EP3023534A1 - Laundry drying device and method for operating same - Google Patents

Abstract

The laundry drying apparatus 1 has a heat pump 3, 4 with an evaporator 3 located in a process air duct P, at least one temperature sensor T for sensing a temperature T of the heat pump 3, 4 and a cleaning device 8, 9, 10 for the evaporator 3, which cleaning device 8, 9, 10 a water collection container 8 and a leading to the evaporator 3, optionally against the water collection container 8 openable and closable downpipe 10, wherein the laundry drying device 1 is adapted to the downpipe 10 in response to a sensed by the at least one temperature sensor 12 Temperature T optional to open and close. A method is used to operate a laundry drying apparatus 1, wherein a down from a water collection 8 to an evaporator heat pump 3, 4 downpipe 10 depending on a temperature T of a heat pump 3, 4 is selectively opened and closed. The invention is particularly advantageously applicable to domestic heat pump dryer, in particular with a compressor heat pump.

Description

The invention relates to a laundry drying apparatus, comprising a heat pump with a located in a process air duct evaporator, at least one temperature sensor for sensing a temperature of the heat pump and a cleaning device for the evaporator, which cleaning device a water collection and leading to the evaporator, optionally against the water collecting container and having closable downpipe. The invention also relates to a method for operating a laundry drying device. The invention is particularly advantageously applicable to domestic heat pump dryer, in particular with a compressor heat pump.

In heat pump dryers, an associated heat pump is a closed process in which, after the heating process, a balance is established between a supplied electrical power and a dissipated thermal power. This balance is regulated in practice via an additional fan, which regulates the waste heat of the refrigeration cycle.

DE 10 2007 049 060 A1 discloses a method for operating a rinsing liquid device in a domestic appliance for the care of laundry, in which the condensate generated during a care process is collected as rinsing liquid in a rinsing and operating phase specifically for removing lint from a heat exchanger of a heat pump of the domestic appliance is passed through this wherein, depending on a specific type of connection of the rinsing liquid device, the rinsing liquid passed through the heat exchanger for the purpose of liquid disposal is automatically conducted into a collecting container of the rinsing liquid device or into an external sewage system.

DE 10 2007 061 984 A1 discloses a household appliance, which is equipped with a solenoid, wherein the solenoid and a PTC resistor with non-linear resistance characteristic are connected in series, wherein the PTC thermistor is heated by a current flow and when a predetermined limit temperature is exceeded is high impedance and wherein the limit temperature is set so that it is achieved before exceeding an allowable duty cycle of the solenoid. The solenoid serves, for example, to open a purge valve of a heat pump dryer.

EP 2 134 896 B1 discloses a method for cleaning a arranged within a process air cycle of a washer or dryer component, in particular an evaporator of a condenser device, by means of condensate water, which is recovered in the process air cycle from the drying of wet laundry and collected in a condensate water tank, from which it to an above the rinsing vessel provided for the evaporator and discharged from the outlet side of the relevant evaporator, wherein the condensate water is discharged from the rinsing container by its sudden opening on the outlet side as a surge of water to the relevant component.

EP 2 207 930 B1 discloses a method for cleaning a component arranged within a process air cycle of a laundry or tumble dryer, in particular an evaporator of a condenser device, by means of condensate water, which is obtained in the process air cycle from the drying of wet laundry and collected in a condensate water tank, from which it is above directed to the component collecting container and discharged from the outlet side to the component in question, the condensate is fed to a rinsing chamber of this and serving as a storage chamber overflow collecting container containing from its rinsing the condensate contained therein by sudden opening of the respective rinsing chamber on the outlet side is discharged as a surge of water to said component and from the storage chamber, the condensate contained therein is discharged for disposal.

EP 2 703 551 A1 discloses a cooling system for a heat pump dryer having a coolant loop including a compressor, an evaporator, and a condenser. The coolant circuit has, upstream of the condenser, a three-way valve configured to partially bypass the condenser at a predetermined distance from its inlet.

DE 40 23 000 C2 discloses a clothes dryer with a process air for heating, which is guided by a motor-driven blower in a closed process air duct through a laundry drying room, and for precipitating the entrained in the process air from the laundry drying room heat pump circuit from condenser, evaporator, compressor and throttle and further with an adjustable exhaust air opening in the process air duct between the condenser and the laundry drying space, wherein a supply air opening is arranged between the evaporator and the condenser in the process air duct, which can be closed by a controllable closure device.

