EP4305231B1 - Condenser tumble dryer having a heat pump and a recirculated-air portion, and method for operating the condenser tumble dryer - Google Patents

Description

The invention relates to a condensation dryer with a heat pump and recirculation component and a method for operating it. The invention relates in particular to a condensation dryer with a drum for laundry items to be dried, a supply air duct, an exhaust air duct from which a recirculation duct branches off, which opens into the supply air duct in front of a drum inlet, a fan, a heat pump with a condenser arranged in the supply air duct, an evaporator arranged in the exhaust air duct, a throttle and a compressor, as well as a control device and a heating device; and a preferred method for operating it.

In general, tumble dryers are operated as exhaust air or condensation dryers. Condensation dryers, which function based on the condensation of moisture from the laundry that has been evaporated by warm process air, enable energy to be recovered from the heated process air, for example by using a heat pump. The condensate that accumulates in the condensation dryer is collected and either pumped out or disposed of by manually emptying a collecting container.

In the case of exhaust air dryers, however, the air that is laden with moisture after passing through a laundry drum is generally led out of the dryer. Heat recovery often does not take place in this case.

However, exhaust air dryers with heat recovery are known. The publication describes DE 30 00 865 A1 a tumble dryer with heat recovery. The tumble dryer consists of a container that holds and moves the laundry, into which a supply air stream heated by a heating element flows, while the moist warm air is led as exhaust air through an outlet. In the supply air stream, a heat exchanger is arranged in front of the heating element, through which the moist, hot exhaust air from the container flows.

The publication DE 197 31 826 A1 describes a tumble dryer with a heat recovery system (e.g. a heat pump), in which the largely closed air circuit can exchange the circulating air with the room air through two openings at two predetermined locations in order to keep the drying and condensation temperatures at the specified values.

In the publication EP 2037034 B1 An exhaust air dryer with a heat pump and a cleaning device for the evaporator is described.

Exhaust air dryers with heat recovery are also mentioned in the publications US 2012/0030960 A1 and DE 10 2008 055 087 A described.

In the publication DE 40 23 000 C2 A tumble dryer with a heat pump circuit is described in which an air supply opening is arranged in the process air duct between the condenser and the evaporator, which can be closed with a controllable closing device.

The publication DE 43 06 217 B4 describes a program-controlled tumble dryer with a laundry drum, in which the process air is conveyed through the laundry drum by means of a fan in a closed process air channel that has closure devices. The tumble dryer also has a heat pump circuit consisting of an evaporator, compressor and condenser that is set up to precipitate the moisture in the process air from the laundry drum. The closure devices are arranged in such a way that the guidance of the process air depends on a process phase.

In an exhaust air dryer with a heat pump, heat is extracted from the exhaust air from the drying chamber, usually a drum, by the heat pump's evaporator, which is then fed back into the supply air via the condenser. Since the exhaust air dryer is an open system, in contrast to a condensation dryer with a closed process air circuit, sensible heat is recovered in addition to latent heat. This means that an exhaust air dryer with heat recovery can have lower energy consumption than a condensation dryer despite a condensation efficiency of less than 50%, for example.

Depending on the efficiency of the heat pump, heat is coupled in from the heat pump's surroundings. However, for more efficient operation, a higher condensation efficiency would be desirable.

In order to be able to increase the condensation efficiency above 80% with an open air flow, the state of the art describes additional heat exchangers in the refrigeration circuit - desuperheaters or subcoolers. In a closed system, the continuously introduced compressor power leads to an increasing heating of the dryer. If this power input is not in balance with an energy loss, for example due to component heating, radiation, convection or leakage, the system can overheat and thus the efficiency of the heat pump can decrease. The use of actively cooled additional heat exchangers in the refrigeration circuit or air-air heat exchangers in the process air is known as a countermeasure. Since in an open system the temperature of the supply air from an installation room remains almost constant and is not higher than the ambient temperature, overheating does not occur under normal installation conditions of the condensation dryer. The constantly low temperature level requires high efficiency of the heat pump.

In contrast, an exhaust air dryer can have the disadvantage of an overall energy balance of the installation location, since the generally warmer room air is exchanged several times with colder outside air. With open air duct systems with condensation efficiencies of more than 80%, this disadvantage is eliminated, since the exhaust air does not have to be led out of the installation room.

