the two systems of header pipes  12  and  13  at a pair of heat exchangers  1  are provided on the front side of the chilling unit where the worker enters the chilling unit. It is therefore possible to provide a sufficient space for the worker to enter the chilling unit  100 , on the front side of the chilling unit  100 . The worker is thus able to easily enter and exit the space defined by the air exchangers. Accordingly, the ease of maintenance of the chilling unit  100  is improved. 
       FIG. 8  is a schematic view illustrating the shapes and positions of air heat exchangers  1  in the chilling unit  100 L of a comparative example. As illustrated in  FIG. 8 , as viewed in a direction orthogonal to the heat transfer tubes  7 , the air heat exchanger  1 A, the air heat exchanger  1 B, the air heat exchanger  1 C, and the air heat exchanger  1 D are each bent at 90 degrees at a location between the middle portion of an associated heat transfer tube  7  and one end portion of the heat transfer tube that is located at an end thereof in the longitudinal direction. That is, the air heat exchanger  1 A, the air heat exchanger  1 B, the air heat exchanger  1 C, and the air heat exchanger  1 D are L-shaped. The air heat exchanger  1 A and the air heat exchanger  1 B are opposite to each other in the lateral direction of the machine room unit  4 , and the air heat exchanger  1 C and the air heat exchanger  1 D are opposite to each other in the lateral direction of the machine room unit  4 . The air heat exchanger  1 A and the air heat exchanger  1 C are arranged side by side in the longitudinal direction of the machine room unit  4 , and the air heat exchanger  1 B and the air heat exchanger  1 D are arranged side by side in the longitudinal direction of the machine room unit  4 . Furthermore, the short-side portion  1 AS of the air heat exchanger  1 A is opposite to the short-side portion  1 BS of the air heat exchanger  1 B in the lateral direction of the machine room unit  4 , and the short-side portion  1 CS of the air heat exchanger  1 C is opposite to the short-side portion  1 DS of the air heat exchanger  1 D in the lateral direction of the machine room unit  4 . The long-side portion  1 AL of the air heat exchanger  1 A and the long-side portion  1 CL of the air heat exchanger  1 C are arranged side by side in the longitudinal direction of the machine room unit  4 , and the long-side portion  1 BL of the air heat exchanger  1 B and the long-side portion  1 DL of the air heat exchanger  1 D are arranged side by side in the longitudinal direction of the machine room unit  4 . Therefore, the air heat exchanger  1 A, the air heat exchanger  1 B, the air heat exchanger  1 C, and the air heat exchanger  1 D form a frame that is rectangular as a whole. The corner portion  1 AE of the air heat exchanger  1 A, the corner portion  1 BE of the air heat exchanger  1 B, the corner portion  1 CE of the air heat exchanger  1 C, and the corner portion  1 DE of the air heat exchanger  1 D, which are corner portions bent at 90 degrees, are located at the corners of the rectangular frame. 
     In the chilling unit  100 L of the comparative example, the end portion of each of the long-side portions of a pair of air heat exchangers  1  is not located at the end portion of the machine room unit  4  in the longitudinal direction. In the chilling unit  100 L, the heat transfer tubes  7  of the air heat exchangers  1  each having an L-shaped bent portion in the longitudinal end portion and arranged as a pair of air heat exchangers in the lateral direction extend in such a manner as to cover the front side of the chilling unit  100 L. Furthermore, in the chilling unit  100 L, two systems of header pipes  12  or distributors of a pair of air heat exchangers  1  are provided on the front side of the chilling unit  100 L where the worker enters the chilling unit  100 L. Therefore, the worker does not easily enter or exit the space defined by the air heat exchangers  1 , and maintenance is not easily performed on the chilling unit  100 L. 
     By contrast, in the chilling unit  100  according to Embodiment 1, the heat-exchanger end portion  1 BT of the long-side portion  1 BL of at least one of a pair of air heat exchangers  1  and the heat-exchanger end portion  1 DT of the long-side portion  1 DL of at least one of another pair of heat exchangers  1  re provided at the respective end portions of the machine room unit  4  in the longitudinal direction. It is therefore possible to provide a sufficient space for the worker to enter the chilling unit  100  on the front side of the chilling unit  100 . The worker is thus able to easily enter and exit the space defined by the air exchangers. The ease of maintenance of the chilling unit  100  can be improved. 
     Of two pairs of air heat exchangers  1 , one pair of air heat exchangers  1  includes the air heat exchanger  1 A having the corner portion  1 AE that is the L-shaped first corner portion and the air heat exchanger  1 B having the corner portion  1 BE that is the L-shaped second corner portion. Of the two pairs of air heat exchangers  1 , the other pair of air heat exchangers  1  includes the air heat exchanger  1 C having the corner portion  1 CE that is the L-shaped third corner portion and the air heat exchanger  1 D having the corner portion  1 DE that is the L-shaped fourth corner portion. Since all the air heat exchangers  1  each the above configuration have the corner portions such as the corner portion  1 AE, it is also possible to increase the area of heat exchange part where heat exchange is performed between air and refrigerant, in the lateral direction (Y-axis direction), and thus to improve the heat exchange performance of the chilling unit  100 . 
