AT514802A4 - Dehumidifier for dehumidifying air for drying hay - Google Patents

Abstract

Dehumidifier (5) for dehumidifying air for drying of drying material, the dehumidifier comprising an evaporator (11) and a condenser (12), wherein the condenser (12) in a flow direction (22) seen behind the evaporator (ll) is arranged and wherein the evaporator (11) of air to be dehumidified in the flow direction (22) can be flowed through. In order to enable a high throughput of the air at constant dehumidification performance, it is inventively provided that a drip tray (18) is provided, over which both the evaporator (11) and the capacitor (12) are arranged.

Description

AIR DEHUMIDIFIERS FOR DEHUMIDIFYING AIR TO DRY HEAT

FIELD OF THE INVENTION

The present invention relates to a dehumidifier for dehumidifying air for drying hay, the dehumidifier comprising an evaporator and a condenser, wherein the condenser is arranged downstream of the evaporator, viewed in a flow direction, and wherein the evaporator is permeable by air to be dehumidified in the flow direction.

Moreover, the present invention relates to the use of an air dehumidifier according to the invention,

STATE OF THE ART

In the drying of hay, which can be used in agriculture as an ideal feed for cattle, it is known to dehumidify air and to blow it through the material to be dried. For this, the drying material is placed in a ventilation box. The air is drawn in via a fan, fed to a dehumidifier and then blown into the ventilation box.

To accelerate the drying, the air used for drying can be heated. It is essential, however, that a sufficiently large amount of dehumidified air in the ventilation box or through the hay can be blown.

Known dehumidifiers, however, limit the essential, air flow rate or provide at high air flow only unsatisfactory dehumidification services.

OBJECT OF THE INVENTION

It is therefore an object of the present invention to provide an improved dehumidifier for dehumidifying air for drying hay, which ensures a high air flow rate with a constant dehumidifying performance, in order to allow high drying effects as a result.

PRESENTATION OF THE INVENTION

An air dehumidifier for dehumidifying sucked air has an evaporator in which refrigerant is vaporized by the heat of the sucked air flowing through the evaporator in a flow direction. As a result, the intake air is cooled below the dew point and condensation of water on the cold surface of the evaporator occurs. The water trickles or drips in succession from the evaporator. To catch the dripping water, a drip tray is placed under the evaporator. Furthermore, the dehumidifier has a condenser, which is arranged downstream of the evaporator, viewed in the direction of flow.

In order now to increase the air flow rate and subsequently to increase the drying effect, the flow rate of the air must be increased while the flow cross-section of the dehumidifier or vaporiser remains the same. However, this causes the dripping water reinforced by the air flowing through the dehumidifier in

Flow direction is freighted. Accordingly, the dripping water no longer lands in the drip tray. The shipment may even go so far that the water is blown up to the condenser which acts as a barrier and drips therefrom. Clearly, the water that does not drip into the drip tray can cause great problems, especially if there is a risk that the water in the following cycle may get to electrical circuits. However, this can be prevented by designing the drip tray so that both the evaporator and the condenser are located above the drip tray.

Accordingly, in a dehumidifier for dehumidifying air for drying hay, the dehumidifier comprising an evaporator and a condenser, wherein the condenser is disposed downstream of the evaporator, as viewed in a flow direction, and wherein the evaporator is permeable with air to be dehumidified in the flow direction, according to the present invention Drip tray is provided, over which both the evaporator and the condenser are arranged.

The refrigerant condenses in the condenser and gives off the heat which is latent. This can be used to warm the dehumidified air. In a preferred variant of the variant of the dehumidifier according to the invention, it is therefore provided that the dehumidified air can also flow through the condenser. In this way, the dehumidified air can be warmed, which also contributes to a faster drying of the drying material.

With the air flow rates achievable in the drying of hay, it is expected that the largest portion of the dripping water will first reach the drip tray in a region closer to the evaporator than to the condenser. It would therefore be desirable if the water could be removed from there. However, it comes especially at high

Air flow rates cause the air to drive the water collected in the drip tray toward the condenser and to form a water layer virtually over the entire area of the drip tray between the evaporator and the condenser. This is detrimental in that the already dehumidified air on its path between evaporator and condenser can resume moisture, which in turn reduces the dehumidification achieved altogether.