It is also known that the energy efficiency of an exhaust air dryer can be improved by using a recirculation system. In this system, the process air loaded with moisture from the laundry in the drying chamber is partially fed back into the drying process via the heating device.

The publication DE 103 49 712 A1 describes a method for drying laundry in a tumble dryer with a program control device, a drying chamber and a process air duct in which a fan for conveying the dry air through the drying chamber and a heating device are arranged, wherein the process air duct is provided with a fresh air supply and an exhaust air discharge and wherein means for separating the dry air flow into an exhaust air portion and a recirculated air portion are arranged in the process air duct.

The publication DE 34 46 468 A1 describes a method for drying laundry in a tumble dryer with a drivable laundry drum, a fan, a heater arranged in the flow path of the drying air and a cooled condenser through which the drying air is guided after exiting the laundry drum, wherein the drying air is split into two partial air streams after exiting the laundry drum. One partial air stream is fed to the condenser and the other is mixed back in with the partial air stream exiting the condenser, bypassing the condenser.

The publication DE 34 19 743 C2 describes a tumble dryer with a laundry drum, a heating unit provided with an air supply connection and an exhaust air connection, whereby different additional units that determine the operating mode of the dryer can be arranged between the air supply connection of the heating unit and the exhaust air connection. In one embodiment of the dryer, a recirculation part is interposed between the air supply connection and the exhaust air connection, in which an air control device is located, whereby the air supply and exhaust air ratio of the dryer can be varied.

The publication DE 10 2007 042969 A1 describes a dryer with a drying chamber for objects to be dried, a process air duct in which there is a heater for heating the process air and a fan for guiding the heated process air from a supply air inlet through the drying chamber to an exhaust air outlet, as well as at least one heat exchanger. The heat exchanger is arranged between the drying chamber and the exhaust air outlet. A recirculation duct branches off from the process air duct behind the drying chamber, through which part of the process air can be guided to the heater. The at least one heat exchanger can be formed by an evaporator and a condenser of a heat pump.

The publication DE 10 2009 002482 A1 discloses a dryer with a drying chamber for objects to be dried, a process air channel, a heater for heating the process air and a first fan, a Program control, a heat exchanger and a humidity sensor arrangement for measuring humidity signals as a measure of the humidity of the process air, wherein the program control has first means for evaluating the humidity signals measured by the humidity sensor arrangement and second means for influencing actuators for operating the dryer and are set up in such a way that a predetermined numerical range for the relative humidity stored in the program control can be maintained in a drying process by influencing the actuators. It is also disclosed that the relative humidity can be measured to control the proportions of circulating air and exhaust air in such a way that the relative humidity is kept within a predetermined numerical range.

1. (a) Messen einer relativen Feuchtigkeit H_rel der Prozessluft mit dem Feuchtesensor;
2. (b) Messen einer Temperatur T_P der Prozessluft mit einem Temperatursensor;
3. (c) Ermitteln einer absoluten Wasserbeladung L_W der Prozessluft aus der relativen Feuchtigkeit H_rel unter Berücksichtigung der Temperatur T_P , wobei ein in der Steuereinrichtung hinterlegter Zusammenhang zwischen einer maximalen Wasserbeladung L_W ^max und der Temperatur T_P herangezogen wird;
4. (d) Verfolgen des zeitlichen Verlaufs der Wasserbeladung L_W ;
5. (e) Heranziehen des zeitlichen Verlaufs der Wasserbeladung L_W zur Bestimmung einer Restfeuchte R_W in den Wäschestücken;
6. (f) Vergleichen der Restfeuchte R_W mit einer vorgegebenen Restfeuchte R_W ^set ; und
7. (g) Beenden des Trocknungsprozesses bei Erreichen oder Unterschreiten der vorgegebenen Restfeuchte R_W ^set.

The publication DE 10 2016 210265 A1 discloses a method for operating a condensation dryer with a process air channel in which process air is moved in a circuit by means of a fan, a heater, a drum with laundry items placed therein, and a control device, wherein a heat exchanger for condensing water from moist, warm process air and at least one humidity sensor are arranged in the process air channel, wherein a drying process comprises the following steps:

1. (a) Measuring a relative humidity H _rel of the process air with the humidity sensor;
2. (b) measuring a temperature T _P of the process air with a temperature sensor;
3. (c) determining an absolute water load L _W of the process air from the relative humidity H _rel taking into account the temperature T _P , whereby a relationship stored in the control device between a maximum water load L _W ^max and the temperature T _P is used;
4. (d) monitoring the time course of the water load L _W ;
5. (e) Using the time course of the water load L _W to determine a residual moisture R _W in the laundry items;
6. (f) comparing the residual moisture R _W with a given residual moisture R _W ^set ; and
7. (g) Termination of the drying process when the specified residual moisture content R _W ^set is reached or falls below.