     In the longitudinal direction of the machine room unit  4 , the corner portion  1 AE that is the first corner portion is located close to the unit end portion  4 D corresponding to one end portion of the machine room unit  4 , and the corner portion  1 BE that is the second corner portion is located close to the middle portion  4 C of the machine room unit  4 . The air heat exchanger  1 A and the air heat exchanger  1 B are arranged in the shape of a quadrangle in the horizontal plane. In the longitudinal direction of the machine room unit  4 , the corner portion  1 CE that is the third corner portion is located close to the unit end portion  4 D corresponding to the other end portion of the machine room unit  4 , and the corner portion  1 DE that is the fourth corner portion is located close to the middle portion  4 C of the machine room unit  4 . The air heat exchanger  1 C and the air heat exchanger  1 D are arranged in the shape of a quadrangle in the horizontal plane. Thus, in the chilling unit  100 , not both the two systems of header pipes  12  and  13  at a pair of heat exchangers  1  are provided on the front side of the chilling unit where the worker enters the chilling unit. It is therefore possible to provide a sufficient space for the worker to enter the chilling unit  100  on the front side of the chilling unit  100 . The worker is thus able to easily enter and exit the space defined by the air exchangers. Accordingly, the ease of maintenance of the chilling unit  100  is improved. 
     The air heat exchangers  1 A and  1 B provided as one pair and the air heat exchangers  1 C and  1 D provided as another pair are arranged symmetrical with respect to the middle portion of the chilling unit  100  in the longitudinal direction (X-axis direction). Thus, in the chilling unit  100 , not both the two systems of header pipes  12  and  13  at a pair of air heat exchangers  1  are provided on the front side of the chilling unit where the worker enters the chilling unit. It is therefore possible to provide a sufficient space for the worker to enter the chilling unit  100  on the front side of the chilling unit  100 . The worker is thus able to easily enter and exit the space defined by the air exchangers. Accordingly, the ease of maintenance of the chilling unit  100  is improved. 
     In addition, in the chilling unit  100 , the first space SA and the second space SB are divided spaces provided by the partition plate  15 . As a result, the air heat exchangers  1 A and  1 B provided as one pair and the air heat exchangers  1 C and  1 D provided as another pair can be operated in different operation modes. In the chilling unit  100 , since the air heat exchangers  1  located in the first space SA and the air heat exchangers  1  located in the second space SB are operated in different operation modes, for example, two systems can individually perform respective defrost operations. Therefore, the chilling unit  100  can reduce a decrease in water temperature, as compared with the case where only the defrost operation can be performed, that is, the systems cannot perform different operations at the same time. 
     Embodiment 2 
     [Configuration of Chilling Unit  100 A] 
       FIG. 9  is a schematic view illustrating the shapes and positions of the air heat exchangers  1  in a chilling unit  100 A according to Embodiment 2.  FIG. 9  is a top view of the chilling unit  100 A, with illustration of some components omitted, and schematically illustrates the shapes and positions of the air heat exchangers  1  as viewed in the direction from the top frame  60  toward the machine room unit  4 . It should be noted that regarding Embodiment 2, components that are the same as those of the chilling unit  100  as illustrated in  FIGS. 1 to 7  are denoted by the same reference signs, and their descriptions will thus be omitted. The chilling unit  100 A according to Embodiment 2 differs from the chilling unit  100  according to Embodiment 1 in the shapes and positions of the air heat exchangers  1 . The chilling unit  100 A will be describe by referring mainly to the differences between the air heat exchangers  1  according to Embodiment 1 and those according to Embodiment 2, and illustration and descriptions of configurations other than configurations related to the differences will be omitted. 
     As illustrated in  FIG. 9 , the air heat exchanger  1 A, the air heat exchanger  1 B, the air heat exchanger  1 C, and the air heat exchanger  1 D are each formed in the shape of a flat plate. That is, the air heat exchanger  1 A, the air heat exchanger  1 B, the air heat exchanger  1 C, and the air heat exchanger  1 D are each I-shaped as viewed in the direction orthogonal to the heat transfer tubes  7 . 
     (Air Heat Exchangers  1 A to  1 D) 
     The air heat exchanger  1 A has the long-side portion  1 AL. The long-side portion  1 AL is a portion of the air heat exchanger  1 A that is elongated in the direction in which the associated heat transfer tubes  7  extend. The long-side portion  1 AL has the heat-exchanger end portion  1 AT. The air heat exchanger  1 B has the long-side portion  1 BL. The long-side portion  1 BL is a portion of the air heat exchanger  1 B that is elongated in the direction in which the associated heat transfer tubes  7  extend. The long-side portion  1 BL has the heat-exchanger end portion  1 BT. The air heat exchanger  1 C has the long-side portion  1 CL. The long-side portion  1 CL is a portion of the air heat exchanger  1 C that is elongated in the direction in which the associated heat transfer tubes  7  extend. The long-side portion  1 CL has the heat-exchanger end portion  1 CT. The air heat exchanger  1 D has the long-side portion  1 DL. The long-side portion  1 DL is a portion of the air heat exchanger  1 D that is elongated in the direction in which associated heat transfer tubes  7  extend. The long-side portion  1 DL has the heat-exchanger end portion  1 DT. The air heat exchanger  1 A, the air heat exchanger  1 B, the air heat exchanger  1 C, and the air heat exchanger  1 D are each formed such that the associated heat transfer tubes  7  extend in the longitudinal direction (X-axis direction). The air heat exchanger  1 A, the air heat exchanger  1 B, the air heat exchanger  1 C, and the air heat exchanger  1 D are each connected with the associated header pipes  12  and  13  at the end portion of each air heat exchanger in the direction in which the associated heat transfer tubes  7  extend. 
