WO2009095318A1

WO2009095318A1 - Condenser dryer comprising a latent heat accumulator, and method for the operation thereof

Info

Publication number: WO2009095318A1
Application number: PCT/EP2009/050466
Authority: WO
Inventors: Andreas Stolze
Original assignee: BSH Bosch und Siemens Hausgeräte GmbH
Priority date: 2008-01-28
Filing date: 2009-01-16
Publication date: 2009-08-06
Also published as: PL2252736T3; EP2252736A1; DE102008006348A1; EP2252736B1; ATE541078T1

Abstract

The invention relates to a condenser dryer (1) comprising a drying chamber (2) for objects that are to be dried and a process air duct (3) which accommodates an electric heater (4), a heat exchanger (5), and a fan (6). The condenser dryer (1) further comprises a latent heat accumulator (7) and a cooling air duct (8). The latent heat accumulator (7) is arranged inside the cooling air duct (8). The invention also relates to a method for operating said condenser dryer (1).

Description

Condensation dryer with a latent heat storage as well

Procedure for its operation

The invention relates to a condensation dryer with a drying chamber for objects to be dried, a process air duct in which there is an electric heater, a heat exchanger and a fan, a latent heat storage and a cooling air duct and a preferred method for its operation.

Such a condensation dryer is apparent from DE 37 10 710 A1.

A tumble dryer, whose operation is based on the condensation of the evaporated by means of warm process air moisture from the laundry - a so-called condensation dryer - unlike a so-called exhaust air dryer, the heated air once passes through the wet laundry and then expels, no exhaust hose for leading out the exhaust air The building in which it is installed and is very popular because it can be used in an internal bathroom or a laundry room of a larger residential complex. Exhaust air dryers and condensation dryers are collectively referred to herein as dryers, unless the context requires otherwise. In a condensation dryer air (so-called process air) is passed through a fan via a heater in a wet laundry containing drum as a drying chamber. The hot air absorbs moisture from the laundry to be dried. After passing through the drum, the now moist process air is directed into a heat exchanger, which is usually preceded by a lint filter.

In the heat exchanger (eg air-air heat exchanger), the moist process air is cooled, so that the water contained in the moist process air condenses. The condensed water is then usually collected in a suitable container and the cooled and dried process air fed back to the heater and then the drum (circulating air dryer) or in the installation room of the dryer (exhaust air dryer). DE 37 10 710 A1 describes a condensation dryer with a closed recirculation circuit in which a circulating air fan, an electric air heater, a laundry container, a heat exchanger and a latent heat storage are arranged with a storage medium, wherein the latent heat storage in the recirculation loop between the heat exchanger and the electric air heater located. The latent heat storage stores at least partially the heat energy dissipated by the moist, warm process air from the drying chamber. If the entire content of the latent heat storage medium has melted on storage medium and the coolant supply to the heat exchanger must be turned on, the electric air heater can be throttled or turned off, because the latent heat storage can be used to heat the process air.

DE 102 24 940 A1 discloses a condensation laundry dryer with a drying chamber, a closed process air circuit, a process air blower, a heating device and a latent heat storage device arranged removably in the process air cycle. This replaces the common, air-working heat exchanger. The removably arranged latent heat accumulator can be discharged separately from the dryer.

From DE 44 03 737 A1 a washing machine or dishwasher is apparent, which has a tub and a heat exchanger, wherein a primary circuit of

Heat exchanger in the course of a leading out of the tub sewer and a secondary circuit in the course of leading into the tub fresh water line. The heat exchanger, in turn, has a cavity filled with a medium for storing latent thermal energy, which in contact with the primary circuit and the secondary circuit in a manner such that, without mixing the medium with the medium

Contents of the primary circuit and the secondary circuit or the contents of the primary circuit and the secondary circuit each other a maximum possible exchange of

Heat energy between the contents in the primary circuit and the medium on the one hand and between the medium and the content in the secondary circuit on the other hand can take place.