It is the object of the present invention to overcome the disadvantages of the prior art at least partially and in particular to provide a simplified possibility for heat adjustment, in particular temperature adjustment, of a heat pump of a heat pump dryer.

This object is achieved according to the features of the independent claims. Preferred embodiments are in particular the dependent claims, the following description and attached drawing removable.

The object is accordingly achieved by a laundry drying apparatus, comprising a heat pump with an evaporator located in a process air duct, comprising at least one temperature sensor for sensing a temperature of the heat pump and having a cleaning device for the evaporator, which cleaning device a water collection and leading to the evaporator, optional has against the water collection container openable and closable downpipe. The laundry drying apparatus is further configured to open the downpipe in response to a sensed by the at least one temperature sensor temperature.

This results in the advantage that cooler ambient air can be introduced into the process air duct at least at the location of the evaporator through the opened downpipe. As a result, energy is withdrawn from the process air duct and there abge the temperature level lowers. The downpipe remains open for a corresponding time depending on the desired temperature level. This may be dispensed in particular with the additional fan of the heat pump.

The clothes dryer may be a stand alone heat pump dryer or a combined washer / dryer ("washer dryer"). The laundry drying appliance may be a household appliance, in particular in the sense of "white goods", in particular a large electric appliance. The clothes drying machine may e.g. be a convection laundry dryer.

The heat pump may be a compressor heat pump. Apart from the evaporator, such has typically also a condenser arranged in the process air duct, which also serves as a heater for the process air. The evaporator may also be referred to as an "evaporator" and the condenser as a "condenser". Also, the compressor heat pump typically has a drive unit in the form of a compressor and a throttle. These components are basically known parts of a working or refrigerant circuit. However, the heat pump may alternatively be a Stirling heat pump or a Vuilleumier heat pump.

The temperature of the heat pump sensed by the at least one temperature sensor may be a temperature sensed by just one temperature sensor, or may include sensed temperatures through a plurality of temperature sensors.

In general, the heat treatment device may be configured to open or close the downpipe depending on whether at least one sensed temperature reaches, exceeds or falls below a predetermined (temperature) threshold. For exactly one temperature sensor, the drop tube may be opened or closed when the associated measured temperature or the associated measured temperature value reaches, exceeds or falls below an associated threshold value. In the case of several temperature sensors, the downpipe may be opened or closed, even if only one measured temperature reaches the respectively associated threshold value, etc., or if several of the associated measured temperatures or the associated measured temperature values jointly reach, exceed or fall below a respectively associated threshold value. For several temperature sensors As an alternative or in addition, the drop tube may be opened or closed when a combination of two or more temperatures or temperature values reaches, exceeds or falls below a predetermined threshold value. For example, the downpipe may be opened or closed when a temperature difference between two temperature sensors reaches, exceeds or falls below a predetermined threshold. Generally, the same threshold may be used to open and close the downcomer. However, different threshold values for opening or closing the downpipe may also be used, wherein the threshold value for closing may lie, in particular, below a threshold value for opening. As a result, a hysteresis can be introduced into the opening behavior of the downpipe.

Under a downpipe may be understood any channel that directs water from the water collection container to the evaporator. The water collecting container is arranged in particular above the evaporator, so that the water is accelerated in the downpipe by its gravity and impinges with a high impulse on the evaporator. The downpipe may be rigid or flexible.

By "water" may be understood condensate obtained from drying wet laundry. The condensate may be mixed with fresh water. However, under "water" basically also pure fresh water can be understood.

The opening may include an opening of the downpipe and automatic time-delayed closing of the downpipe. For this purpose, a valve or a closure device can be opened electrically actuated, but automatically close with a time delay. The opening may include an optional opening and closing of the downpipe, since an opening period can be set particularly precisely. The optional opening and closing of the downpipe may be achieved, for example, by activating and deactivating a closure device. The optional opening and closing of the drop tube comprises in particular that both an opening time and a closing time of the drop tube can be controlled.

It is an embodiment that at least one temperature sensor for sensing a temperature of the evaporator is provided or arranged and arranged. This allows a particularly low-delay control of a temperature of the heat pump, in particular the evaporator can be achieved. In addition, the temperature at the evaporator is a suitable measure for a heat load or for a thermal state of the heat pump. The temperature sensor can implement this embodiment, the temperature for example directly (eg by contacting) on the evaporator or indirectly in an area in the vicinity of the Measure evaporator.

