Dryer

Abstract

The invention relates to a dryer comprising a housing, a treatment chamber arranged in the housing for a material to be dried, and a process air circuit (12) into which the treatment chamber is integrated and in which process air is guided for drying the material to be dried, wherein a heater (2) for heating the process air in the process air circuit (12) is integrated upstream of the treatment chamber. To provide a further improved dryer, it is proposed that the heater (2) be designed as at least one PTC element (6, 8, 10) arranged in a process air duct (4) of the process air circuit (12).

Description

[0001] The invention relates to a dryer of the type mentioned in the preamble of patent claim 1.

[0002] Such dryers are already known in the prior art in a variety of embodiments and comprise a housing, a treatment chamber for a material to be dried arranged in the housing, and a process air circuit into which the treatment chamber is integrated and through which process air for drying the material to be dried is conducted. Upstream of the treatment chamber, a heater for heating the process air is integrated into the process air circuit. The known dryers serve, for example, for drying laundry. Dryers can be designed both as household appliances and as commercial appliances for professional use.

[0003] For example, DE 31 13 471 A1, which describes a dryer with a heat pump, is already known. To achieve drying times comparable to those of vented and condenser dryers, a resistance heater is provided downstream of the heat pump's radiator.

[0004] EP 1 992 730 A1 discloses a washer-dryer with an electric heater arranged in the process air duct for heating the process air.

[0005] DE 10 2014 219 457 A1 generally discloses a heat pump tumble dryer.

[0006] The document DE 102016 110 023 A1 discloses a heater for a tumble dryer comprising a PTC element with a fin structure attached thereto.

[0007] The invention therefore poses the problem of providing a further improved dryer.

[0008] According to the invention, this problem is solved by a dryer having the features of patent claim 1, which is characterized in that the heater is designed as at least one PTC element arranged in a process air duct of the process air circuit. The abbreviation "PTC" stands for "Positive Temperature Coefficient," which in German is also referred to as "Kaltleiter." PTC elements are very process-reliable and robust. Advantageous embodiments and further developments of the invention are set out in the following subclaims.

[0009] The advantage achievable with the invention lies in the particular fact that the dryer is further improved. Due to the inherent intrinsic safety of the at least one PTC element, it is possible to optimize the dryer material without reducing the safety of the dryer. For example, unlike tubular heaters or the like, it is not necessary to design the heater with a high thermal inertia for safety reasons. Furthermore, due to the inherent intrinsic safety of the at least one PTC element, it is possible to operate a dryer designed as a heat pump dryer with propane or the like as the coolant for the dryer's heat pump. Unlike other heaters, it can be guaranteed, especially in the event of a fault, that a limit temperature for a surface of the heater, for example 350°C for propane, is reliably not exceeded.With other heaters, however, there is a risk that this limit temperature will be exceeded, at least briefly, in the event of a fault.

[0010] In principle, the dryer according to the invention can be freely selected within wide, suitable limits in terms of type, mode of operation, material, dimensions and arrangement of the respective components.

[0011] An advantageous development of the dryer according to the invention provides that the PTC element has a depth of less than or equal to 4 mm, preferably less than or equal to 3 mm, running transversely to a main dimension of the PTC element. In this way, the dryer is further optimized in terms of material and can be designed very compactly.

[0012] A further advantageous development of the dryer according to the invention provides that the at least one PTC element has a total electrical power consumption of less than or equal to 1200 W in steady state. This reliably enables compliance with the limit temperatures required for conventional dryers.

[0013] The dryer according to the invention provides that the heater comprises a two-part heating element, preferably one made of aluminum, with the PTC element arranged within the heating element. This significantly improves the heat transfer from the at least one PTC element to the process air. Furthermore, the preferred embodiment of this refinement is easy to manufacture and saves weight. However, a construction of the PTC elements using so-called thick-film technology is also conceivable.

[0014] An advantageous development of the aforementioned embodiment of the dryer according to the invention provides that the heater has a wall thickness of less than or equal to 3 mm, preferably less than or equal to 2 mm. This further optimizes the dryer's material. Furthermore, this enables faster heating of the process air by means of the at least one PTC element, since the thermal inertia of the heater surrounding the at least one PTC element is reduced. Furthermore, the compact design thus made possible allows for a reduction in the pressure loss in the process air.

[0015] The dryer according to the invention provides that a cross-sectional area of the heating element extending transversely to the flow direction increases in the flow direction of the process air. Preferably, the heating element has heating fins, with a fin height of the heating fins increasing in the flow direction of the process air. This enables a fluidically advantageous geometry. Furthermore, it is possible, for example, to keep the pressure conditions in the area of the heating element essentially constant in a process air duct that widens in the flow direction of the process air.

