Patent Publication Number: US-2021164154-A1

Title: Tumble dryer

Description:
FIELD OF THE INVENTION 
     The present disclosure relates to a tumble dryer comprising a housing, a rotatable drum in the housing being accessible from a front side of the housing, a fan arrangement for producing a flow of process air passing through the drum, and a heat pump for drying the process air before entering the drum, wherein the heat pump comprises a condenser, a compressor, and an evaporator. 
     TECHNICAL BACKGROUND 
     Such a tumble dryer is shown for instance in EP-3118365-A1, describing a tumble dryer with a heat pump. Although such tumble dryers are usually more energy efficient than tumble dryers with simple electric heating elements that recirculate less of the heat energy of process air leaving the drum, one problem with such tumble dryers is how to improve their energy efficiency further. 
     SUMMARY OF THE INVENTION 
     One object of the present disclosure is therefore to provide a tumble dryer with improved energy efficiency. This object is achieved by means of a tumble dryer as defined in claim  1 . More specifically, in a tumble dryer of the initially mentioned kind, the compressor is located in the flow of process air, between the evaporator and the condenser. This means that heat dissipated by the compressor and the motor driving the compressor will contribute with heating the relatively cold process air leaving the evaporator. This improves the energy efficiency of the tumble dryer even further, and at the same time accomplishes efficient forced cooling of the compressor and the associated motor. 
     The condenser may be located behind the tumble dryer drum as seen from the housing front side, and above the compressor. This makes good use of the available space in the tumble dryer housing. 
     The condenser may be carried by a support arrangement forming a common frame which takes up the load of the condenser on either or both sides of the compressor as seen from the housing front side. This means that the load of the condenser need not be taken up by the tumble dryer housing behind the drum, which facilitates providing the heat pump as a separate, replaceable unit. The support arrangement may comprise a top frame carried by a plurality of legs, and the compressor may be located in between the legs. The condenser may be supported by a top frame supporting the condenser at the edges of the condenser bottom surface, such that process air may pass through said bottom surface at inner parts thereof. 
     The evaporator may be located in front of the compressor as seen from the housing front side, such that it can reach into the space under the tumble dryer drum which may not be completely occupied by fan arrangements and the like. 
     The evaporator, the compressor and the condenser may be arranged as components making up a heat pump unit, which may be removed from the tumble dryer without separating the components from each other. The heat pump unit may form a complete closed refrigerant loop and further include an expansion valve. 
     The components of the heat pump unit may be enclosed in an insulating shell, for instance made of expanded polypropylene, EPP. The shell may comprise an air inlet and an air outlet, as well as a drain tube for leading water out of the shell. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective view of a tumble dryer. 
         FIG. 2  illustrates schematically the flow of process air through a heat pump tumble dryer according to the present disclosure. 
         FIG. 3  shows a perspective view of a heat pump unit. 
         FIG. 4  shows a side view of the heat pump unit. 
         FIG. 5  shows a side view of a shell for the heat pump unit. 
         FIG. 6-7  show the rear side of a tumble dryer before and after installing a heat pump unit. 
         FIG. 8  shows a perspective view of a heat pump shell as seen from the front thereof. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates generally to a tumble dryer which is provided with a heat pump in order to achieve energy-efficient drying of laundry. An example of a tumble dryer  1  is illustrated in  FIG. 1 . The tumble dryer  1  has a front side  3  which is provided with a door  5  or hatch, attached to the front side  3  with hinges  7 , which provides access to a tumble dryer drum behind the door  5  where wet laundry can be loaded. 
     In a heat pump tumble dryer, process air drying the laundry can circulate within the outer enclosure of the tumble dryer.  FIG. 2  illustrates schematically and in a cross section, components of such a tumble dryer as well as a process air path  21 . As mentioned, the tumble dryer comprises a drum  11  in which wet laundry is placed. While the drum  11  rotates, a flow  21  of relatively dry process air is fed therethrough. The flow is provided by a fan  13  or blower, which in the illustrated case is located in a space under the drum  11 . 
     The tumble dryer includes a heat pump arrangement with an evaporator  15 , a compressor  17 , a condenser  19 , and an expansion valve  16  (cf.  FIG. 3 ). A refrigerant medium is forced through the heat pump arrangement by the compressor  17 , and gathers energy in the evaporator  15  which is released in the condenser  19 , as is well known per se. 
     As illustrated in  FIG. 2 , an air flow  21  is achieved where hot, humid air is extracted from the perforated drum  11  by means of the fan  13 . The air flow passes a filter  12  before reaching the fan  13  and arrives at the evaporator  15 , which cools the air flow such that moisture therein condenses into liquid water. This water is collected in the bottom section of the tumble dryer and is drained therefrom through a tube  39  (cf.  FIG. 5 ). 
     The process air flow  21 , which is now cooler and contains less water, is passed to the rear section of the tumble dryer and subsequently passes the condenser  19 , which heats the air again. Then the heated, dry air is reintroduced into the drum  11  where it is again capable of absorbing water from the laundry therein. 