Therefore, in order to counteract the formation of this large area of water layer, in a preferred embodiment of the inventive dehumidifier, the drip tray has a batten dividing the drip pan into a first collection section and a second collection section with the evaporator disposed above the first collection section. The water in the first collection section, which makes up the bulk of the drained water, is thus propelled by the air flowing against the railing bar and can no longer travel the entire drip tray. Of course, water drops still end up in the second collection area. However, tests have shown that their amount is not large enough in practice to form a closed water layer over the entire second collection area. An undesirable moistening of the air immediately after its dehumidification can thus be effectively prevented.

Of course, care must be taken that the collected water can be removed to avoid overflowing the drip tray. Therefore, in a preferred embodiment of the dehumidifier according to the invention it is provided that a drain opening of the drip tray is arranged between the first collecting section and the second collecting section. In order to promote the flow of the water collected in the second collecting section towards the discharge opening, either the entire drainage trough may be inclined accordingly or the second collecting section may be designed with a corresponding inclination. In any case, due to the air flow, the water in the first collection section is driven toward the drain port.

Optimum accessibility of the discharge opening - both for the water in the first collecting area and for the water in the second collecting area - results when the discharge opening interrupts the storage bar. Accordingly, it is provided in a preferred embodiment of the dehumidifier according to the invention that the drain opening interrupts the bar. Preferably, the discharge opening can be arranged centrally in the longitudinal direction of the storage bar, which promotes a particularly uniform draining of the collected water. For best effect of the spar bar, the arrangement of the spar bar, the evaporator and the condenser relative to one another is crucial, as determined in experiments. Thus, in a preferred embodiment of the inventive dehumidifier, the evaporator and the condenser are spaced apart at least three times, preferably is at least five times as large as a distance between the evaporator and the batten bar, the distances in the flow direction being measured.

With regard to the absolute dimensions, the absolute air flow rates and / or flow rates to be achieved must be taken into account. For the air throughputs of 200 m3 / h per square meter of pit area, mB2, up to 600 m3 / h / mB2, preferably 400 m3 / h / mB2, to be achieved by hay drying, a distance between evaporator and condenser of at least 50 cm and / or a distance between evaporator and Stauleiste of 7 cm to 15 cm, preferably 10 cm proved to be particularly favorable. Here, the pit surface is understood to mean the inflatable surface of the ventilation box in which the hay is arranged to dry, with the hay being arranged on the box surface.

Preferably, the hay is substantially loose in the aeration box, i. especially not in the form of round bales. Of course, however, it is also possible to dry the hear in a round bale shape. In this case, the inflatable box area is limited to the area on which the round bale rests or rest. This may preferably be realized by disposing a drying round bale over each opening in an initial area of the breather box, with the air used for drying being blown through the baffle into the breather box or directly onto the respective bale. The opening may be made as a circular hole and is adapted to the diameter of the round bales, i. the diameter of the opening corresponds substantially to the diameter of the round bale and is therefore e.g. between 1.2 m and 2 m. For example, so that the round bale does not fall into the opening, the opening may be covered with a grid. Accordingly, in this case, air flow rates are from 850 m3 / h to 2000 m3 / h per opening or per round bale.

Accordingly, in a preferred embodiment of the dehumidifier according to the invention, it is provided that the distance between evaporator and condenser is at least 50 cm. Likewise, it is provided in a particularly preferred embodiment of the dehumidifier according to the invention that the distance between the evaporator and the column bar is 7 cm to 15 cm, preferably 10 cm.

The said distance between evaporator and condenser is also particularly advantageous in that it is sufficiently large to conveniently place an additional heat source between evaporator and condenser.

With the additional heat source, the dehumidified air can be additionally warmed in order to further promote or accelerate the drying. Therefore, in a preferred embodiment of the dehumidifier according to the invention, it is provided that a heat source is arranged between the evaporator and the condenser in order to additionally heat the air which has passed through the evaporator.

In this case, there is no need to resort to additional heating, e.g. an additional electric heater, be resorted to. This is because the dehumidification includes a compressor to compress the refrigerant evaporated in the evaporator. Thus, as the compressor delivers heat, the compressor is also suitable as an additional source of heat, which moreover can be conveniently accommodated between the evaporator and the condenser, without significantly affecting the flow of air from the evaporator to the condenser. Therefore, in a preferred embodiment of the dehumidifier according to the invention, it is provided that the dehumidifier comprises a compressor which at least partially, preferably completely, forms the heat source.

