Classifications

• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F58/00—Domestic laundry dryers
  • D06F58/20—General details of domestic laundry dryers 
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F58/00—Domestic laundry dryers
  • D06F58/20—General details of domestic laundry dryers 
  • D06F58/206—Heat pump arrangements
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06F—LAUNDERING, DRYING, IRONING, PRESSING OR FOLDING TEXTILE ARTICLES
  • D06F58/00—Domestic laundry dryers
  • D06F58/20—General details of domestic laundry dryers 
  • D06F58/24—Condensing arrangements

Definitions

• the present invention concerns the field of laundry drying techniques.
• the present invention refers to a laundry dryer equipped with a heat pump system.
• Laundry treating machines capable of carrying out a drying process on laundry hereinafter simply indicated as laundry dryers, generally comprise a drying chamber for accommodating therein the laundry to be dried.
• a heated and dehumidified drying medium typically air
• the heated and dehumidified drying air takes up humidity and at the same time cools down.
• the drying air then exits the drying chamber, thereby discharging humidity from the drying chamber and the laundry.
• the drying air is cooled down and dehumidified and then heated up in the heat pump system and finally reinserted again into the drying chamber.
• the heat pump system typically comprises a refrigerant flowing in a closed-loop refrigerant circuit constituted by a condenser, an expansion device, an evaporator and a compressor.
• the condenser heats up the drying air while the evaporator cools and dehumidifies the drying air leaving the drying chamber.
• the refrigerant flows in the refrigerant circuit where it is compressed by the compressor and expanded in the expansion device.
• compressors utilized in said refrigerant circuit typically comprise a compression mechanism section wherein the refrigerant is compressed.
• Known compression mechanisms comprise moving parts, such as rotary shafts, bearings, pistons, etc., which force the refrigerant to be compressed into an airtight chamber.
• the moving parts are advantageously driven by an electric motor opportunely connected thereto.
• Compressors typically used in heat pump system are rotary or scroll compressors, either hermetic or semihermetic.
• the compressor opportunely comprises a proper quantity of lubricant, such as oil.
• lubricant promotes a safe hydrodynamic lubrication inside the compressor by creating a thin film between the moving parts (rotary shafts, bearings, pistons, etc.).
• the lubricant flowing inside the compressor removes heat from the compressor motor.
• the lubricant thus acts as cooling lubricant.
• An effective way for helping the lubricant to return inside the compressor is placing the compressor at a lower level with respect the other components of the heat pump system.
• the lubricant advantageously returns to the compressor by gravity.
• the heat pump system is typically confined in a small area in the basement of the same laundry dryer.
• the compressor and the other components of the heat pump system are therefore arranged at substantially the same level.
• a first drawback of the known heat pump system is therefore constituted by the fact that the lubricant does not return to the compressor by gravity.
• the correct quantity of lubricating is not maintained inside the compressor and the compressor life and/or reliability of the compressor is therefore reduced.
• a quantity of lubricant is trapped along the refrigerant circuit.
• This quantity of lubricant may be deposited on the internal surfaces of the condenser and/or the evaporator.
• the presence of lubricant oil on said surfaces reduces the thermal conductivity (or increase the thermal resistivity) of the condenser and/or the evaporator, thus reducing the heat transfer between the refrigerant and the drying air and hence reducing the drying efficiency of the laundry dryer.
• the heating efficiency of the condenser for the drying air is therefore reduced.
• the dehumidifying effect of the evaporator for the drying air exiting the drying chamber is reduced.
• the drying cycle may last longer than desired and/or the drying effect of the laundry may not be acceptable.
• the quantity of lubricant trapped along the refrigerant circuit may accumulate in particular zones along the refrigerant circuit, for example in curves of piping connecting the components of the heat pump system. Such lubricant accumulation zones are detrimental for the heat pump functioning and therefore for the drying efficiency.