It is still an embodiment that the heat drying device is adapted to open the downpipe depending on the sensed temperature (in particular for temperature control) only when a level in the water collection container has not reached or exceeded a predetermined level or below this Level is. Thus, it can be prevented that a large amount of water drops like a splash on the evaporator or rinses it like a splash. Such a configuration is particularly suitable for heat pumps, in which a compressor must be switched off before flushing and also a certain period of time after switching off must remain switched off, e.g. three minutes. It is a development of the fact that the heat drying device is adapted to open the downpipe depending on the sensed temperature (in particular for temperature control) only when the water collecting container is empty. If, on the other hand, water is in the water collecting container, the supply of the water to the evaporator there can cause a cooling effect by utilizing a heat of vaporization and / or a thermal entrainment.

However, in an alternative or additional embodiment, the heat drying apparatus may be arranged to open and close the downcomer depending on the sensed temperature, regardless of the level in the water reservoir. This may be useful in particular to be able to carry out a regulation in a particularly timely manner. Such a configuration is particularly suitable for heat pumps, in which a compressor does not need to be switched off for surge-like flushing. The compressor may in particular in this case have a BLDC motor as a drive. In this embodiment, it may therefore happen that with the opening of the downpipe and a significant amount of water is discharged to the evaporator, which may also be sufficient for purging the evaporator.

During a laundry drying cycle, the water collecting container may not be emptied at will, for example flushing in a flush manner, ie in particular independently of a temperature of the heat pump, in particular of the evaporator. Triggering a purge to clean the evaporator by opening the downcomer against the water collection container may be particularly dependent on progress of a heat drying cycle.

A drying cycle may, in particular, be understood to mean a part or section of a drying process or a drying program in which the laundry filled in the laundry drying device is dried by active addition of heat. The drying cycle may be characterized in particular by operation of the heat pump. For example, a mere turning of a laundry drum at the end of a drying program for preventing wrinkling of the dried laundry may not be counted to the drying cycle.

It is a further embodiment that, in order to open and close the downpipe, an electrically operable valve is arranged fluidically between an upper inlet opening of the downpipe and the water collecting container. The valve may be a separate component, integrated into the water reservoir, or integrated into the downcomer. Due to the electrical operability, the valve can be actuated at any time and thus be used particularly easily for a temperature control of the evaporator or the process air duct. The electric valve may be coupled to a controller of the laundry dryer. In particular, the valve may have an electrically operable lifting magnet which, when actuated, lifts a closing flap from the inlet opening of the dropping tube and otherwise closes the inlet opening.

It is a further development that the process air duct forms part of a closed process air cycle, eg in the sense of a recirculating air laundry drying apparatus, and a fan ("process air blower") for circulating the process air in the process air duct is present in the process air duct. The process air blower is arranged in particular between the evaporator and an inlet opening of a laundry drum, so that the evaporator is arranged on the suction side to the process air blower. As a result, cooler air can be sucked through the downpipe. The process air blower in particular likes be arranged between the condenser and the inlet opening of the laundry drum. A pressure equalization in the process air duct can be achieved by leakage or leakage openings of the process air circuit.

It is yet another embodiment that the laundry drying device is adapted to fill the water collection container delayed. So can -. B. even a corresponding time before or after a surge-like emptying of the water collection container - the downpipe are opened for introducing the cooler air without water flows in appreciable volume through the downpipe. The delayed filling is in particular in contrast to the previously customary practice to fill the water collection container promptly after generating a sufficient amount of condensate through the evaporator, in particular immediately after a surge-like emptying of the water collection container to refill. In the case of the delayed filling, however, the condensate is temporarily stored for a suitable period of time in a buffer store (for example in a water collecting tray arranged below the evaporator). A suitable length of the period depends, for example, on a level of the buffer and / or a desire for a cleaning of the evaporator. In the case of a sufficiently large buffer, the opening and closing of the downpipe for temperature control may also do without any intermediate filling of the water collection container.

It is a development of the fact that the laundry drying device is set up to fill the water collection container with open downpipe with water or refill. Thus it can be prevented in a particularly simple manner that nachgefördertes water flows directly into the downpipe again.

It is still a further development that the laundry drying device is set up to fill the water tank only immediately before a targeted performing a cleaning of the evaporator.

