Patent Publication Number: US-2021164668-A1

Title: Window air conditioner

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present disclosure claims the benefit of Chinese Patent application with No. 201911196277.5, filed on Nov. 28, 2019 and entitled “Window Air Conditioner”, and Chinese Patent application with No. 201922096576.3, filed on Nov. 28, 2019 and entitled “Window Air Conditioner”, the entirety of which is hereby incorporated herein by reference for all purposes. No new matter has been introduced. 
     FIELD 
     The present disclosure relates to the technical field of air conditioning, and in particular to a window air conditioner. 
     BACKGROUND 
     Nowadays, people have more and more demands for fresh air. There is also a strong demand for PTAC (Packaged Terminal Air Conditioner) window machine, which is the most commonly used refrigeration system for middle-end and high-end hotels in the U.S. market. However, now people not only require fresh air, but also put forward new demands for the comfort of fresh air. In this way, a number of PTACs with fresh air and fresh air dehumidification function have appeared on the market. However, for these PTACs, in order to meet the demand for fresh air dehumidification, only an independent dehumidification module has been added to the original air conditioning system, and it has not been integrated with the original refrigeration system. In this way, dual compressors and dual refrigeration systems must be used. That is, one air conditioner needs to be provided with two refrigeration systems, including two compressors, two motors, two evaporators, two condensers, and two capillaries. The disadvantages of this dual system are high cost, low energy efficiency, high noise, and poor production technology and efficiency. 
     Although the fresh air blowing to the indoor is dehumidified, since the volume of the fresh air is not very large, it cannot change the air effect in the entire room. Even if the PTAC has the dehumidification function turned on, the temperature of the dehumidified indoor air will be very low, which will make the user feel very uncomfortable. 
     The above content is only used to assist in understanding the technical solution of the disclosure, and does not mean that the above content is recognized as prior art. 
     SUMMARY 
     An aspect of the present disclosure provides a window air conditioner, which can solve one or more of the technical problems mentioned above. 
     The window air conditioner provided in this disclosure includes: 
     a casing, defining an indoor air duct; 
     an indoor heat exchanger, provided inside the casing and including:
         a first indoor heat exchanger; and   a second indoor heat exchanger; and,   where:
           the first indoor heat exchanger and the second indoor heat exchanger are configured to be stacked in an air inlet direction of the indoor air duct; and   in the constant temperature dehumidification mode, one of the first indoor heat exchanger and the second indoor heat exchanger is configured to be in a heating mode, and the other one of the first indoor heat exchanger and the second indoor heat exchanger is configured to be in a cooling mode; and   
               

     a fresh air device, configured to deliver fresh air to the indoor air duct and including:
         a fresh air inlet, communicating with outdoor air;   a fresh air outlet, communicating with the indoor air duct; and   a fresh air duct, communicating the fresh air inlet and the fresh air outlet.       

     In an embodiment, the casing includes:
         an indoor casing, where:   the indoor casing defines the indoor air duct;   the fresh air outlet is configured to be defined on a rear side wall surface of the indoor casing;   an indoor air inlet is configured to be defined on a front side wall surface of the indoor casing; and   the first indoor heat exchanger and the second indoor heat exchanger are configured to be stacked in a front-rear direction of the casing.       

     In an embodiment, a heat exchange surface of the first indoor heat exchanger is provided corresponding to the indoor air inlet. 
     In an embodiment, the window air conditioner further includes:
         an outdoor air duct, defined inside the casing, an air outlet side of the outdoor air duct being configured to be in communication with the fresh air duct;   an outdoor heat exchanger, provided inside the outdoor air duct; and   an outdoor fan, provided inside the outdoor air duct and configured to send air into the outdoor air duct and the fresh air duct.       

     In an embodiment, where:
         the casing further includes:
           an outdoor casing, defining the outdoor air duct; and   
           the fresh air device includes:
           a fresh air casing, defining the fresh air duct; and,   
           where:
           the fresh air casing is configured to be connected to the outdoor casing, and the fresh air inlet is configured to be defined at a junction between the fresh air casing and the outdoor casing.   
               

     In an embodiment, the window air conditioner further includes an air guide louver provided at the fresh air inlet. 
     In an embodiment, the fresh air casing is provided between the outdoor heat exchanger and the indoor heat exchanger. 
     In an embodiment, an air-passing area of the fresh air inlet of the fresh air casing is configured to be smaller than an air-passing area of the fresh air outlet of the fresh air casing. 
     In an embodiment, the fresh air casing is configured to be at least partially gradually expanded from the fresh air inlet to the fresh air outlet. 
     In an embodiment, at least one inner side wall surface of the fresh air casing is configured to be a curved surface, and the curved surface is configured to be recessed from an outside of the fresh air casing toward an inside of the fresh air casing. 
     In an embodiment, the fresh air device includes: a fresh air fan, provided inside the fresh air duct and configured to introduce airflow from the fresh air inlet to the indoor air duct. 
     In an embodiment, the window air conditioner further includes:
         a chassis, the fresh air device being installed on the chassis; and   a compressor, installed on the chassis; and,   where:
           the fresh air device is configured to be located on one side of the chassis in a longitudinal direction of the chassis, and the compressor is configured to be located on the other side of the chassis in the longitudinal direction of the chassis.   
               

     In an embodiment, the casing includes:
         two opposite side walls, at least one of the two opposite side walls defining an outdoor air inlet communicating with an air inlet end of the outdoor air duct; and   a rear end wall, connecting the two opposite side walls and defining an outdoor air outlet communicating with an air outlet end of the outdoor air duct.       

     In an embodiment, the window air conditioner further includes:
         an indoor fan, provided inside the indoor air duct; and,   where:
           the casing further includes:
               an indoor air inlet, communicating with the indoor air duct; and   an indoor air outlet, communicating with the indoor air duct and located above the indoor air inlet.   
               
