Patent Application
20240167215
The invention relates to a condenser tumble dryer having a heat pump and a recirculated air portion and a method for the operation thereof. The invention relates, in particular, to a condenser tumble dryer having a drum for laundry items to be dried, a supply air channel, an exhaust air channel, a recirculated air channel branching off therefrom and discharging into the supply air channel upstream of a drum inlet, a blower, a heat pump having a condenser which is arranged in the supply air channel, an evaporator which is arranged in the exhaust air channel, a throttle and a compressor, as well as a control facility and a heating facility; as well as a preferred method for the operation thereof.
Generally tumble dryers are operated as exhaust air dryers or condenser tumble dryers. Condenser tumble dryers, the mode of operation thereof being based on the condensation of the moisture from the laundry which has been evaporated by means of warm process air, permit an energy recovery from the heated process air, for example by using a heat pump. The condensate arising in the condenser tumble dryer is collected and either pumped out or disposed of by manually emptying a collection container.
In exhaust air dryers, however, generally after passing through a laundry drum the moisture-laden air is conducted out of the tumble dryer. A heat recovery often does not take place here.
Exhaust air dryers with heat recovery are known, however. Thus the publication DE 30 00 865 A1 describes a tumble dryer with heat recovery. The tumble dryer consists of a moving container which receives the laundry and into which a supply air flow heated by a heating element discharges, while the moist warm air is routed as exhaust air via an outlet. A heat exchanger, through which the moist warm exhaust air flows from the container, is arranged in the supply air flow upstream of the heating element.
The publication DE 197 31 826 A1 describes a tumble dryer having a system for heat recovery (for example a heat pump) in which the substantially closed air circuit can exchange the circulating air with the room air at two predetermined points through two openings, in order to keep the drying temperature and the condensation temperature at the predetermined values.
An exhaust air dryer having a heat pump and a cleaning facility for the evaporator is described in the publication EP 2037034 B1.
Exhaust air dryers with heat recovery are also described in the publications US 2012/0030960 A1 and DE 10 2008 055 087 A.
A tumble dryer having a heat pump circuit is described in the publication DE 40 23 000 C2, in which a supply air opening which can be closed by a controllable closure apparatus is arranged in the process air channel between the condenser and the evaporator.
The publication DE 43 06 217 B4 describes a program-controlled tumble dryer having a laundry drum in which the process air is conveyed through the laundry drum by means of a blower in a closed process air channel which has closure facilities. The tumble dryer also has a heat pump circuit consisting of an evaporator, compressor and condenser designed for precipitating the moisture in the process air from the laundry drum. The closure facilities are arranged such that the process air is routed as a function of a process phase.
In an exhaust air dryer having a heat pump, heat is removed from the exhaust air from the drying chamber, generally a drum, by the evaporator of the heat pump, the heat being supplied back to the supply air via the condenser. Since the exhaust air dryer is an open system, in contrast to a condenser tumble dryer with a closed process air circuit, sensible heat is also recovered in addition to the latent heat. As a result, in spite of a condensation efficiency of, for example, less than 50% an exhaust air dryer with heat recovery can have a lower energy consumption than a condenser tumble dryer.
Depending on the efficiency of the heat pump, heat is coupled in from the surroundings of the heat pump. For a more efficient operation, however, a greater condensation efficiency might be desirable.
In order to be able to increase the condensation efficiency above 80% with open air routing, additional heat exchangers—desuperheaters or sub-coolers—in the cold circuit are described in the prior art. In a closed system, the continuously introduced compressor power leads to increasing heating of the tumble dryer. If this power input is not balanced with an energy loss, for example by component heating, radiation, convection or leakage, the system can overheat and thereby the efficiency of the heat pump can be reduced. As a countermeasure, the use of actively cooled additional heat exchangers in the refrigeration circuit or air-air heat exchangers in the process air are known. Since in an open system the temperature of the supply air from an installation space remains virtually constant and is not greater than the ambient temperature, it does not lead to overheating under normal installation conditions of the condenser tumble dryer. The constant low temperature level determines high levels of efficiency of the heat pump.
However, in an exhaust air dryer the drawback can arise of a total energy balance of the installation location, since the room air which is generally warmer is repeatedly exchanged for colder external air. With open air routing systems with levels of condensation efficiency of greater than 80%, this drawback is eliminated since the exhaust air does not have to be routed out of the installation space.
It is also known that the energy efficiency of an exhaust air dryer can be improved by a recirculated air system. Here the process air which is laden with moisture from the laundry in the drying chamber is partially supplied back to the drying process via the heating device.