     In the tumble dryer of the present disclosure, the compressor  17  is located in the flow of process air  21 , between the evaporator  15  and the condenser  19 . This means that heat dissipated from the compressor, which heat would otherwise become more or less wasted, is used to pre-heat the flow of process air  21  before it reaches the condenser  19 . At the same time, the compressor  17  becomes cooled by the process air flow  21 , which to a great extent renders other cooling arrangements, used to avoid overheating of the compressor  17 , unnecessary. This allows for a more energy efficient tumble dryer  1 , that can be produced at a lower cost. 
     As shown in  FIG. 2  and in greater detail in the side view of  FIG. 4 , such a configuration can be obtained by locating the condenser  19  behind the drum  11  as seen from the front side  3  of the tumble dryer, and above the compressor  17 . As shown in the perspective view of a heat pump unit in  FIG. 3 , the evaporator  15  can extend horizontally from the compressor  17 , and can as shown in  FIG. 2  be located in front of the compressor  17  as seen from the housing front side  3 . The evaporator  15  may then partly reach into the space below the rotatable drum  11 , and may connect to the fan arrangement  13  to receive a flow of process air therefrom. There may be provided a framework  25 ,  27 ,  29  to which the compressor  17 , the evaporator  15  and the condenser  19  are attached, such that there is formed a heat pump unit  43  which may be mounted as a whole in a tumble dryer. The heat pump unit may thus comprise a complete closed refrigerant loop, and may also include an expansion valve  16 , as shown in  FIG. 3 . 
     The condenser  19  is carried by a support arrangement  25 ,  27  of this framework. The support arrangement may comprise a top frame  25  on which the condenser  19  rests. This top frame  25  may be rectangular to carry the condenser  19  at the outer edges of the condenser bottom surface, but may provide a large opening at the inner parts of this bottom surface to allow process air to flow through the condenser to be heated. The top frame  25  may be supported by a plurality of legs  27 , in the illustrated case four legs  27 , each located at a corner of the top frame  25 . The compressor  17  may be located in between the legs  27 , and the legs may be attached to a bottom frame  29 . The condenser  19  is supported by the top frame  25  at the edges of the condenser bottom surface, such that process air may pass through this bottom surface  24  at inner parts thereof, as shown in  FIG. 2 . 
     The framework may be produced as sheet metal parts, such as aluminum or steel. Other framework configurations are possible. In order to allow the heat pump to be provided as a unit that can be installed or removed as a whole, it is preferred to provide a framework which takes up the load of the condenser  19  on either or both sides of the compressor  17  as seen from the housing front side  3 , rather than for instance letting the condenser be suspended from an inner wall in the tumble dryer. 
     It is advantageous to keep the heat pump as a unit where the evaporator  15 , the compressor  17  and the condenser  19  are included as components together with an expansion valve, and where the unit may be removed from or mounted in the tumble dryer without separating the components from each other, and instead handling them as a whole unit. The closed refrigerant medium loop in the heat pump is preferably filled and sealed in a central location, before being assembled in the tumble dryer. This also makes it simpler to replace a heat pump in an existing tumble dryer in the field. It is even possible to replace e.g. a gas heating unit in an existing tumble dryer with a heat pump. 
     The provision of the heat pump as a complete unit also makes it possible to enclose the heat pump as a whole in an insulating shell  23  as shown in  FIG. 5  as well as in the cross section of  FIG. 2 . Such a shell  23  includes openings  38 ,  40 , one air inlet  38  in the bottom part providing access to the evaporator and facing the fan arrangement, and one air outlet  40  located over the condenser and being connected to the rotating drum. The shell may be assembled from multiple parts and may be made in a suitable insulating material such as expanded polypropylene, EPP. The insulating shell improves the energy efficiency of the tumble dryer even further. 
     The heat pump unit together with the insulating shell  23  may be provided with wheels  41  that facilitate moving the heat pump unit on a floor, for instance when replacing a heat pump unit in the field. 
       FIG. 6-7  show the rear side of a tumble dryer before and after installing a heat pump unit. As illustrated in  FIG. 6 , the rear side of the tumble dryer may reveal an opening  31  or recess by taking away a back wall (not shown). The opening space is sufficient space to enclose the heat pump unit, and once fitted therein, the back wall may again be attached to the tumble dryer. 
     As shown in  FIG. 6 , there is provided openings to the rotatable drum  11  and to the fan arrangement  13  that fit with the openings  38 ,  40  in the heat pump shell  23 . There may further be provided slots  37  in the floor  35  of the rear opening  31  into which slots any wheels of the heat pump unit can project once the heat pump unit is in place, such that the heat pump unit rests firmly on the rear opening floor  35 . 
       FIG. 7  shows the same perspective view as  FIG. 6  when the heat pump unit is mounted into the rear opening. This can be done simply by rolling the heat pump unit in place in the rear opening  31 , attaching some connection points of the heat pump to the tumble dryer e.g. by means of screws, and connecting the heat pump to the electric system of the tumble dryer. 
       FIG. 8  shows a perspective view of a heat pump shell  23  as seen from the front thereof, i.e. the side which connects to the tumble dryer drum  11 . The drawing shows the openings  38 ,  40  in the bottom and upper parts connecting to the fan arrangement and to the drum, respectively. In addition to those openings, the shell may comprise electric wiring leading in and out of the shell as well as the aforementioned drain tube leading water out of the shell. 
     The present disclosure is not restricted to the above-described embodiment, and may be varied and altered in different ways within the scope of the appended claims.