               

     In an embodiment, an angle between an air supply direction of the indoor air outlet and a horizontal plane is configured to be greater than 0 degrees and less than 90 degrees. 
     In an embodiment, the casing includes: an indoor casing, defining the indoor air duct, the indoor air outlet being located on a top and/or lateral side of the indoor casing. 
     In an embodiment, the window air conditioner further includes:
         a compressor;   an outdoor heat exchanger;   a refrigerant circulation pipe;   a discharge pipe, provided at a refrigerant outlet of the compressor; and   a suction pipe, provided at a refrigerant inlet of the compressor; and,       

     where:
         the discharge pipe, the outdoor heat exchanger, the first indoor heat exchanger, the second indoor heat exchanger, and the suction pipe are configured to be sequentially communicated with one another through the refrigerant circulation pipe.       

     In an embodiment, the refrigerant circulation pipe includes:
         a first piping, connecting the discharge pipe and the outdoor heat exchanger; and   a second piping, connecting the suction pipe and the second indoor heat exchanger; and,   where:   the window air conditioner further includes:
           a switch, serially connected to the first piping and the second piping and having a first switching state and a second switching state; and,   where:
               in the first switching state, the first piping connected to two ends of the switch is configured to be turned on, and the second piping connected to another two ends of the switch is configured to be turned on; and   in the second switching state, the first piping between the discharge pipe and the switch is configured to be in communication with the second piping between the switch and the second indoor heat exchanger, and the first piping between the outdoor heat exchanger and the switch is configured to be in communication with the second piping between the suction pipe and the switch.   
               
               

     In an embodiment, the window air conditioner further includes: 
     a refrigerant radiator, serially connected to the refrigerant circulation pipe between the outdoor heat exchanger and the first indoor heat exchanger; 
     a one-way throttle valve, serially connected to the refrigerant circulation pipe between the outdoor heat exchanger and the refrigerant radiator, an inlet of the one-way throttle valve being adjacent to the refrigerant radiator, an outlet of the one-way throttle valve being adjacent to the outdoor heat exchanger; 
     a first one-way valve; and 
     a second one-way valve; and, 
     where:
         the refrigerant circulation pipe further includes:
           a third piping, connecting the refrigerant radiator and the first indoor heat exchanger; and   a fourth piping, connecting the refrigerant radiator and the first indoor heat exchanger and arranged in parallel with the third piping; and,   
           where:
           the first one-way valve is configured to be serially connected to the third piping, an inlet of the first one-way valve being adjacent to the refrigerant radiator, an outlet of the first one-way valve being adjacent to the first indoor heat exchanger; and   the second one-way valve is configured to be serially connected to the fourth piping, an inlet of the second one-way valve being adjacent to the first indoor heat exchanger, an outlet of the second one-way valve being adjacent to the refrigerant radiator.   
               

     Regarding the window air conditioner of the present disclosure, the first indoor heat exchanger and the second indoor heat exchanger are stacked in the air inlet direction of the indoor air duct, and the heat exchange modes of the first indoor heat exchanger and the second indoor heat exchanger may be reversed, and at the same time, the fresh air outlet of the fresh air duct communicates with the indoor duct. In this way, the first indoor heat exchanger and the second indoor heat exchanger may be set to one in the cooling mode and the other in the heating mode. In this way, both fresh air and indoor air may be dehumidified and heated, not only all the indoor air is dehumidified again with improving the dehumidification efficiency, but also the purpose of constant temperature dehumidification is achieved, so that the entire indoor temperature of the window air conditioner will not drop in the dehumidification mode, so that the user may feel the fresh air, and the temperature of the dehumidified air is very comfortable, and there will be no cool feeling. At the same time, the indoor heat exchanger can be fully utilized during dehumidification, and there is no need to additionally install a fresh air condenser and a fresh air evaporator, which greatly reduces the manufacturing cost and power. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to explain the technical solutions in the embodiments of the present disclosure or the prior art more clearly, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can be obtained according to the structure shown in the drawings without creative efforts. 
         FIG. 1  is a schematic structural view of a window air conditioner according to an embodiment of the present disclosure; 
         FIG. 2  is a schematic structural view of the window air conditioner according to another embodiment of the present disclosure, in which a casing of the window air conditioner is removed; 
         FIG. 3  is a schematic front view of the window air conditioner in  FIG. 2 ; 
         FIG. 4  is a schematic top view of the window air conditioner in  FIG. 3 ; 
         FIG. 5  is a schematic left side view of the window air conditioner in  FIG. 3 ; 
         FIG. 6  is a schematic rear view of the window air conditioner in  FIG. 3 ; 
         FIG. 7  is a schematic structural view of the window air conditioner according to another embodiment of the present disclosure; 
         FIG. 8  is a schematic structural view of the window air conditioner according to still another embodiment of the present disclosure; and 
         FIG. 9  is a schematic structural view of the window air conditioner according to further another embodiment of the present disclosure. 
     