The publication DE 103 49 712 A1 describes a method for drying laundry in a tumble dryer having a program control facility, a drying chamber and a process air channel in which a blower for conveying the dry air through the drying chamber and a heating facility are arranged, wherein the process air channel is configured with a fresh air supply and an exhaust air discharge and wherein means are arranged in the process air channel for separating the dry air flow into an exhaust air portion and a recirculated air portion.
The publication DE 34 46 468 A1 describes a method for drying laundry in a tumble dryer having a drivable laundry drum, a blower, a heater arranged in the flow path of the drying air and a cooled condenser via which the drying air is routed after exiting from the laundry drum, wherein after exiting from the laundry drum the drying air is split into two partial air flows. The one partial air flow is supplied to the condenser and the other partial air flow is mixed again with the partial air flow exiting from the condenser, bypassing the condenser.
The publication DE 34 19 743 C2 describes a tumble dryer having a laundry drum, a heating unit provided with a supply air connection and an exhaust air connection, wherein various additional units which determine the mode of operation of the tumble dryer can be arranged to be switchable between the supply air connection of the heating unit and the exhaust air connection. In one embodiment of the tumble dryer, a recirculation part, in which an air control facility is located, is interposed between the supply air connection piece and the exhaust air connection piece, whereby the ratio between the supply air and the exhaust air of the tumble dryer can be varied.
The publication DE 10 2007 042969 A1 describes a tumble dryer having a drying chamber for objects to be dried, a process air channel, a heater for heating the process air and a blower for routing the heated process air from a supply air inlet through the drying chamber to an exhaust air outlet, and at least one heat exchanger, being located therein. The heat exchanger is arranged between the drying chamber and the exhaust air outlet. A recirculated air channel branches off from the process air channel downstream of the drying chamber, a part of the process air being able to be routed through this recirculated air channel to the heater. The at least one heat exchanger can be formed by an evaporator and a condenser of a heat pump.
Against this background, it was the object of the present invention to provide a condenser tumble dryer which has an open air system and a heat pump for heat recovery, and which has high energy efficiency. A portion of the moist warm process air from the drum is designed to be used as recirculated air. It was a further object of the present invention to provide a method for the operation thereof.
This object is achieved according to this invention by a condenser tumble dryer and a method for the operation thereof having the features of the respective independent claims. Preferred embodiments of the condenser tumble dryer according to the invention and the method according to the invention are set forth in the corresponding dependent claims. Preferred embodiments of the condenser tumble dryer according to the invention correspond to preferred embodiments of the method according to the invention and vice versa, even when this is not explicitly stated herein.
A subject of the invention is thus a condenser tumble dryer having a drum for receiving laundry items to be dried, a supply air channel, an exhaust air channel, a recirculated air channel branching off therefrom and discharging into the supply air channel upstream of a drum inlet, a blower, a heat pump having a condenser which is arranged in the supply air channel, an evaporator which is arranged in the exhaust air channel, a throttle and a compressor, as well as a control facility and a heating facility, wherein the condenser tumble dryer is designed such that, in a drying program carried out therein, moist warm process air flows out of the drum in an exhaust air channel part defined downstream by the evaporator, substantially in the same direction as the supply air in an inlet region of the supply air channel containing the condenser, and the process air leaving the drum has a relative air humidity Frel, to which Frelmin≤Frel≤Frelmax applies, wherein Frelmin is a predetermined minimum value and Frelmax is a maximum value of the relative air humidity which can be achieved in the drying program.
It has been found that an increase in the relative air humidity of the process air at the drum outlet improves the drying efficiency and/or the drying speed of a condenser tumble dryer. The air status at the drum outlet is influenced by the size of the air volume flow, by the temperature in the drum and the relative air humidity of the process air at the drum inlet, the air routing through the drum and the laundry load and the type of laundry.
The relative air humidity is an indirect measurement of the portion of sensible heat of the process air. With an open air routing with a heat pump, as is the case in the condenser tumble dryer according to the invention, the sensible heat and energy is recovered and the drying speed increased thereby, but for a high condensation efficiency this portion should be small relative to the latent heat.
The dimensioning of an additional heat exchanger for fulfilling the condensation efficiency, for example a sub-cooler, can thus be smaller. In any case the efficiency of the condenser tumble dryer increases in the present invention.
By adding the air portion with a higher water load, the water load of the process air increases upstream or downstream of the condenser. The relative air humidity at the drum inlet becomes greater, as does that of the process air at the drum outlet.
In a preferred embodiment of the condenser tumble dryer according to the invention, the recirculated air channel discharges into the supply air channel in the direction of flow of the supply air downstream of the condenser.