In the previously known condensation tumble dryers with a latent heat storage, the moist, warm process air heats the cooling medium in one Heat exchanger (eg air-air heat exchanger), without the heat contained in the heated cooling medium is recovered.

The object of the present invention is therefore to improve the energy efficiency in a different way in a condensation dryer with latent heat storage. In particular, in a condensation dryer in which an air-to-air heat exchanger is used, the heat energy released during the cooling of the moist process air to the cooling air can be utilized.

The solution of this object is achieved according to this invention by a condensation dryer with the features of the corresponding independent claim and the method having the features of the corresponding independent claim.

Preferred embodiments of the condensation dryer according to the invention are listed in the dependent claims, as are preferred embodiments of the method.

The invention thus relates to a condensation dryer with a drying chamber for objects to be dried, a process air duct in which there is an electric heater, a heat exchanger and a blower, a latent heat storage and a cooling air duct, wherein the latent heat storage is arranged in the cooling air duct.

The stored in the latent heat storage by cooling of heated cooling air heat energy can be used to heat process air in the process air duct and / or the drying chamber. According to the invention it is preferred if the heating of the process air in the drying chamber, i. as a result of a heat exchange between latent heat storage and drying chamber takes place.

In a preferred embodiment of the condensation dryer, therefore, a surface of the latent heat accumulator facing away from the cooling air channel is spaced from the drying chamber by a maximum of 5 cm, preferably a maximum of 3 cm and particularly preferably a maximum of 2 cm. It is also preferred that the surface of the latent heat accumulator facing away from the cooling air channel is concave. In this embodiment, moreover, it is preferable that a distance between the concave surface and an outer surface of the drying chamber is between 0.5 and 5 cm.

The latent heat storage used according to the invention generally contains a storage medium for heat energy, wherein the storage medium is preferably surrounded by a good thermal conductivity latent heat storage wall.

The latent heat accumulator used in the condensation dryer according to the invention preferably has ribs on a surface of the latent heat accumulator facing the cooling air passage. These ribs can serve to guide the cooling air through the latent heat storage. Alternatively or additionally, the ribs may be filled with a storage medium.

In a further embodiment of the condensation dryer according to the invention, the latent heat storage is rotatable about an axis. In this embodiment, the latent heat storage is preferably cylindrical. In this case, the rotation axis of the cylindrical latent heat accumulator is particularly preferably parallel to a rotation axis of the drying chamber. In this arrangement, it is possible in a further preferred embodiment of the invention that the latent heat storage is driven by a drum as a drying chamber. This allows a better heat transfer from the heated cooling air to the latent heat storage but also take place from the latent heat storage on the drying chamber.

For the operation of the condensation dryer according to the invention, it has proved to be advantageous if in each case a temperature sensor is arranged in the cooling air passage in front of and behind the latent heat storage. The temperatures measured by the two temperature sensors, in particular their difference, allow a determination of the state of charge of the latent heat accumulator. Here, state of charge means the extent of the phase transition from the liquid to the solid state in the storage medium of the latent heat storage. The state of charge is thus a measure of the ability of the latent heat storage for storing heat energy. The temperature sensors are preferably connected to a control device which automatically triggers a shutdown or connection of the electric heater.

In a preferred embodiment of the condensation dryer, the latent heat store contains a storage medium with a phase transition from the liquid to the solid state in the temperature range of 30 to 65 ° C, more preferably in the temperature range of 35 to 60 ° C and most preferably in the temperature range of 45 to 55 ° C.

It is also preferred that the latent heat storage contains a storage medium containing an inorganic salt hydrate and / or an organic compound. In a particularly preferred embodiment of the invention contains the used

Storage medium is a salt hydrate, wherein the salt hydrate preferably at least one salt from the group consisting of sodium acetate, sodium thiosulfate, magnesium nitrate and

Magnesium chloride consists, contains. As additions to other salts, potassium nitrate, ammonium nitrate and lithium nitrate may also be used.