    
    
     DESCRIPTION OF REFERENCE NUMERALS 
       
     
       
         
           
               
               
               
             
               
                   
                   
               
               
                   
                 Reference 
                   
               
               
                   
                 numeral 
                 Name 
               
               
                   
                   
               
             
            
               
                   
                 100 
                 Casing 
               
               
                   
                 110 
                 Indoor air 
               
               
                   
                   
                 duct 
               
               
                   
                 120 
                 Indoor 
               
               
                   
                   
                 casing 
               
               
                   
                 121 
                 Indoor air 
               
               
                   
                   
                 inlet 
               
               
                   
                 122 
                 Indoor air 
               
               
                   
                   
                 outlet 
               
               
                   
                 123 
                 Indoor 
               
               
                   
                   
                 fan 
               
               
                   
                 130 
                 Outdoor 
               
               
                   
                   
                 air duct 
               
               
                   
                 140 
                 Outdoor 
               
               
                   
                   
                 casing 
               
               
                   
                 150 
                 Chassis 
               
               
                   
                 160 
                 Outdoor 
               
               
                   
                   
                 air outlet 
               
               
                   
                 170 
                 Outdoor 
               
               
                   
                   
                 air inlet 
               
               
                   
                 200 
                 Indoor 
               
               
                   
                   
                 heat 
               
               
                   
                   
                 exchanger 
               
               
                   
                 210 
                 First indoor 
               
               
                   
                   
                 heat 
               
               
                   
                   
                 exchanger 
               
               
                   
                 220 
                 Second 
               
               
                   
                   
                 indoor heat 
               
               
                   
                   
                 exchanger 
               
               
                   
                 300 
                 Fresh air 
               
               
                   
                   
                 device 
               
               
                   
                 310 
                 Fresh air 
               
               
                   
                   
                 inlet 
               
               
                   
                 320 
                 Fresh air 
               
               
                   
                   
                 outlet 
               
               
                   
                 330 
                 Fresh air 
               
               
                   
                   
                 duct 
               
               
                   
                 340 
                 Fresh air 
               
               
                   
                   
                 casing 
               
               
                   
                 341 
                 Curved 
               
               
                   
                   
                 surface 
               
               
                   
                 400 
                 Outdoor 
               
               
                   
                   
                 heat 
               
               
                   
                   
                 exchanger 
               
               
                   
                 500 
                 Outdoor 
               
               
                   
                   
                 fan 
               
               
                   
                 600 
                 Compressor 
               
               
                   
                 610 
                 Discharge 
               
               
                   
                   
                 pipe 
               
               
                   
                 620 
                 Suction 
               
               
                   
                   
                 pipe 
               
               
                   
                 710 
                 First 
               
               
                   
                   
                 piping 
               
               
                   
                 720 
                 Second 
               
               
                   
                   
                 piping 
               
               
                   
                 730 
                 Third 
               
               
                   
                   
                 piping 
               
               
                   
                 740 
                 Fourth 
               
               
                   
                   
                 piping 
               
               
                   
                 800 
                 Switch 
               
               
                   
                 900 
                 Refrigerant 
               
               
                   
                   
                 radiator 
               
               
                   
                 910 
                 One-way 
               
               
                   
                   
                 throttle 
               
               
                   
                   
                 valve 
               
               
                   
                 920 
                 First 
               
               
                   
                   
                 one-way 
               
               
                   
                   
                 valve 
               
               
                   
                 930 
                 Second 
               
               
                   
                   
                 one-way 
               
               
                   
                   
                 valve 
               
               
                   
                 940 
                 First valve 
               
               
                   
                 950 
                 Second 
               
               
                   
                   
                 valve 
               
               
                   
                   
               
            
           
         
       
