EP2852702B1 - Method for operating a dryer with a latent heat accumulator, and dryer suitable for this purpose - Google Patents

Description

The invention relates to a method for operating a dryer with a latent heat storage, in particular of such a tumble dryer, and a dryer suitable for this purpose. In particular, the invention relates to a method for operating a dryer with a drying chamber for objects to be dried, a drive motor, a control device and a process air duct in which a heater, a heat exchanger, a process air blower and a latent heat accumulator are located.

When using a household appliance, the economic handling of the energy used is very important. Especially much energy in the form of heat falls in water-bearing household appliances such. Washing machines, tumble dryers and dishwashers. It is therefore known to store heat energy that is no longer required in a domestic appliance in a latent heat storage device contained therein. Dryers with a latent heat storage are known per se.

The DE 3710710 A1 describes a condensation dryer with a closed recirculation circuit in which a recirculation fan, an electric air heater, a laundry container, a heat exchanger and a latent heat storage are arranged with a latent heat storage means, wherein the latent heat storage is in the recirculation loop between the heat exchanger and the electric air heater. The latent heat accumulator absorbs heat energy from the moist, warm process air which flows out of the drying chamber, by melting a medium contained in the latent heat accumulator. If the entire contents of the latent heat storage has melted and the coolant supply to the heat exchanger must be turned on, the electric air heater can be throttled or turned off, because the latent heat storage can then be used to heat the process air.

The DE 102 24 940 A1 discloses a condensation dryer with a drying chamber, a closed process air circuit, a process air blower, a heater and a removably arranged in the process air circuit latent heat storage. This replaces the common, air-working heat exchanger. The latent heat accumulator can be discharged separately from the dryer by removing it so that it can deliver the heat outside the dryer.

The DE 10 2008 006 348 A1 describes a condensation dryer with a drying chamber for objects to be dried, a process air duct in which there are an electric heater, a heat exchanger and a blower, a latent heat storage and a cooling air duct, the latent heat storage is arranged in the cooling air duct.

The WO 2011/054895 A1 describes a dryer with a drying chamber for objects to be dried and a latent heat storage, which has a heat-conductive filler, which is in particular a metal foam. Preferably, the storage medium is introduced into the foam. As a result, an improvement in the efficiency of the latent heat storage is achieved.

The DE 10 1009 026 649 A1 relates to a method for controlling a drying process and a household appliance for drying a moist material, which is set up for carrying out such a method.

The WO 2012/098010 A1 relates to a latent heat storage comprising two storage media whose phase transition temperatures are different from each other.

The DE 10 2007 031 481 A1 relates to a washer-dryer with a sorbent-containing sorbent unit in which a heater is arranged. During a wash cycle or rinse cycle, a heated desorbate released from the sorbent by means of the heater can be released from the sorbent unit, at least part of the heat of the desorbate reaching a washing or rinsing liquor. During a drying cycle, however, a stream of moist air from the laundry to the sorbent unit, and a stream of air from the sorber unit back to the laundry feasible.

The heat transfer to the latent heat storage is particularly efficient when the heat transfer takes place in a temperature range in which takes place in the storage medium used in the latent heat storage a phase change. Otherwise, a heat transfer would only lead to a heating of the storage medium, the medium absorbs only relatively little energy.

When using a latent heat storage in a condensation dryer (hereinafter abbreviated as "dryer") are usually connected to the drying chamber, generally a laundry drum, a classic heat exchanger and the latent heat storage in series. A classic heat exchanger in this case is a heat exchanger, is passed through a coolant, in particular an air-to-air heat exchanger or the evaporator of a heat pump. During the charging of the latent heat storage, for example by means of a initiated by the heat transfer from the humid process air phase change in the storage medium from solid to liquid, condenses in the moisture at the latent heat storage, the classical heat exchanger is usually off. This can be done, for example, that no cooling air is passed through an air-to-air heat exchanger or through the evaporator of a heat pump no refrigerant is passed, which can absorb heat by evaporation of the refrigerant. As soon as the latent heat accumulator is charged and thus the moist, warm process air from the drying chamber can no longer cool, the heater is generally switched off and the heat exchanger is switched on. As a result, the moist, warm process air is cooled from the drying chamber in the heat exchanger by condensation of the moisture contained in it and then heated by passage through the latent heat storage by heat exchange with this again. The heated process air then passes again to the drying of wet laundry in the drying chamber, etc. If the latent heat accumulator discharged, the heater is turned on again and turned off the heat exchanger to allow recharging the latent heat storage. These operations, collectively referred to as "cycle", are repeated, with the highest possible number of cycles is desirable for the most economical operation of the dryer.