The publication DE 10 2018 203158 A1 discloses a device for drying laundry, having at least one open process air system with at least one drying chamber accommodating laundry to be dried and at least one heat pump thermally coupled to the process air system, which has at least one evaporator serving as a heat sink for process air discharged from the drying chamber and at least one condenser serving as a heat source for process air to be supplied to the drying chamber, wherein the evaporator and the condenser are arranged laterally next to one another and offset in height from one another, wherein either on the one hand a section of a first process air line connecting the drying chamber to the evaporator runs above the condenser and a section of a second process air line connecting the condenser to the drying chamber runs below the evaporator or on the other hand a section of the first process air line runs below the condenser and a section of the second process air line runs above the evaporator.

The publication DE 10 2005 041145 A1 discloses a tumble dryer in which the warm air used to dry the laundry is heated using a heat pump heating system, the heat pump heating system containing a compressor with variable output. Preferably, the tumble dryer contains a control device which controls or regulates the output of the compressor depending on the settings made to the tumble dryer by the user thereof.

Against this background, the object of the present invention was to provide a condensation dryer with an open air system and a heat pump for heat recovery that has a high energy efficiency. A portion of the warm, moist process air from the drum is to be used as recirculated air. Another object of the present invention was to provide a method for its operation.

The solution to this problem is achieved according to this invention by a condensation dryer and a method for its operation with the features of the respective independent patent claims. Preferred embodiments of the The condensation dryer according to the invention and the method according to the invention are set out in the corresponding dependent patent claims. Preferred embodiments of the condensation dryer according to the invention correspond to preferred embodiments of the method according to the invention and vice versa, even if this is not explicitly stated herein.

The subject matter of the invention is thus a condensation dryer with a drum for receiving laundry items to be dried, a supply air duct, an exhaust air duct, from which a recirculation duct branches off, which opens into the supply air duct in front of a drum inlet, a fan, a heat pump with a condenser arranged in the supply air duct, an evaporator arranged in the exhaust air duct, a throttle and a compressor, as well as a control device and a heating device, wherein the condensation dryer is set up in such a way that, in a drying program carried out therein, moist, warm process air from the drum in an exhaust air duct part delimited downstream by the evaporator flows essentially in the same direction as supply air in an inlet area of the supply air duct containing the condenser, and the process air leaving the drum has a relative air humidity F ^rel for which F ^rel _min ≤ F ^rel ≤ F ^rel _max applies, wherein F ^rel _{min is} a predetermined minimum value and F ^rel _max is a maximum value achievable in the drying program of the relative humidity, and the exhaust duct part and the condenser have a common wall which has a plurality of holes forming the recirculation duct.

It has been found that increasing the relative humidity of the process air at the drum outlet improves the drying efficiency and/or the drying speed of a condensation dryer. The air condition at the drum outlet is influenced by the size of the air volume flow, the temperature in the drum and the relative humidity of the process air at the drum inlet, the air flow through the drum as well as the laundry load and the type of laundry.

The relative humidity is an indirect measure of the proportion of sensible heat in the process air. In an open air system with a heat pump, as is the case in the condensation dryer according to the invention, the sensible heat is recovered as energy and the drying speed is thereby increased, but for To achieve a high condensation efficiency, this proportion should be small in relation to the latent heat.

The dimensions of an additional heat exchanger to meet the condensation efficiency, e.g. a subcooler, can then be smaller. The efficiency of the condensation dryer increases in any case with the present invention.

By adding the air portion with a higher water load, the water load of the process air before and after the condenser increases. The relative humidity at the drum inlet increases and that of the process air at the drum outlet also increases.

In a preferred embodiment of the condensation dryer according to the invention, the recirculation duct opens into the supply air duct after the condenser in the flow direction of the supply air.

In a more preferred embodiment of the condensation dryer according to the invention, the recirculation duct opens into the supply air duct in the flow direction of the supply air before or at the condenser, thus leading to an increased air flow through the condenser.

According to the invention, it is preferred that a flow measuring device is arranged in the supply air duct before and after the condenser. This allows a proportion of added recirculated air from the drum to be determined.