Examples of suitable salt hydrates are, for example:

- a mixture of 58.7% by weight of Mg (NOA) ₂ "6 H ₂ O and 41 wt .-% 3 MgCl ₂ ^■ 6H ₂ O having a melting point of 59 ° C, - a mixture of 61, 5 % By weight of Mg (NO ₃ ) ₂ ^.6H ₂ O and 38.5% by weight of NH ₄ NO ₃ with a melting point of 52 ° C .;

CH ₃ COONa (sodium acetate) ^■ 3 H ₂ O with a melting point of 54 ° C; and Na ₂ S ₂ O ₃ (sodium thiosulfate) ^■ 5 H ₂ O with a melting point of 48 ° C.

In a further particularly preferred embodiment of the invention, the storage medium contains an organic compound. Examples of suitable organic compounds or mixtures of organic compounds are:

Paraffins (heat peels) with different melting points; Myristic acid with a melting point of 58 ° C; - A mixture of 89 wt .-% palmitic acid and 11 wt .-% acetamide with a

Melting point of 57.2 ° C; a mixture of 74.9 wt .-% palmitic acid and 25.1 wt .-% propionamide having a melting point of 50 ° C. Moreover, as a storage medium in the latent heat storage and a mixture of organic and inorganic compounds can be used. An example of this is a mixture of 80 wt .-% acetamide and 20 wt .-% NaNO ₃ with a melting point of 59 ° C.

The melting point of the storage medium corresponds to the discharge temperature of the latent heat storage. The volume flow and the power of the air-to-air heat exchanger are generally tuned to the discharge temperature, so that the difference between the discharge temperature and the temperature of the cooling air at the exit from the heat exchanger is sufficiently large to allow efficient charging of the latent heat accumulator. This temperature difference is generally 3 to 25 ° C, preferably 5 to 20 ° and most preferably 8 to 15 ° C. Under these conditions, the heat exchange is particularly favorable.

The storage media which can be used in accordance with the invention show a more or less pronounced tendency to hypothermia, which are described in so-called hot packs, as described, for example, in US Pat. can be used as a pocket warmer, find application. In these, heat energy is deliberately released by triggering a crystallization process in the supercooled solution at temperatures below the melting point (discharge temperature).

Although a storage medium in the form of a supercooled solution can be used according to the invention. Preferably, however, supercooling is avoided. For this purpose, a nucleating agent is added to the storage medium. A nucleating agent is, for example, a solid substance dispersed in the storage medium and chemically inert with respect to the storage medium, which melts at no temperature which can be expected in the latent heat storage and thus represents seeds from which the storage medium passing into the solid phase can form crystals. Examples include quartz (silica) and talc (magnesium silicate). The person skilled in the art is aware of suitable nucleating agents for various storage media.

In one embodiment of the invention with an improved heat exchange with the storage medium, the latent heat storage of the inventive Condensation dryer in its interior means for generating a flow in the storage medium.

In a preferred embodiment of the condensation dryer, the air-to-air heat exchanger is removable. This is particularly advantageous because a removable heat exchanger can be cleaned more easily from lint.

In a further preferred embodiment of the invention, the latent heat storage is removable. The discharge of the latent heat storage can then take place independently of the condensation dryer.

The invention also relates to a method for operating a condensation dryer with a drying chamber for objects to be dried, a process air duct, in which there is an electric heater, a heat exchanger and a blower, a latent heat storage and a cooling air duct, wherein the latent heat storage is arranged in the cooling air duct, and wherein when the electric heater is switched on in the heat exchanger heated cooling air is fed to the storage medium containing latent heat storage and the latent heat storage is charged by heat energy contained in the heated cooling air is stored in the storage medium.

In a preferred embodiment of this method, a phase transition in the storage medium from solid to liquid is used for the storage of the heat energy contained in the heated cooling air. Preferably, in this case, the storage of thermal energy is carried out until the phase transition in the storage medium is completed from solid to liquid.

