Methods for drying laundry and dryers

Abstract

A method for drying laundry, wherein heated air is passed through at least one drying chamber containing the laundry to be dried, and at least a portion of the exhaust air leaving the drying chamber is recirculated to the drying chamber, characterized in that the exhaust air leaving the at least one drying chamber is at least partially dried and recirculated to the at least one drying chamber as dried recirculated air, wherein the moist exhaust air leaving the drying chamber is dried by condensation, and the exhaust air or recirculated air leaving the drying chamber is dried by at least one condensation heat exchanger (14), wherein the liquid heated by the condensation heat exchanger (14) during the drying of the moist exhaust air from the drying chamber is used in another laundry treatment device that requires warm liquid or fresh water.

Description

Description:

[0001] The invention relates to a method for drying laundry according to the preamble of claim 1 and to a dryer according to the preamble of claim 8.

[0002] Dryers for commercial laundries have at least one heat source for heating the air used for drying. For example, a burner, preferably a gas burner, is used as the heat source.

[0003] The heated air is passed through a dryer drum containing the laundry to be dried, preferably a rotating drum, or through another type of drying chamber, which may also be stationary. During this process, the air absorbs moisture from the laundry. The moist air then exits the dryer as exhaust air.

[0004] At the beginning of a drying process, the dried exhaust air contains the most moisture. Therefore, it has been common practice to reuse this exhaust air not at all, or only to a very small extent, as recirculated air by venting the highly humid exhaust air to the outside. At the start of the drying process, only a small amount of recirculated air is used. Then, a large amount of fresh air is supplied to the dryer. This cold fresh air must be heated completely. This is evident, for example, from DE 40 23 000 A1, DE 10 2012 223 485 A1, US 2005 / 0 198 852 A1, US 2011 / 0198 405 A1, DE 10 2010 039 354 A1, and DE 10 2009 011 673 A1.

[0005] The invention is based on the objective of creating a method for drying laundry and a dryer that can be operated economically with a fairly large proportion of recirculated air or with recirculated air only.

[0006] A method for solving the problem comprises the measures of claim 1. Accordingly, it is provided that the exhaust air leaving the at least one drying chamber is at least partially dried and returned to the drying chamber as dried recirculated air. As a result of drying the exhaust air, it is possible to reuse even very humid exhaust air, and thus at least partially the humid exhaust air generated at the beginning of the drying process, by returning it to the drying chamber as dried recirculated air. This allows humid exhaust air to be reused as recirculated air, which increases the efficiency of the drying process. Furthermore, the humid exhaust air leaving the drying chamber is dried by condensation. This at least partially liquefies the moisture from the humid exhaust air, so that it can be discharged and only a smaller proportion of moisture remains in the exhaust air to be reused as recirculated air.Preferably, the exhaust air is dried to such an extent that the residual moisture in the exhaust air allows for economical reuse as dehumidified recirculated air, which can then be fed back into the drying chamber as dehumidified and therefore less humid supply air. Furthermore, it is provided that the exhaust air, after leaving the at least one drying chamber, is passed through at least one condensation heat exchanger and is at least partially dried by it. Cold liquid, for example, fresh water, or optionally cold or colder air, is also passed through the condensation heat exchanger. This cools the humid exhaust air, causing condensate to collect on the heat exchanger surfaces of the condensation heat exchanger, thereby reducing the moisture content of the humid exhaust air and thus drying it.During this process, the temperature of the exhaust air decreases, while the temperature of the fresh water or fresh air used for condensation increases. The condensate in the condensation heat exchanger flows off the preferably cooler heat exchanger plates and is collected and drained away in a suitable manner.

[0007] A preferred method for reusing the liquid, particularly fresh water, heated during the condensation of moist exhaust air at or within the at least one condensation heat exchanger is to supply this heated liquid or preheated fresh water to another laundry machine that requires heated liquids. This could be, for example, a washing machine, especially a continuous flow washing machine, or possibly a finisher or ironer. This allows at least some of the energy extracted during the drying of the exhaust air, particularly the moist exhaust air, to be reused.

