EP2202347A1 - Dryer with heat pump and recirculation component and method for its operation - Google Patents

Abstract

The dryer (1) has a drying chamber (3) for an object i.e. cloth, to be dried, and a heat pump with an evaporator (22), a condenser (21) and a programmable controller (10). A process air path arrangement obtains and maintains a preset minimum difference between an evaporator entry temperature and a dryer entry temperature and a preset lower threshold for the evaporator entry temperature. A connection point (27) is provided between the condenser and an inlet air access (28) for connecting a recirculating air duct (14) to an inlet air duct (15). The process air path arrangement includes the programmable controller, the recirculating air duct, the inlet air duct, an exhaust air outlet (16), the condenser, the evaporator, controllable closure devices (18, 23), a vent opening, the connection point and the air inlet access. An independent claim is also included for a method for operating a dryer.

Description

The invention relates to a dryer with heat pump and recirculated air and a preferred method for its operation.

In general, tumble dryers are operated as exhaust air or condensation dryers. Condensation dryers whose operation is based on the condensation of moisture vaporized by means of warm process air from the laundry, allow energy recovery from the heated process air, for example by using a heat pump. The condensate produced in the condensation dryer is collected and either pumped off or disposed of by manually emptying a collection container.

In the case of exhaust air dryers, on the other hand, air laden with moisture after passage through a laundry drum is generally discharged from the dryer. Heat recovery often does not take place here.

Exhaust air dryers with heat recovery are known. This is how the writing describes DE 30 00 865 A1 a clothes dryer with heat recovery. The tumble dryer consists of a container receiving and moving the laundry, into which a supply air flow heated by a heating element opens, while the moist hot air is conducted as exhaust air via an outlet. In the supply air flow, a heat exchanger is arranged in front of the heating element, which is flowed through by the moist hot exhaust air from the container.

In the DE 40 23 000 C2 a clothes dryer is described with a heat pump circuit, in which a supply air opening is arranged in the process air duct between the condenser and the evaporator, which is closable with a controllable closure device.

The DE 197 31 826 A1 describes a clothes dryer with a system for heat recovery (eg a heat pump), in which the largely closed Air circulation at two predetermined points through two openings which can exchange circulating air with the room air to keep the drying and condensation temperature at the predetermined values.

The DE 43 06 217 B4 discloses a program-controlled laundry dryer with a laundry drum, in which the process air is conveyed through the laundry drum by means of a blower in a closed process air duct, which has closure devices. The tumble dryer also has a set for precipitation of the moisture in the process air from the laundry drum heat pump circuit of evaporator, compressor and condenser. The closure devices are arranged so that the guidance of the process air depends on a process phase.

In the case of an exhaust air dryer with a heat pump, heat is withdrawn from the exhaust air through the evaporator of the heat pump, which is returned to 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, not only the latent heat but also sensible heat is recovered. As a result, an exhaust air dryer with heat recovery, despite a condensation efficiency of, for example, less than 50% lower energy consumption than a condensation dryer. Depending on the efficiency of the heat pump, heat from the environment of the heat pump is injected. Nevertheless, for more efficient operation, higher condensation efficiency would be desirable.

It is also known that the energy efficiency of an exhaust air dryer can be improved by a recirculation system. In this case, the process air laden with moisture from the laundry in the drying chamber is partially returned to the drying process via the heater.

The 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 blower for conveying the dry air through the drying chamber and a heater are arranged, wherein the process air duct is formed with a fresh air supply and an exhaust air discharge and in the Process air duct means for separating the dry air flow are arranged in an exhaust air portion and a recirculation portion.

The DE 34 46 468 A1 discloses according to its claim 1, a method for drying laundry in a tumble dryer with a drivable laundry drum, a fan, a arranged in the flow path of the drying air heater and a cooled condenser through which the drying air is passed after exiting the laundry drum, wherein the drying air after Exit from the laundry drum is divided into two partial air streams. The one partial air flow is fed to the condenser and the other, bypassing the condenser, is mixed again with the partial air flow leaving the condenser.

The DE 34 19 743 C2 describes a clothes dryer with a laundry drum, a heating unit provided with a supply air connection and an exhaust air connection, wherein between supply air connection of the heating unit and exhaust air connection different, the mode of operation of the dryer defining additional units are to be arranged switchable. In one embodiment of the dryer, a recirculation part is interposed between the supply air connection piece and the exhaust connection piece, in which an air control device is located, whereby the supply and exhaust air ratio of the dryer can be varied. There is the possibility of a winter-summer switching. During winter operation, cold air is supplied from the outside and directed into the dryer. The warm exhaust air of the dryer enters the room and contributes to the heating of the room air.