A latent heat storage generally includes a phase change storage medium (hereinafter also referred to as "PCM storage medium" or abbreviated as "storage medium") in which heat energy is stored about its use for a phase change (phase transition) of the storage medium. In the case of heat absorption of a latent heat accumulator, the storage medium, such as e.g. a paraffin or a salt hydrate. The largest storage density lies in the temperature range of the phase change. It is therefore desirable to rapidly reach this temperature range when using a latent heat storage in a dryer.

Against this background, the object of the present invention was to provide an improved method for operating a dryer, in particular a tumble dryer, with a latent heat store. Preferably, a more efficient and faster charging of the latent heat storage is to be achieved. The object of the invention was also to provide a suitable for carrying out this process dryer.

The solution of this object is achieved according to this invention by a method for operating a dryer and a suitable dryer with the features of the corresponding independent claims. Preferred embodiments of the method according to the invention and of the dryer according to the invention are listed in the respective dependent claims. Preferred embodiments of the method according to the invention correspond to preferred embodiments of the dryer according to the invention and vice versa, even if it is not explicitly stated herein.

• (a) der Antriebs motor gleich Zeitig den Antrieb des Prozessluftgebläses und des Kühlluftgebläses bewirkt, und
• (b) in einer Aufladungsphase der Latentwärmespeicher durch Wärmeübertragung von der feuchtwarmen Prozessluft aus der Trocknungskammer aufgeladen wird, während das Prozessluftgebläse betrieben wird, um die Prozessluft mit einer Luftströmungsgeschwindigkeit F1 durch den Latentwärmespeicher zu leiten; und
• (c) nach Aufladung des Latentwärmespeichers zur Einleitung einer Entladungsphase die Heizung abgeschaltet oder mit einer gegenüber Schritt (b) verminderten Leistung betrieben wird; und
• (d) das Prozessluftgebläse in der Entladungsphase betrieben wird, um die Prozessluft mit einer Luftströmungsgeschwindigkeit F2, die größer ist als F1, durch den Latentwärmespeicher zu leiten.

The invention thus relates to a method for operating a dryer with a drying chamber for objects to be dried, a drive motor, a control device and a process air duct in which a heater, a heat exchanger, a process air blower and a latent heat storage are located, and a cooling air duct, in the the heat exchanger and a cooling air blower are located, wherein

• (A) the drive motor at the same time causes the drive of the process air blower and the cooling air blower, and
• (b) in a charging phase, the latent heat storage is charged by heat transfer from the moist, warm process air from the drying chamber while the process air blower is operated to pass the process air through the latent heat storage at an air flow rate F1; and
• (C) after charging the latent heat storage to initiate a discharge phase, the heater is switched off or operated at a reduced power compared to step (b); and
• (D) the process air blower is operated in the discharge phase to the process air with an air flow rate F2, which is greater than F1, to pass through the latent heat storage.

The heater is in particular an electric heater or a gas heater, wherein an electric heater is preferably used.

In an advantageous embodiment of this method step (b) for a predetermined period .DELTA.t _a and / or step (c) for a predetermined period .DELTA.t _b performed, wherein in the controller, a relationship between .DELTA.t _a and / or .DELTA.t _b and a loading of Drying chamber is deposited with objects to be treated and / or a moisture content of objects to be treated. This embodiment takes into account the fact that the duration of charge and discharge of the latent heat storage depend on the drying process in the drying chamber, and thus in particular on a loading of the drying chamber with objects to be dried, eg items of laundry. Based on empirical values in experiments with different loads, in which the temperature profile or the course of the charging and discharging of the latent heat storage was tracked as a function of time in a drying process, approximately such a time-controlled method can be determined, stored in the controller and as Embodiment of the method according to the invention are performed.

Preferably, the heater is turned off in step (c) after a full charge of the latent heat storage. "Complete discharge" here means, in particular, that a phase change in the storage medium is completely completed and only a cooling or heating of the storage medium takes place.

In a preferred embodiment, the latent heat accumulator is provided with at least one temperature sensor, and the charging and / or the discharge of the latent heat accumulator is followed by temperature measurements by means of the at least one temperature sensor.