     (Air Heat Exchanger  1 A and Air Heat Exchanger  1 B) 
     The air heat exchanger  1 A and the air heat exchanger  1 B are opposite to each other in the lateral direction (Y-axis direction) of the machine room unit  4 . The long-side portion  1 AL of the air heat exchanger  1 A is parallel to the long-side portion  1 BL of the air heat exchanger  1 B in the longitudinal direction (X-axis direction) of the machine room unit  4 . In the longitudinal direction (X-axis direction) of the machine room unit  4 , the heat-exchanger end portion  1 AT of the long-side portion  1 AL of the air heat exchanger  1 A is located close to the associated unit end portion  4 D of the chilling unit  100 A. In the longitudinal direction (X-axis direction) of the machine room unit  4 , one heat-exchanger end portion  1 BT of the long-side portion  1 BL of the air heat exchanger  1 B is located close to the unit end portion  4 D of the chilling unit  100 A. 
     (Air Heat Exchanger  1 C and Air Heat Exchanger  1 D) 
     The air heat exchanger  1 C and the air heat exchanger  1 D are opposite to each other in the lateral direction (Y-axis direction) of the machine room unit  4 . The long-side portion  1 CL of the air heat exchanger  1 C is parallel to the long-side portion  1 DL of the air heat exchanger  1 D in the longitudinal direction (X-axis direction) of the machine room unit  4 . In the longitudinal direction (X-axis direction) of the machine room unit  4 , one heat-exchanger end portion  1 CT of the long-side portion  1 CL of the air heat exchanger  1 C is located close to the associated unit end portion  4 D of the chilling unit  100 A. In the longitudinal direction (X-axis direction) of the machine room unit  4 , the heat-exchanger end portion  1 DT of the long-side portion  1 DL of the air heat exchanger  1 D is located close to the unit end portion  4 D of the chilling unit  100 A. 
     (Overall Configuration of Air Heat Exchangers  1 ) 
     The air heat exchangers  1 A and  1 B provided as one pair and the air heat exchangers  1 C and  1 D provided as another pair are arranged symmetrical with respect to the middle portion of the chilling unit  100 A in the longitudinal direction (X-axis direction). The air heat exchanger  1 A and the air heat exchanger  1 C are arranged symmetrical the middle portion of the chilling unit  100 A in the longitudinal direction (X-axis direction). The air heat exchanger  1 B and the air heat exchanger  1 D are arranged symmetrical with respect to the middle portion of the chilling unit  100 A in the longitudinal direction (X-axis direction). 
     In a pair of air heat exchangers  1  arranged in the lateral direction (Y-axis direction) of the machine room unit  4 , the heat-exchanger end portion  1 AT of the long-side portion  1 AL is located close to the associated unit end portion  4 D of the machine room unit  4  in the longitudinal direction (X-axis direction). In the pair of air heat exchangers  1  arranged in the lateral direction of the machine room unit  4 , the heat-exchanger end portion  1 BT of the long-side portion  1 BL is located close to the unit end portion  4 D of the machine room unit  4  in the longitudinal direction (X-axis direction). In another pair of air heat exchangers  1  arranged in the lateral direction of the machine room unit  4 , the heat-exchanger end portion  1 CT of the long-side portion  1 CL is provided close to the associated unit end portion  4 D of the machine room unit  4  in the longitudinal direction (X-axis direction). In the other pair of air heat exchangers  1  arranged in the lateral direction of the machine room unit  4 , the heat-exchanger end portion  1 DT of the long-side portion  1 DL is located close to the unit end portion  4 D of the machine room unit  4  in the longitudinal direction (X-axis direction). 
       FIG. 10  is a schematic view illustrating a modification of the chilling unit  100 A according to Embodiment 2. The chilling unit  100 A according to the modification includes the partition plate  15 . 
     [Advantages of Chilling Unit  100 A] 
     Of two pairs of air heat exchangers  1 , one pair of air heat exchangers  1  includes the air heat exchanger  1 A, which is formed in the shape of a flat plate, and the air heat exchanger  1 B, which is parallel to the air heat exchanger  1 A in the longitudinal direction and formed in the shape of a flat plate. Of the two pairs of air heat exchangers  1 , the other pair of air heat exchangers  1  includes the air heat exchanger  1 C, which is formed in the shape of a flat plate, and the air heat exchanger  1 D, which is parallel to the air heat exchanger  1 C in the longitudinal direction and formed in the shape of a flat plate. Therefore, in the chilling unit  100 A, the heat transfer tubes  7  of a pair of air heat exchangers  1  disposed in the lateral direction do not extend in such a manner to cover the front side of the chilling unit  100 A. Thus, in the chilling unit  100 A, not both the two systems of header pipes  12  and  13  at a pair of heat exchangers  1  or not both the distributors at the pair of air heat exchangers  1  are provided on the front side of the chilling unit where the worker enters the chilling unit. It is therefore possible to provide a sufficient space for the worker to enter the chilling unit  100 A on the front side of the chilling unit  100 A. The worker is thus able to easily enter and exit the space defined by the air exchangers. Accordingly, the ease of maintenance of the chilling unit  100 A is improved. Furthermore, the air heat exchangers  1  on the front side of the chilling unit  100 A are not bent in the lateral direction, and thus the space on the front side the chilling unit  100 A is not closed by the air heat exchangers  1 . It is possible to provide a larger space for the worker to enter the chilling unit  100 A, on the front side of the chilling unit  100 A. The worker is thus able to easily enter and exit the space defined by the air heat exchangers  1 . The ease of maintenance of the chilling unit  100 A is improved. 