In the condensation dryer according to the invention, the exhaust air duct part and the condenser have a common wall which has a plurality of holes which form the recirculation duct. It is again preferred that the plurality of holes are located in an inlet area of the condenser.

The shape and number of holes is not limited, provided that the large number of these holes allows the desired proportion of recirculated air to be achieved according to the invention.

In any case, a condensation dryer is preferred in which the plurality of holes is designed in order to create an air volume flow through the condenser in a drying program carried out in the condensation dryer in cooperation with the fan so that it consists of 15 to 50% by volume, preferably 20 to 40% by volume, of recirculated air. The air volume flow through the condenser, which is thereby significantly increased in relation to the evaporator, also leads to an improvement in the efficiency of the heat pump. With unchanged efficiency, the heat exchangers, in particular an additional heat exchanger, can be made smaller. However, if the air volume flow through the condenser is not increased, the volume flow of the supply and exhaust air is reduced, with the result that the noise level of the condensation dryer is reduced with the same efficiency.

According to the invention, an increase in the proportion of recirculated air can be achieved, for example, by increasing the blower output and thus the conveying capacity of the blower. Increasing the blower output leads to an increase in the negative pressure in the supply air duct and an increase in the positive pressure in the exhaust air duct. This increases the pressure difference for the passage of process air from the drum or the exhaust air duct into the supply air duct, in particular into the inlet area of the condenser.

The number, positioning and size of the holes are generally fixed and therefore cannot be changed. However, the condensation dryer can advantageously have a device which allows control of a total effective opening area of the plurality of holes. For example, such a device can be designed to cover some holes completely or partially, whereby the cover can also be made, for example, with a partially air-permeable foam which impedes the passage of air. Another covering option is to use an adjustable blind.

In an advantageous embodiment of the condensation dryer according to the invention, the heat pump contains an additional cooler, also referred to as a subcooler. This allows the functioning of the heat pump to be better controlled and, in particular, its overheating to be prevented.

However, the present invention makes it possible to avoid the use of an additional cooler. This is the case if the proportion of process air in the recirculation duct, which in embodiments of the invention goes directly into the condenser, is sufficiently large. In an alternative, more preferred embodiment of the invention, the heat pump therefore does not contain an additional cooler.

According to the invention, a condensation dryer is also preferred in which a relationship between a rotational speed u of the fan and a ratio r between an air flow speed vc in the condenser and an air flow speed vε in the evaporator is stored in the control device. This enables better control of the recirculated air proportion in the condensation dryer according to the invention.

Finally, a condensation dryer is also preferred in which a humidity sensor is arranged at the outlet from the drum to determine the relative humidity F ^rel of the process air leaving the drum. This is because it is possible to carry out the invention based on empirical values for the relative humidity and its dependence on various parameters. However, measuring the relative humidity F ^rel leads to more precise results. The additional use of a temperature sensor at the outlet from the drum is advantageous.

Adjustable closure devices can be located in the individual ducts, such as the supply air duct, the recirculation air duct and the exhaust air duct, in order to improve the control of the air flows and in particular the proportion of supply air in an air flow through the condenser. Adjustable closure devices can be, for example, flaps that can be opened to different widths independently or dependently on one another.

The dryer preferably comprises an electric heating device so that process air can be heated both by means of the condenser and by means of the electric heating device. Since the energy required for drying decreases as the degree of drying of the laundry items to be dried in the condensation dryer progresses, it is expedient to regulate the heating device accordingly, ie as the degree of drying progresses degree of drying to reduce their heating power. In the condensation dryer of the present invention, the proportion of recirculated air can also be reduced depending on the temperature if the evaporator inlet temperature is too high.

By using a recirculation duct or passing the hot, moisture-laden recirculation air through the recirculation duct to the heater, the air temperature in front of the heater is generally increased. However, due to the increased air flow over the heater, the drum inlet temperature can remain within an acceptable range.

In order to accelerate the heating of the process air after the condensation dryer is switched on, the amount of supply air in the supply air duct can be controlled, for example using adjustable closing devices, so that in an initial phase of a drying program the supply of supply air is stopped and only recirculated air is used as process air.

According to the invention, it is preferred if exhaust air, supply air and/or refrigerant are each passed through the corresponding heat exchangers in a cross-current or countercurrent process.