Depending on the ambient temperature and the relative humidity of the air to be dehumidified, the evaporator can become very cold. This may go so far as to form ice on the surface of the evaporator, but this dehumidifies performance and is therefore undesirable. To prevent this, it is provided in a preferred embodiment of the dehumidifier according to the invention that a bypass line and a changeover valve are provided to at least partially re-circulate refrigerant which has been heated in the evaporator and converted into the gaseous state - and not directly to the condenser - supply. The change-over valve is disposed after the compressor and preferably operates automatically, for example as a thermostat-controlled solenoid valve. By thus returning hot gaseous refrigerant, which has been converted to the gaseous state in the evaporator, from the compressor to the evaporator via the bypass line, too much cooling of the evaporator and thus ice formation on the evaporator is prevented. Should ice formation already take place on the evaporator, the bypass line allows the evaporator to be defrosted by means of the hot gaseous refrigerant. If there is no longer any risk of icing of the evaporator, i. if the evaporator is warm enough and / or the ambient temperature is sufficiently high and / or the relative humidity sufficiently low, or if the defrost has occurred, the changeover valve switches again and the hot gaseous refrigerant is again fed directly from the compressor to the condenser. In particular, the bypass line and the change-over valve allow the compressor to be operated at very high power, thus enabling high performance of the dehumidifier and at the same time making the compressor a particularly good heat source for heating the dried air without the evaporator freezing.

The evaporator consists of fins, in which the coolant is led. The lamellae have a lamellar spacing in a direction normal to the direction of flow, which allows the air to be dehumidified to flow through the evaporator or between the lamellae. Tests have shown that the fin spacing can be adjusted to the air flow rates usually achieved when drying hay to allow further enhancement of air dehumidification performance. Therefore, in a preferred embodiment of the dehumidifier according to the invention, it is provided that the evaporator has fins spaced apart from each other in a direction normal to the flow direction with a blade pitch of 1.5 mm to 2 mm, preferably 1 x 8 mm. These values have been found to be optimal for the use of the dehumidifier when drying hay.

As already described condensed water from the dehumidifying air on the evaporator or on the lamella of the evaporator. Although this water drips from the lamellae into the drip tray, the water affects the air dehumidifying performance as long as it is on the louvers, as the water on the louvers prevents the direct contact of the air to be dehumidified with the fins or their surface. In order to reduce this impairment or to increase the dehumidifying performance, it is therefore provided in a preferred embodiment of the dehumidifier according to the invention that the slats have a non-stick coating to promote a flow of condensed water from the slats. Basically, a variety of non-stick coatings known per se are suitable for this purpose In particular, such a non-stick coating is advantageous when the fins are made of aluminum. Aluminum generally forms on its surface an oxide layer which causes some roughness and hence a large surface area. This in turn causes the water to adhere more strongly to the lamellae via capillary action. The coating of the lamellae with a non-stick coating causes a reduction in the roughness of the lamellar surface and thus a reduction in capillary action, so that the water can drip off better.

In order to prevent dirt and / or dust and / or insects from getting caught in the vents of the vaporizer, in a preferred embodiment of the dehumidifier according to the invention it is provided that in the flow-through direction before the vaporizer a grid is arranged whose mesh width is smaller than the vane spacing. This is particularly important at the aforementioned relatively small fin spacing as this relatively small fin spacing can be clogged relatively easily by dirt / dust / insects or the like, which in turn would negatively impact airflow.

As has been shown in experiments, with the dehumidifier according to the invention, not only when drying hay but also when drying foodstuffs, excellent results can be obtained or in these cases the use of the dehumidifier according to the invention has a positive effect on the achievable air flow rates and drying performances. In particular, the fast drying achievable by means of the dehumidifier according to the invention makes it possible to maximize the flavor of the food.

Therefore, the invention provides the use of an inventive dehumidifier for dehumidifying air for drying food. As a special case of this, hops can be considered or according to the invention the use of an inventive dehumidifier for drying hops is provided. The achievable, rapid drying also allows for maximum preservation of the aroma in the case of hops.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be explained in more detail with reference to an embodiment. The drawings are exemplary and should be the

Although the idea of the invention is to be stated, it is by no means exhaustive or even exhaustive.

It shows:

Fig. 1 is a schematic plan view of an inventive dehumidifier

FIG. 2 is an enlarged view of an evaporator of the dehumidifier of FIG. 1. FIG

Fig. 3 is a schematic side view of the dehumidifier of Fig. 1, with coolant lines, a bypass line and a changeover valve not shown for clarity

Fig. 4 is a schematic representation of the use of an inventive dehumidifier for dehumidifying air to dry hay

WAYS FOR CARRYING OUT THE INVENTION

1 shows a schematic plan view of a dehumidifier 5 according to the invention, which can be used for the dehumidification of air during the drying of the material to be dried, in particular hay 1 (see FIG.