Thus, it has proved to be advantageous for the operation of a condensation dryer when in each case a temperature sensor is arranged in front of and behind the therein latent heat storage in the process air duct. The temperatures measured by the two temperature sensors, in particular their difference, allow a determination of the state of charge of the latent heat accumulator. In this case, the state of charge means the extent of the phase transition from the liquid to the solid state in the phase change storage medium of the latent heat accumulator. The state of charge is thus a measure of the ability of the latent heat storage for storing heat energy. The temperature sensors are preferably connected to a control device which can automatically trigger a shutdown or connection of the heater.

The process air blower used in the method according to the invention preferably has a preferred direction of rotation. That is, in particular due to the design of the fan blades at the same speed, the amount of air carried per unit time in the one direction of rotation of the blower greater than in the opposite direction. Thus, in a simple manner, in that the rotational speed of a drive motor does not have to be changed, a variation of the air flow velocity F can be achieved.

In a preferred embodiment of the method according to the invention, therefore, the process air blower on a preferred direction of rotation and is rotated in step (b) against the preferred direction of rotation and in step (c) in the preferred direction of rotation.

Alternatively or in addition to this, however, a drive motor with a variable speed can also be used, so that the variation of the air flow rate F provided according to the invention can be achieved by changing the rotational speed of a drive motor.

According to the invention, it is preferred that the steps (c) and (d) are carried out up to a predetermined discharge, ie a predetermined low state of charge, of the latent heat store and then the steps (b) to (d) are repeated several times. The number of times of performing steps (b) to (d) is the number of cycles. With the present invention, an increase in the number of cycles per unit time can be achieved so that a more efficient operation of the latent heat storage and thus of the dryer can be realized.

A predetermined low state of charge can be realized, for example, by taking advantage of the fact that after a completed solidification of the storage medium, ie after a completed phase transition, only a further cooling of the storage medium takes place. The predetermined low state of charge can thus be realized by reaching a predetermined lower threshold temperature or a predetermined cooling rate.

Accordingly, a predetermined charge of the latent heat storage can be detected by reaching a predetermined upper threshold temperature or a predetermined heating rate.

In general, the lower and / or upper threshold temperature as well as the predetermined cooling rates and heating rates for the storage medium are then stored in the control device.

Preferably, these may vary depending on a desired drying process.

It is also preferred that at least during the performance of step (c) a cooling medium is passed through the heat exchanger. According to the type of heat exchanger is not limited, so that the cooling medium may be, for example, the refrigerant of a heat pump or cooling air of an air-to-air heat exchanger.

In the method according to the invention, however, an air-air heat exchanger is preferably used, so that the cooling medium is preferably cooling air. Preferably, a cooling air duct is then present in the heat exchanger, is passed through the air, in particular from a storage room of the dryer, as a cooling medium by means of a cooling air blower. In this case, the cooling air blower preferably has a preferred direction of rotation. In a preferred embodiment of the invention, the cooling air is then such passed through the cooling air passage that the cooling air blower is rotated in step (b) against its preferred direction of rotation and in step (c) in its preferred direction of rotation. However, the cooling-air blower can alternatively or in addition to this also be operated by the speed in step (b) is lower than in step (c).

In general, the drying space is a drum driven by an electric drive motor, which may use the same motor as that used for the process air blower or a separate motor.

In an advantageous embodiment of the invention, a so-called single engine concept is realized in which drying chamber, process air blower and, a cooling air blower are operated with the same drive motor.

The type of drive motor, generally an electric drive motor, is not limited according to the invention. However, it has proved to be particularly advantageous if a BLDC motor is used as the drive motor. A BLDC motor is a brushless DC motor, in which the usual mechanical commutator with brushes for power application is replaced by an electronic drive circuit. Typically, in BLDC motors, the rotor is realized with permanent magnets and the fixed stator comprises coils that are driven by an electronic circuit offset in time to produce a rotating field, which generates a torque at the permanent magnet rotor. With BLDC motors it is possible to make the electronic commutation dependent on the rotor position, the rotor speed and the torque. In this case, a sensor-controlled and a sensorless commutation are used to detect the rotor position and speed.