The evaporator of the heat pump is located in the exhaust air duct in order to extract heat from the warm, moist air from the drum, which generally flows into an installation room via the exhaust air duct.

In a condensation dryer equipped with a heat pump, the cooling of the warm, moisture-laden process air takes place mainly in the heat pump's evaporator, where the transferred heat is used to evaporate a coolant used in the heat pump circuit. The heat pump's coolant, which has evaporated due to the heating, is fed via a compressor to the heat pump's condenser, where heat is released due to the condensation of the gaseous coolant, which is used to heat the process air or the supply air before it enters the drying chamber.

In the dryer according to the invention, the fan is preferably arranged directly after the condenser or directly before the condenser.

The invention also relates to a method for operating a condensation dryer with a drum for receiving laundry items to be dried, a supply air duct, an exhaust air duct, from which a recirculation duct branches off, which opens into the supply air duct in front of a drum inlet, a fan, a heat pump with a condenser arranged in the supply air duct, an evaporator arranged in the exhaust air duct, a throttle and a compressor, as well as a control device and a heating device, wherein the condensation dryer is set up in such a way that, in a drying program carried out therein, moist, warm process air from the drum in an exhaust air duct part delimited downstream by the evaporator flows essentially in the same direction as supply air in an inlet area of the supply air duct containing the condenser, and the process air leaving the drum has a relative air humidity F ^rel for which F ^rel _min ≤ F ^rel ≤ F ^rel _max applies, where F ^rel _min is a predetermined minimum value and F ^rel _max is a value specified in the drying program. achievable maximum value of the relative humidity, and the exhaust air duct part and the condenser have a common wall which has a plurality of holes which form the recirculation duct, wherein the fan is controlled by the control device such that the process air leaving the drum has a relative humidity F ^rel for which F ^rel _min ≤ F ^rel ≤ F ^rel _max applies.

The expression "flows essentially in the same direction" is intended to take into account the fact that the recirculated air portion, i.e. the portion of the process air that flows through the plurality of holes as an embodiment of the circulation channel used according to the invention in embodiments of the invention, occurs transversely or even vertically to this direction and therefore influences the flow in the exhaust air and recirculated air channel.

In a preferred embodiment of the method according to the invention, the fan is controlled by the control device such that an air volume flow through the condenser consists of 15 to 50 volume%, preferably 20 to 40 volume%, of recirculated air.

According to the invention, a method is further preferred in which a ratio r between an air flow velocity vc in the condenser and an air flow velocity vε in the evaporator is greater than 1, preferably greater than 1.2.

Finally, the method according to the invention is preferably carried out after a predetermined minimum temperature of the process air leaving the drum has been reached. At this point in time, there is generally a very high relative air humidity Frei at the drum outlet, preferably even a maximum relative air humidity F ^rel _max . The invention then makes it possible to maintain such a high relative air humidity. The method according to the invention is therefore preferably carried out in a main drying phase.

However, during the course of a drying program, the relative humidity F ^rel of the process air leaving the drum decreases, particularly when the main drying phase, in which most of the moisture content of the laundry items is removed, has ended. It is therefore very advantageous to increase the relative humidity F ^rel at the drum outlet in such a final phase of a drying program following the main drying phase, for example by increasing the speed u of the fan.

As already stated, the load of laundry items also has an influence on the relative humidity F ^rel of the process air. It is therefore advantageous to determine the load of laundry items in the drum in a known manner. It is then advantageous to store a connection between the load and F ^rel _min or F ^rel _max in the control device so that these values can be set more precisely.

The condensation dryer according to the invention and the method according to the invention have the advantage that the condensation dryer can operate in an energy-efficient manner with a high condensation efficiency. In particular, the condensation dryer according to the invention can be operated with an open air system, a heat pump for heat recovery and, in addition, a portion of the process air which is branched off after the outlet from the drum and used as By recirculating air, the efficiency and/or noise level of the condenser dryer can be improved.