• Another drawback of the known heat pump system is constituted by the fact that, due to the partial solubility of the refrigerant into the lubricant oil, a portion of lubricant oil remains separated from the refrigerant. This portion of lubricant oil may return to the compressor thanks to the dragging action of the refrigerant on the same lubricant oil.
• the dragging action depends on the speed of the refrigerant along the refrigerant circuit. Nevertheless, the speed of the refrigerant at the condenser typically has the lowest value along the refrigerant circuit. This may cause a certain difficulty for the refrigerant to drag the lubricant, which may accumulate at the condenser.
• the presence of lubricant at the condenser reduces the thermal conductivity (or increase the thermal resistivity) of the condenser, thus reducing the heat transfer between the refrigerant and the drying air and hence reducing the drying efficiency of the laundry dryer.
• the aim of the present invention is therefore to solve the noted drawbacks.
• a laundry dryer of the type comprising a heat pump system having a refrigerant circuit where a refrigerant flows and comprising a drying air circuit in communication with a laundry container suited for receiving laundry to be dried using drying air, the refrigerant circuit comprising: a first heat exchanger for heating said drying air; a second heat exchanger for cooling said drying air; a refrigerant expansion device arranged between the first heat exchanger and the second heat exchanger, and a compressor arranged between the second heat exchanger and the first heat exchanger, said compressor comprising a compressor chamber for the refrigerant and a lubricant, by providing said compressor with lubricant so that the ratio of the amount of said lubricant to the volume of the compressor chamber is comprised between 5 and 15 ml/cc, it is possible to obtain a laundry dryer having an increased reliability and/or efficiency compared to the laundry dryers of known type.
• the present invention relates, therefore, to a laundry dryer of the type comprising a heat pump system having a refrigerant circuit where a refrigerant flows and comprising a drying air circuit in communication with a laundry container suited for receiving laundry to be dried using drying air, said refrigerant circuit comprising:
• a first heat exchanger for heating said drying air and cooling said refrigerant
• a second heat exchanger for cooling said drying air and heating said refrigerant
• a refrigerant expansion device arranged in said refrigerant circuit between said first heat exchanger and said second heat exchanger
• a rotary or a scroll compressor arranged in said refrigerant circuit between said second heat exchanger and said first heat exchanger, said compressor comprising a compressor chamber for said refrigerant and a lubricant;
• the compressor is driven at a variable rotational speed.
• the compressor is driven by means of an inverter motor.
• the drying air circuit 10 forms, therefore, a closed-loop for the drying air A.
• Laundry dryer 1 with drying air A forming a closed-loop belongs to laundry dryers known as condense laundry dryers.
• the refrigerant is advantageously a gas, such as C0 2 , which maintains its gaseous state along all the closed-loop circuit.
• a gas such as C0 2
• the gas temperature changes while passing through the first heat exchanger and the second heat exchanger.
• the first heat exchanger and the second heat exchanger act, respectively, as a gas cooler and a gas heater.
• the compressor 24 may be rotated at a fixed rotational speed or, in different preferred embodiments, it may be driven at a variable rotational speed.
• the compressor 24 used in the heat pump system 20 according to the present invention preferably comprises a rotary compressor or a scroll compressor.
• a scroll compressor uses two interleaving scrolls to compress the refrigerant R.
• one of the scrolls is fixed, while the other orbits eccentrically without rotating, thereby trapping and compressing pockets of refrigerant between the scrolls.
• Another method for producing the compression motion is co-rotating the scrolls, in synchronous motion, but with offset centers of rotation.
• the rotary shaft 250 extends downward from the rotor 242b, and is rotatably supported by a main bearing 245 and a sub bearing 248 of the compression mechanism 244.
• the sub bearing 248 is provided with a valve gear 253 for discharging a refrigerant gas compressed in the compression mechanism 244 into the sealed container 241.
• the compression mechanism 244 comprises a cylinder 246, and a piston roller 247 is contained in the cylinder 246.