[0008] Due to the energy extracted during the drying of the moist exhaust air, it is necessary to reheat the dried exhaust air, which is to be returned to the drying chamber as recirculated air, before it enters the drying chamber. An advantageous further development of the process involves supplying a heating device, for example a burner, to heat the dried exhaust air used as recirculated air. This air is heated in at least one burner or other device and then returned to the at least one drying chamber as heated and dried supply air.

[0009] If necessary, only a portion of the moist exhaust air can be dried, particularly by passing it through a condensation heat exchanger. This makes it possible, in cases of very moist exhaust air that cannot be sufficiently dried by the at least one condensation heat exchanger, to recirculate only as much moist exhaust air back into the drying chamber as can be adequately dried by the at least one condensation heat exchanger. A mixture of the typically large portion of the moist exhaust air (dried recirculated air) and fresh air is then supplied to the drying chamber and the heating system from the drying chamber to heat the dried exhaust air (recirculated air) and the fresh air.In this way, the condensation heat exchanger can be operated economically, and the heated supply air to at least one drying chamber can be supplied with a residual moisture content that leads to the most economical drying of the laundry.

[0010] It is preferable to introduce fresh air between the condensation heat exchanger and the heating unit to preheat the at least partially dried exhaust air or recirculated air. The fresh air, which normally does not require further dehumidification because it is sufficiently dry, thus does not burden the condensation heat exchanger.

[0011] A dryer for solving the aforementioned problem has the features of claim 8. The dryer, preferably used for carrying out the previously described method, has a recirculating air line between the outlet of the exhaust air from the drying chamber and the inlet of the recirculated, treated exhaust air into the drying chamber, as well as at least one condensation heat exchanger. This causes the moist exhaust air from the drying chamber, used as recirculated air, to condense and thus be dried, so that drier or dry exhaust air can be reintroduced to the drying chamber as recirculated air.

[0012] Preferably, the heating device, preferably the at least one burner, is positioned downstream of the at least one condensing heat exchanger in the direction of airflow through the recirculation duct. This allows the moist exhaust air used as recirculation to be reheated after drying and the resulting cooling.

[0013] In a preferred design of the dryer, at least one closable drain opening is provided upstream of the condensation heat exchanger and / or at least one closable fresh air supply opening downstream of the condensation heat exchanger. The closable drain opening allows moist exhaust air to be discharged, at least partially or completely, into the open air. Accordingly, depending on the moisture content of the exhaust air, either all or only a portion of it is dried. Similarly, the fresh air supply opening can be completely or partially closed. With the fresh air supply opening closed, only moist exhaust air, after drying and heating, is reintroduced into the drying chamber as supply air for the drying process.If the fresh air supply opening is only partially closed, the drying chamber receives a mixture of partially dried exhaust air and partially fresh air after any necessary heating. The proportion of exhaust air to be dried can be controlled and regulated as needed, particularly depending on the moisture content of the exhaust air, by opening or closing the drain / exhaust air opening and / or the fresh air supply opening.

[0014] It is also conceivable to route the recirculating air duct to and / or through the heating system, particularly the burner. This ensures that the heating system is supplied with sufficient combustion air from the recirculating air duct, which can be dried exhaust air or a mixture of dried exhaust air and fresh air. Passing the recirculated air, which contains at least a portion of dried exhaust air, through the heating system is particularly suitable when heating the drying air with a burner, especially a gas-fired burner.

[0015] Preferred embodiments of the invention are explained in more detail below with reference to the drawing. This drawing shows: Fig. 1 a schematic side view of a dryer comprising a condensation heat exchanger and a circulation line, and Fig. 2 a second embodiment of a dryer comprising a condensation heat exchanger and a circulation line.

[0016] The dryer 10, shown schematically in the figures, is used for highly effective and energy-efficient drying of laundry not shown in the figures. Such a dryer 10 is primarily used in commercial laundries.