In an even further preferred embodiment of the condenser tumble dryer according to the invention, the recirculated air channel discharges into the supply air channel in the direction of flow of the supply air upstream of or at the condenser, i.e. it leads to increased air flow through the condenser.
According to the invention, it is preferred that in each case a flow measuring facility is arranged in the supply air channel upstream and downstream of the condenser. Thus it is possible to determine a portion of added recirculated air from the drum.
According to the invention, a condenser tumble dryer is quite particularly preferred in which the exhaust air channel part and the condenser have a common wall which has a plurality of holes which form the recirculated air channel. It is also preferred here that the plurality of holes is located in an inlet region of the condenser.
The shape and number of the holes is not limited, provided a desired recirculated air portion according to the invention can be produced by this plurality of holes.
In any case, a condenser tumble dryer is preferred in which the plurality of holes is configured in a drying program carried out in the condenser tumble dryer in cooperation with the blower to form an air volume flow through the condenser, such that it consists of 15 to 50% by volume, preferably 20 to 40% by volume, of recirculated air. The air volume flow via the condenser, which is significantly increased relative to the evaporator, also leads to the improvement of the efficiency of the heat pump. With an unchanged efficiency, the heat exchanger, in particular also an additional heat exchanger, can have smaller dimensions. If the air volume flow via the condenser is not increased, however, the volume flow of the supply air and exhaust air is reduced, with the result that with the same efficiency the noise level of the condenser tumble dryer is lowered.
According to the invention, an increase in the recirculated air portion can be implemented, for example, by the blower output and thus a conveying capacity of the blower being increased. The increase in the blower output leads to an increase in the negative pressure in the supply air channel and an increase in the positive pressure in the exhaust air channel. This results in an increase in the pressure difference for the passage of process air from the drum or the exhaust air channel into the supply air channel, in particular into the inlet region of the condenser.
The number, positioning and size of holes are generally fixed in the embodiment with a plurality of holes in a common wall and thus cannot be changed. However, the condenser tumble dryer can advantageously have an apparatus which permits a total effective opening surface of the plurality of holes to be controlled. Thus such an apparatus can be designed, for example, to cover some holes entirely or partially, wherein the covering can also be implemented, for example, by a foam which is partially permeable to air and which hinders the passage of air. A further covering option is in the use of an adjustable blind.
In one advantageous embodiment of the condenser tumble dryer according to the invention, the heat pump contains an additional cooler which is also denoted as a sub-cooler. Thus the mode of operation of the heat pump can be better controlled and, in particular, the overheating thereof prevented.
However, the present invention makes it possible to avoid the use of an additional cooler. This is the case if the portion of process air in the recirculated air channel, which in the embodiments of the invention passes directly into the condenser, is sufficiently great. In an alternative further preferred embodiment of the invention, therefore, the heat pump does not contain an additional cooler.
According to the invention, a condenser tumble dryer is preferred in which a relationship between a rotational speed u of the blower and a ratio r between an air flow speed VC in the condenser and an air flow speed VE in the evaporator is stored in the control facility. This permits an improved control of the portion of recirculated air in the condenser tumble dryer according to the invention.
Finally, a condenser tumble dryer is also preferred in which a humidity sensor is arranged at the outlet of the drum for determining the relative air humidity Frel of the process air leaving the drum. Thus it is possible to implement the invention using empirical values for the relative air humidity and the dependencies thereof on different parameters. A measurement of the relative air humidity Frel, however, leads to more accurate results. The additional use of a temperature sensor at the outlet of the drum is advantageous.
Adjustable closure apparatuses can be located in the individual channels, such as the supply air channel, the recirculated air channel and the exhaust air channel, in order to improve the control of the air flows and, in particular, the portion of supply air in an air flow through the condenser. For example, flaps can be used as adjustable closure apparatuses which can be opened to different degrees independently of one another or as a function of one another.
The tumble dryer preferably comprises an electrical heating apparatus so that process air can be heated by means of the condenser and also by means of the electrical heating apparatus. Since the energy required for the drying decreases with the progressive degree of drying of the laundry items to be dried in the condenser tumble dryer, it is expedient to adjust the heating apparatus correspondingly, i.e. to reduce the heating power thereof with a progressive degree of drying. In the condenser tumble dryer of the present invention, with the presence of an evaporator inlet temperature which is too high, the recirculated air portion can also be reduced as a function of the temperature.
By the use of a recirculated air channel or by conducting the hot recirculated moisture-laden air through the recirculated air channel to the heating apparatus, generally the air temperature upstream of the heating apparatus is raised. Due to the increased air flow via the heating apparatus, however, the drum inlet temperature can remain in a permissible range.