The filling of the water collecting tank may be feasible by means of a pump (hereinafter referred to as "condensate pump" without restriction of generality). This pump likes water from a buffer, eg from a water catch trough, pump off, which can absorb water drip tray dripping condensate from the evaporator and discharged from the downpipe to the evaporator water.

It is still an embodiment that the heat drying device is adapted to refill water with the downpipe in the water collection container. As a result, when aerating water through the downpipe on the evaporator, but not gushing and thus with a comparison with the surge-like cleaning only small volume flow. Also, by such a supply of water and thereby generated use of heat of vaporization and / or heat capture, a cooling effect or energy removal may be enhanced at least at the evaporator.

It is also an embodiment that the heat treatment device is adapted to open or close the downpipe depending on whether at least one sensed temperature reaches at least a predetermined threshold, exceeds or falls below and that the predetermined threshold in the course of a drying cycle 'changeable , As a result, the temperature change in the process air duct, in particular on the evaporator, can also be used to set drying conditions.

It is an embodiment of the heat treatment apparatus being adapted to lower at least one temperature threshold for opening the downpipe to an end of the drying cycle towards an advanced portion of the drying cycle. This lowers a temperature at the evaporator. The resulting larger temperature difference to the process air causes that typically increases by the end of a drying cycle 'down relative humidity of the process air a condensation rate. Under the advanced, in particular a last, section of the drying cycle 'may thus be understood in particular a section in which the laundry has already dried so far that there is a significant drop in the humidity of the process air at the outlet of the laundry drum. The object is also achieved by a method for operating a laundry drying apparatus, wherein a downcoming from a water collection container to an evaporator of a heat pump down pipe is opened in response to a sensed by at least one temperature sensor temperature of a heat pump. The method can be designed analogously to the laundry drying apparatus described above and has the same advantages.

The above-described characteristics, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following schematic description of an embodiment which will be described in detail in conjunction with the accompanying drawings.

The single FIGURE of the accompanying drawing shows a sectional side view of a greatly simplified sketch of a household circulating air drying machine 1, for example a circulating air dryer. The laundry drying apparatus 1 may, for example, as shown in FIG EP 2 134 896 B1 or EP 2 207 930 B1 be further detailed.

The laundry drying apparatus 1 has a closed process air circuit K for process air P, which has a rotatable laundry drum 2, an evaporator 3 acting as a condenser, a condenser 4 acting as a heater and a process air blower 5 in the flow direction of the process air P contained therein. The process air blower 5 circulates the process air P in the direction indicated by the arrows.

The evaporator 3 and the condenser 4 are also components of a heat pump, which additionally has a compressor (not shown) as a drive and a throttle (not shown). Such closed process air circuits and heat pumps are basically known and need not be further described here.

From in the laundry drum 2 befindlicher to be dried laundry (o. Fig.) Moisture is released, which is absorbed by the warm process air P. The now humid process air P flows, sucked by the process air fan 5, to the evaporator 3. There it is cooled and condensed. The now cooler and dryer process air P then passes to the condenser 4, where it is reheated, and then reintroduced into the laundry drum 2.

The condensation condensed on the evaporator 3 or condensed water is collected in a buffer in the form of a condensate water pan or water sump 6. Condensate stored in the water collecting tray 6 can be pumped by means of a pump 7 into a water collecting container located above the evaporator 3 (hereinafter referred to as "washing container" 8 without restriction of generality), as indicated by the dot-dashed arrows. The washing container 8 has a bottom-side drain opening, to which a valve 9 is connected. The valve 9 selectively opens or closes the sump 8 opposite a downcomer 10. The valve 9 may e.g. a magnetic lifting element which can lift a cover flap (not shown) which rests on an upper inlet opening of the downpipe 10. By raising the cover flap, this inlet opening is released against the washing container 8. The state of the open and closed valve 9 can also be referred to as "open downpipe" 10 or "closed downpipe" 10. The components 8, 9, 10 represent components of a cleaning device for cleaning the evaporator 3.

When the rinse tank 8 is full, water (ie at least the pumped-up condensate) is discharged through the downpipe 10 when the valve 9 is opened. This water is discharged through a lower end of the drop tube 10 with a high pulse to the evaporator 3, which is thereby cleaned of lint, etc. These lint can be released from the drying laundry and accumulate during the condensation of the process air P to the evaporator 3. The drained water also enters the water collecting tray 6 and can be pumped up again into the washing container 8. At the end of a drying program, possibly water containing lint may be pumped into the rinsing container 8 in the water collecting tray 6 in order to be emptied by a user. Alternatively, water located in the water collecting sump 6 may be automatically pumped out of the laundry drying apparatus 1 through a drain.