[0017] The dryer 10 has an outer housing 11, preferably a closed, box-shaped housing 11, in which at least one drying chamber is provided. For example, the drying chamber can be a dryer drum that rotates about a rotary axis. The dryer drum serves to hold a batch of laundry to be dried. It has a loading and unloading opening, which is not shown in the figures. In particular, the outer shell of the dryer drum is designed to be air-permeable so that drying air can flow through the dryer drum and the moist laundry contained therein.

[0018] Hot drying air can be supplied to the dryer drum through an air inlet opening in the housing 11 (not shown). After this drying air has circulated around the dryer drum and the laundry to be dried inside, the moisture-laden drying air flows out of the housing 11 as moist exhaust air through an exhaust vent 12 located elsewhere on the housing 11.

[0019] The exhaust air opening 12 and the intake air opening of the dryer 10, in particular of its housing 11, are connected by a recirculation duct 13 of the dryer 10 located outside the housing 11. This is a stationary pipe. A condensation heat exchanger 14 and a heating element of the dryer 10 are integrated into the recirculation duct 13. In the illustrated embodiment, the heating element is designed as a burner 15, preferably a gas-fired burner.

[0020] A starting point 16 of the recirculation duct 13 is directly connected to the exhaust air opening 12. The recirculation duct 13 extends from the exhaust air duct 12 to an inlet 17 of the condensing heat exchanger 14. At the rear outlet 19 of the condensing heat exchanger 14 (viewed in the direction of airflow 18, particularly the exhaust air flowing through the recirculation duct 13 and the condensing heat exchanger 14), the tubular recirculation duct 13 continues to the inlet 20 of the burner 15 on the dryer housing 11, which is located behind the condensing heat exchanger 14 (viewed in the direction of airflow 18). The outlet 20 of the burner 15, located on the dryer housing 11, is not shown in the figures. The supply air opening for warmed, dry drying air is located at the outlet of the burner 15, which supplies the drying drum and the laundry inside.

[0021] The condensation heat exchanger 14 is designed as a plate heat exchanger. It features, for example, upright, adjacent heat exchanger plates that slope slightly downwards from the inlet side 17 to the outlet side 19 of the condensation heat exchanger 14. The heat exchanger plates are preferably designed as so-called cushion plates with internal flow channels. Due to the downward slope of the heat exchanger plates, their longitudinal edges slope slightly downwards towards the outlet side 19 for condensate drainage. For further details of the condensation heat exchanger 14, explicit reference is made to EP 2 182 106 A1. A liquid, preferably fresh water, flows through the internal flow channels of the heat exchanger plates.At the lower end of the condensing heat exchanger 14, near the outlet side 19, there is an inlet connection 21, and at the upper end, near the inlet side 17, an outlet connection 22. The flow channels of the heat exchanger plates are thus traversed diagonally in counterflow by the liquid, preferably fresh water to be heated. The exhaust air from the dryer 10, flowing in the direction of flow 18 through the circulation line 13, flows along the outside of the heat exchanger plates and is returned to the dryer 10 as recirculated air.

[0022] The circulation line 13, the condensation heat exchanger 14 and the burner 15 associated with the dryer 10 are part of the dryer 10, even though they are located outside its housing 11.

[0023] The Fig. Figure 2 shows a dryer that is largely the same as the one in the Fig. 1 corresponds to, which is why the same reference numbers are used for identical parts. The differences of the dryer 10 in the Fig. 2 to the one in the Fig. 1 consist in that a kind of diverter 23 is provided in front of the inlet side 17 of the condensing heat exchanger 14 and, in the direction of flow 18 of the exhaust air or recirculated air through the circulation line 13, a further, rear diverter 24 is provided behind the outlet side 19 of the condensing heat exchanger 14.