The dehumidifier 5 comprises an evaporator 11 in which refrigerant {not shown) by the heat of air flowing in a flow direction 22 through the evaporator 11b. between fins 27 (see Fig. 2) of the evaporator 11 flows therethrough, is evaporated. This cools the air below the dew point and causes condensation of water on the cold surface of the evaporator 11. The water subsequently drips from the evaporator 11 into a drip tray 18. The air flowing through is thereby dehumidified and can subsequently be used to dry the material to be dried or the hay 1.

The gaseous refrigerant passes via a coolant line 32 (arrowheads indicate the direction of flow) from the evaporator 11 into a compressor 13 of the dehumidifier 5, where it is further compressed. Subsequently, the hot gaseous coolant from the compressor 13 is passed via a further coolant line 32 into a condenser 12 of the dehumidifier 5, which is arranged downstream of the evaporator 11, viewed in the flow direction 22. In the condenser 12, the refrigerant condenses and releases the latent heat. This can be used to heat the dehumidified air by also the condenser 12 can be traversed by the air, which also contributes to a faster drying of the drying material. Finally, the liquid refrigerant is returned via a further coolant line 32 from the condenser 12 to the evaporator 11, where the cycle begins anew.

In order to prevent icing of the evaporator 11, which is e.g. the humidifier 5 according to the invention also has a bypass line 31 and a change-over valve 30. To heat the evaporator 11 andggf. By means of the switching valve 30, hot gas refrigerant can be fed back from the compressor 13, instead of directly into the condenser 12, back into the evaporator 11. When the evaporator 11 is warm enough or defrosted, the switching valve 30 switches again and the refrigerant is again supplied directly to the condenser 12 from the compressor 13. The switching over of the switching valve 30 may be effected by means of automation, for example in that the switching valve 30 is designed as a thermostat-controlled solenoid valve.

To the desired in the drying of hay 1 Luftdurchsatzbzw. generally high air flow rates and thus the drying effect to " increase, the flow rate of the air must be correspondingly high '. However, this results in that the dripping water is increasingly transported by the air flowing through the dehumidifier 5 in the flow direction 22. Nevertheless, in order to be able to catch all of the dripping water, the drip tray 18 is designed such that both evaporator 11 and condenser 12 can be arranged above the drip tray 18.

In order to prevent the air flowing through driving the water collecting in the drain pan 18 in the direction of the condenser 12 and thereby forming a large-area water layer between the evaporator 11 and the condenser, a bar 19 is provided. This divides the drip tray 18 into a first collecting section 25 and a second wobbling section 26, wherein the evaporator 11 is arranged above the first collecting section 25. The water collecting in the first collecting section 25 can only be driven by the air flowing through to the storage bar 19, whereby the formation of a large-area water layer is prevented. This ensures that the already dehumidified air can not regain moisture on its way from the evaporator 11 to the condenser 12.

To discharge the accumulated water, a drain port 20 is provided in the drip tray 18. In the embodiment of Fig. 1, the drainage port 20 is arranged to interrupt the railing bar 19 so that water can flow away from both the first collecting section 25 and the second collecting section 26. Seen in a longitudinal direction 29 of the jetty bar 19, the jam bar 19 is interrupted by the discharge opening 20 in the middle, which favors a particularly uniform draining of the collected water. In the illustrated embodiment, the longitudinal direction 29 is substantially normal to the flow direction 22. However, other configurations of the batten bar 19 are contemplated that provide oblique-angled configurations from the longitudinal direction 29 to the flow direction 22.

The arrangement of the rail bar 19 relative to the position of the evaporator 11 and the condenser 12 is chosen so that the majority of the dripping water is collected in the first collecting section 25. For example, a distance 23 between evaporator 11 and condenser 12 is at least 50 cm and a distance 24 between evaporator 11 and column bar 19 is 7 cm to 15 cm, preferably 10 cm, whereby the distances 23, 24 are measured in the direction of flow 22. These distances 23, 24 are in FIG 3, wherein the illustration of coolant lines 32, the bypass line 30 and the switching valve 31 has been omitted for the sake of clarity.

It is also clear from Fig. 3 that there is enough space between evaporator 11 and condenser 12 to arrange the compressor 13 such that the air can flow substantially unimpeded between evaporator 11 and condenser 12. The waste heat of the compressor 13 can also be used to heat the already dehumidified air, which positively affects the speed of the drying process.