• the volume between the cylinder 246 and the piston roller 247 defines the compression chamber 260.
• the piston roller 247 is mounted to a crank portion 250a of the rotary shaft 250, and eccentrically rotated in accordance with the rotation of the rotary shaft 250.
• the compression mechanism 244 is immovably- supported in the sealed container 241, having the cylinder 246 welded to the inner periphery of the sealed container 241.
• the compressed refrigerant R expelled from the compression mechanism 244 which flows into the upper space of the motor portion 242 via refrigerant paths 243 also cools down the motor portion 242 of the compressor, in particular the stator 242a.
• the ratio of the amount Q of said lubricant L to the volume Vb of the compressor chamber 260 is comprised between 5 and 10 ml/cc.
• the applicant has found that with said preferred ratio the quantity of refrigerant R trapped in the lubricant L is reduced.
• Another effect is that a lower quantity of lubricant oil L is deposited on the surfaces of one or both the heat exchangers, the condenser 21 or the evaporator 23. Thermal conductivity (or thermal resistivity) of the condenser 21 and/or the evaporator 23 is therefore not negatively affected. Heat transfer between refrigerant R and drying air A is adequately maintained and also the efficiency of the heat pump system 20 is maintained at a desired value.
• FIG. 6 shows in details the heat pump system 20 according to a preferred embodiment of the invention.
• the heat pump system 20 connects via piping 65 the first heat exchanger 23 (condenser), the expansion device 22 such as a choke, a valve or a capillary tube (not visible), the second heat exchanger 23 (evaporator) and the compressor 24.
• said components of the heat pump system 20 are confined in a small area in the basement 44.
• the components are arranged at substantially the same level with respect to the plane of the ground (X", Y").
• the laundry dryer 1 of the invention preferably comprises the removable water container 14 (shown only in fig. 1) which collects the condensed water produced, when the laundry dryer 1 is in operation, inside evaporator 23 by condensation of the surplus moisture in the drying air A arriving from the drum 9.
• the water container 14 is located at the bottom of the evaporator 23.
• the collected condensed water is sent in a reservoir located in correspondence of the highest portion of the laundry dryer 1 so as to facilitate manual discharge of the water by the user.
• First and/or second heat exchanger 21, 23 include one or more heat exchanger modules 40 located along the drying air A path.
• the evaporator can include a different number of modules from the condenser (as per the appended figure 6 where the evaporator 23 includes two modules 40 and the condenser four modules 40).
• modules 40 are located in correspondence of the basement 44 of laundry dryer 1.
• the refrigerant flow within channels 57 is substantially perpendicular to the drying air flow.
• the direction of the drying air stream and the direction of the refrigerant flow can alternatively form an angle therebetween.
• each heat exchange layer 58 includes a plurality of channels 57 which are preferably adjacent and parallel to each other. More preferably, each module 40 includes a plurality of heat exchange layers 58, more preferably all layers 58 are stacked one above the other(s) in a stacking direction Z and even more preferably parallel to each other, substantially forming a plurality of parallel rows.
• the stacking direction Z is the vertical direction, i.e., Z and Z' ' are parallel to each other.
• the stacking direction Z and the vertical direction Z" can form an angle therebetween.
• heat exchange layer 58 includes a single tube, having for example an elongated cross section, including two substantially parallel flat surfaces 59a, 59b. Within the tube, separators 58a are realized in order to longitudinally divide the interior of the tube in the plurality of channels 57. Such a structure is schematically depicted in the cross section of a heat exchange layer 58 of Figure 9. The cross section of the single channel 57 can be arbitrary. Each heat exchange layer 58 has a width W which depends on the number of channels which are located one adjacent to the other (see figure 7b).
• the width W of the layer 58 defines a direction Y which, together with the longitudinal direction X of channels 57, defines in turn a heat exchange layer plane (X,Y).
• the heat exchange layer plane (X, Y) might be, when the module 40 is mounted on the laundry dryer 1, either parallel to the horizontal plane (X", Y") defined by the laundry dryer 1 or tilted with respect to the same.