     The air heat exchangers  1 A and  1 B and the air heat exchangers  1 C and  1 D are arranged symmetrical with respect to the middle portion of the chilling unit  100 A in the longitudinal direction (X-axis direction). Thus, in the chilling unit  100 A, not both the two systems of header pipes  12  and  13  at a pair of air heat exchangers  1  are provided on the front side of the chilling unit where the worker enters the chilling unit. It is therefore possible to provide a sufficient space for the worker to enter the chilling unit  100 A. The worker is thus able to easily enter and exit the space defined by the air exchangers. The ease of maintenance of the chilling unit  100 A is improved. 
     Embodiment 3 
     [Configuration of Chilling Unit  100 B] 
       FIG. 11  is a schematic view illustrating the shapes and positions of the air heat exchangers  1  in a chilling unit  100 B according to Embodiment 3.  FIG. 11  is a top view of the chilling unit  100 B, and schematically illustrates the shapes and positions of the air heat exchangers  1  as viewed in the direction from the top frame  60  toward the machine room unit  4 , with illustration of some components omitted. It should be noted that components that are the same as those of the chilling units  100  as illustrated in  FIGS. 1 to 10  are denoted by the same reference signs, and their descriptions will thus be omitted. The chilling unit  100 B according to Embodiment 3 differs from the chilling unit  100  according to Embodiment 1 in the shapes and positions of the air heat exchangers  1 . The chilling unit  100 B will be descried by referring mainly to the differences between the air heat exchangers  1  according to Embodiment 3 and those according to Embodiment 1 and illustration and descriptions of configurations other than configurations related to the differences will be omitted. 
     As illustrated in  FIG. 11 , as viewed in the direction orthogonal to the heat transfer tubes  7 , the air heat exchanger  1 A, the air heat exchanger  1 B, the air heat exchanger  1 C, and the air heat exchanger  1 D are each bent at 90 degrees at a location between the middle portion and one end portion of each of associated heat transfer tubes  7  that is located at an end thereof in the longitudinal direction. That is, the air heat exchanger  1 A, the air heat exchanger  1 B, the air heat exchanger  1 C, and the air heat exchanger  1 D are L-shaped as viewed in the direction from the top frame  60  toward the machine room unit  4 . 
     (Air Heat Exchangers  1 A to  1 D) 
     The air heat exchanger  1 A has the long-side portion  1 AL, the corner portion  1 AE, and the short-side portion  1 AS. The air heat exchanger  1 B has the long-side portion  1 BL, the corner portion  1 BE, and the short-side portion  1 BS. The air heat exchanger  1 C has the long-side portion  1 CL, the corner portion  1 CE, and the short-side portion  1 CS. The air heat exchanger  1 D has the long-side portion  1 DL, the corner portion  1 DE, and the short-side portion  1 DS. 
     (Air Heat Exchanger  1 A and Air Heat Exchanger  1 B) 
     The air heat exchanger  1 A and the air heat exchanger  1 B are opposite to each other in the lateral direction (Y-axis direction) of the machine room unit  4 . More specifically, in the lateral direction (Y-axis direction) of the machine room unit  4 , an end portion of the short-side portion  1 AS of the air heat exchanger  1 A is opposite to an end portion of the long-side portion  1 BL of the air heat exchanger  1 B, and an end portion of the short-side portion  1 BS of the air heat exchanger  1 B is opposite to an end portion of the long-side portion  1 AL of the air heat exchanger  1 A. The air heat exchanger  1 A and the air heat exchanger  1 B are arranged symmetrical with respect to a point. 
     In the longitudinal direction (X-axis direction) of the machine room unit  4 , an end portion of the short-side portion  1 AS of the air heat exchanger  1 A is located close to an associated unit end portion  4 D of the chilling unit  100 B, and an end portion of the short-side portion  1 BS of the air heat exchanger  1 B is located close to the middle portion  4 C of the chilling unit  100 B. The header pipes  12  and  13  connected to the air heat exchanger  1 A are located close to the unit end portion  4 D of the chilling unit  100 B, and the header pipes  12  and  13  connected to the air heat exchanger  1 B are located close to the middle portion  4 C of the chilling unit  100 B. 
     The long-side portion  1 AL of the air heat exchanger  1 A is parallel to the long-side portion  1 BL of the air heat exchanger  1 B in the longitudinal direction (X-axis direction) of the machine room unit  4 . In the longitudinal direction of the machine room unit  4 , the heat-exchanger end portion  1 AT of the long-side portion  1 AL of the air heat exchanger  1 A is located close to the middle portion  4 C of the chilling unit  100 B. In the longitudinal direction of the machine room unit  4 , the heat-exchanger end portion  1 BT of the long-side portion  1 BL of the air heat exchanger  1 B is located close to the unit end portion  4 D of the chilling unit  100 B. 
     The air heat exchanger  1 A and the air heat exchanger  1 B, which are L-shaped, are disposed such that the orientations of the short-side portion  1 AS and the long-side portion  1 AL of the air heat exchanger  1 A are reverse to those of the short-side portion  1 BS and the long-side portion  1 BL of the air heat exchanger  1 B in the longitudinal direction (X-axis direction) of the machine room unit. Accordingly, the air heat exchanger  1 A and the air heat exchanger  1 B are arranged in the shape of a quadrangle in the horizontal plane. The air heat exchanger  1 A and the air heat exchanger  1 B, which are provided as a pair of air heat exchangers  1 , are arranged in the shape of a quadrangle as viewed in plan view. 