     
     The implementation, functional characteristics and advantages of the present disclosure will be further described in conjunction with the embodiments and with reference to the drawings. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     It should be noted that if there is a directional indicator (such as up, down, left, right, front, back, etc.) in the embodiment of the present disclosure, the directional indication is only used to explain the relative positional relationship, movement, etc. of the various components in a specific posture (as shown in the drawings), if the specific posture changes, the directional indicator will change accordingly. 
     In addition, if there are descriptions related to “first”, “second”, etc. in the embodiments of the present disclosure, the descriptions of “first”, “second”, etc. are only used for description purposes, and cannot be understood to indicate or imply its relative importance or to imply the number of technical features indicated. Therefore, the features defined as “first” and “second” may explicitly or implicitly include at least one of the features. In addition, the meaning of “and/or” appearing throughout the text is to include three parallel solutions. Taking “A and/or B” as an example, it includes solution A, or solution B, or solution that both A and B satisfy. 
     This disclosure provides a window air conditioner. 
     In an embodiment of the present disclosure, as shown in  FIGS. 1 to 6 , the window air conditioner includes a casing  100 , an indoor heat exchanger  200  and a fresh air device  300 . An indoor air duct  110  is defined inside the casing  100 . The indoor heat exchanger  200  is provided inside the casing  100 . The indoor heat exchanger  200  includes a first indoor heat exchanger  210  and a second indoor heat exchanger  220 , which are stacked in an air inlet direction of the indoor air duct  110 . The window air conditioner has a constant temperature dehumidification mode. In the constant temperature dehumidification mode, one of the first indoor heat exchanger  210  and the second indoor heat exchanger  220  is in a heating mode, and the other one of the first indoor heat exchanger  210  and the second indoor heat exchanger  220  is in a cooling mode. The fresh air device  300  is configured to deliver fresh air to the indoor air duct  110 . The fresh air device  300  includes a fresh air inlet  310  communicating with outdoor air or outdoor environment, a fresh air outlet  320  communicating with the indoor air duct  110 , and a fresh air duct  330  communicating the fresh air inlet  310  and the fresh air outlet  320 . 
     In this embodiment, the shape of the casing  100  may be square, cylindrical, or the like, which may be selected according to specific application requirements, and is not specifically limited herein. Generally, in order to facilitate manufacturing and molding, the shape of the casing  100  can be substantially square. The cross-sectional shape of the indoor air duct  110  may be rectangular, circular, irregular, etc., which is not specifically limited herein. The extending direction of the indoor air duct  110  generally coincides with the longitudinal direction of the casing  100 . It should be noted that the first indoor heat exchanger  210  and the second indoor heat exchanger  220  are stacked, and the heat exchange surfaces of the two may be closely arranged, or may have a certain gap therebetween. 
     It can be understood that the casing  100  defines an indoor air inlet  121  and an indoor air outlet  122 . An air inlet end of the indoor air duct  110  communicates with the indoor air inlet  121 , and an air outlet end of the indoor air duct  110  communicates with the indoor air outlet  122 . Both the indoor air inlet  121  and the indoor air outlet  122  may be defined on a front side wall surface of the casing  100 . Alternatively, the indoor air inlet  121  can be located on the front side wall surface of the casing  100 , and the indoor air outlet  122  can be located on a top surface of the casing  100 . Alternatively, the indoor air outlet  122  may also be located at a junction of the front side wall surface and the top surface of the casing  100 . The indoor air inlet  121  may be defined on a left side wall surface and/or a right side wall surface of the casing  100 . It may be selected and designed according to the usage requirements and the type of an indoor fan  123 . The indoor fan  123  may also be provided inside the indoor air duct  110 , and the indoor fan  123  may be a centrifugal fan or a cross-flow fan. By stacking the first indoor heat exchanger  210  and the second indoor heat exchanger  220  in the air inlet direction of the indoor air duct  110 , the fresh air flow from the fresh air duct  330  may be firstly blown out from the indoor air outlet  122  under the action of the indoor fan  123 . The fresh air is mixed with the indoor air in the room. Afterwards, the mixed air flow is introduced from the indoor air inlet  121  by the indoor fan  123 , and sequentially passes through the first indoor heat exchanger  210  and the second indoor heat exchanger  220 . Finally, the processed air is blown out through the indoor air outlet  122 . In this way, the air conditioner can not only implement constant temperature dehumidification for fresh air, but also implement circulating constant temperature dehumidification for indoor air, achieving better overall constant temperature dehumidification effect. 
     In an embodiment, the casing  100  further defines the indoor air inlet  121  communicating with the indoor air duct  110  and the indoor air outlet  122  communicating with the indoor air duct  110 . The indoor fan  123  is provided inside the indoor air duct  110 , and the indoor air outlet  122  is located above the indoor air inlet  121 . In this way, both the indoor air inlet  121  and the indoor air outlet  122  may be defined on the front side wall surface of the casing  100 , and the indoor air outlet  122  may be located above the indoor air inlet  121 . Alternatively, the indoor air inlet  121  may be defined on the front side wall surface of the casing  100 , and the indoor air outlet  122  may be defined on the top surface of the casing  100 . Alternatively, the indoor air inlet  121  may be defined on the front side wall surface of the casing  100 , and the indoor air outlet  122  may be defined at the junction of the front side wall surface and the top surface of the casing  100 , so that air is blown out from the air outlet obliquely upwardly. By making the indoor air outlet  122  above the indoor air inlet  121 , on the one hand, it is convenient for the indoor heat exchanger  200  to correspond to the indoor air inlet  121 ; and on the other hand, when the indoor fan  123  sends fresh air from the indoor air outlet  122 , since the humidity of the fresh air is large, the fresh air flow from the indoor air outlet  122  will flow downwardly. As a result, the mixing effect of the fresh air and the indoor air is satisfactory, and the fresh air can be more readily drawn into the indoor air duct  110  by the indoor fan  123  from the indoor air inlet  121  below the indoor air outlet  122  for constant temperature dehumidification. 