The operation of the pump 7 and the valve 9 can be controlled by means of a control device 11, which controls, for example, the operation of the heat pump 3, 4 (eg, a compressor power) and the components of the process air cycle K. So like the rinse tank 8 filled and then the valve 9 targeted for cleaning the evaporator 3 are opened. The cleaning may be triggered, for example, at predetermined times of a drying program and / or when an efficiency deterioration of the evaporator 3 has been determined.

The laundry drying device 1 further has a temperature sensor 12 in the region of the evaporator 3 (ie, in the vicinity of the evaporator 3 or in contact with the evaporator 3), which is set up and arranged to have a temperature T or a temperature value of the evaporator 3 or to sense a representative temperature. Also, the temperature sensor 12 is coupled to the controller 11 (not shown), so that the controller 11 can monitor the temperature T. If the measured temperature T reaches or exceeds a first (temperature) threshold value T1, the control device 11 activates the valve 9, which then opens. By opening the valve 9 cool air can be sucked through the downpipe 10 to the evaporator 3, whereby its temperature T decreases. If the temperature T reaches or falls below a second threshold value T2, the control device 11 deactivates the valve 9, which then closes. Thus, a temperature control of the evaporator 3 and thus also of the entire heat pump 3, 4 can be implemented without having to cool e.g. an additional fan is needed or where an additional fan may be smaller. The laundry drying apparatus 1 is thus configured to selectively open and close the downpipe 10 as a function of the temperature T of the evaporator 3 sensed by the temperature sensor 12.

The first threshold T1 may be equal to the second threshold T2. The second threshold value T2 may also lie below the first threshold value T1, that is to say T2 <T1, in order to introduce a hysteresis which prevents an otherwise possibly occurring rapid consecutive repeated opening and closing of the valve 9.

If water is in the rinsing container 8, this is drained with and amplifies a cooling of the evaporator. 3

The laundry drying apparatus 1, in particular its control device 11, can be set up such that the downpipe 10 is opened and closed by means of the valve 9 as a function of the sensed temperature T only when a level in the rinsing container 8 has not yet reached a predetermined level or has exceeded. For example, the control device 11 may activate the valve only when the washing container 8 is virtually empty. This may be useful, for example, if the operation of the heat pump 3, 4 would be adversely affected by a water incidence on the evaporator 3, for example if the compressor of the heat pump 3, 4 would have to be stopped. Also, this variant is advantageous in order to avoid an excessive lowering of the temperature T at the evaporator 3 and thus to facilitate a temperature control. This variant may include, for example, that the washing compartment 8 is filled only for cleaning and possibly for emptying after completion of a drying program and is otherwise kept empty.

Also, the controller 11 may fill the rinse tank 8 by appropriate activation of the pump 7 only to a level below the maximum level. The water volume then drained when the valve 9 is activated is preferably so small that the operation of the heat pump 3, 4 is not impaired, but is so great that a noticeable additional temperature cooling is achieved as a result. Thus, a faster regulating temperature control may be provided. To clean the evaporator 3, the washing container 8 may continue to be filled. The additional temperature cooling is predetermined above the level of the water in the washing container 8 and may be varied.

The laundry drying apparatus 1, in particular its control device 11, but can also be arranged so that the downpipe 10 and the associated valve 9 is opened and closed regardless of the level in the washing compartment 8. This includes the case that the rinse tank 8 may also be considerably or fully filled when opening the valve 9 for temperature control, e.g. also sufficient for a cleaning of the evaporator 3. This variant may, for. B. are used when the operation of the heat pump 3, 4 is not affected by the discharge of water from the rinse tank 8 even with larger amounts of water.

In most, or even in all cases, the valve 9 is kept open so long that the drop tube 10 after draining the water - if any - even cooler air from the washing container 8 can lead to the evaporator 3. That may be easier be that the washing compartment 8 is open against its environment, for example, by providing ventilation openings in its lid (o. Fig.).