• Fig. 1 zeigt eine perspektivische Ansicht eines Kondensationstrockners aus dem Stand der Technik mit einer Wärmepumpe, wobei kein Zuluftkanal zur teilweisen Rückführung von Prozessluft aus der Trommel verwendet wird.
• Fig. 2 zeigt einen vertikalen Schnitt durch den Kondensationstrockner von Fig. 1, in dem die Luftführung durch Zuluftkanal, Trommel und Abluftkanal gezeigt ist.
• Fig. 3 zeigt einen vertikalen Schnitt durch einen erfindungsgemäßen Kondensationstrockner gemäß einer ersten Ausführungsform, bei der ein Teil der Prozessluft aus der Trommel über einen Umluftkanal einem Verflüssiger im Zuluftkanal zugeführt wird.
• Fig. 4 zeigt wie Fig. 3 einen vertikalen Schnitt durch den erfindungsgemäßen Kondensationstrockner gemäß einer ersten Ausführungsform, bei der ein Teil der Prozessluft aus der Trommel über einen Umluftkanal einem Verflüssiger im Zuluftkanal zugeführt wird. Im Unterschied zu Fig. 3 sind hier aus Übersichtsgründen keine Pfeile vorhanden, die das Fließen der Luft im Kondensationstrockner zeigen.
• Fig. 5 zeigt ein Schema, dass den Fluss von Prozessluft durch den Verflüssiger, die Trommel, den Verdampfer und einen Unterkühler gemäß einer zweiten Ausführungsform des erfindungsgemäßen Kondensationstrockners zeigt (dicke Pfeile), wobei die dünnen Pfeile den Fluss eines Kältemittels durch die Komponenten der verwendeten Wärmepumpe zeigen.
• Fig. 6 zeigt ein Schema, dass den Fluss von Prozessluft durch den Verflüssiger, die Trommel, den Verdampfer und einen Unterkühler gemäß einer dritten Ausführungsform des erfindungsgemäßen Kondensationstrockners zeigt (dicke Pfeile), wobei die dünnen Pfeile den Fluss eines Kältemittels durch die Komponenten der verwendeten Wärmepumpe zeigen.
• Fig. 7 zeigt eine perspektivische Draufsicht auf einen unteren Teil eines erfindungsgemäß verwendeten Kondensationstrockners, bei der insbesondere eine den Verflüssiger vom Abluftkanal trennende gemeinsame Wand zu sehen ist, die in einem Eingangsbereich des Verflüssigers eine Vielzahl von Löchern aufweist, die als ein Umluftkanal fungieren können.

Further details of the invention emerge from the following description of non-limiting embodiments of the condensation dryer according to the invention and a method using this condensation dryer. Reference is made to the Figures 1 to 7 .

• Fig. 1 shows a perspective view of a prior art condensation dryer with a heat pump, where no supply air duct is used for partial recirculation of process air from the drum.
• Fig. 2 shows a vertical section through the condensation dryer of Fig. 1 , which shows the air flow through the supply air duct, drum and exhaust air duct.
• Fig. 3 shows a vertical section through a condensation dryer according to the invention according to a first embodiment, in which part of the process air from the drum is fed via a recirculation duct to a condenser in the supply air duct.
• Fig. 4 shows how Fig. 3 a vertical section through the condensation dryer according to the invention according to a first embodiment, in which part of the process air from the drum is fed via a recirculation duct to a condenser in the supply air duct. In contrast to Fig. 3 For reasons of clarity, there are no arrows showing the flow of air in the condenser dryer.
• Fig. 5 shows a diagram showing the flow of process air through the condenser, the drum, the evaporator and a subcooler according to a second embodiment of the condensation dryer according to the invention (thick arrows), wherein the thin arrows show the flow of a refrigerant through the components of the heat pump used.
• Fig. 6 shows a scheme showing the flow of process air through the condenser, the drum, the evaporator and a subcooler according to a third embodiment of the condensation dryer according to the invention (thick arrows), whereby the thin arrows show the flow of a refrigerant through the components of the heat pump used.
• Fig. 7 shows a perspective top view of a lower part of a condensation dryer used according to the invention, in which in particular a common wall separating the condenser from the exhaust air duct can be seen, which has a plurality of holes in an inlet area of the condenser, which can function as a recirculation duct.

Fig. 1 shows a perspective view of a condensation dryer 1 from the prior art with a heat pump, of which the condenser 8 and the evaporator 9 can be seen here. In this condensation dryer, no supply air duct is used for the partial return of process air from the drum 2. The air flow through the condensation dryer is illustrated by the arrows. The light arrow means supply air from a room in which the condensation dryer is installed, which is conveyed in the supply air duct 3 due to the use of a fan (not shown here). This supply air is heated in the condenser 8 and the then heated process air is then passed on to and into the drum 2. The then warm and humid process air leaves the drum 2 at the drum outlet 18. The process air has the comparatively highest temperature here, which is shown by the black arrows. The warm and humid process air is cooled by condensation (not shown here) of the moisture in the evaporator 9 and conveyed in the exhaust air duct 4 into a room in which the condensation dryer 1 is installed. 17 means a subcooler in the heat pump circuit.