     (Air Heat Exchanger  1 C and Air Heat Exchanger  1 D) 
     The air heat exchanger  1 C and the air heat exchanger  1 D are opposite to each other in the lateral direction (Y-axis direction) of the machine room unit  4 . More specifically, in the lateral direction (Y-axis direction) of the machine room unit  4 , the end portion of the short-side portion  1 CS of the air heat exchanger  1 C is opposite to the end portion of the long-side portion  1 DL of the air heat exchanger  1 D, and the end portion of the short-side portion  1 DS of the air heat exchanger  1 D is opposite to the end portion of the long-side portion  1 CL of the air heat exchanger  1 C. The air heat exchanger  1 C and the air heat exchanger  1 D are arranged symmetrical with respect to a point. 
     In the longitudinal direction (X-axis direction) of the machine room unit  4 , the end portion of the short-side portion  1 CS of the air heat exchanger  1 C is located close to the middle portion  4 C of the chilling unit  100 B, and the end portion of the short-side portion  1 DS of the air heat exchanger  1 D is located close to an associated unit end portion  4 D of the chilling unit  100 B. The header pipes  12  and  13  connected to the air heat exchanger  1 C are located close to the middle portion  4 C of the chilling unit  100 B, and the header pipes  12  and  13  connected to the air heat exchanger  1 D are located close to the unit end portion  4 D of the chilling unit  100 B. 
     The long-side portion  1 CL of the air heat exchanger  1 C is parallel to the long-side portion  1 DL of the air heat exchanger  1 D in the longitudinal direction (X-axis direction) of the machine room unit  4 . In the longitudinal direction (X-axis direction) of the machine room unit  4 , the heat-exchanger end portion  1 CT of the long-side portion  1 CL of the air heat exchanger  1 C is located close to the unit end portion  4 D of the chilling unit  100 B. In the longitudinal direction (X-axis direction) of the machine room unit  4 , the heat-exchanger end portion  1 DT of the long-side portion  1 DL of the air heat exchanger  1 D is located close to the middle portion  4 C of the chilling unit  100 B. 
     The air heat exchanger  1 C and the air heat exchanger  1 D, which are L-shaped, are disposed such that the orientations of the short-side portion  1 CS and the long-side portion  1 CL of the air heat exchanger  1 C are reverse to those of the short-side portion  1 DS and the long-side portion  1 DL of the air heat exchanger  1 D in the longitudinal direction (X-axis direction) of the machine room unit. Therefore, the air heat exchanger  1 C and the air heat exchanger  1 D are arranged in the shape of a quadrangle in the horizontal plane. The air heat exchanger  1 C and the air heat exchanger  1 D, which are provided as another pair of air heat exchangers  1 , are arranged in the shape of a quadrangle as viewed in plan view. 
     (Overall Configuration of Air Heat Exchangers  1 ) 
     In the chilling unit  100 B, the air heat exchangers  1  are arranged symmetrical with respect to a point in shape and position. More specifically, the air heat exchanger  1 A and the air heat exchanger  1 D are arranged symmetrical with respect to a point. Furthermore, the air heat exchanger  1 B and the air heat exchanger  1 C are arranged symmetrical with respect to a point. The air heat exchangers  1 A and  1 B and the air heat exchangers  1 C and  1 D are arranged to have the same shape and on the opposite sides with respect to the middle position of the chilling unit  100 B in the longitudinal direction (X-axis direction). 
     At least the air heat exchanger  1 B, which is at least one air heat exchanger  1  of a pair of air heat exchangers  1  disposed in the lateral direction (Y-axis direction) of the machine room unit  4 , has the heat-exchanger end portion  1 BT of the long-side portion  1 BL at one end portion of the machine room unit  4  in the longitudinal direction. At least the air heat exchanger  1 C, which is at least one air heat exchanger  1  of a pair of air heat exchangers  1  disposed in the lateral direction of the machine room unit  4 , has the heat-exchanger end portion  1 CT of the long-side portion  1 CL at another end portion of the machine room unit  4  in the longitudinal direction. Two pairs of air heat exchangers  1  are arranged side by side in the longitudinal direction (X-axis direction) of the machine room unit  4 . That is, the air heat exchangers  1 A and  1 B, which are provided as one pair of air heat exchangers  1 , and the air heat exchangers  1 C and  1 D, which are provided as another pair of air heat exchangers  1 , are arranged side by side in the longitudinal direction (X-axis direction) of the machine room unit  4 . 
     In the longitudinal direction of the machine room unit  4 , the corner portion  1 AE that is the first corner portion is located close to the unit end portion  4 D corresponding to the one end portion of the machine room unit  4 , and the corner portion  1 BE that is the second corner portion is located close to the middle portion  4 C of the machine room unit  4 . The air heat exchangers  1 A and  1 B are arranged in the shape of a quadrangle in the cross section. In the longitudinal direction of the machine room unit  4 , the corner portion  1 CE that is the third corner portion is located close to the middle portion  4 C of the machine room unit  4 , and the corner portion  1 DE that is the fourth corner portion is located close to the unit end portion  4 D corresponding to the other end portion of the machine room unit  4 . The air heat exchangers  1 C and  1 D are arranged in the shape of a quadrangle in the cross section. From each of the heat-exchanger end portion  1 BT and the heat-exchanger end portion  1 CT, heat transfer tubes  7  do not extend. That is, heat transfer tubes  7  that protrude from the fin  8  corresponding to the outermost one of the fin  8  in the direction where the fins  8  are arranged and that extend linearly in the lateral direction (Y-axis direction) do not extend from each of the heat-exchanger end portion  1 BT and the heat-exchanger end portion  1 CT. 
       FIG. 12  is a schematic view illustrating a modification of the chilling unit  100 B according to Embodiment 3. The chilling unit  100 B according to the modification includes the partition plate  15 . 