The laundry drying device 1, in particular its control device 11, can now be set up to fill the washing container 8 with a delay. This may mean here that the control device 11 keeps the pump 7 deactivated when the valve 9 is open. The pump 7 and the valve 9 are thus not activated simultaneously. The delayed filling leads to the fact that the water is not also newly pumped into the washing tank 8 water flows through the downpipe 10.

The laundry drying device 1, in particular its control device 11, but can also be adapted to refill water from the water collecting tray 6 into the washing container 8 when the valve 9 or the downpipe 10 is open. For this purpose, the control device 11 activate the pump 7 with the valve 9 open. As a result, even water with a low volume flow (optionally adjustable by the pump volume) flows through the downpipe 10 with the air, which may enhance a cooling effect on the evaporator 3.

The laundry drying apparatus 1 is further adapted to lower the threshold value T1 for opening the valve 9 (and thus also the downpipe 10) and / or the threshold value T2 for closing the valve 9 in an advanced section of a drying cycle. This advanced section may, in particular, be a section in which a quantity of water discharged by the already markedly dried amount of laundry drops, which causes the humidity of the process air P to drop. By lowering the threshold values T1 and / or T2, the effectiveness of the laundry drying can be increased.

Of course, the present invention is not limited to the embodiment shown. Generally, "on", "an", etc. may be taken to mean a singular or a plurality, in particular in the sense of "at least one" or "one or more", etc., as long as this is not explicitly excluded, eg by the expression "exactly a "etc. Also, a number can include both exactly the specified number and a usual tolerance range, as long as this is not explicitly excluded.

LIST OF REFERENCE NUMBERS

1

Laundry drying device

2

washing drum

3

Evaporator

4

condenser

5

Process air fan

6

Water trough

7

pump

8th

rinse tank

9

Valve

10

downspout

11

control device

12

temperature sensor

K

Process air circuit

P

process air

T1

First temperature threshold

T2

Second temperature threshold

Claims (10)

Clothes drying apparatus (1), comprising a heat pump (3, 4) with an evaporator (3) located in a process air duct (P), - At least one temperature sensor (T) for sensing a temperature (T) of the heat pump (3, 4) and - A cleaning device (8, 9, 10) for the evaporator (3), which cleaning device (8, 9, 10) a water collection container (8) and to the evaporator (3) leading, optionally against the water collection container (8) openable and has closable downpipe (10), - wherein the laundry drying apparatus (1) is adapted to open the downpipe (10) in response to a sensed by the at least one temperature sensor (12) temperature (T). Laundry drying apparatus (1) according to claim 1, wherein at least one temperature sensor (12) for sensing a temperature (T) of the evaporator (3) is provided. Laundry drying apparatus (1) according to one of claims 1 or 2, wherein the heat drying apparatus (1) is adapted to open the downpipe (10) in dependence on the sensed temperature (T) only when a level in the water collecting container (8). has not reached or exceeded a predetermined level. The laundry drying apparatus (1) according to any one of claims 1 or 2, wherein the heat drying apparatus is arranged to open and close the downpipe (10) depending on the sensed temperature (T) and independently of a level in the water collecting container (8). Laundry drying apparatus (1) according to any one of the preceding claims, wherein for opening and closing the downpipe (10), an electrically actuable valve (9) is arranged fluidly between an upper inlet opening of the downpipe (10) and the water collecting container (8). Laundry drying device (1) according to one of the preceding claims, wherein the laundry drying device (1) is adapted to the water collection container (8) to fill with delay. Laundry drying apparatus (1) according to one of the preceding claims, wherein the heat drying apparatus (1) is adapted to refill the water collecting container (8) with the downpipe (10) open. Laundry drying apparatus (1) according to one of the preceding claims, wherein the heat drying apparatus (1) is adapted to open or close the downpipe (10) depending on whether at least one sensed temperature (T) at least a predetermined threshold value (T1, T2 ), exceeds or falls below and wherein the predetermined threshold (T1, T2) in the course of a drying cycle 'changeable. The laundry drying apparatus (1) according to claim 8, wherein the heat drying apparatus (1) is adapted to lower a temperature threshold (T1) for opening the downcomer (10) to an end of the drying cycle toward an advanced portion of the drying cycle. Method for operating a laundry drying apparatus (1), wherein a down from a water collecting container (8) to an evaporator of a heat pump (3, 4) leading downpipe (10) depending on a temperature (T) of a heat pump (3, 4) selectively open and is closed.

Images