[0024] The front diverter 23 has an inlet opening 25 and two outlet openings 26 and 27. Moist exhaust air from the dryer 10 is supplied to the diverter 23 via the circulating line 13 through the inlet opening 25. One outlet opening 26 is connected to the inlet side 17 of the condensing heat exchanger 14, while the second outlet opening 27 leads to the outside. The rear diverter 24 is configured analogously. The inlet opening 28 of the diverter 24, which is connected to the outlet side 19 of the condensing heat exchanger 14, branches into an inlet opening 29 for fresh air and an outlet opening 30. A lower outlet opening 30 opens into the section of the circulating line 13 leading to the burner 15. The opposite inlet opening 30 also leads to the outside in the case of the diverter 24.

[0025] Each of the switches 23, 24 makes it possible to completely close one of the drain openings 26, 27 or one of the inlet openings 28, 29, thereby opening the second drain opening 26, 27 or inlet opening 28, 29, or to bring it into intermediate positions, one of which is in the Fig. Figure 2 shows that in these intermediate positions, a portion of the exhaust air or recirculated air flows through each of the drain openings 26, 27 and the inlet openings 29, 30 of the respective diverter 23, 24.

[0026] In the illustrated embodiment, each switch 23, 24 has a flap 31, 32, preferably pivotable by a drive. The oppositely pivotable flaps 32, 31 make it possible to close one of the outflow openings 26, 27 or the inflow openings 29, 30 of each switch 23, 24 or to set intermediate positions as shown in the illustration. Fig. 2. Then both outflow openings 26, 27 and inflow openings 29, 30 of the switches 23, 24 are partially open, whereby the opening ratio of the two outflow openings 26, 27 and analogously the inflow openings 29, 30 of each switch 23, 24 can be changed according to requirements by the set angle of the flaps 31, 32.

[0027] The in the Fig. 1 and Fig. The dryers 10 shown in Figure 2 each have at least one flow generator, preferably a fan, for generating a circulating airflow in the circulation line 13. The fan transports the air in the direction of flow 18 through the circulation line 13 and the condensing heat exchanger 14, as well as through the burner 15 and the dryer drum containing the laundry to be dried. For example, such a fan can be located at the exhaust opening 12 of the housing 11, preferably on the housing 11. In this case, the pressure side of the fan forms the exhaust opening 12 for connecting the circulation line 13. Alternatively or additionally, it is also conceivable to provide a fan at the end of the circulation line 13, for example, between the inlet side of the burner 15 and the end of the circulation line 13, i.e., practically above the burner 15.

[0028] The inventive method is explained in more detail below: In the dryer 10 with the circulation line 13 and the condensation heat exchanger 14 according to the Fig. 1. Warm air, namely drying air, heated by burner 15, is supplied to the dryer drum, which is loaded with damp laundry to be dried. Moisture-enriched drying air leaves the dryer drum and the housing 11 as moist exhaust air. This moist exhaust air enters the beginning 16 of the circulation line 13 and flows from there in the direction of flow 18 via the inlet side 17 into the condensation heat exchanger 14. The moist exhaust air flows in the direction of flow 18 through the condensation heat exchanger 14 to its outlet side 19. Through the rear section of the circulation line 13, which connects to the outlet side 19 of the condensation heat exchanger 14, the exhaust air or recirculated air dried by the condensation heat exchanger 14 flows as dried air to the burner 15. From the burner 15, the dried recirculated air or exhaust air is reheated and directed as drying air back into the rotating dryer drum containing the laundry to be dried.

[0029] The drying of the moist exhaust air, which is circulated in the recirculation line 13 in the direction of flow 18, takes place in the condensation heat exchanger 14. The moist exhaust air flows along the outside of the heat exchanger plates of the condensation heat exchanger 14, which are arranged parallel to each other at a distance. Fresh water is supplied to flow channels inside the heat exchanger plates from the inlet connection 21. This fresh water flows through the flow channels inside the heat exchanger plates and exits the condensation heat exchanger 14 at the outlet connection 22. Due to the arrangement of the inlet connection 21 near the outlet side 19 of the condensation heat exchanger 14, the fresh water flows through the condensation heat exchanger 14 in counterflow or cross-counterflow to the moist exhaust air.The moist exhaust air is cooled at the outer surfaces of the heat exchanger plates by the colder fresh water flowing through them, causing at least a large portion of the moisture in the moist exhaust air to condense on the outer surfaces of the heat exchanger plates. The condensate is preferably drained at the lowest point of the condensation heat exchanger 14 through a lower condensate drain opening 33 near the outlet side 19 of the condensation heat exchanger 14.