     [Advantages of Chilling Unit  100 B] 
     In the longitudinal direction of the machine room unit  4 , the corner portion  1 AE that is the first corner portion is provided close to the unit end portion  4 D corresponding to the other end portion of the machine room unit  4 , and the corner portion  1 BE that is the second corner portion is provided close to the middle portion  4 C of the machine room unit  4 . The air heat exchanger  1 A and the air heat exchanger  1 B are arranged in the shape of a quadrangle in the horizontal plane. In the longitudinal direction of the machine room unit  4 , the corner portion  1 CE that is the third corner portion is provided close to the middle portion  4 C of the machine room unit  4 , and the corner portion  1 DE that is the fourth corner portion is provided close to the unit end portion  4 D corresponding to the other end portion of the machine room unit  4 . The air heat exchanger  1 C and the air heat exchanger  1 D are arranged in the shape of a quadrangle in the horizontal plane. Thus, in the chilling unit  100 B, not both the two systems of header pipes  12  and  13  at a pair of air heat exchangers  1  are provided on the front side of the chilling unit where the worker enters the chilling unit. It is therefore possible to provide a sufficient space for the worker to enter the chilling unit  100 B on the front side of the chilling unit  100 B. The worker is thus able to easily enter and exit the space defined by the air exchangers. The ease of maintenance of the chilling unit  100 B is improved. 
     The air heat exchangers  1 A and  1 B and the air heat exchangers  1 C and  1 D are arranged in the same manner and on the opposite sides with respect to the middle position of the chilling unit  100 B in the longitudinal direction (X-axis direction) 
     Embodiment 4 
     [Configuration of Chilling Unit  100 C] 
       FIG. 13  is a schematic view illustrating the shapes and positions of the air heat exchangers  1  in a chilling unit  100 C according to Embodiment 4.  FIG. 13  is a top view of the chilling unit  100 C and schematically illustrates the shapes and positions of the air heat exchangers  1  as viewed in the direction from the top frame  60  toward the machine room unit  4 , with illustration of some components omitted. It should be noted that regarding Embodiment 4, components that are the same as those of any of the chilling units  100  as illustrated in  FIGS. 1 to 12  are denoted by the same reference signs, and their descriptions will thus be omitted. The chilling unit  100 C according to Embodiment 4 differs from the chilling unit  100  according to Embodiment 1 in the shapes and positions of the air heat exchangers  1 . The chilling unit  100 C will be described by referring mainly to the differences between the air heat exchangers  1  in the chilling unit  100 C and those according to Embodiment 1, and illustration and descriptions of configurations other than configurations related to the differences will be omitted. 
     As illustrated in  FIG. 13 , as viewed in the direction orthogonal to the heat transfer tubes  7 , the air heat exchanger  1 A and the air heat exchanger  1 D are each bent at 90 degrees at a location between the middle portion and one end portion of each of associated heat transfer tubes  7  in the extending direction thereof. That is, the air heat exchanger  1 A and the air heat exchanger  1 D are L-shaped as viewed in the direction from the top frame  60  toward the machine room unit  4 . The air heat exchanger  1 B and the air heat exchanger  1 C are each formed in the shape of a flat plate. That is, the air heat exchanger  1 B and the air heat exchanger  1 C are each I-shaped as viewed in the direction orthogonal to the heat transfer tubes  7 . 
     (Air Heat Exchangers  1 A to  1 D) 
     The air heat exchanger  1 A has the long-side portion  1 AL, the corner portion  1 AE, and the short-side portion  1 AS. The air heat exchanger  1 B has the long-side portion  1 BL. The air heat exchanger  1 C has the long-side portion  1 CL. The air heat exchanger  1 D has the long-side portion  1 DL, the corner portion  1 DE, and the short-side portion  1 DS. 
     (Air Heat Exchanger  1 A and Air Heat Exchanger  1 B) 
     The air heat exchanger  1 A and the air heat exchanger  1 B are opposite to each other in the lateral direction (Y-axis direction) of the machine room unit  4 . More specifically, in the lateral direction (Y-axis direction) of the machine room unit  4 , the end portion of the short-side portion  1 AS of the air heat exchanger  1 A is opposite to the end portion of the long-side portion  1 BL of the air heat exchanger  1 B. 
     In the longitudinal direction (X-axis direction) of the machine room unit  4 , the end portion of the short-side portion  1 AS of the air heat exchanger  1 A is located close to the unit end portion  4 D of the chilling unit  100 C. The header pipe  12  and the header pipe  13  connected to the air heat exchanger  1 A are located close to one unit end portion  4 D of the chilling unit  100 C, and the header pipe  12  and the header pipe  13  connected to the air heat exchanger  1 B are located close to the middle portion  4 C of the chilling unit  100 C. 
     The long-side portion  1 AL of the air heat exchanger  1 A is parallel to the long-side portion  1 BL of the air heat exchanger  1 B in the longitudinal direction (X-axis direction) of the machine room unit  4 . In the longitudinal direction (X-axis direction) of the machine room unit  4 , the heat-exchanger end portion  1 AT of the long-side portion  1 AL of the air heat exchanger  1 A is located close to the middle portion  4 C of the chilling unit  100 C. In the longitudinal direction (X-axis direction) of the machine room unit  4 , the heat-exchanger end portion  1 BT of the long-side portion  1 BL of the air heat exchanger  1 B is located close to the unit end portion  4 D of the chilling unit  100 C. 