The not pre-published DE 10 2008 035797 A1 describes a clothes treating apparatus having a cabinet with a receiving space that receives laundry; an air supply device that delivers hot air to the receiving space; and a control unit that determines the dryness of the laundry based on the temperature difference measured at two sensors to control the air supply device. The sensors may include a first sensor that measures the temperature of air drawn into the receiving space and a second sensor that measures the temperature of air discharged from the receiving space. The air supply device may be configured with a heat pump having an evaporator, a compressor, a condenser, and an expansion valve.

The not pre-published DE 10 2007 042969 A1 describes a dryer with a drying chamber for objects to be dried, a process air duct in which a heater for heating the process air and a blower for guiding the heated process air from a Zulufteingang through the drying chamber to an exhaust outlet and at least one heat exchanger. The heat exchanger is arranged between the drying chamber and the exhaust air outlet. From the process air duct branches off behind the drying chamber from a recirculation duct, through which a part of the process air to the heating is feasible. The at least one heat exchanger may be formed by an evaporator and a condenser of a heat pump.

The CH 690 038 A5 describes a laundry drying cabinet with a drying room and an apparatus part with a heat pump, comprising an evaporator, a compressor and a condenser, and a recirculation fan for circulating the air in the laundry dryer cabinet. The tumble dryer cabinet also has a supply air fan for supplying outside air into the tumble dryer cabinet and an exhaust air valve for removing air from the clothes dryer cabinet. Maintaining a specific temperature in the tumble dryer cabinet is considered critical to achieving high efficiency.

Object of the present invention is therefore to provide a vented dryer with high energy efficiency, which uses a proportion of circulating air and in which the disadvantage of a low condensation efficiency can be overcome. In addition, it is an object of the present invention to provide a method for its operation.

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

The invention thus relates to a dryer with a drying chamber for the objects to be dried, a supply air duct, a process air duct, an exhaust duct, a recirculating air duct, a fan, a heat pump with an evaporator and a condenser and a program control, the dryer a Prozessluftwegsanordnung to achieve and maintaining a predetermined minimum difference ΔT ^set between an evaporator inlet temperature T ₂ and a drier inlet temperature T ₁ and a predetermined lower limit T ₂ ^set for the evaporator inlet temperature.

The predetermined minimum difference ΔT ^set between an evaporator inlet temperature T ₂ and a drier inlet temperature T ₁ is preferably in the range of 25 to 55 ° C, more preferably in the range of 30 to 50 ° C, and most preferably in the range of 35 to 45 ° C.

The dryer inlet temperature T ₁ is generally in the range of 15 to 35 ° C and preferably in the range of 19 to 25 ° C.

Preferred evaporator inlet temperatures are therefore for example in the range of 50 to 70 ° C, in particular in the range of 55 to 65 ° C.

The temperatures T ₁ and / or T ₂ are generally measured by means of a suitable temperature sensor at the inlet inlet and / or directly in front of the evaporator. The temperature values are then generally supplied to a program control, which in preferred embodiments can control the proportion of circulating air and exhaust air.

In a preferred embodiment of the dryer is located in the process air path arrangement, a connection point of circulating air duct with supply air duct between the condenser and a supply air. As a result, an increase in the volume flow of the process air and the efficiency of the condenser is surprisingly achieved, while still the inlet temperature of the process air is increased in the evaporator. The higher moisture content of the process air associated with the higher evaporator inlet temperature T ₂ may cause the condensation efficiency to increase above 80%. The proportion of sensible heat of the process air is reduced Although, but still contributes enough to improve the energy consumption of the dryer.

In a further preferred embodiment, in the case of the process air path arrangement, the condenser is located between a connection point of circulating air duct with supply air duct and a supply air access. Due to the increase in the temperature of the process air after the mixture of supply air and circulating air and thus an increase in a drum inlet temperature and the evaporator inlet temperature T ₂ increases.

In general, in this embodiment, a condenser is used, which is adapted to low flow rates of the process air. A particular advantage of this embodiment is that the condenser is protected from leaching.

Both of the aforementioned embodiments generally result in a reduced volume flow of the process air via the condenser, so that it is less susceptible to contamination.

In the circulating air channel is preferably a first controllable closure device and in the supply air duct preferably a second controllable closure device. Finally, in the exhaust duct is preferably a third controllable closure device. In this way, the proportions of air flowing in these channels can be regulated. As a controllable closure devices, for example, flaps can be used, which can be opened independently or independently depending on different widths.