[0030] The energy extracted from the moist exhaust air for condensation is transferred to the colder fresh water in the condensation heat exchanger 14, thereby warming it. Warmed or preheated fresh water therefore exits the condensation heat exchanger 14 through the drain connection 22. This can be used to operate laundry treatment equipment requiring warm fresh water, for example, washing machines, especially continuous flow washing machines.

[0031] As a result of the at least partial condensation of the moisture contained in the humid exhaust air at or within the condensation heat exchanger 14, dehumidified exhaust air exits it. The exhaust air is thus at least partially dried in the condensation heat exchanger 14. The dried or dehumidified exhaust air leaves the outlet side 19 of the condensation heat exchanger 14 and passes through the section of the recirculation line 13 following the flow direction 18 to the burner 15, where the dehumidified and / or dried exhaust air is reheated so that the humid exhaust air has been reconditioned to be reused as drying air for drying laundry in the dryer drum.

[0032] As a result of the connection between the exhaust air openings 12 of the dryer housing 11 10 and the supply air opening for drying air in the housing 11, the moist exhaust air from the dryer 10 is recirculated. The exhaust air flowing as recirculated air through the recirculation duct 13 and the condensation heat exchanger 14 is treated for reuse, namely dried in the condensation heat exchanger 14 and then reheated by the burner 15. This process transforms the moist exhaust air and recirculated air back into drying air, which can then be used again for drying laundry.

[0033] In the exemplary embodiment of the Fig. 1. The entire moist exhaust air leaving the housing 11 is circulated as recirculated air through the recirculation line 13 and thereby dried in the condensation heat exchanger 14, and the dry air or drier recirculated air or exhaust air is reheated by the burner 15 to be reused as drying air.

[0034] In the exemplary embodiment of the Fig. Due to the diverters 23 and 24, it is possible to reuse either all or only a portion of the moist exhaust air as recirculated air after drying and heating, for re-drying the laundry in the dryer drum. The diverter 33, located before the condensation heat exchanger 14, controls the proportion of moist exhaust air supplied to the condensation heat exchanger 14 as recirculated air and the amount of moist exhaust air vented to the outside. Alternatively, by adjusting the position of the flap 31, all moist exhaust air can be supplied to the condensation heat exchanger 14, and, if desired, all exhaust air can be vented to the outside.

[0035] The diverter valve 24 downstream of the condensing heat exchanger 14 allows the dried exhaust air to be mixed with fresh air. By adjusting the angle of the damper 32, the mixing ratio of the dried exhaust air and fresh air can be adapted to specific requirements. It is also possible to supply only fresh air or only dried exhaust air via the diverter valve 24 to the section of the recirculation duct 13 leading to the burner 15, provided the damper 32 closes the inlet opening 28 or the inlet opening 29.

[0036] Preferably, the control of the flaps 31 and 32 of the two diverter valves 23 and 24 is dependent. For example, if all the moist exhaust air from the condensation heat exchanger 14 is dried and recirculated to the laundry being dried, no fresh air is supplied. In this case, the outlet opening 27 and the inlet openings 29 are completely closed by the flaps 31 and 32. Furthermore, if required, it is possible to discharge only a predetermined portion of the moist exhaust air to the outside via the outlet opening 27.