     For example, an angle between an air supply direction of the indoor air outlet  122  and a horizontal plane is greater than 0 degrees and less than 90 degrees. Then, the air blowing direction of the indoor air outlet  122  is obliquely upward. For example, the angle between the air supply direction of the indoor air outlet  122  and the horizontal plane may be 10 degrees, 20 degrees, 35 degrees, 45 degrees, 60 degrees, 70 degrees, 80 degrees, and so on. By making the indoor air outlet  122  blow air obliquely upwardly, on the one hand, the air may be prevented from blowing directly to the user and the ceiling; and on the other hand, the airflow may be blown farther. As a result, the mixing effect is satisfactory, and the indoor temperature distribution is more uniform. Optionally, the angle between the air supply direction of the indoor air outlet  122  and the horizontal plane can be 45 degrees. In this way, it is easy to mold and manufacture, and makes the overall consistency better. 
     The fresh air inlet  310  and the fresh air outlet  320  may be rectangular, circular, elongated, elliptical, or of a plurality of micro-holes, which are not specifically limited herein. The fresh air device  300  is configured to supply fresh air to the indoor air duct  110 , and a fresh air fan may be provided inside the fresh air duct  330  to introduce airflow from the fresh air inlet  310  into the indoor air duct  110 . It is also possible to use only the negative pressure of the indoor fan  123  to press the outdoor air flow into the indoor air duct  110 . At this time, the fresh air outlet  320  should be defined on an air inlet side of the indoor fan  123 . An indoor temperature sensing device and a humidity sensing device may be used to judge whether cooling or constant temperature dehumidification is needed by the window air conditioner. 
     It should be noted that in addition to the constant temperature dehumidification mode, the window air conditioner may also have modes, such as, individual cooling and individual heating. When the window air conditioner is in the constant temperature dehumidification mode, the first indoor heat exchanger  210  may be in a cooling mode (acting as an evaporator), and the second indoor heat exchanger  220  may be in a heating mode (acting as a condenser), or the first indoor heat exchanger  210  may be in the heating mode, and the second indoor heat exchanger  220  may be in the cooling mode. In this way, when the fresh air enters the indoor air duct  110  and is blown out by the indoor air outlet  122 , the mixed air flow of the indoor air and the fresh air may be sucked into the indoor air duct  110  by the indoor fan  123  again, and then dehumidified/heated by the first indoor heat exchanger  210 , and heated/dehumidified by the second indoor heat exchanger  220 . Thus, the purpose of constant temperature dehumidification is achieved, so that the indoor air and fresh air may reach a comfortable temperature after dehumidification. In order to improve the dehumidification effect, the air flow is heated by the condenser first, and subsequently dehumidified by the evaporator. That is, in the constant temperature dehumidification mode, the first indoor heat exchanger  210  acts as a condenser, and the second indoor heat exchanger  220  acts as an evaporator. 
     It can be understood that the heat exchange modes of the first indoor heat exchanger  210  and the second indoor heat exchanger  220  may also be the same, so that when the window air conditioner needs to be cooled or heated separately, the first indoor heat exchanger  210  and the second heat exchanger  220  may be both in the cooling mode (simultaneously acting as evaporators) or the heating mode (simultaneously acting as condensers). In this way, after dual-cooled or dual-heated by the first indoor heat exchanger  210  and the second indoor heat exchanger  220 , the indoor air may be quickly cooled or heated to meet the needs of users for rapid cooling or heating. 
     Regarding the window air conditioner of the present disclosure, the first indoor heat exchanger  210  and the second indoor heat exchanger  220  are stacked in the air inlet direction of the indoor air duct  110 , and the heat exchange modes of the first indoor heat exchanger  210  and the second indoor heat exchanger  220  may be reversed, and at the same time, the fresh air outlet  320  of the fresh air duct  330  communicates with the indoor duct  110 . In this way, the first indoor heat exchanger  210  and the second indoor heat exchanger  220  may be set, such that one indoor heat exchanger is in the cooling mode and the other indoor heat exchanger is in the heating mode. In this way, both fresh air and indoor air may be dehumidified and heated. Thus, all the indoor air can be dehumidified again, which improves the dehumidification efficiency. Moreover, constant temperature dehumidification can be achieved, so that the entire indoor temperature of the window air conditioner will not drop in the dehumidification mode. Therefore, the user may feel the fresh air, and the temperature of the dehumidified air is comfortable, and there will be no cool feeling. At the same time, the indoor heat exchangers may be fully utilized during dehumidification, and there is no need to additionally install a fresh air condenser and a fresh air evaporator, which greatly reduces the manufacturing cost and the entire power requirement of the air conditioner. At the same time, a compressor  600  may be used for the dehumidification system and the heat exchange system, so that the whole machine occupies less space, the noise is small, and the production process and efficiency are improved. 
     Referring to  FIGS. 2 and 6 , the casing  100  includes an indoor casing  120 . The indoor casing  120  defines the indoor air duct  110 . The fresh air outlet  320  is defined on a rear side wall surface of the indoor casing  120 . The indoor air inlet  121  is defined on a front side wall surface of the indoor casing  120 . The first indoor heat exchanger  210  and the second indoor heat exchanger  220  are stacked in a front-rear direction of the casing  100 . 
     In this embodiment, the indoor casing  120  may be directly defined by a part of the casing  100 . Alternatively, the casing  100  may be a separate structure, and in this case, the indoor casing  120  is provided inside the casing  100 . The fresh air outlet  320  and the indoor air inlet  121  may be rectangular, circular, elongated, elliptical, or of a plurality of micro-holes, which are not specifically limited herein. By defining the indoor air inlet  121  on the front side wall surface of the casing  100  and defining the fresh air outlet  320  on the rear side wall surface of the indoor casing  120 , the fresh air outlet  320  and the indoor air inlet  121  are arranged oppositely, and both are located at the air inlet side of the indoor fan  123 . In this way, fresh air and indoor air may be more effectively drawn into the indoor air duct  110  by the indoor fan  123  for heat exchange. Moreover, the indoor air inlet  121  is defined on the front side wall surface, so that a large amount of indoor airflow may flow into the indoor air duct  110 . The heat exchange surface of the first indoor heat exchanger  210  may be provided corresponding to the indoor air inlet  121 , so that the airflow flowing in from the air inlet may quickly flow into the first indoor heat exchanger  210  and the second indoor heat exchanger  220  for heat exchange. By stacking the first indoor heat exchanger  210  and the second indoor heat exchanger  220  in the front-rear direction of the casing  100 , the overall structure may be more compact, thereby reducing the space occupied by the indoor heat exchanger  200  and further reducing the overall volume. The indoor air outlet  122  may be defined on a top side and/or a lateral side of the indoor casing  120 . 