In any case, the use of a BLDC motor as a drive motor also allows a change in the speed in a simple manner and in particular a high speed. Thus, by using a BLDC motor, a better implementation of the method according to the invention is possible. In particular, a rotational speed ω _{1 of} the drive motor in step (b), which is smaller than a rotational speed ω ₂ in step (c). Preferably, the rotational speed ω ₁ is smaller by about 10 to 50% than the rotational speed ω ₂ . In addition, it has been found that when using a BLDC motor under otherwise identical conditions, in particular the same speed, a higher energy efficiency compared to other electric motors is given.

1. (a) in einer Aufladungsphase der Latentwärmespeicher durch Wärmeübertragung von der feuchtwarmen Prozessluft aus der Trocknungskammer aufgeladen wird, während das Prozessluftgebläse betrieben wird, um die Prozessluft mit einer Luftströmungsgeschwindigkeit F1 durch den Latentwärmespeicher zu leiten;
2. (b) nach Aufladung des Latentwärmespeichers zur Einleitung einer Entladungsphase die Heizung (4) abgeschaltet oder mit einer gegenüber Schritt (a) verminderten Leistung betrieben wird; und
3. (c) das Prozessluftgebläse in der Entladungsphase betrieben wird, um die Prozessluft mit einer Luftströmungsgeschwindigkeit F2 > F1 durch den Latentwärmespeicher zu leiten.

The invention also relates to a dryer with a drying chamber for objects to be dried, a drive motor, a control device and a process air duct in which a heater, a heat exchanger, a process air blower and a latent heat storage are located, and a cooling air duct in which the heat exchanger and a cooling air blower are located, wherein the drive motor simultaneously causes the drive of the process air blower and the cooling air blower and the control device is designed to perform a method in which:

1. (A) is charged in a charging phase of the latent heat storage by heat transfer from the moist heat process air from the drying chamber, while the process air blower is operated to direct the process air with an air flow rate F1 through the latent heat storage;
2. (B) after charging the latent heat storage to initiate a discharge phase, the heater (4) is switched off or operated at a reduced power compared to step (a); and
3. (C) the process air blower is operated in the discharge phase to pass the process air through the latent heat storage with an air flow rate F2> F1.

Preferably, the latent heat storage in the dryer according to the invention comprises a phase change storage medium containing at least one inorganic salt hydrate and / or an organic compound.

Preferably, the dryer in the latent heat storage contains a phase change storage medium having a phase transition from the liquid to the solid state in the temperature range of 30 to 65 ° C, more preferably in the temperature range of 35 to 60 ° C and most preferably in the temperature range of 45 to 55 ° C.

In a preferred embodiment of the invention, the phase change storage medium used in the dryer contains a salt hydrate, wherein the salt hydrate preferably contains at least one salt from the group consisting of sodium acetate, sodium thiosulfate, magnesium nitrate, ammonium nitrate and magnesium chloride. As additions to other salts, potassium nitrate and lithium nitrate may also be used.

• eine Mischung von 58,7 Gew-% Mg(NO₃)₂ · 6 H₂O und 41,3 Gew.-% MgCl₂ · 6 H₂O mit einem Schmelzpunkt von 59°C;
• eine Mischung von 61,5 Gew.-% Mg(NO₃)₂ 6 H₂O und 38,5 Gew.-% NH₄NO₃ mit einem Schmelzpunkt von 52°C;
• CH₃COONa (Natriumacetat) · 3H₂O mit einem Schmelzpunkt von 54°C; und
• Na₂S₂O₃ (Natriumthiosulfat) · 5H₂O mit einem Schmelzpunkt von 48°C.

Examples of suitable salt hydrates are, for example:

• a mixture of 58.7% by weight of Mg (NO _{3) 2} · 6H ₂ O and 41.3 wt .-% MgCl ₂ · 6 H ₂ O having a melting point of 59 ° C;
• a mixture of 61.5 wt% Mg (NO ₃ ) ₂ 6 H ₂ O and 38.5 wt% NH ₄ NO ₃ with a melting point of 52 ° C;
• CH ₃ COONa (sodium acetate) .3H ₂ O with a melting point of 54 ° C .; and
• Na ₂ S ₂ O ₃ (sodium thiosulfate) · 5H ₂ O with a melting point of 48 ° C.