Fig. 2 shows a vertical section through the condensation dryer 1 of Fig. 1 , in which the air flow through supply air duct 3, drum 2 and exhaust air duct 4 is shown. The same reference numerals have the same meaning here as in Fig. 1 . 7 means a fan.

Fig. 3 shows a vertical section through a condensation dryer 1 according to the invention according to a first embodiment, in which part of the process air from the drum 2 is fed via a recirculation channel 5 to a condenser 8 in the supply air channel 3. The recirculation channel 5 is located here in an inlet part 13 of the supply air channel 3. 12 means an exhaust air part channel in which the process air in the Essentially flows in the same direction as in the supply air duct, i.e. in particular in the condenser 8. 7 means a fan and 17 a subcooler. The splitting thick arrow illustrates how part of the warm, moist process air from the drum 2 is introduced into the condenser 8 as recirculated air after the drum outlet 18 in the area of the condenser.

Fig. 4 shows how Fig. 3 a vertical section through the condensation dryer 1 according to the invention according to a first embodiment, in which part of the process air from the drum 2 is fed via a recirculation duct 5 to a condenser 8 in the supply air duct 3. In contrast to Fig. 3 For reasons of clarity, there are no arrows showing the flow of air in the condensation dryer 1. Other reference symbols have the same meaning as in Fig. 3 .

Fig. 5 shows a diagram showing the flow of process air through the condenser 8, the drum 2, the evaporator 8 and a subcooler 17 according to a second embodiment of the condensation dryer 1 according to the invention (thick arrows), whereby the thin arrows show the flow of a coolant through the components of the heat pump used. The coolant is guided in the coolant circuit, which here also has a throttle 10 and a compressor 11. The curved thick arrow shows here that part of the process air from the drum 2 after the condenser 8 is returned to the supply air duct (not shown here) containing the condenser 8.

Fig. 6 shows a diagram which, represented by thick arrows, shows the flow of process air through the condenser 8, the drum 2, the evaporator 9 and a subcooler 17 according to a third embodiment of the condensation dryer 1 according to the invention, wherein the thin arrows show the flow of a coolant through the components of the heat pump used. The coolant is guided in the coolant circuit, which here additionally has a throttle 10 and a compressor 11. The curved thick arrow shows here that part of the process air from the drum 2 in comparison to Fig. 5 According to the invention, it is preferably returned before or at the condenser 8 into the supply air duct (not shown here) containing the condenser 8.

Fig. 7 shows a perspective top view of a lower part of a condensation dryer used according to the invention, in which in particular a common wall 14 can be seen which separates the condenser 8 from the exhaust air duct (not shown here), which has a plurality of holes 15 in an inlet area 16 of the condenser 8. 13 indicates an inlet part of the supply air duct (also not shown here).

list of reference symbols

1. 1 condensation dryer
2. 2 drums for holding laundry items to be dried
3. 3 supply air duct
4. 4 exhaust air duct
5. 5 recirculation duct
6. 6 drum input
7. 7 fans
8. 8 condensers
9. 9 evaporators
10. 10 throttle
11. 11 compressor
12. 12 exhaust air duct part
13. 13 Entrance area (of the supply air duct)
14. 14 Common wall of condenser and recirculation duct part
15. 15 multitude of holes (in the common wall)
16. 16 Inlet area of the condenser
17. 17 Additional cooler, subcooler (in the heat pump)
18. 18 Outlet (for process air from the drum), drum outlet

Claims (14)