     In one embodiment, as shown in  FIGS. 4 and 5 , an outdoor air duct  130  is further defined inside the casing  100 , and an air outlet side of the outdoor air duct  130  is configured to be in communication with the fresh air duct  330 . The window air conditioner further includes an outdoor heat exchanger  400  provided inside the outdoor air duct  130 , and an outdoor fan  500  provided inside the outdoor air duct  130  and configured to send air into the outdoor air duct  130  and the fresh air duct  330 . 
     In this embodiment, it can be understood that the casing  100  defines an outdoor air inlet  170  and an outdoor air outlet  160 , an air inlet end of the outdoor air duct  130  communicates with the outdoor air inlet  170 , and an air outlet end of the outdoor air duct  130  communicates with the outdoor air outlet  160 . The cross-sectional shape of the outdoor air duct  130  may be rectangular, circular, irregular, etc., which is not specifically limited herein. The extending direction of the outdoor air duct  130  generally coincides with the longitudinal direction of the casing  100 . The outdoor fan  500  may be an axial fan. The air outlet side of the outdoor air duct  130  refers to an air outlet end of the outdoor fan  500 . By communicating the air outlet side of the outdoor air duct  130  with the fresh air duct  330 , the outdoor fan  500  may be fully utilized, and the outdoor airflow may be blown to the outdoor air outlet  160  while being blown to the fresh air duct  330  by the outdoor fan  500 . In this way, there is no need to additionally install a fresh air fan in the fresh air duct  330 , which avoids an additional fan and reduces the overall cost. The airflow flowing into the fresh air duct  330  through the outdoor air duct  130  may be the airflow after heat exchange through the outdoor heat exchanger  400  or the airflow before heat exchange. If the airflow flowing into the fresh air duct  330  is the airflow after heat exchange through the outdoor heat exchanger  400 , the airflow may also be heated, and the power of the indoor condenser does not need to be set high, thereby improving energy efficiency. 
     In an embodiment, as shown in  FIG. 1 , the casing includes two opposite side walls and a rear end wall connecting the two opposite side walls. The rear end wall defines an outdoor air outlet  160  communicating with an air outlet end of the outdoor air duct  130 . At least one of the two opposite side walls defines an outdoor air inlet  170  communicating with an air inlet end of the outdoor air duct  130 . In this way, the airflow enters from the outdoor air inlet  170  on the side wall of the casing  100  and is sucked into the outdoor air duct  130  by the outdoor fan  500  to radiate heat to the outdoor heat exchanger  400  and then flows out of the outdoor air outlet  160 . This makes the arrangement of the outdoor air inlet  170  and the outdoor air outlet  160  more reasonable. In other embodiments, the outdoor air inlet  170  may also be defined on the rear end wall. 
     Referring to  FIGS. 5 and 6 , the casing  100  further includes an outdoor casing  140 , and the outdoor casing  140  defines the outdoor air duct  130 . The fresh air device  300  includes a fresh air casing  340 , and the fresh air casing  340  defines the fresh air duct  330 . The fresh air casing  340  is configured to be connected to the outdoor casing  140 , and the fresh air inlet  310  is configured to be defined at a location where the fresh air casing  340  and the outdoor casing  140  are connected. The outdoor casing  140  may be directly defined by a part of the casing  100 . Alternatively, the casing  100  may be a separate structure, and in this case, the outdoor casing  140  is provided inside the casing  100 . An inner cavity of the fresh air casing  340  defines the fresh air duct  330 . The cross-sectional shape of the fresh air duct  330  may be rectangular, circular, elliptical, etc., which is not specifically limited herein. The shape of the fresh air inlet  310  may be circular, rectangular, elliptical, etc., which is not specifically limited herein. The fresh air inlet  310  is defined at a location where the fresh air casing  340  and the outdoor casing  140  are connected. The airflow inside the fresh air duct  330  all flows in from the outdoor air duct  130 , so that the outdoor fan  500  drives the fresh air into the fresh air duct  330  with a better effect. Optionally, in order to facilitate the introduction of fresh air, an air guide louver may be provided at the fresh air inlet  310 . 
     In an embodiment, as shown in  FIGS. 4 and 5 , the fresh air casing  340  is provided between the outdoor heat exchanger  400  and the indoor heat exchanger  200 . By disposing the fresh air casing  340  between the outdoor heat exchanger  400  and the indoor heat exchanger  200 , on the one hand, the overall structure is more compact, and the space inside the casing  100  is used more efficiently; on the other hand, the length of the fresh air duct  330  can be reduced, that is, the path of fresh air flowing from the outdoor air duct  130  to the indoor air duct  110  is shorter, so that the air loss is reduced, the air speed and the air volume are increased, and the airflow inflow frequency is faster. 
     On the basis of the foregoing embodiments, further referring to  FIG. 4 , an air-passing area of the fresh air inlet  310  of the fresh air casing  340  is smaller than an air-passing area of the fresh air outlet  320  of the fresh air casing  340 . In this way, the air-passing area of the fresh air outlet  320  can be increased, so that enough fresh air may be blown toward the indoor air duct  110 . The air-passing area of the fresh air inlet  310  is small, so that the installation of the fresh air casing  340  and the outdoor casing  140  may be facilitated. 
     Further, the fresh air casing  340  is configured to be at least partially gradually expanded from the fresh air inlet  310  to the fresh air outlet  320 . The fresh air casing  340  may be gradually expanded from the fresh air inlet  310  to the fresh air outlet  320 , or may only be gradually expanded in the middle section, the section near the fresh air inlet  310  or the section near the fresh air outlet. By making the fresh air casing  340  at least partially gradually expanded, when the fresh air flows from the fresh air inlet  310  to the fresh air outlet  320 , the flow may be expanded at the gradually expanding section, thereby effectively reducing noise, allowing the air flow more smoothly, and meets the needs of fresh air flow. 