• Paraffine (Wärmeparaffine) mit unterschiedlichen Schmelzpunkten;
• Myristinsäure mit einem Schmelzpunkt von 58°C;
• eine Mischung von 89 Gew.-% Palmitinsäure und 11 Gew.-% Acetamid mit einem Schmelzpunkt von 57,2°C;
• eine Mischung von 74,9 Gew.-% Palmitinsäure und 25,1 Gew.-% Propionamid mit einem Schmelzpunkt von 50°C.

In a further preferred embodiment of the invention, the storage medium contains an organic compound. Examples of suitable organic compounds or mixtures of organic compounds are:

• Paraffins (heat paraffins) with different melting points;
• Myristic acid with a melting point of 58 ° C;
• a mixture of 89% by weight of palmitic acid and 11% by weight of acetamide having a melting point of 57.2 ° C;
• a mixture of 74.9 wt .-% palmitic acid and 25.1 wt .-% propionamide having a melting point of 50 ° C.

Moreover, as a storage medium in the latent heat storage and a mixture of organic and inorganic compounds can be used. An example of this is a mixture of 80 wt .-% acetamide and 20 wt .-% NaNO ₃ with a melting point of 59 ° C.

Particularly preferred according to the invention is a dryer in which the storage medium contains or consists of organic compounds. It is particularly preferred in this case if the storage medium contains a paraffin.

In order to improve the thermal conductivity and thus for more efficient heat transfer, the latent heat storage may have the heat conductivity improving additives, e.g. Carbon nanotubes, which are then preferably used in an amount of 0.1 to 15 wt .-%, based on the total mass of the latent heat storage, in particular based on the total mass of storage medium and carbonaceous additive.

These carbon nanotubes (CNTs) are, in particular, microscopic tubular structures made of carbon atoms, which occupy a honeycomb structure with hexagons and three bonding partners each and are single or multiwalled. Carbon nanotubes generally have a diameter of 0.4 nm to 50 nm and a length of 10 μm to 10 mm. Preferably, multi-walled carbon nanotubes are used, in particular those having an average diameter of the tubes in the range of 10 to 20 nm, preferably 13 to 16 nm. The carbon nanotubes which can be used for use in a latent heat store are, for example, those described in US Pat US 2009/0134363 A produced manufacturing method described.

The latent heat storage device used in the dryer according to the invention generally has a latent heat storage wall, which generally comprises the storage medium. Since the latent heat storage absorb heat but must also give off, that is also functioning as a heat exchanger, the latent heat storage wall is generally composed, at least at the part intended for heat exchange, of a good heat-conducting material, e.g. a metal such as aluminum or copper, or a thermoplastic which is preferably provided with improved thermal conductivity.

In a preferred embodiment of the dryer according to the invention, the latent heat storage wall comprises a thermoplastic material. In this case, it is again preferred that the heat conductivity-improving additives are contained in the latent heat storage wall.

The thermoplastic is preferably selected from the group consisting of polyolefins, olefin copolymers and styrene copolymers. In a preferred embodiment, the polyolefin is polypropylene. In a further preferred embodiment, the styrene copolymer is an acrylonitrile-butadiene-styrene copolymer (ABS).

In a particularly preferred embodiment of the invention, the latent heat storage also contains expanded graphite, preferably in an amount of at most 15 wt .-%, based on the total mass of storage medium and carbonaceous additives.

For example, a latent heat storage can be used, as in the Scriptures WO 98/04644 A which relates to a method or a system for storing heat or cold in a storage composite material, such a storage composite material and a method for its production. The composite memory material has a phase change passing material (PCM), eg, a paraffin embedded in a matrix of expanded graphite.

The inventively usable storage media generally tend to hypothermia. Although a storage medium in the form of a supercooled solution can be used. Preferably, however, supercooling is avoided. For this purpose, a nucleating agent is often added to the storage medium, whereby suitable nucleating agents are known to the person skilled in the art for various storage media.

In one embodiment of the invention with an improved heat exchange with the storage medium, the latent heat storage of the dryer according to the invention has in its interior means for generating a flow in the storage medium.

The dryer according to the invention is in particular a tumble dryer per se or a washer-dryer. A washer-dryer here is a combination device that has a washing function for washing laundry and a drying function for drying wet laundry.