For accelerating the heating of the process air after the condenser tumble dryer has been switched on, the quantity of supply air in the supply air channel can be controlled, for example by using adjustable closure apparatuses, such that in a starting phase of a drying program the supply of supply air is stopped and the condenser tumble dryer is operated only with recirculated air as the process air.
According to the invention, it is preferred if exhaust air, supply air and/or refrigerant are routed in each case in a cross-flow or counter-flow method through the corresponding heat exchangers.
The evaporator of the heat pump is located in the exhaust air channel in order to remove heat from the moist warm air from the drum, which generally flows into an installation space via the exhaust air channel.
In a condenser tumble dryer provided with a heat pump, the warm moisture-laden process air is substantially cooled in the evaporator of the heat pump, wherein the transmitted heat is used for the evaporation of a refrigerant introduced into the heat pump circuit. The refrigerant of the heat pump, which is evaporated by being heated, is supplied via a compressor to the condenser of the heat pump, where heat is released due to the condensation of the gaseous refrigerant, the heat being used for heating the process air or the supply air upstream of the inlet into the drying chamber.
In the condenser tumble dryer according to the invention, the blower is preferably arranged directly downstream of the condenser or directly upstream of the condenser.
A further subject of the invention is a method for operating a condenser tumble dryer having a drum for receiving laundry items to be dried, a supply air channel, an exhaust air channel, a recirculated air channel branching off therefrom and discharging into the supply air channel upstream of a drum inlet, a blower, a heat pump having a condenser which is arranged in the supply air channel, an evaporator which is arranged in the exhaust air channel, a throttle and a compressor, as well as a control facility and a heating facility, wherein the condenser tumble dryer is designed such that, in a drying program carried out therein, moist warm process air flows out of the drum in an exhaust air channel part defined downstream by the evaporator, substantially in the same direction as the supply air in an inlet region of the supply air channel containing the condenser, and the process air leaving the drum has a relative air humidity Frel, to which Frelmin≤Frel≤Frelmax applies, wherein Frelmin is a predetermined minimum value and Frelmax is a maximum value of the relative air humidity which can be achieved in the drying program, wherein the blower is controlled by the control facility such that the process air leaving the drum has a relative air humidity Frel, to which Frelmin≤Frel≤Frelmax applies.
The expression “flows substantially in the same direction” is intended to be understood to take into account that the recirculated air portion, i.e. the portion of process air which, in embodiments of the invention, flows through the plurality of holes as an embodiment of the recirculated air channel used according to the invention, takes place transversely to this direction or even vertically and thus influences the flow in the exhaust air channel and recirculated air channel.
In a preferred embodiment of the method according to the invention, the blower is controlled by the control facility such that an air volume flow through the condenser consists of 15 to 50% by volume, preferably 20 to 40% by volume, of recirculated air.
According to the invention, a method is also preferred in which a ratio r between an air flow speed VC in the condenser and an air flow speed VE in the evaporator is greater than 1, preferably greater than 1.2.
Finally, the method according to the invention is preferably carried out after the process air leaving the drum has reached a predetermined minimum temperature. At this time, generally a very high relative air humidity Frel is present at the drum outlet, preferably even a maximum relative air humidity Frelmax. The invention thus makes it possible to maintain such a high relative air humidity. The method according to the invention is thus preferably carried out in a main drying phase.
In the course of a drying program, however, in particular with the termination of the main drying phase in which the largest part of the moisture content of the laundry is removed, the relative air humidity Frel of the process air leaving the drum is reduced. Thus in such an end phase of a drying program, following the main drying phase, an increase in the relative air humidity Frel can be very advantageously achieved at the drum outlet, for example by increasing the rotational speed u of the blower.
As already established, the loading with laundry items also has an influence on the relative air humidity Frel of the process air. Advantageously, a loading of the drum with laundry items is also determined in a manner known per se. Advantageously, a relationship between the loading and Frelmin or Frelmax can be stored in the control facility, so that these values can be set in a more targeted manner.
The condenser tumble dryer according to the invention and the method according to the invention have the advantage that the condenser tumble dryer can be operated in an energy-efficient manner with a high condensation efficiency. In particular, the efficiency and/or the noise level of the condenser tumble dryer can be improved in the condenser tumble dryer according to the invention which has an open air system, a heat pump for heat recovery and also a portion of the process air which branches off from the drum downstream of the outlet and which is supplied back as recirculated air upstream or downstream of the condenser.
Further details of the invention are found in the following description of non-limiting exemplary embodiments of the condenser tumble dryer according to the invention and a method using this condenser tumble dryer. Reference is made to
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 202 230.8 | Mar 2021 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/053928 | 2/17/2022 | WO |