Preferably, in the process air path arrangement in the process air duct in front of the drying chamber, a blow-out opening is arranged. In this case, the blower is generally arranged in the direction of the flowing process air in front of the drying chamber. The blow-off opening can preferably be opened and closed to varying degrees via a fourth controllable closure device.

The process air path arrangements used in the dryer according to the invention are preferably designed such that they achieve a condensation efficiency of at least 70% and in particular of at least 80%.

The dryer preferably comprises an electric heater, so that process air can be heated both by means of the condenser and by means of the electric heater. Since, as the degree of drying of the articles to be dried in the dryer decreases, the energy required for drying decreases, it is appropriate to regulate the heating accordingly, that is to say, to reduce the drying time. with increasing degree of drying to reduce their heat output. Moreover, in the dryer of the present invention, if the evaporator inlet temperature is too high depending on the temperature, the recirculating air ratio can be reduced.

By using a circulating air channel or the passage of hot, laden with moisture circulating air through the circulating air channel for heating the air temperature is generally raised before the heater. However, due to the increased airflow through the heater, the drum inlet temperature may remain within the allowable range. To achieve and maintain according to the present invention a desired difference .DELTA.T ^set between the evaporator inlet temperature T ₂ and the dryer inlet temperature T ₁ , wherein the evaporator inlet temperature does not fall below a predetermined lower limit T ₂ ^set , the air flow of the exhaust air, the circulating air and / or the supply air be regulated, for example by using a first controllable closure device in the circulating air duct and / or a second controllable closure device in the supply air duct. To accelerate the heating of the process air after switching on the dryer, the amount of supply air through the second controllable closure device in the supply air duct can be controlled so that the supply of supply air is stopped and is operated only with circulating air as process air.

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

The evaporator of the heat pump is generally in contact with the exhaust duct to extract heat from the moist-warm air from the drying chamber, which generally flows into an installation room via the exhaust duct.

In a dryer equipped with a heat pump, the cooling of the warm, moisture-laden process air essentially takes place in the evaporator of the heat pump, where the heat transferred is used to evaporate a refrigerant used in the heat pump cycle. The refrigerant of the heat pump vaporized due to the heating is supplied via a compressor to the condenser of the heat pump, where due to the condensation of the gaseous refrigerant heat is released, which is used to heat the process air or the supply air before entering the drying chamber.

The blower is preferably arranged in the dryer according to the invention directly after the condenser or directly in front of the condenser.

The invention also relates to a method for operating a dryer with a drying chamber for the objects to be dried, a supply air duct, a process air duct, an exhaust duct, a recirculating air duct, a fan, a heat pump with an evaporator and a condenser and a program control, wherein the dryer a Prozessluftwegsanordnung for achieving and maintaining a predetermined minimum difference .DELTA.T ^set between an evaporator inlet temperature T ₂ and a dryer inlet temperature T ₁ and a predetermined lower limit T ₂ ^set for the evaporator inlet temperature, wherein process air directed through the supply air duct, the condenser and the drying chamber and in a first partial air flow in the circulating air duct and in a second partial air flow is split in the exhaust duct, that a minimum difference .DELTA.T ^set = (T ₂ -T ₁ ) between an evaporator inlet temperature T ₂ and a Trocknereintrittstempe T ₁ achieved and maintained and a predetermined lower limit T ₂ ^set for the evaporator inlet temperature is achieved and maintained.

In a preferred embodiment of this method, a volume ratio between the first partial air flow and the second partial air flow is in the range of 1.5 to 10, and particularly preferably in the range of 3 to 8.

Moreover, it is preferred that the first partial air flow is 200 to 300 m ³ / h. The second partial air flow is preferably less than 100 m ³ / h. Particularly preferably, the second partial air flow in the exhaust duct is 40 to 80, in particular 50 to 70 m ³ / h.

Preferably, in the method according to the invention for achieving the minimum difference ΔT ^set = (T ₂ -T ₁ ) and a lower limit T ₂ ^set for the evaporator inlet temperature, an exhaust opening is at least partially opened. The blowing out is preferably carried out in a targeted manner by opening the blow-off opening at specific times or when a predefined lower limit for an evaporator inlet temperature is reached. By blowing out it can be achieved that the air temperature in front of the evaporator does not drop too much. Since this guidance of the process air is comparatively unfavorable, the amount of air blown out is preferably adapted to a desired condensation rate. However, the energy loss can be smaller than the recovered sensible energy, so that overall results in a reduced energy consumption of the dryer.

The dryer according to the invention has the advantage that it can work in an energy-efficient manner with a high condensation efficiency.