The stored in the latent heat storage by cooling of heated cooling air heat energy can be used for heating process air in the process air duct and / or the drying chamber. Thus, according to the invention, the heating of the process air in the drying chamber, i. as a result of a heat exchange between latent heat storage and drying chamber, take place. In this case, it is preferable for a surface of the latent heat store to be at a distance of at most 5 cm, preferably at most 3 cm and particularly preferably at most 2 cm from the drying chamber, and is preferably concave. In this embodiment, moreover, it is preferable that a distance between the concave surface and an outer surface of the drying chamber is between 0.5 and 5 cm.

A latent heat accumulator inserted in a condensation dryer preferably has ribs on a surface of the latent heat accumulator facing the process air duct. These ribs can serve to guide the process air through the latent heat storage. Alternatively or additionally, the ribs may be filled with a storage medium.

The invention has the advantage that a dryer with a latent heat storage can be operated with improved efficiency by the number of cycles (charging and discharging of the latent heat storage per unit time) is increased. This is possible in particular because the solidification times and melting times of an inserted storage medium can be set short. In embodiments of the invention, moreover, the heat energy can be better utilized by improving the heat exchange between the latent heat store and a heat-absorbing or donating component in the dryer. As a result, a large surface of the latent heat storage can be unnecessary, so that it can be flexibly adapted to the space conditions in the dryer. The higher efficiency can thus result from a high loading and unloading dynamics of the latent heat storage, high charge and discharge currents and high power densities.

In embodiments, the invention enables greatly reduced process air flows and cooling air flows in the charging phase, so that a significant reduction of the charging time is possible. As a result, higher cycle times can be realized. Finally, larger process air flows and cooling air flows can be realized in the discharge phase be so that a faster cooling and in particular discharge of the latent heat storage can be realized. This also leads to an increase in the number of cycles per unit of time.

In a preferred embodiment, the dryer also has a display device for different states of the dryer. For this purpose, an optical display device is preferably used. The display device can provide information about the operation of the dryer, for example, by outputting a text or by lighting different colored LEDs, for example via a charging phase or a discharge phase of the latent heat storage.

Further details of the invention will become apparent from the following description of a non-limiting embodiment of a dryer according to the invention with reference to the sole figure of the drawing, in which a method according to the invention can be carried out.

The figure shows a vertically cut dryer, in particular tumble dryer, according to a first embodiment, in which a latent heat storage in the process air duct, in particular in the circulating air duct is subsequently arranged on a drying chamber and a heat exchanger.

The dryer 1 shown in the sole figure of the drawing has a drum rotatable about a horizontal axis as a drying chamber 2, within which drivers 15 are mounted for moving laundry during a drum rotation. Process air is guided by means of a process air blower 6 in the process air duct 3 via an electric heater 4 through the drum 2. After exiting the drum 2, the process air laden with moisture is guided through a part of the process air duct designated as recirculating air channel 24. In the recirculating air channel 24, the moist, warm process air is passed through an air-air heat exchanger 5, where a heat exchange with cooling air can take place when the cooling air flows from a cooling air inlet 16 to a cooling air outlet 17. In the circulating air channel 24 is also a latent heat storage 7 with a phase change storage medium 8, on which also a heat exchange with the process air can take place. In this case, the latent heat accumulator 7 withdraws the moist, warm process air from the drum 2 in a charging phase heat. In contrast, in a discharge phase, the latent heat accumulator 7 gives off heat to cooled process air.

The moist, warm process air cools down in each case by condensation of the moisture contained in it and is in turn passed through the process air blower 6 and the electric heater 4 in the drying chamber 2, whereby the process air circuit is closed. The condensed at the air-air heat exchanger 5 and / or the latent heat storage 7 moisture is collected in a condensate tank, not shown in the figure.

The cooled process air in the recirculating air channel 24 then passes again by means of the process air blower 6 into the process air duct 3.

In the dryer of the figure, a cooling air duct is arranged in the air-air heat exchanger 5, in which a cooling air blower 10 is located.

The cooling air blower 10 has a preferred direction of rotation. The cooling air from the installation room of the dryer is then passed through the cooling air duct 9 such that the cooling air blower 10 is rotated in its preferred direction of rotation in step (a) and in its preferential direction of rotation in step (b).

It is used as the drive motor 12 in the embodiment of a dryer shown here, a BLDC motor, which simultaneously causes the drive of the process air blower 6 and the cooling air blower 10 and the drum 2.