The air dehumidification performance of the dehumidifier 5 can be further increased by optimizing the distance of the fins 27 of the evaporator 11 in view of the air flow to be handled. Fig. 2 shows an enlarged view of the evaporator 11, in which the fins 27 are easily recognizable. These are normal to each other in a direction to the flow direction 22 with a fin spacing 28von. 1.5 mm to 2 mm, preferably spaced apart from 1.8 mm, which in tests has shown to be optimal for the air throughputs to be managed in the drying of hay 1.

The surface of the fins 27 is also provided with a non-stick coating (not shown) to allow for rapid dripping of the water condensed on the fins 27.

In order to avoid clogging of the relatively narrow openings between the individual lamellae 27 by dirt, dust or insects, which are transported along with the air, a fly screen 21 is provided. The fly screen 21 is arranged upstream of the evaporator 11 in the flow direction 22 and has a mesh width which is smaller than the fin spacing 28.

Finally, Fig. 4 shows a schematic representation of a use of the dehumidifier 5 for dehumidifying air when drying hay 1. The hay 1 is arranged in a ventilation box 2 between a starting area 15 and an end area 16. The ventilation box 2 is roofed with a roof 3, so that the hay 1 protected from weather conditions st.

The hay 1 rests on a box surface 33. The box surface 33 can be inflowed with air by, for example, realizing the box surface 33 by a reinforcing steel grid, which rests on grate carriers (not shown) and is arranged at a certain distance, for example 40 cm, above a base 34. As a result, an air channel 17 is formed in the initial region 15, through which air can be blown onto the box surface 33 or into the ventilation box 2.

In order to blow the air into or through the aeration box 2, the device for hay drying shown in Fig. 4 has one

Fan 4, the arrows in Fig. 4 symbolize possible air flows. The air to be blown into the ventilation box 2 is first sucked by means of the fan 4, whereby preferably all of the sucked air is sucked through the dehumidifier 5, in which dehumidifier 5 the air is dehumidified.

The air flow rate may be influenced by a control of the fan 4, i. the amount of sucked air and thus the amount of air blown into the ventilation box 2 can be regulated. Usually, air flow rates or. Amounts of intake air from 200 m3 / h per square meter box area 22, ma2, to 600 m3 / h / mB2, preferably 400m3 / h / mB2 can be set to allow rapid drying of the hay 1.

It should be noted that the density of the hay 1 can vary - typically between 100 kg / m3 to 250 kg / m3, which results in a different resistance for the air blown into the ventilation box 2. Accordingly, the power or the rotational speed of the fan 4 must be controllable, whereby frequency converters are provided for this purpose (not shown). Preferably

Frequency converter also used to control the performance of the dehumidifier 5 and the compressor 13 of the dehumidifier 5.

In doing so, the compressor 13 may typically be operated by up to 50% more power by means of frequency converters than usual. This allows on the one hand to achieve a high drying performance of the dehumidifier 5, on the other hand, the associated increased waste heat of the compressor 13 can be used specifically for heating the dried air, which is blown into the ventilation box 2. Typically, additional means for heating the air can be completely eliminated, and nevertheless one can

Indoor temperature increases inside the ventilation box 2 and thus the hay drying performance can be increased. The bypass line 30 and the switching valve 31, in particular, have a positive effect on this operation of the high-power compressor 13, or only allow this operation since, despite the high capacity of the compressor 13, icing of the evaporator 11 is prevented.

In the embodiment of Fig. 4, there is provided a change-over flap 6 which is disposed in the end portion 16 and can be reciprocated by means of an electric cylinder 10 between a first position 7 and a second position 8. In the first position 7 shown in Fig. 4, the changeover damper operates 6, that air can only be sucked out of the aeration box 2. This air is subsequently fed to the dehumidifier 5 and re-injected into the ventilation box 2. That in this case, there is a closed air circuit in the device for hay drying.

In contrast, in the second position 8, which is indicated by the dashed line in FIG. 4, the air is preferably completely aspirated from the outside or from outside the ventilation box 2. Specifically, for this purpose, an air duct 9 is formed under the roof 3. By passing the air sucked in from outside under the roof 3, heat transfer between this air and the roof 3 is promoted. In this way, if the roof 3 is warm due to solar radiation, then the air drawn in from the outside - in the end by solar energy - can be warmed up. The switch-over flap 6 thus makes it possible to use air that can be sucked in from the outside in order to achieve a desired temperature of the air in the ventilation box 2 or in its starting area 15 and / or end area 16, i. to achieve a desired interior temperature.