• the heat exchange layer plane (X, Y) can be perpendicular to the stacking direction Z or form an angle with the same.
• each heat exchange layer 58 can also be not planar, but for example curved, e.g., having a concavity pointing either up or down along the stacking direction.
• the cross section of the headers 55, 56 is circular, as shown in the appended drawings, or oblong.
• the cross section of the header refers to the cross section of the header along a plane perpendicular to the stacking direction Z.
• the oblong cross section is such that its smallest diameter, i.e., the smallest cord passing through the geometrical center of the cross section, is smaller than the width W of the layer 58.
• the refrigerant R entering the module 40 via the inlet header 55 can come from the outlet header 56 of another module 40, from the compressor 24 or from the capillary tube/expansion valve 22. Additionally, the refrigerant R exiting the outlet may be directed towards the inlet header 56 of another module 40, towards the capillary tube/expansion valve 22 or towards the compressor 24.
• the connection between the compressor 24, modules 40 and capillary tube 22 and between modules 40 is made via piping 65, as it can be seen in figure 6.
• the flow of the refrigerant R will be indicated with a dotted line having a pointing arrow in the direction of the flow.
• the two headers 55, 56 are mounted vertically (i.e. their axis Z is the vertical axis Z" of the dryer 1) on the basement 44 of the laundry dryer 1, parallel one to the other, and the channels 57 connecting the two headers 55, 56 are substantially straight along the longitudinal direction X.
• the stacking direction Z is parallel to the vertical direction Z" .
• Channels 57 are divided in heat exchange layers 58, each of which includes a different tube defining upper and lower surfaces 59a, 59b within which the channels 57 are realized.
• a plurality of heat exchange layers 58 connects the inlet 55 to the outlet header 56, all heat exchange layers 58 having a first end 58b and a second end 58c longitudinally opposite to each other, the first end 58b being connected to the inlet header 55 and the second end 58c being connected to the outer header 56.
• Heat exchange layers 58 are stacked one on the other along the vertical direction Z.
• each heat exchange layer 58 has a width direction Y perpendicular to the longitudinal extension X of the channels 57. In the present embodiment, this width direction Y is parallel to the horizontal plane (X", Y") and to the air flow direction; i.e. the layer planes (X, Y) are horizontal (parallel to the horizontal plane (X", Y").
• the module 40 is mounted so that the heat exchange layers 58 form parallel horizontal planes between which the process air flows.
• a plurality of apertures 57a are realized, in each aperture 57a a channel 57 being inserted.
• the so-formed rows of apertures 57a are parallel one to the other and perpendicular to the longitudinal extension Z of the header 55, 56.
• the refrigerant R enters the inlet header 55 of module 40 via an inlet aperture 55in along a flow direction parallel to the longitudinal extension Z of header 55 and branches off into the various channels 57 via apertures 57a.
• the heat exchange layers 58 are "parallel" to each other according to the refrigerant flow direction.
• the flow of the refrigerant is substantially parallel to the flow direction of the refrigerant R in the other channels 57 and has the same direction.
• the refrigerant R then exits the module 40 via an outlet aperture 56out of outlet header 56.
• the direction of flow of refrigerant in the headers 55, 56 is perpendicular to the drying air flow.
• the flow of the refrigerant in the inlet header 55 is parallel to the flow of the refrigerant in the outlet header 56, but with opposite direction.
• the module 40 includes only two headers 55, 56, the inlet and the outlet header.
• the headers are lying on the horizontal plane (X, Y) and more preferably are disposed along the air flow direction Y.
• not all layers are connected to both inlet and outlet headers 55, 56, on the contrary only the topmost and the lowermost layers are connected to the inlet and the outlet layer, respectively.
• All other layers 58 have their ends 58b, 58c connected to their adjacent layers, e.g. one end to their lower and one end to their upper layer.
• the various layers 58 are substantially formed by a single channels' tube bending on itself several times in order to form the stacked layers.