For drying of laundry items not shown here in detail in the drum 2 is heated by the electric heater 4 from the rear, ie from the dryer door 18 opposite side of the drum 2, passed through the perforated bottom in the drum 2, comes there with the drying laundry into contact and flows through the filling opening of the drum 2 to a lint filter 19 within the filling door closing the drying door 18. Subsequently, the air flow in the dryer door 18 is deflected downward. The drum 2 is mounted in the embodiment shown in the figure at the rear bottom by means of a pivot bearing and front by means of a bearing plate 20, wherein the drum 2 with a brim on a sliding strip 21 on the bearing plate 20th rests and is held at the front end. The control of the dryer via the control device 22, which can be controlled by the user via an operating unit 23.

The phase change storage medium 8 is here a paraffin. The paraffin can store heat energy by a phase transition from solid to liquid. In the paraffin 8 storage medium, as the conductivity-improving additive, multi-walled carbon nanotubes having a mean tube diameter of 13 to 16 nm are dispersed in an amount of 5% by weight based on the total mass of the storage medium and carbonaceous additives. In the embodiment shown here, not separately shown is a proportion of expanded graphite as a second carbonaceous additive in an amount of 4 wt .-% based on the total mass of storage medium and carbonaceous additives. In the latent heat storage 7, the storage medium 10 is surrounded by a latent heat storage wall 11, in the present case of a thermoplastic material with a share of 5 wt .-% carbon nanotubes with a mean diameter of the tubes 13-16 nm, based on the total mass of thermoplastic material and Carbon nanotubes, is formed.

In the dryer of the figure, a method for operating a dryer 1 is performed, wherein in a charging phase of the latent heat storage 7 is charged by heat transfer from the moist heat process air from the drying chamber 2, while the process air blower 6 is operated to the process air with an air flow velocity F1 through the To conduct latent heat storage 7. After completion of the phase transition in the storage medium 8 of the latent heat storage 7 is charged. This state can be detected by a decrease in the temperature sensors arranged upstream of and behind the latent heat accumulator 7, a first temperature sensor 13 and a second temperature sensor 14. The temperature difference is transmitted to a control device 22, which evaluates it with regard to the charging of the latent heat accumulator 7 and can cause a shutdown of the electric heater 4. After charging the latent heat accumulator 7, the electric heater 4 is thus switched off or operated with a reduced power compared to step (a) to initiate a discharge phase. In this case, the process air blower 6 is operated so that the process air is passed through the latent heat accumulator 7 with an air flow speed F2 greater than F1.

The temperature of the entering into the drying chamber 2 process air drops down and the drying is continued due to the heat transfer from the latent heat storage 7 to the drying chamber 3 at a lower temperature level. The distance between the drying chamber 2 and the latent heat storage 7 is presently from 5 to 10 mm.

In a detected discharge of the latent heat accumulator 7 (termination of the phase transition in the storage medium from liquid to solid), which can also be determined by evaluating the temperature measurements by means of the two temperature sensors 13 and 14, the electric heater 4 can be turned on again. Step (a) is again carried out and the process air is passed through the latent heat accumulator with an air flow speed F1 less than F2 by reversing the direction of rotation of drive motor 12. The temperature of the process air and the cooling air after passing through the air-air heat exchanger 5 rise, so that the latent heat storage 7 is recharged. This cycle is repeated until the drying process is completed. The duration of the drying process may be predetermined or automatically determined by means of a moisture measurement not shown here.

The dryer of the figure also allows the implementation of a method in which step (a) for a predetermined period .DELTA.t _a and / or step (b) for a predetermined period .DELTA.t _{b are} performed, wherein in the controller 22, a relationship between .DELTA.t _a and / or At _b and a loading of the drying chamber 2 and / or a moisture content of objects to be treated is deposited.

LIST OF REFERENCE NUMBERS

1

Dryer, condensation dryer

2

Drying chamber, drum

3

Process air duct

4

Heating, especially electric heating

5

heat exchangers

6

Process air fan

7

Latent heat storage

8th

Storage medium, phase change storage medium

9

Cooling air duct

10

Cooling fan

11

Latent heat storage wall

12

Drive motor, in particular BLDC motor

13

First temperature sensor

14

Second temperature sensor

15

(Wash) driver

16

Cooling air inlet

17

Cooling air outlet

18

dryer door

19

lint

20

end shield

21

lubricating strip

22

control device

23

operating unit

24

return air duct

25

display device

Claims (14)