     In an embodiment, referring to  FIG. 4  again, at least one inner side wall surface of the fresh air casing  340  is configured to be a curved surface  341 , and the curved surface  341  is configured to be recessed from an outside of the fresh air casing  340  toward an inside of the fresh air casing  340 . When the fresh air casing  340  is arranged in a rectangular shape and has a plurality of inner side wall surfaces, at least one of the inner side wall surfaces has a curved surface  341 . When the fresh air casing  340  is arranged in a circular shape and has only one inner side wall surface, the inner wall surface of the fresh air casing  340  is a curved surface  341 . By making at least one inner side wall surface of the fresh air casing  340  a curved surface  341 , the flow of air flow is smoother, and the air resistance and air loss are reduced. By making the curved surface  341  recessed from an outside of the fresh air casing  340  toward an inside of the fresh air casing  340 , compared with the convex configuration, the air flow may be prevented from forming turbulence in the fresh air duct  330 , thereby further reducing noise. 
     In an embodiment, as shown in  FIGS. 2, 4 and 6 , the casing  100  includes a chassis  150 , and the fresh air device  300  is installed on the chassis  150 . The window air conditioner further includes the compressor  600  that is installed on the chassis  150 . The fresh air device  300  and the compressor  600  are disposed on two sides of the chassis  150  in a longitudinal direction of the chassis  150 . The chassis  150  provides installation and support for the compressor  600 , the heat exchanger and other structures. The compressor  600  usually occupies a large space and has a large weight. By positioning the fresh air device  300  and the compressor  600  on two sides of the chassis  150  in a longitudinal direction of the chassis  150 , on the one hand, the layout is more reasonable, the overall arrangement is more compact, and the installation space on the chassis  150  is fully utilized, and on the other hand, the weight distribution on the chassis  150  is more uniform, which prevents deformation of the chassis  150  due to uneven distribution of gravity, and facilitates the installation of the entire machine. 
     The working system of the entire window air conditioner will be described as follows. 
     In an embodiment, referring to  FIG. 7 , the window air conditioner further includes the compressor  600 , the outdoor heat exchanger  400 , and a refrigerant circulation pipe. 
     A discharge pipe  610  is provided at a refrigerant outlet of the compressor  600 , and a suction pipe  620  is provided at a refrigerant inlet of the compressor  600 . 
     The discharge pipe  610 , the outdoor heat exchanger  400 , the first indoor heat exchanger  210 , the second indoor heat exchanger  220 , and the suction pipe  620  are configured to be sequentially communicated with one another through the refrigerant circulation pipe. 
     In this embodiment, the compressor  600  may be a variable frequency compressor or a fixed frequency compressor. By making the compressor  600  a variable frequency compressor, a dual system of refrigeration and constant temperature dehumidification may be readily achieved, and one compressor can be spared, thereby making the overall structure compact, reducing cost and power, and greatly improving energy efficiency. It can be understood that a first valve  940  may be provided on the refrigerant circulation pipe between the outdoor heat exchanger  400  and the first indoor heat exchanger  210 , and a second valve  950  may be provided on the refrigerant circulation pipe between the first indoor heat exchanger  210  and the second indoor heat exchanger  220 . The first valve  940  and the second valve  950  may be solenoid valves, electronic expansion valves, or throttle valves, which can control the on-off or flow rate of the piping where they are located. By providing the first valve  940  and the second valve  950 , it is possible to control whether the refrigerant flows into the first indoor heat exchanger  210  and the second indoor heat exchanger  220 , thereby controlling whether the first indoor heat exchanger  210  and the second indoor heat exchanger  220  participate in cooling or heating. 
     When the dehumidification mode needs to be turned on, the high-temperature refrigerant from the compressor  600  enters the outdoor heat exchanger  400  (condenser), so that the high-temperature refrigerant from the outdoor heat exchanger  400  reaches the first valve  940 . At this time, the first valve  940  may be fully or mostly opened, so that the temperature of the first indoor heat exchanger  210  is equal to or slightly lower than the temperature of the outdoor heat exchanger  400 . At this time, the first indoor heat exchanger  210  acts as a condenser to heat the airflow. And then the secondary high-temperature refrigerant flowing out of the first indoor heat exchanger  210  reaches the second valve  950 , and the second valve  950  acts as a capillary throttling. After the throttling, the refrigerant turns to low-temperature refrigerant and flows through the second indoor heat exchanger  220 . At this time, the second indoor heat exchanger  220  acts as an evaporator to cool the airflow, that is, dehumidify the airflow, and the refrigerant flowing out of the second indoor heat exchanger  220  returns to the compressor  600 . In this way, the mixed air of the fresh air and indoor air is heated by the first indoor heat exchanger  210  first, and then cooled and dehumidified by the second indoor heat exchanger  220 , and afterwards enters the indoor air duct  110  and is blown out of the indoor air outlet  122 , so that the indoor dehumidification is achieved without blowing cold air and the dehumidification effect is better. Certainly, the first indoor heat exchanger  210  may act as an evaporator, and the second indoor heat exchanger  220  may act as a condenser. Then, the fresh air and the indoor air are first cooled and dehumidified, and then heated, and the purpose of constant temperature dehumidification may also be achieved. 
     When dehumidification is not required and only the cooling mode needs to be turned on, the high-temperature refrigerant flowing out of the compressor  600  enters the outdoor heat exchanger  400  (condenser), so that the high-temperature refrigerant coming out of the outdoor heat exchanger  400  reaches the first valve  940 . At this time, a small part of the first valve  940  is opened to play the role of capillary throttling, so that the temperature of the first indoor heat exchanger  210  is much lower than the temperature of the outdoor heat exchanger  400 . At this time, the first indoor heat exchanger  210  acts as an evaporator playing the role of cooling. And then the low-temperature refrigerant flowing out of the first indoor heat exchanger  210  reaches the second valve  950 . The second valve  950  is fully or mostly opened, playing the role to completely pass or re-throttle. The refrigerant passing through the second valve  950  flows through the second indoor heat exchanger  220 . At this time, the second indoor heat exchanger  220  acts as an evaporator, playing the role of secondary cooling. The refrigerant flowing out of the second indoor heat exchanger  220  returns to the compressor  600 . In this way, the mixed air of the fresh air and indoor air is cooled by the first indoor heat exchanger  210  first, and then further cooled by the second indoor heat exchanger  220 , and afterwards enters the indoor air duct  110  and is blown out of the indoor air outlet  122 , so that the rapid cooling of indoor may be achieved. 