[0016] A further advantageous development of the dryer according to the invention provides that the heater and the process air duct are designed to be coordinated with one another in such a way that the pressure in the process air duct is essentially constant. In this way, the process air in the process air duct is optimized in terms of flow.

[0017] Another advantageous development of the dryer according to the invention provides that the heater is arranged in a region of the process air duct in which the process air flow is essentially laminar. This further improves the flow characteristics of the process air flowing in the process air duct.

[0018] A further advantageous development of the dryer according to the invention provides that the process air duct has a first duct part and a second duct part, wherein the first duct part is formed in the housing and the second duct part is formed as a cover, and wherein, in order to design the process air duct so that it is coordinated with the heater, only the second duct part is designed to match the heater. This makes it possible to offer the dryer design according to the invention as a retrofit kit or the like. Accordingly, conventional dryers without the design according to the invention can also be retrofitted to a dryer according to the invention without much effort. For example, only the heater and the cover adapted to the heater need to be retrofitted. For this purpose, the heater is arranged entirely in the second duct part and fastened to the second duct part.

[0019] A particularly advantageous development of the dryer according to the invention provides that the dryer is designed as a heat pump dryer and has a condenser for heating the process air in the process air duct upstream of the heater, wherein the heater is designed such that a surface temperature of the heater does not exceed a limit of 350°C in any operating state of the dryer. This ensures the safe operation of this dryer according to the invention, designed as a heat pump dryer with, for example, propane as the refrigerant, in all operating states of the dryer. The term "operating state" is to be interpreted broadly and also includes faulty operating states in which an unintentionally high surface temperature of the heater can occur in conventional dryers without the inventive design.Accordingly, the dryer according to the invention is particularly advantageous for the design of the dryer as a heat pump dryer with a highly flammable refrigerant, such as propane.

[0020] An embodiment of the invention is shown purely schematically in the drawings and is described in more detail below. It shows Figure 1 shows an embodiment of the dryer according to the invention in a first partial view, with the heater in a bottom view, Figure 2 shows the embodiment in a second partial view, with the heater in a front view and Figure 3 shows the embodiment in a third partial view, with the heater in a side view.

[0021] In the Fig. 1 bis 3 An exemplary embodiment of the dryer according to the invention is shown by way of example. The dryer is designed as a heat pump dryer for laundry (not shown) and comprises a housing (not shown), a treatment chamber (also not shown) for the laundry, i.e. the material to be dried, arranged in the housing, and a process air circuit, into which the treatment chamber is integrated and in which a process air (not shown) for drying the laundry is guided, wherein upstream of the treatment chamber a heater 2 for heating the process air is integrated in the process air circuit. The heater 2 has a total of three PTC elements 6, 8, 10, which are arranged in a process air duct 4 of the process air circuit. The process air circuit is in the Fig 1 and 3 each symbolized by an arrow 12, wherein the arrow 12 indicates the flow direction of the process air in the process air circuit.

[0022] The Fig. 2 The front view shown shows the heater 2 facing the process air circuit. The heater 2 is designed such that a surface temperature of the heater 2 does not exceed a limit of 350°C in any operating state of the dryer, i.e., in both normal and abnormal operating states of the dryer. A condenser (not shown) of a heat pump (also not shown) of the heat pump dryer for heating the process air is integrated upstream of the heater 2 in the process air circuit 12, namely, arranged in the process air duct 4.

[0023] The PTC elements 6, 8, 10 each have an installation depth of approximately 3 mm perpendicular to a main expansion dimension of the individual PTC element running in the flow direction 12. Due to the shallow installation depth of the PTC elements, the heating element and thus the heater as a whole can be designed very narrow. In the present embodiment, the PTC elements 6 and 10 each have a length of 80 mm in their main expansion dimension and a width of 28 mm perpendicular to their main expansion dimension, while the PTC element 8 has a length of 104 mm in its main expansion dimension and a width of 28 mm perpendicular to its main expansion dimension. In total, the electrical power consumption of the three PTC elements 6, 8, 10 is approximately 1200 W in the steady state.

[0024] Furthermore, the heater 2 has a two-part heater body 14 made of die-cast aluminum, wherein the PTC elements 6, 8, 10, except for two electrical contacts each, are arranged in the heater body 14. Aluminum die-cast parts enable lightweight, thin-walled, yet stable heater parts and also have high dimensional accuracy and a high surface quality. Series production of aluminum die-cast parts is also particularly cost-effective. The parting line between the two parts of the two-part heater body 14 runs in the image plane of Fig. 2 horizontally and in the image plane of Fig. 3 perpendicular.