1. Condenser tumble dryer (1) having a drum (2) for receiving laundry items to be dried, a supply air channel (3), an exhaust air channel (4), a recirculated air channel (5) branching off therefrom and discharging into the supply air channel (3) upstream of a drum inlet (6), a blower (7), a heat pump (8, 9, 10, 11) having a condenser (8) which is arranged in the supply air channel (3), an evaporator (9) which is arranged in the exhaust air channel (4), a throttle (10) and a compressor (11), as well as a control facility and a heating facility,
   wherein the condenser tumble dryer (1) is designed such that, in a drying program carried out therein, moist warm process air flows out of the drum (2) in an exhaust air channel part (12) defined downstream by the evaporator (9), substantially in the same direction as the supply air in an inlet region (13) of the supply air channel (3) containing the condenser (8), characterised in that the process air leaving the drum (2) has a relative air humidity F^rel, to which F^rel _min ≤ F^rel ≤ F^rel _max applies, wherein F^rel _min is a predetermined minimum value and F^rel _max is a maximum value of the relative air humidity which can be achieved in the drying program, and the exhaust air channel part (12) and the condenser (8) have a common wall (14) which has a plurality of holes (15) which form the recirculated air channel (5).
2. Condenser tumble dryer (1) according to claim 1, characterised in that the recirculated air channel (5) discharges into the supply air channel (3) in the direction of flow of the supply air downstream of the condenser (8).
3. Condenser tumble dryer (1) according to claim 1, characterised in that the recirculated air channel (5) discharges into the supply air channel (3) in the direction of flow of the supply air upstream of or at the condenser (8).
4. Condenser tumble dryer (1) according to claim 3, characterised in that in each case a flow measuring facility is arranged in the supply air channel (3) upstream and downstream of the condenser (8).
5. Condenser tumble dryer (1) according to one of claims 1 to 4, characterised in that the plurality of holes (15) is located in an inlet region (16) of the condenser (8).
6. Condenser tumble dryer (1) according to one of claims 1 to 5, characterised in that the plurality of holes (15) is configured in a drying program carried out in the condenser dryer (1) in cooperation with the blower (7) to form an air volume flow through the condenser (8), such that it consists of 15 to 50% by volume, preferably 20 to 40% by volume, of recirculated air.
7. Condenser tumble dryer (1) according to one of claims 1 to 6, characterised in that it has an apparatus which permits a total effective opening surface of the plurality of holes (15) to be controlled.
8. Condenser tumble dryer (1) according to one of claims 1 to 7, characterised in that the heat pump (8, 9, 10, 11) contains an additional cooler (17).
9. Condenser tumble dryer (1) according to one of claims 1 to 8, characterised in that a relationship between a rotational speed u of the blower (7) and a ratio r between an air flow speed vc in the condenser (8) and an air flow speed v_E in the evaporator (9) is stored in the control facility.
10. Condenser tumble dryer (1) according to one of claims 1 to 9, characterised in that a humidity sensor is arranged at the outlet (18) of the drum (2) for determining the relative air humidity F^rel of the process air leaving the drum (2).
11. Method for operating a condenser tumble dryer (1) having a drum (2) for receiving laundry items to be dried, a supply air channel (3), an exhaust air channel (4), a recirculated air channel (5) branching off therefrom and discharging into the supply air channel (3) upstream of a drum inlet (6), a blower (7), a heat pump (8, 9, 10, 11) having a condenser (8) which is arranged in the supply air channel (3), an evaporator (9) which is arranged in the exhaust air channel (4), a throttle (10) and a compressor (11), as well as a control facility and a heating facility, wherein the condenser tumble dryer (1) is designed such that, in a drying program carried out therein, moist warm process air flows out of the drum (2) in an exhaust air channel part (12) defined downstream by the evaporator (9), substantially in the same direction as the supply air in an inlet region (13) of the supply air channel (3) containing the condenser (8), and the process air leaving the drum (2) has a relative air humidity F^rel, to which F^rel _min ≤ F^rel ≤ F^rel _max applies, wherein F^rel _min is a predetermined minimum value and F^rel _max is a maximum value of the relative air humidity which can be achieved in the drying program, and the exhaust air channel part (12) and the condenser (8) have a common wall (14) which has a plurality of holes (15) which form the recirculated air channel (5), wherein the blower (7) is controlled by the control facility such that the process air leaving the drum (2) has a relative air humidity F^rel, to which F^rel _min ≤ F^rel ≤ F^rel _max applies.
12. Method according to claim 11, characterised in that the blower (7) is controlled by the control facility such that an air volume flow through the condenser (8) consists of 15 to 50% by volume, preferably 20 to 40% by volume, of recirculated air.
13. Method according to claim 11 or 132, characterised in that a ratio r between an air flow speed vc in the condenser (8) and an air flow speed v_E in the evaporator (9) is greater than 1, preferably greater than 1.2.
14. Method according to one of claims 11 to 13, characterised in that it is carried out after the process air leaving the drum (2) has reached a predetermined minimum temperature.

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