     In an embodiment, as shown in  FIGS. 8 and 9 , the refrigerant circulation pipe includes a first piping  710  connecting the discharge pipe  610  and the outdoor heat exchanger  400 ; and a second piping  720  connecting the suction pipe  620  and the second indoor heat exchanger  220 . The window air conditioner further includes a switch  800 . 
     The switch  800  is serially connected to the first piping  710  and the second piping  720  and having a first switching state and a second switching state. 
     In the first switching state, the first piping  710  connected to two ends of the switch  800  is turned on, and the second piping  720  connected to another two ends of the switch  800  is turned on. 
     In the second switching state, the first piping  710  between the discharge pipe  610  and the switch  800  is configured to be in communication with the second piping  720  between the switch  800  and the second indoor heat exchanger  220 , and the first piping  710  between the outdoor heat exchanger  400  and the switch  800  is configured to be in communication with the second piping  720  between the suction pipe  620  and the switch  800 . 
     In this embodiment, the switch  800  may be a four-way valve or other switch  800  so that the refrigerant does not enter the outdoor heat exchanger  400  and the second indoor heat exchanger  220  at the same time. By providing the switch  800 , the function of the air conditioner may be enriched. It can be understood that the switch  800  is serially connected to the first piping  710  and the second piping  720 , that is, two ends of the switch  800  communicate with the first piping  710 , and another two ends of the switch  800  communicate with the second piping  720 . 
     When the switch  800  is in the first switching state, the high-temperature refrigerant flowing out of the discharge pipe  610  of the compressor  600  flows to the outdoor heat exchanger  400  through the first piping  710 , and then sequentially flows into the first indoor heat exchanger  210  and the second indoor heat exchanger  220 , and finally flows back to the compressor  600  via the second piping  720  and the suction pipe  620 . By controlling the opening degrees of the first valve  940  and the second valve  950 , the first indoor heat exchanger  210  may be controlled to be in a cooling state or a heating state, so that the entire system may be controlled in a constant temperature dehumidification mode or a dual refrigeration mode. 
     When the switch  800  is in the second switching state, the high-temperature refrigerant flowing out of the discharge pipe  610  of the compressor  600  flows into the second indoor heat exchanger  220  through the first piping  710  and the second piping  720 , and then flows to the first indoor heat exchanger  210  and the outdoor heat exchanger  400 , and finally flows back to the compressor  600  through the first piping  710 , the second piping  720 , and the suction pipe  620 . By controlling the opening degrees of the first valve  940  and the second valve  950 , the first indoor heat exchanger  210  may be controlled to be in a cooling state or a heating state, so that the entire system may be controlled in a constant temperature dehumidification mode or a dual heating mode. Regarding an embodiment in which it is controlled whether the first indoor heat exchanger  210  is in a cooling state or a heating state through the first valve  940  and the second valve  950 , it is similar to the above-mentioned embodiment without switching states, which will not be repeated here. 
     In an embodiment, referring to  FIG. 9  again, the window air conditioner further includes a refrigerant radiator  900 , a one-way throttle valve  910 , a first one-way valve  920 , and a second one-way valve  930 . 
     The refrigerant radiator  900  is serially connected to the refrigerant circulation pipe between the outdoor heat exchanger  400  and the first indoor heat exchanger  210 . 
     The one-way throttle valve  910  is serially connected to the refrigerant circulation pipe between the outdoor heat exchanger  400  and the refrigerant radiator  900 . An inlet of the one-way throttle valve  910  is adjacent to the refrigerant radiator  900 , and an outlet of the one-way throttle valve  910  is adjacent to the outdoor heat exchanger  400 . 
     The refrigerant circulation pipe further includes a third piping  730  connecting the refrigerant radiator  900  and the first indoor heat exchanger  210 ; and a fourth piping  740  connecting the refrigerant radiator  900  and the first indoor heat exchanger  210 . The fourth piping  740  is arranged in parallel with the third piping  730 . 
     The first one-way valve  920  is configured to be serially connected to the third piping  730 . An inlet of the first one-way valve  920  is adjacent to the refrigerant radiator  900 , and an outlet of the first one-way valve  920  is adjacent to the first indoor heat exchanger  210 . 
     The second one-way valve  930  is configured to be serially connected to the fourth piping  740 . An inlet of the second one-way valve  930  is adjacent to the first indoor heat exchanger  210 , and an outlet of the second one-way valve  930  is adjacent to the refrigerant radiator  900 . 
     In this embodiment, it should be noted that the refrigerant radiator  900  may reduce the temperature of the electronic control system and ensure the installability of the electronic control system. The one-way throttle valve  910  means that the flow path is throttled only in one direction, and the entire flow path is completely circulated in the other direction. The one-way throttle valve  910  is serially connected to the refrigerant circulation pipe between the outdoor heat exchanger  400  and the refrigerant radiator  900 , and may be unidirectionally throttled from the refrigerant radiator  900  to the outdoor heat exchanger  400 , so that the temperature of the refrigerant entering the outdoor heat exchanger  400  may be controlled. The first one-way valve  920  is serially connected to the third piping  730 , so that a unidirectional flow path may be provided from the refrigerant radiator  900  to the first indoor heat exchanger  210 . The second one-way valve  930  is serially connected to the fourth piping  740 , so that a unidirectional flow path may be provided from the first indoor heat exchanger  210  to the refrigerant radiator  900 . By providing the one-way throttle valve  910 , the first one-way valve  920 , and the second one-way valve  930 , it can be ensured that the temperature of the refrigerant passing through the refrigerant radiator  900  is not lower than the ambient temperature. By providing the refrigerant radiator  900 , the one-way throttle valve  910 , the first one-way valve  920 , and the second one-way valve  930 , heat radiation of the refrigerant as controlled by the electronic control device may be achieved and the condensation may be improved. 
     The above are only exemplary embodiments of the present disclosure, and do not therefore limit the patent scope of the present disclosure. Under the invention conception of the present disclosure, any equivalent structural transformation made by using the contents of specification and attached drawings of the present disclosure, or directly/indirectly applied in other relevant technical fields, shall be included in the scope of patent protection of the present disclosure.