• Fig. 1 einen vertikalen Schnitt durch einen Trockner gemäß einer ersten Ausführungsform, bei der sich ein Verflüssiger zwischen einer Verbindungsstelle von Umluftkanal mit Zuluftkanal und einem Zuluftzugang befindet;
• Fig. 2 einen vertikalen Schnitt durch einen Trockner gemäß einer zweiten Ausführungsform, bei der sich ein Verflüssiger zwischen einer Verbindungsstelle von Umluftkanal mit Zuluftkanal und einem Zuluftzugang befindet; und
• Fig. 3 einen vertikalen Schnitt durch einen Trockner gemäß einer dritten Ausführungsform, bei der sich eine Verbindungsstelle des Umluftkanals mit dem Zuluftkanal zwischen einem Verflüssiger und einem Zuluftzugang befindet.

Further details of the invention will become apparent from the following description of non-limiting embodiments of the dryer according to the invention and a method using this dryer. Reference is made to the FIGS. 1 to 3 the attached drawing. Show it:

• Fig. 1 a vertical section through a dryer according to a first embodiment, in which a condenser is located between a junction of the recirculating air duct with supply air duct and a supply air inlet;
• Fig. 2 a vertical section through a dryer according to a second embodiment, in which a condenser is located between a junction of the recirculating air duct with supply air duct and a supply air inlet; and
• Fig. 3 a vertical section through a dryer according to a third embodiment, in which there is a connection point of the circulating air duct with the supply air duct between a condenser and a supply air.

Fig. 1 shows a vertical section through a dryer according to a first embodiment, in which a condenser 21 between a junction 27 of the recirculating air duct 14 with supply air duct 15 and a supply air inlet 28 is located.

The in Fig. 1 shown dryer 1 has a drum rotatable about a horizontal axis as a drying chamber 3, are mounted within which driver 4 for moving laundry during a drum rotation. Process air is guided by means of a blower 12 via an electric heater 11 and through a drum 3, in a process air duct 2. The process air channel 2 is supplied from a Zulufteingang 28 via a supply air duct 15 room air or sucked by the blower 12. After passing through the drum 3, the process air duct 2 splits into a recirculating air duct 14 and an exhaust air duct 13, so that the moist, warm process air is divided into a recirculating air stream in the recirculating air duct 14 and an exhaust air stream in the exhaust air duct 13.

The warm, laden with moisture process air from the drum 3 passes in the exhaust duct 13 in the evaporator 22 of a heat pump circuit 19,20,21,22. The cooled process air is then supplied via an exhaust air outlet 16 of the room air. The resulting in the evaporator 22 condensate is collected in a condensate pan 17, from where it can be disposed of by emptying or pumping. The vaporized in the evaporator 22 refrigerant of the heat pump is passed through a compressor 19 to the condenser 21. In the condenser 21, the refrigerant liquefies with heat to the coming into the supply air duct 15 from the supply air inlet 28 process air. The refrigerant, which is now in liquid form, is in turn conducted via a throttle valve 20 to the evaporator 22, whereby the refrigerant circuit is closed. A portion of the exiting from the drying chamber 3 warm, laden with moisture process air is diverted into a recirculating air duct 14 and passed through the heater 11 in turn into the drying chamber 3.

In the dryer 1 is heated by the heater 11 from the rear air, ie from a door 5 opposite side of the drum 3, passed through the perforated bottom in the drum 3, comes there with the laundry to be dried in contact and flows through the filling of the Drum 3 to a lint filter 6 within a closing the filling opening door 5. Subsequently, the process air flow in the door 5 is deflected downwards. The air supplied to the dryer 1 as supply air via the supply air duct 15 is additionally heated by the condenser 21 and then before entering the drying chamber 3 by means of the heater 11.

At the in Fig. 1 In the embodiment shown, the branched process air from the recirculating air duct 14 and the supply air preheated in the condenser 21 combine in front of the electric heater 11. The circulating air flow can be regulated by a first controllable closing device 23 and the supply air flow by a second controllable closing device 18. Finally, the exhaust air flow can be regulated by a third controllable closure device 26. As a controllable closure devices, for example, flaps can be used, which can be opened independently or independently depending on different widths.

The drum 3 is at the in the Fig. 1 to 3 shown embodiments at the rear bottom by means of a pivot bearing and front mounted by means of a bearing plate 7, the drum 3 rests with a brim on a sliding strip 8 on the bearing plate 7 and is held at the front end. The control of the condensation dryer via a control device 10, which can be controlled by the user via an operating unit 9.

In the in the Fig. 2 and 3 shown second and third embodiments have the same reference numerals to like parts. The following is therefore only on the differences to the in Fig. 1 shown embodiment.