[0025] The heating element 14 has a dimension of 130 mm in the flow direction 12 and 154 mm transverse to the flow direction 12. The heating element 14 has a wall thickness of less than or equal to 3 mm, preferably less than or equal to 2 mm. Due to the small wall thickness, the heating element 14 has only a low thermal inertia, so that the process air guided in the process air duct 4 for drying the laundry in the treatment room can be heated particularly quickly by means of the heater 2. In the present exemplary embodiment, the PTC elements 6, 8, 10 are clamped between the two parts of the heating element 14 by means of a predetermined contact pressure, thus also ensuring good heat conduction from the PTC elements 6, 8, 10 to the heating element 14.

[0026] The outer contours of the heating element 14 facing the process air guided in the process air duct 4 are, as can be seen from the Fig. 1 bis 3 visible, rounded. See for example the Fig. 3 , near arrow 12. On the one hand, this facilitates the manufacture of the heater 14 as an aluminum die-cast part. On the other hand, it reduces the flow resistance of the heater 14 during the flow of process air in the process air duct 4 in the region of the heater 14, so that the pressure loss of the process air in the process air duct 4 is reduced.

[0027] A cross-sectional area of the heating element 14 extending transversely to the flow direction 12 also increases in the flow direction 12 of the process air, wherein the heating element 14 has heating fins 16, the fin height of which increases in the flow direction 12 of the process air. See in particular the Fig. 3The heating fins 16 result in improved heat transfer from the heater 14 on one side to the process air conveyed in the process air duct 4 on the other side. Furthermore, this makes it possible to keep the pressure conditions in the process air duct 4, which expands in the flow direction 12 of the process air, essentially constant in the area of the heater 2.

[0028] Generally speaking, in the present exemplary embodiment, the heater 2 and the process air duct 4 are designed to be coordinated with one another in such a way that the pressure in the process air duct 4 is essentially constant. For example, in the present exemplary embodiment of the dryer according to the invention, the distance between the heater 2 on the one side and the process air duct 4 on the other side is kept essentially constant for this purpose. Accordingly, approximately the same amount of free flow cross-section is available to the process air in each cross-section in the region of the heater 2. For the purpose of further improving the flow technology, the free flow cross-section is widened, preferably continuously, in the flow direction 12 upstream of the heater 2, so that the process air has an inlet length available in the flow direction 12 upstream of the heater 2.

[0029] In order to further improve the flow technology of the process air guided in the process air duct 4 in the area of the heater 2, the heater 2 is arranged in a region of the process air duct 4 in which the flow of the process air is essentially laminar.

[0030] The process air duct 4 has a first duct part (not shown) and a second duct part 18, wherein the first duct part is formed in the housing and the second duct part 18 is formed as a cover 18. In order to configure the process air duct 4 so that it is matched to the heater 2, only the second duct part 18 is designed to match the heater 2. The heater 2 is arranged entirely in the second duct part 18 and fastened to the second duct part 18.

[0031] In the present exemplary embodiment, the second duct part 18 is designed such that it can be connected to the first duct part of conventional dryers without the inventive design. Accordingly, the geometry of the process air duct 4, namely the first duct part, of the conventional dryer can be retained unchanged, thus saving tool costs. A seal used between the first duct part and the second duct part of the conventional dryer can also be used for the second duct part 18 according to the inventive dryer. This makes it possible to offer the inventive design of the dryer according to the present exemplary embodiment as a retrofit kit or the like.

[0032] This advantageous design is further enhanced in the present embodiment by the fact that the cover, i.e., the second duct part 18, is formed as part of a two-part upper part of the process air duct 4. A second part of the upper part (not shown) is designed such that the second part, analogous to the first duct part, is structurally identical to the second parts of conventional dryers. Accordingly, the above explanations also apply to the second part.

[0033] Accordingly, even conventional dryers without the inventive design can be retrofitted to an inventive dryer according to the present embodiment without much effort. For example, only the heater 2 and the cover 18 adapted to the heater 2 need to be retrofitted.

[0034] Due to the inherent intrinsic safety of the PTC elements 6, 8, 10, it is thus possible to optimize the dryer material without reducing the safety of the dryer. For example, unlike tubular heaters or the like, it is not necessary to design the heater 2 with a high thermal inertia for safety reasons. Furthermore, due to the inherent intrinsic safety of the PTC elements 6, 8, 10, it is possible to operate the dryer designed as a heat pump dryer with propane as the coolant for the dryer's heat pump. Unlike other heaters, it can be guaranteed that a limit temperature of 350°C for a surface of the heater 2 will definitely not be exceeded, especially in the event of a fault. With other heaters, however, there is a risk that this limit temperature will be exceeded, at least briefly, in the event of a fault.