     (Air Heat Exchanger  1 C and Air Heat Exchanger  1 D) 
     The air heat exchanger  1 D and the air heat exchanger  1 C are opposite to each other in the lateral direction (Y-axis direction) of the machine room unit  4 . More specifically, in the lateral direction (Y-axis direction) of the machine room unit  4 , the end portion of the short-side portion  1 DS of the air heat exchanger  1 D is opposite to the end portion of the long-side portion  1 CL of the air heat exchanger  1 C. 
     In the longitudinal direction (X-axis direction) of the machine room unit  4 , the end portion of the short-side portion  1 DS of the air heat exchanger  1 D is located close to the unit end portion  4 D of the chilling unit  100 C. The header pipe  12  and the header pipe  13  connected to the air heat exchanger  1 D are located close to the other unit end portion  4 D of the chilling unit  100 C, and the header pipe  12  and the header pipe  13  connected to the air heat exchanger  1 C are located close to the middle portion  4 C of the chilling unit  100 C. 
     The long-side portion  1 DL of the air heat exchanger  1 D is parallel to the long-side portion  1 CL of the air heat exchanger  1 C in the longitudinal direction (X-axis direction) of the machine room unit  4 . In the longitudinal direction (X-axis direction) of the machine room unit  4 , the heat-exchanger end portion  1 DT of the long-side portion  1 DL of the air heat exchanger  1 D is located close to the middle portion  4 C of the chilling unit  1000 . In the longitudinal direction (X-axis direction) of the machine room unit  4 , the heat-exchanger end portion  1 CT of the long-side portion  1 CL of the air heat exchanger  1 C is located close to the unit end portion  4 D of the chilling unit  100 C. 
     (Overall Configuration of Air Heat Exchangers  1 ) 
     Of two pairs of air heat exchangers  1 , one pair of air heat exchangers  1  includes the air heat exchanger  1 A having the L-shape corner portion  1 AE and the air heat exchanger  1 B, which is formed in the shape of a flat plate; and the other pair of air heat exchangers  1  includes the air heat exchanger  1 C, which is formed in the shape of a flat plate, and the air heat exchanger  1 D having the L-shaped corner portion  1 DE. 
     In the chilling unit  1000 , the air heat exchangers  1  are arranged symmetrical in shape and position with respect to a point. More specifically, the air heat exchanger  1 A and the air heat exchanger  1 D are arranged symmetrical with respect to a point. Furthermore, the air heat exchanger  1 B and the air heat exchanger  1 C are arranged symmetrical with respect to a point. 
     In at least the air heat exchanger  1 B, which is at least one air heat exchanger  1  of a pair of air heat exchangers  1  disposed in the lateral direction (Y-axis direction) of the machine room unit  4 , the heat-exchanger end portion  1 BT of the long-side portion  1 BL is provided at one end portion of the machine room unit  4  in the longitudinal direction. In at least the air heat exchanger  1 C, which is at least one air heat exchanger  1  of a pair of air heat exchangers  1  disposed in the lateral direction of the machine room unit  4 , the heat-exchanger end portion  1 CT of the long-side portion  1 CL is provided at the other end portion of the machine room unit  4  in the longitudinal direction. Two pairs of air heat exchangers  1  are arranged side by side in the longitudinal direction (X-axis direction) of the machine room unit  4 . That is, the air heat exchangers  1 A and  1 B provided as one pair and the air heat exchangers  1 C and  1 D provided as another pair are arranged side by side in the longitudinal direction (X-axis direction) of the machine room unit  4 . From each of the heat-exchanger end portion  1 BT and the heat-exchanger end portion  1 CT, heat transfer tubes  7  do not extend. That is, heat transfer tubes  7  do not extend: the heat transfer tubes  7  that protrude from the fin  8  corresponding to the outermost one of the fins  8  in the direction in which the fins  8  are arranged and that extend linearly in the lateral direction (Y-axis direction) do not extend from each of the heat-exchanger end portion  1 BT and the heat-exchanger end portion  1 CT. 
       FIG. 14  is a schematic view illustrating a modification of the chilling unit  100 C according to Embodiment 4. The chilling unit  100 C according to the modification includes the partition plate  15 . 
     [Advantages of Chilling Unit  100 C] 
     Of two pairs of air heat exchangers  1 , one pair of air heat exchangers  1  includes the air heat exchanger  1 A having the L-shaped corner portion  1 AE and the air heat exchanger  1 B formed in the shape of a flat plate: and the other pair of air heat exchangers  1  includes the air heat exchanger  1 C formed in the shape of a flat plate and the air heat exchanger  1 D having the L-shaped corner portion  1 DE. Thus, in the chilling unit  100 C, the heat transfer tubes at one of a pair of air heat exchangers  1  disposed in the lateral direction do not extend in such a manner as to cover the front side of the chilling unit  100 C. Therefore, in the chilling unit  100 C, not both the two systems of header pipes  12  and  13  or both the distributors at a pair of air heat exchangers  1  are provided on the front side of the chilling unit where the worker enters the chilling unit. It is therefore possible to provide a sufficient space for the worker to enter the chilling unit  100 C on the front side of the chilling unit  1000 . The worker is thus able to easily enter and exit the space defined by the air exchangers. The ease of maintenance of the chilling unit  100 C is improved. Furthermore, on the front side of the chilling unit  100 C, the air heat exchanger  1 B and the air heat exchanger  1 C are not bend in the lateral direction. Thus, the space on the front side the chilling unit  100 C is not blocked by the air heat exchanger  1 B. It is therefore possible to provide a sufficient space for the worker to enter the chilling unit  100 C on the front side of the chilling unit  100 C. The worker is thus able to easily enter and exit the space defined by the air heat exchangers  1 . The ease of maintenance of the chilling unit  100 C can be improved. 