Fig. 2 shows a vertical section through a dryer according to a second embodiment, in which a condenser 21 between a junction 27 of the recirculating air duct 14 with supply air duct 15 and a supply air inlet 28 is located. The blower 12 is here arranged directly in front of the drum 3. From the process air channel 2 branches off between the connection point 27 and the heater 11 from a blowout 24, which can be opened and closed by means of a fourth controllable closure device 25.

Fig. 3 shows a vertical section through a dryer according to a third embodiment, in which a junction 27 of the recirculating air duct 14 with supply air duct 15 between a condenser 21 and a supply air access 28 is located. Thus, the third embodiment differs from the second embodiment only in the location of the condenser 21.

Claims (14)

Dryer (1) with a drying chamber (3) for the objects to be dried, a supply air duct (15), a process air duct (2), an exhaust duct (13), a recirculating air duct (14), a fan (12), a heat pump (19 , 20,21,22) (with an evaporator 22) and a condenser (21) and a program controller (10), characterized in that the dryer (1) a process air path arrangement (10,14,15,16,18,21, 22, 23, 24, 27, 28) for achieving and maintaining a predetermined minimum difference ΔT ^set between an evaporator inlet temperature T ₂ and a dryer inlet temperature T ₁ and a predetermined lower limit T ₂ ^set for the evaporator inlet temperature. Dryer (1) according to claim 1, characterized in that in the process air path arrangement (10,14,15,16,18,21,22,23,24,27,28) a connection point (27) of the recirculating air duct (14) Supply air duct (15) between the condenser (21) and a supply air inlet (28) is located. Dryer (1) according to claim 1, characterized in that in the process air path arrangement (10, 14, 15, 16, 18, 21, 22, 23, 24, 27, 28) the condenser (21) is connected between a connection point (27). from recirculation duct (14) with supply air duct (15) and a supply air inlet (28) is located. Dryer (1) according to one of claims 1 to 3, characterized in that in the process air path arrangement (10,14,15,16,18,21,22,23,24,27,28) in the process air channel (2) in front of the drying chamber (3) an exhaust opening (24) is arranged. Dryer (1) according to one of claims 1 to 4, characterized in that the process air path arrangement (10,16,18,21,22,23) is designed to provide a condensation efficiency of at least 70%. Dryer (1) according to one of claims 1 to 5, characterized in that it comprises an electric heater (11). Dryer (1) according to one of claims 1 to 6, characterized in that the evaporator (22) is in contact with the exhaust air duct (13). Dryer (1) according to one of claims 1 to 7, characterized in that a first controllable closure device (23) is arranged in the circulating air channel (14). Dryer (1) according to one of claims 1 to 8, characterized in that in the supply air duct (15) a second controllable closure device (18) is arranged. Method for operating a dryer (1) with a drying chamber (3) for the objects to be dried, a supply air duct (15), a process air duct (2), an exhaust air duct (13), a recirculating air duct (14), a blower (12), a heat pump (19, 20, 21, 22) with an evaporator (22) and a condenser (21), a program controller (10) and a process air path arrangement (10, 14, 15, 16, 18, 21, 22, 23, 24) , 27-28) comprises for achieving and maintaining a predetermined minimum difference .DELTA.T ^set between an evaporator inlet temperature T ₂ and a dryer inlet temperature T ₁ and a predetermined lower limit T ₂ ^set for the evaporator inlet temperature, characterized in that process air in such a way (by the air supply channel 15) , the condenser (21) and the drying chamber (3) passed and in a first partial air flow in the recirculation air duct (14) and in a second partial air flow in the exhaust duct (13) is split, that a minimum difference .DELTA.T ^set = (T ₂ - T ₁ ) z between an evaporator inlet temperature T ₂ and a dryer inlet temperature T _{1 is} achieved and maintained and a predetermined lower limit T ₂ ^set for the evaporator inlet temperature is achieved and maintained. A method according to claim 10, characterized in that a volume ratio between the first partial air flow and the second partial air flow is in the range of 1.5 to 10. A method according to claim 11, characterized in that the volume ratio between the first partial air flow and the second partial air flow is in the range of 3 to 8. Method according to one of claims 10 to 12, characterized in that the first partial air flow is 200 to 300 m ³ / h and the second partial air flow is less than 100 m ³ / h. Method according to one of claims 10 to 13, characterized in that to achieve the minimum difference ΔT ^set = (T ₂ - T ₁ ) and a lower limit T ₂ ^set for the evaporator inlet temperature, a blow-out opening (24) is at least partially opened.

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