[0037] The amount of moist exhaust air discharged to the outside is controlled or regulated by the position of the damper 31. When the damper 31 is in a position that is within the Fig. In the intermediate position shown in Figure 2, which allows for the partial discharge of moist exhaust air to the outside, flap 32 is in a corresponding intermediate position according to the Fig.2, in which preferably the proportion of moist exhaust air that has been directed to the outside is replaced by a correspondingly large quantity of fresh air flowing in through the inlet opening 29.

[0038] If desired and necessary, the flap 31 can even completely close the inlet side 17 of the condensation heat exchanger 14, so that all the moist exhaust air is directed to the outside. Then, the flap 32 behind the condensation heat exchanger 14 completely closes its outlet side 19, so that only fresh air is supplied through the inlet opening 29 of the drying drum in the dryer 10. In this case, there is no recirculation operation and no moist exhaust air needs to be dried in the condensation heat exchanger 14. Reference symbol list: 10 dryers 11 cases 12 Exhaust opening 13 Circulation line 14 Condensation heat exchangers 15 burners 16 Beginning 17 Entrance page 18 Flow direction 19 Home page 20 Entrance page 21 Inlet connection 22 Drain connection 23 Switch 24 switches 25 Inlet opening 26 Drain opening 27 Drain opening 28 Inlet opening 29 Inlet opening 30 Drain opening 31 flap 32 flap 33 Condensate drain opening

Claims

[1] Method for drying laundry, wherein heated air is passed through at least one drying chamber containing the laundry to be dried and at least part of the exhaust air leaving the drying chamber is recirculated to the drying chamber as recirculated air, characterized by , that the exhaust air leaving the at least one drying chamber is at least partially dried and returned to the at least one drying chamber as dried recirculated air, wherein the moist exhaust air leaving the drying chamber is dried by condensation and the exhaust air or recirculated air leaving the drying chamber is dried by at least one condensation heat exchanger (14), wherein liquid heated by the condensation heat exchanger (14) during the drying of the moist exhaust air from the drying chamber is used in another laundry treatment facility with a requirement for warm liquid or fresh water. [2] Method according to claim 1, characterized by, that at the condensation heat exchanger (14) the temperature of the moist exhaust air is reduced and a cooler medium, preferably a liquid, which is passed through the condensation heat exchanger (14) is heated. [3] Method according to one of claims 1 or 2, characterized by , that fresh water heated by the condensation heat exchanger (14) during the drying of the moist exhaust air from the drying chamber is used in another laundry treatment facility that requires warm liquid or fresh water. [4] Method according to any one of the preceding claims, characterized by that the exhaust air leaving the drying chamber, in particular moist exhaust air or recirculated air, is fed to a heating device and heated by it. [5] Method according to claim 4, characterized by that the heating device is supplied with at least partially dried exhaust air from the drying chamber and / or recirculated air. [6] Method according to any one of the preceding claims, characterized by , that only a portion of the moist exhaust air is dried, in particular by passing it through the at least one condensation heat exchanger (14). [7] Method according to any one of claims 4 to 6, characterized by , that fresh air is supplied to at least partially dried exhaust air or dried recirculated air, preferably behind the condensation heat exchanger (14) and in front of the heating device. [8] Laundry dryer (10) with a rotating dryer drum for the laundry to be dried, which has an air inlet and an exhaust air outlet connected by a circulation line (13) and a heating device for heating the recirculated air flowing through the circulation line, characterized by, that at least one condensation heat exchanger (14) is arranged in the circulation line (13), wherein, viewed in the direction of flow (18) of the recirculated air, a closable exhaust air opening is provided before the condensation heat exchanger (14) or before the first condensation heat exchanger (14) and / or a closable fresh air supply opening is provided behind the condensation heat exchanger (14) or the last condensation heat exchanger (14). [9] Dryer according to claim 8, characterized by , that in the direction of flow (18) of the recirculated air through the circulation line (13) the heating device, preferably a burner (15), follows the condensing heat exchanger (14) or the last condensing heat exchanger (14). [10] Dryer (10) according to one of claims 8 or 9, characterized by that the circulation line (13) is routed to and / or through the heating device, preferably the burner (15).

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