Most preferably, in the method according to the invention, the electric heater is switched off after completion of the phase transition. As a result, the temperature of the process air and the cooling air generally decreases. The process air in the drying chamber is then heated by the heat energy stored in the storage medium. The drying of laundry in the drying chamber then generally takes place at a lower temperature level than with the exclusive use of an electric heater.

According to the invention, it is preferred if process air and cooling air are passed through the heat exchanger in a crossflow or countercurrent process.

The invention has the advantage that a condensation dryer with a latent heat storage can be operated with higher efficiency. In addition, the invention allows the operation of a condensation dryer at a relatively high ambient temperature at which a discharge of heated cooling air in the installation room of the dryer is not desirable.

Further details of the invention will become apparent with reference to Figures 1 and 2 from the following description of a non-limiting embodiment of the condensation dryer according to the invention and the method for operating this condensation dryer.

FIG. 1 shows a vertically sectioned condensation dryer (hereinafter also abbreviated to "dryer") according to one embodiment of the invention, in which a latent heat accumulator is arranged in the cooling air duct in the immediate vicinity of the drying chamber.

Figure 2 shows a section of a condensation dryer according to the invention, in which the arrangement of a provided with ribbed latent heat storage in the immediate vicinity of the drying chamber can be seen even more clearly.

The dryer 1 shown in Figure 1 has a rotatable about a horizontal axis drum as a drying chamber 2, within which drivers 15 are fixed for moving laundry during a drum rotation. Process air is guided by means of a blower 6 in the process air duct 3 via an electric heater 4 through the drum 2. After exiting the drum 2, the process air laden with moisture in the process air duct 3 is passed through an air-air heat exchanger 5, where a heat exchange with cooling air, which originates from a cooling air inlet 16 takes place. The Process air cools down by condensation of the moisture contained in it and is in turn passed through the fan 6 and the electric heater 4 in the drying chamber 2, whereby the process air circuit is closed. The condensed moisture is collected in a condensate tank not shown in FIG. The heated in the air-air heat exchanger 5 cooling air is passed through a latent heat accumulator 7, where it is cooled by transfer of heat energy from the heated cooling air to a storage medium. The storage medium not shown in detail here is a salt hydrate, which can store heat energy by a phase transition from solid to liquid. The cooled cooling air is then passed through a cooling air outlet 17 into the installation room of the dryer 1.

For drying of laundry items not shown in detail in the drum 2 is heated by the electric heater 4 heated air from behind, i. from the opposite side of a door 5 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 opening of the drum 3 to a lint filter 19 within a closing the filling opening door 18th Subsequently, the air flow in the door 18 is deflected downward and directed to the air-to-air heat exchanger 5.

After completion of the phase transition in the storage medium of the latent heat storage 7 is charged. This condition can be detected by a decrease in the temperature difference measured by two temperature sensors 13 and 14 arranged in front of and behind the latent heat accumulator 7. The temperature difference becomes one

Control device 22 transmits, which they in terms of charging the

Latent heat accumulator 7 evaluates and causes a shutdown of the electric heater 4. The temperature of the entering into the drying chamber 3 process air drops down and the drying is due to the heat transfer from

Latent heat storage 7 on the drying chamber 3 at a lower

Temperature level continued. For efficient heat transfer in the embodiment of the invention shown here, the distance between the drying chamber 2 and the latent heat storage 7 of 5 to 10 mm.

In a detected discharge of the latent heat accumulator 7 (termination of the phase transition in the storage medium from liquid to solid), which also by Evaluation of the temperature measurements can be determined by means of the temperature sensors 13 and 14, the electric heater 4 can be turned on again. Thereafter, the temperature of the process air and thus the cooling air rises after passing through the air-air heat exchanger 5, so that the latent heat storage 7 is recharged.

The drum 3 is mounted in the embodiment shown in Fig. 1 at the rear bottom by means of a pivot bearing and front by means of a bearing plate 20, wherein the drum 3 rests with a brim on a sliding strip 21 on the bearing plate 20 and is held at the front end. The control of the dryer via the control device 22, which can be controlled by the user via an operating unit 23.