     Embodiment 5 
     [Configuration of Chilling Unit  100 D] 
       FIG. 15  is an enlarged view of an end portion of the air heat exchanger  1  in a chilling unit  100 D according to Embodiment 5.  FIG. 16  is an enlarged view of an end portion of another air heat exchanger  1  in the chilling unit  100 D according to Embodiment 5. Each of  FIGS. 15 and 16  illustrates an end portion of the air heat exchanger  1  of the chilling unit  100  on the left side of the figure and an end portion of the air heat exchanger  1  of the chilling unit  100 D on the right side of the figure. It should be noted that although the air heat exchanger  1 A is illustrated as an air heat exchanger  1 , the air heat exchanger  1  is not limited to the air heat exchanger  1 A but may be the air heat exchanger  1 B, the air heat exchanger  1 C, or the air heat exchanger  1 D. The chilling unit  100  may be the chilling unit  100 A, the chilling unit  100 B, or the chilling unit  100 C. It should be noted that regarding Embodiment 5, components that are the same as those of any of the chilling units  100  as illustrated in  FIGS. 1 to 14  will be denoted by the same reference signs and their descriptions will thus omitted. 
     The chilling unit  100 D according to Embodiment 5 includes heat transfer tubes  7 A that differ in shape from the heat transfer tubes  7  of the chilling unit  100  according to Embodiment 1. The chilling unit  100 D will be described by referring mainly to the differences between the heat transfer tubes  7 A and hose according to Embodiment 1, and illustration and descriptions of configurations other than configurations related to the differences will thus be omitted. 
     Each heat transfer tube  7 A has a bent portion  7 A 1  that is an end portion of the heat transfer tube  7 A in the direction in which the heat transfer tube  7 A extends and that has a tube passage bent at an exposed portion that does not penetrate the fins  8 . It is preferable that the heat transfer tubes  7 A be aluminum flat tubes. The bent portion  7 A 1  is L-shaped, for example, as viewed in plan view. However, the shape of the bent portion  7 A 1  is not limited to the L-shape. 
     [Advantages of Chilling Unit  100 D] 
     Each heat transfer tube  7 A has the bent portion  7 A 1 , which is an end portion thereof in a direction in which the heat transfer tube  7 A and has a tube passage that is bent to the exposed portion that does not penetrate the fins  8 . Since each heat transfer tube  7 A is bent, it is possible to provide a sufficient space for the worker to enter and exit the chilling unit  100 D can be provided on the front side of the chilling unit  100 D. The worker is thus able to easily enter and exit the space defined by the air heat exchangers  1 , and the ease of the maintenance of the chilling unit  100 D is improved. Furthermore, since each heat transfer tube  7 A is bent, the air heat exchangers  1  of the chilling unit  100 D can be elongated in the longitudinal direction (X-axis direction). It is therefore possible to provide increase the area of the heat exchange portion where heat exchange is performed between air and refrigerant, and improve the heat exchange performance of the chilling unit  100 , as compared with the case where the chilling unit  100  does not employ the heat transfer tubes  7 A. 
     The configurations described above with respect to the embodiments are descried merely as examples. These configurations can be each of combined with any of other known techniques, or can be partially omitted or changed without departing from the gist of the present disclosure. 
     REFERENCE SIGNS LIST 
       1 : air heat exchanger,  1 A: air heat exchanger,  1 AE: corner portion,  1 AL: long-side portion,  1 AS: short-side portion,  1 AT: heat-exchanger end portion,  1 B: air heat exchanger,  1 BE: corner portion,  1 BL: long-side portion,  1 BS: short-side portion,  1 BT: heat-exchanger end portion,  1 C: air heat exchanger,  1 CE: corner portion,  1 CL: long-side portion,  1 CS: short-side portion,  1 CT: heat-exchanger end portion,  1 D: air heat exchanger,  1 DE: corner portion,  1 DL: long-side portion,  1 DS: short-side portion,  1 DT: heat-exchanger end portion,  3 : heat exchanger,  4 : machine room unit,  4 C: middle portion,  4 D: unit end portion,  5 : fan,  5 A: fan,  5 B: fan,  5 C: fan,  5 D: fan,  6 A: bell mouth,  6 B: bell mouth,  6 C: bell mouth,  6 D: bell mouth,  7 : heat transfer tube,  7 A: heat transfer tube,  7 A 1 : bent portion,  8 : fin,  10 : base,  11   a : upper end portion,  11   b : lower end portion,  12 : header pipe,  13 : header pipe,  14 : air outlet,  15 : partition plate,  17 : fan guard,  31 : compressor,  32 : control box,  33 : flow switching device,  40 : frame,  41 : underframe,  42 : gatepost,  42 A: gatepost,  42 B: gatepost,  42 C: gatepost,  42 D: gatepost,  43 : intermediate post,  43 A: intermediate post,  43 B: intermediate post,  43 C: intermediate post,  43 D: intermediate post,  44 : top beam,  45 : side wall,  45   a : first side wall,  45   b : second side wall,  50 : side panel,  51 : side panel,  51   a : upper edge portion,  51   b : lower edge portion,  55 : drain pan,  57 : heater,  60 : top frame,  70 : support post,  100 : chilling unit,  100 A: chilling unit,  100 B: chilling unit,  100 C: chilling unit,  100 D: chilling unit,  100 L: chilling unit.