• the inlet and the outlet headers 55, 56 disposed within the basement 44 substantially parallel to the drying air flow direction Y, also the resulting refrigerant flow within the headers is parallel to horizontal plane (X", Y").
• the inlet and outlet headers 55, 56 are located within the basement 44 at different height along the vertical direction Z", so the plurality of layers 58 all formed by the single tube are stacked one above the other in a stacking direction Z which still corresponds to the vertical direction Z".
• Channels layers 58 are parallel to each other and their longitudinal extension X is perpendicular to the process air flow direction Y.
• the single tube within which the various channels 57 are realized has a first rectilinear portion 58e defining the first channels layer connected to the inlet header 55 via one of its ends 58b, it then includes a U-shaped bend 58f and it extends for a second rectilinear portion 58g parallel to the first rectilinear portion 58e defining the second channels layer, and so on, till the last rectilinear portion 58z forming the last layer, which is connected by one of its ends 58c to the outlet header 56.
• a single row of apertures 57a is formed in each header 55, 56 and the flow of refrigerant in the various layers 58 can be considered in series with respect to the refrigerant flow.
• the flows of refrigerant within the various channels 57 forming the channels layers are parallel to each other. Additionally, the channels layer planes (X, Y) are parallel to the horizontal plane (X", Y").
• the flows of the refrigerant R in the inlet and outlet headers 55, 56 are preferably parallel to each other.
• the two flows can have the same direction, or opposite directions.
• the channels 57 above described of both embodiments are cylindrical tubes, i.e. have a circular cross section.
• said channels 57 have a hydraulic diameter DH smaller or equal than 5 mm, i.e. DH ⁇ 5.
• the channels 57 may have different shape with different cross section shape. Accordingly, the hydraulic diameter DH of each of the channel, where the hydraulic diameter DH is defined as
• A is the cross sectional area of the channel and P is the wetted perimeter of the cross-section of the channel 57, is smaller or equal than 5 mm, i.e. DH ⁇ 5 mm, more preferably DH ⁇ 3 mm, even more preferably DH ⁇ 1 mm.
• first and/or second heat exchanger generally includes a plurality of channels to enable the refrigerant R to flow therethrough.
• said channels Preferably, said channels have a hydraulic diameter smaller than 5 mm.
• the amount of refrigerant R (refrigerant charge) used in such heat pump laundry dryer is preferably smaller or equal than 300gr.
• hydrocarbons as refrigerants, which are flammable, can be therefore also considered, due to the low amount required.
• the amount of refrigerant R (refrigerant charge) may be bigger than 300gr.
• the amount Q of lubricant L is set at a value so that the ratio of the amount Q of lubricant L to the amount of refrigerant R is preferably comprised between 0,2 and 0,5 ml/gr, in particular when the refrigerant charge is smaller or equal than 300gr.
• the amount Q of lubricant L is set at a value so that the ratio of the amount Q of lubricant L to the amount of refrigerant R is preferably smaller than 0,25 ml/gr, in particular when the refrigerant charge is bigger than 300gr.
• the refrigerant R used in the refrigerant circuit 30 of the heat pump system 20 according to the present invention may be preferably one of the refrigerants of the group comprising: HydroFluoroCarbons (HFC), such as R134a and R407C; HydroFluoroHolefins (HFOs) or hydrocarbons (HC), such as R290 or R441a.
• Hydrocarbons (HC) are particularly preferred in a heat pump system using at least one heat exchanger with channels having a hydraulic diameter smaller than 5 mm.
• the present invention allows the set objects to be achieved.
• it makes it possible to obtain a laundry dryer having an increased reliability and/or energy efficiency.

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• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Detail Structures Of Washing Machines And Dryers (AREA)

Applications Claiming Priority (1)

Publications (2)

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ID=50693639

Family Applications (1)

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• 2014
  • 2014-04-28 EP EP14723374.6A patent/EP3137674B1/de active Active
  • 2014-04-28 WO PCT/EP2014/058587 patent/WO2015165487A1/en active Application Filing
  • 2014-04-28 AU AU2014392299A patent/AU2014392299A1/en not_active Abandoned
  • 2014-04-28 CN CN201480078444.5A patent/CN106255780B/zh active Active

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