2 shows a section of a condensation dryer 1 according to the invention, in which the arrangement of a latent heat accumulator 7 provided with ribs 12 in the immediate vicinity of the drying chamber 2 can be seen even more clearly. On the cooling air channel 8 facing surface 1 1 of the latent heat accumulator 7 ribs 12 are arranged. The cooling air channel 8 facing away from the surface 9 of the latent heat accumulator 7 is concave and shaped so that it has the same width as the drying chamber 2, from the outer surface 10, it has a distance of 5 to 10 mm. 24 means a deflector, which deflects the cooling air exiting horizontally from the air-air heat exchanger 5 upwards. The arrows indicate the flow direction of the cooling air. The latent heat storage 7 is designed in this embodiment as a removable part.

Claims

1. Condenser dryer (1) with a drying chamber (2) for objects to be dried, a process air duct (3) in which an electric heater (4), a heat exchanger (5) and a fan (6), a latent heat storage (7 ) and a cooling air channel (8), characterized in that the latent heat accumulator (7) in the cooling air channel (8) is arranged.

2. condensation dryer (1) according to claim 1, characterized in that a cooling air channel (8) facing away from the surface (9) of the latent heat accumulator (7) of the drying chamber (2) is a maximum of 5 cm apart.

3. Condenser dryer (1) according to claim 2, characterized in that the cooling air channel (8) facing away from the surface (9) of the latent heat accumulator (7) is concave.

4. condensation dryer (1) according to claim 3, characterized in that a distance between the concave surface (9) and an outer surface (10) of the

Drying chamber (2) is between 0.5 and 5 cm.

5. Condenser dryer (1) according to one of claims 1 to 4, characterized in that a cooling air channel (8) facing surface (11) of the latent heat accumulator (7) has ribs (12).

6. condensation dryer (1) according to claim 1 or 2, characterized in that the latent heat accumulator (7) is rotatable about an axis.

7. condensation dryer (1) according to claim 6, characterized in that the latent heat accumulator (7) is cylindrical.

8. condensation dryer (1) according to one of claims 1 to 7, characterized in that in the cooling air channel (8) in front of and behind the latent heat accumulator (7) each have a temperature sensor (13, 14) is arranged.

9. condensation dryer (1) according to one of claims 1 to 8, characterized in that the latent heat storage (7) is a storage medium with a

Phase transition from the liquid to the solid state in the temperature range of 30 to 65 ° C contains.

10. condensation dryer (1) according to one of claims 1 to 8, characterized in that the latent heat storage (7) contains a storage medium containing at least one inorganic salt hydrate and / or an organic compound.

1 1. Condenser dryer (1) according to claim 10, characterized in that a salt hydrate is used which contains at least one salt from the group consisting of

Sodium thiosulfate, magnesium nitrate and magnesium chloride exists.

12. condensation dryer (1) according to one of claims 1 to 11, characterized in that the latent heat accumulator (7) has in its interior means for generating a flow in the storage medium.

13. A method for operating a condensation dryer (1) with a drying chamber (2) for objects to be dried, a process air duct (3) in which an electric heater (4), a heat exchanger (5) and a blower (6) is located, a latent heat accumulator (7) and a cooling air duct (8), wherein the

Latent heat storage (7) in the cooling air channel (8) is arranged, characterized in that when the electric heater (4) in the heat exchanger (5) heated cooling air to the storage medium containing latent heat storage (7) is guided and the latent heat storage (7) is charged, by storing heat energy contained in the heated cooling air in the storage medium.

14. The method according to claim 13, characterized in that for the storage of the heat energy contained in the heated cooling air, a phase transition in the storage medium from solid to liquid is used.

15. The method according to claim 14, characterized in that the storage of the heat energy is carried out until the phase transition is completed in the storage medium from solid to liquid.

16. The method according to claim 15, characterized in that the electrical heater (4) is switched off after completion of the phase transition and the heating of the process air in the drying chamber (2) via the stored in the storage medium

Heat energy takes place.