To the. Automated drying process can be automated, a control unit 14 is provided, which is preferably carried out as a programmable logic controller. The control unit 14 processes signals from sensors (not shown) about the air temperature and relative humidity in the ventilation box 2 and outside the ventilation box 2. The execution of the control unit 14 as the programmable controller also allows the actual amount of the hay 1 to be dried to be increased take into account and set thresholds for the indoor temperature, the temperature outside the aeration box 2, the humidity and the air flow rate. Based on these data, the control unit 14 drives the switching door 6 and the electric cylinder 10, respectively, and regulates the power of the fan 4 and the ventilator 5 and the compressor 13, respectively.

REFERENCE LIST 1 Hay 2 Ventilation box 3 Roof 4 Fan 5 Dehumidifier 6 Reversing door 7 First position of changeover door 8 Second position of changeover door 9 Air duct 10 Electric cylinder 11 Evaporator 12 Condenser 13 Compressor 14 Control unit 15 Start area 16 End area 17 Air duct in start area 18 Drip tray 19 Bar 20 Outflow opening 21 Fly screen 22 Throughflow direction 23 Distance between evaporator and condenser 24 Distance between evaporator and stacking bar 25 'First collection section of the drip tray 26 Second collecting section of the drip tray 27 Slats 28. Slat spacing 29 Lengthwise of the batten bar 30 Bypass line 31 Change-over valve 32 Coolant line 33 Pit area 34 Floor

Claims (14)

1. Dehumidifier (5) for dehumidifying air for drying hay, the dehumidifier comprising an evaporator (11) and a condenser (12), wherein the condenser (12) is arranged behind the evaporator (11) in a flow direction (22) and wherein the evaporator (11) can be traversed by air to be dehumidified in the direction of flow (22), characterized in that a drip tray (18) is provided, above which both the evaporator (11) and the condenser (12) are arranged. A dehumidifier (5) according to claim 1, characterized in that the drip tray (18) has a damming rail (19) dividing the drip tray (18) into a first collection section (25) and a second collection section (26), above the first Collection section (25) of the evaporator (11) is arranged. 3. dehumidifier (5) according to claim 2, characterized in that between the first collecting portion (25) and the second collecting portion " (26) an outflow opening (20) of the drip tray (18) is arranged. Dehumidifier (5) according to claim 3, characterized in that the discharge opening (20) interrupts the bar (19). A dehumidifier (5) according to any one of claims 2 to 4, characterized in that the evaporator (11) and the condenser (12) have a distance (23) from one another at least three times, preferably at least five times, a distance (24 ) between the evaporator (11) and the storage bar (19), wherein the distances (23, 24) in the flow direction (22) are measured. 6. Dehumidifier (5) according to claim 5, characterized in that the distance (23) between the evaporator (il) and condenser (12) is at least 50 cm I. Dehumidifier (5) according to one of claims 5 to 6, characterized in that the distance (24) between the evaporator (11) and the storage bar (19) is 7 cm to 15 cm, preferably 10 cm. 8. Dehumidifier (5) according to one of claims 1 to 7, characterized in that also the capacitor (12) can be flowed through by the dehumidified air. A dehumidifier (5) according to any one of claims 1 to 8, characterized in that a heat source is arranged between the evaporator (11) and the condenser (12) for additionally heating the air which has passed through the evaporator (11). A dehumidifier (5) according to claim 9, characterized in that the dehumidifier (5) comprises a compressor (13) which at least partially, preferably completely, forms the heat source. II. Dehumidifier (5) according to any one of claims 1 to 10, characterized in that a bypass line (30) and a switching valve (31) are provided to at least partially recover refrigerant which has been heated in the evaporator and converted into the gaseous state to feed the evaporator (11). A dehumidifier (5) according to any one of claims 1 to 11, characterized in that the evaporator (11) has fins (27) facing each other in a direction normal to the flow direction (22) with a fin spacing (28) of 1.5 mm to 2 mm, preferably spaced from 1.8 mm. A dehumidifier (5) according to claim 12, characterized in that the fins (27) have an anti-adherent coating to promote drainage of condensed water from the fins (27). 14. dehumidifier (5) according to any one of claims 12 to13, characterized in that in the flow direction (22) seen in front of the evaporator (11), a grid (21) is arranged, the mesh size is smaller than the lamella distance (28). Use of an air dehumidifier according to any one of claims 1 to 14 for dehumidifying air for drying foodstuffs. Use of an air dehumidifier according to any one of claims 1 to 14 for dehumidifying air for drying hops.