[0035] The dryer according to the invention according to the present exemplary embodiment can thus be reduced in terms of the required material thicknesses and dimensions for the heater, thereby reducing the space requirement, weight, and material costs. Furthermore, due to the compact design of the heater, the pressure loss of the process air guided in the process air duct is also reduced. Furthermore, the pressure loss is also reduced by the above-explained, coordinated structural design of the heater 2 on the one hand and the process air duct 4 on the other. Due to the low material thicknesses, the thermal inertia of the heating element 14 during its heating is reduced in the desired manner, thus enabling rapid heating of the process air.

[0036] At the same time, the safety of the dryer according to the invention according to the present embodiment is ensured in every operating state of the dryer, since the surface temperature of the heater 2 does not exceed a limit of 350°C in any operating state of the dryer. This ensures the safe operation of this dryer, designed as a heat pump dryer with, for example, propane as the refrigerant, in all operating states of the dryer. The term "operating state" is to be interpreted broadly and also includes faulty operating states in which an unintentionally high surface temperature of the heater can occur in conventional dryers without the inventive design.

[0037] The invention is not limited to the present embodiment and the related explanations. For example, the invention can also be advantageously used in other dryer types, such as vented dryers or condenser dryers. The dryer according to the invention can be either a household appliance or a commercial appliance, i.e., a dryer for professional use.

[0038] The number and structural design of the at least one PTC element is also not limited by the exemplary embodiment explained. Thus, more than three or fewer than three PTC elements can be used. Furthermore, the dimensions of the at least one PTC element and its arrangement relative to the heating element can be freely selected within wide, suitable limits, so that the invention can be tailored to the respective needs of a multitude of different applications. Furthermore, the heating element can also be implemented in a different structural manner. The material of the heating element can also be freely selected within wide, suitable limits. Alternatively or in addition to the heating system being designed with a heating element, the at least one PTC element can also be designed, for example, using thick-film technology or in another suitable manner.Accordingly, embodiments are conceivable in which the heater does not have a separately designed radiator.

Claims

1. Dryer, comprising a housing, a processing chamber arranged in the housing for a material to be dried, and a process air circuit (12) into which the processing chamber is integrated and in which process air for drying the material to be dried is guided, wherein, upstream of the processing chamber, a heater (2) for heating the process air is integrated in the process air circuit (12), characterised in that the heater (2) is designed as at least one PTC element (6, 8, 10) arranged in a process air channel (4) of the process air circuit (12), wherein the heater (2) comprises a two-part heating member (14), preferably a heating member (14) made of aluminium, wherein the PTC element (6, 8, 10) is arranged in the heating member (14), characterised in that a cross-sectional area, running transversely to the flow direction (12), of the heating member (14) increases in the flow direction (12) of the process air, and in that the process air channel (4) widens in the flow direction (12) in the region of the heater (14).

2. Dryer according to claim 1, characterised in that the PTC element (6, 8, 10) has a construction depth of less than or equal to 4 mm, preferably less than or equal to 3 mm, running transversely to a main extension dimension of the PTC element (6, 8, 10).

3. Dryer according to claim 1 or 2, characterised in that the at least one PTC element (6, 8, 10) has a total electrical power consumption of less than or equal to 1200 W in the steady state.

4. Dryer according to claim 3, characterised in that the heating member (14) has a wall thickness of less than or equal to 3 mm, preferably less than or equal to 2 mm.

5. Dryer according to claim 3 or 4, characterised in that the heating member (14) comprises heating fins (16), wherein a fin height of the heating fins (16) increases in the flow direction (12) of the process air.

6. Dryer according to any of claims 1 to 5, characterised in that the heater (2) and the process air channel (4) are coordinated with one another in such a way that the pressure in the process air channel (4) is substantially constant.

7. Dryer according to any of claims 1 to 6, characterised in that the heater (2) is arranged in a region of the process air channel (4) in which the flow of the process air is substantially laminar.

8. Dryer according to any of claims 1 to 7, characterised in that the process air channel (4) comprises a first channel part and a second channel part (18), wherein the first channel part is formed in the housing and the second channel part (18) is formed as a cover, and wherein the heater is arranged entirely in the second channel part and is fixed to the second channel part.

9. Dryer according to any of claims 1 to 8, characterised in that the dryer is designed as a heat pump dryer and comprises, in the process air channel (4) upstream of the heater (2), a condenser for heating the process air, wherein the heater (2) is designed such that a surface temperature of the heater (2) does not exceed a threshold value of 350°C in any operating state of the dryer.

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