1. Method for operating a dryer (1) having a drying chamber (2) for items to be dried, a drive motor (12), a control device (22), a process air duct (3), in which a heater (4), a heat exchanger (5), a process air fan (6) and a latent heat accumulator (7) are disposed, and a cooling air duct (9), in which the heat exchanger (5) and a cooling air fan (10) are disposed, characterised in that

   (a) the drive motor (12) simultaneously produces the drive of the process air fan (6) and the cooling air fan (10), and

   (b) in a charging phase, the latent heat accumulator (7) is charged by the heat transfer of the warm and humid process air from the drying chamber (2), while the process air fan (6) is operated in order to route the process air with an air flow speed F1 through the latent heat accumulator (7); and

   (c) after charging the latent heat accumulator (7), the heater (4) is switched off or operated with a reduced power compared with step (a) in order to introduce a discharge phase; and

   (d) the process air fan (6) is operated in the discharge phase in order to route the process air with an air flow speed F2 of greater than F1 through the latent heat accumulator (7).
2. Method according to claim 1, characterised in that step (a) for a predetermined period Δt_a and/or step (b) for a predetermined period Δt_b are performed, wherein an association between Δt_a and/or Δt_b and a loading of the drying chamber (2) with items to be dried and/or a moisture of items to be treated is stored in the control device.
3. Method according to claim 1 or 2, characterised in that the heater (4) is switched off in step (b) after a complete charging of the latent heat accumulator (7).
4. Method according to claim 3, characterised in that the latent heat accumulator (7) is provided with at least one temperature sensor (13, 14), and the charging of the latent heat accumulator (7) is monitored using temperature measurements with the aid of the at least one temperature sensor (13, 14).
5. Method according to one of claims 1 to 4, characterised in that the process air fan (6) has a preferred direction of rotation and is rotated counter to its preferred direction of rotation in step (a) and in its preferred direction of rotation in step (b).
6. Method according to one of claims 1 to 5, characterised in that the steps (b) and (c) are performed up to a predetermined discharge of the latent heat accumulator (7) and then the steps (a) to (c) are repeated again.
7. Method according to one of claims 1 to 6, characterised in that a cooling medium is passed through the heat exchanger (5) at least during the performance of step (b).
8. Method according to claim 7, characterised in that present in the heat exchanger (5) is a cooling air duct (9), through which air is passed as a cooling medium by means of a cooling air fan (10), which has a preferred direction of rotation, such that the cooling air fan (10) is rotated counter to its preferred direction of rotation in step (a) and in its preferred direction of rotation in step (b).
9. Method according to one of claims 1 to 8, characterised in that the drying space (2) is a drum, which is likewise driven by the drive motor (12).
10. Method according to one of claims 1 to 9, characterised in that a BLCD motor is used as a drive motor (12).
11. Dryer (1) having a drying chamber (2) for items to be dried, a drive motor (12), a control device (22), a process air duct (3), in which a heater (4), a heat exchanger (5), a process air fan (6) and a latent heat accumulator (7) are disposed, and a cooling air duct (9), in which the heat exchanger (5) and a cooling air fan (10) are disposed, characterised in that the drive motor (12) simultaneously produces the drive of the process air fan (6) and of the cooling air fan (10) and the control device (22) is embodied to perform a method, in which;

    (a) in a charging phase, the latent heat accumulator (7) is charged by the heat transfer of the warm and humid process air from the drying chamber (2), while the process air fan (6) is operated in order to route the process air with an air flow speed F1 through the latent heat accumulator (7); and

    (c) after charging the latent heat accumulator (7), the heater (4) is switched off or operated with a reduced power compared with step (a) in order to introduce a discharge phase; and

    (d) the process air fan (6) is operated in the discharge phase in order to route the process air with an air flow speed F2 of greater than F1 through the latent heat accumulator (7).
12. Dryer (1) according to claim 11, characterised in that the latent heat accumulator (7) comprises a phase change storage medium (8), which has at least one inorganic salt hydrate and/or one organic compound.
13. Dryer according to claim 12, characterised in that the phase change storage medium (8) has a phase transition from the liquid into the solid state in the temperature range of 30 to 65°C.
14. Dryer according to one of claims 12 to 13, characterised in that the phase change storage medium (8) is a salt hydrate, which contains at least one salt from the group consisting of natrium acetate, natrium thiosulphate, magnesium nitrate, ammonium nitrate and magnesium chloride.

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