EP2227585B1 - Washing/drying device comprising a moisture determining device and method for operating a washing/drying device - Google Patents

Abstract

A laundry drying device having a washing drum; a moisture determining device to determine a moisture content of process air evacuated from the washing drum, wherein the moisture determining device has at least one temperature sensor; and a cooling body to cool the process air, wherein the cooling body has an inlet side, an outlet side, and an inlet for a medium that flows through the cooling body or that is located in the cooling body. A first temperature sensor is arranged behind the inlet of the cooling body; a second temperature sensor is arranged at the outlet side of the cooling body to measure an outlet temperature of the medium; and a third temperature sensor is arranged at the inlet side of the cooling body to measure an inlet temperature of the medium. The medium is the process air or a coolant.

Description

The invention relates to a laundry drying apparatus having a laundry drum, a moisture determination device for determining a moisture content of the process air discharged from the laundry drum and a cooling body for cooling the process air, wherein the moisture determination device has at least one temperature sensor, and the at least one temperature sensor behind an inlet of the heat sink for a Cooling medium flowing through or arranged in the heat sink medium is arranged.

In addition, the invention relates to a method for operating a laundry drying apparatus in which a moisture content of discharged from a laundry drum process air is determined and at least partially condensed with a heat sink from the process air humidity, wherein the moisture determination by measuring at least one temperature for a Cooling medium flowing through or a medium in the heat sink and determined by evaluating the measured temperature.

Such a clothes dryer and such a method will be apparent from the Scriptures DE 10 2006 020 579 A1 ,

From the Scriptures DE 10 2005 062 938 A1 goes out a laundry dryer with a heat sink for process air and arranged outside the heat sink moisture determination device; this includes two temperature sensors and is designed as a psychrometer.

From the Scriptures WO 2005/054563 A1 is a laundry dryer with a heat sink for process air, a temperature outside the heat sink arranged temperature sensor and also arranged outside the heat sink moisture sensor forth.

Generally known is a laundry drying apparatus with a laundry drum, a moisture determination device for determining a moisture content of discharged from the laundry drum process air and a heat sink for cooling the process air. Water condensed from the process air is collected in a liquid container or discharged via a water outlet. In this case, laundry drying devices are known, which are referred to as condensation dryer and have a heat sink, which is filled with a coolant before the start of the laundry dryer. Preferably, this is tap water, which is embedded in a heat sink and renewed when needed.

Furthermore, there are laundry drying devices, which have a heat pump to condense a moisture content in the process air. Such heat pumps consist in particular of a compressor or condenser for liquefying a coolant and of an evaporator for evaporating the coolant. Process air passed past the evaporator is cooled correspondingly, so that moisture contained therein at least partially condenses out.

Such clothes drying devices are designed for drying laundry, and are controlled by a controller so that they can detect a remaining moisture in the laundry to automatically stop the drying process when sufficient drying is achieved. As a result, a drying time and corresponding energy consumption can be reduced. In order to make this possible, such laundry drying devices are designed with a moisture-determining device which, in the form of a moisture sensor in conjunction with the control device, measures moisture directly in the process air leaving the laundry drum. Corresponding humidity sensors are available depending on the manufacturer in different design and technology. However, a direct measurement of the moisture or moisture content of process air discharged from the laundry drum is always measured by such humidity sensors. The disadvantage here is that the humidity sensors are complicated to manufacture and correspondingly expensive components.

It is the object of the present invention to improve a laundry drying device with a moisture determination device or a method for operating such a laundry drying device such that structurally simpler and thus more favorable in terms of cost components can be used.

This object is achieved by a laundry drying device with a moisture determination device and the further features according to claim 1 or by a method for operating a laundry drying device according to the features of claim 13. Advantageous embodiments are in particular the subject of dependent claims.

In the laundry drying apparatus according to the invention with a laundry drum, a moisture determination device for determining a moisture content of the process air discharged from the laundry drum and a cooling body for cooling the process air, wherein the moisture determination device has at least one temperature sensor, and the at least one temperature sensor behind an inlet of the heat sink for a heat sink Accordingly, the medium is selected from the group containing the process air and a coolant, the at least one temperature sensor for measuring an outlet temperature of the medium is arranged on the outlet side of the heat sink and is another temperature sensor for Measuring an inlet temperature of the medium disposed on the inlet side of the heat sink.

Such an arrangement makes it possible to circumvent the use of an expensive humidity sensor, since at least one temperature sensor is used for the indirect determination of the moisture content instead of a humidity sensor for the direct measurement of a moisture content. In addition, a lifetime of the sensor or sensors can be achieved in comparison to a humidity sensor. The temperature sensors, unlike dedicated humidity sensors, do not need to be cooled and detection accuracy is increased.

The at least one temperature sensor is arranged behind an inlet of the heat sink for a medium flowing through the heat sink (eg, process air or coolant) or for a medium (eg, coolant) located in the heat sink. At a In such an arrangement, the process air has already been able to transfer latent heat to the coolant, so that moisture could condense out of the process air.

It is preferred that the at least one temperature sensor for measuring a temperature of the process air is arranged on the outlet side of the heat sink. When measuring the temperature of the process air, the outlet side of the heat sink can both be understood as meaning that the temperature sensor is still arranged within a cooling section of the heat sink, and preferably understood to be arranged outside the cooling section of the heat sink. It is important that the process air could transfer at least as much latent heat to the coolant that moisture could condense out of the process air. Since overheating of clothing to be dried is usually not to be feared, as long as it is still wet and the process air is preferably enriched to saturation with moisture, the use of a single such temperature sensor is sufficient.

The at least one temperature sensor is in particular arranged behind a coolant inlet of the heat sink for measuring a temperature of a coolant flowing through the heat sink (eg in the case of a heat exchanger).

Additionally or alternatively, the at least one temperature sensor may be arranged behind a coolant inlet of the heat sink for measuring a temperature of a coolant located in the heat sink (eg in the case of some water-cooled heat sinks). When measuring the temperature of the coolant can be understood by the outlet side of the coolant both that the temperature sensor is preferably disposed within a cooling path of the heat sink, as well as be understood that the temperature sensor is arranged outside behind a cooling path of the heat sink. It is again crucial that the process air behind a relative inlet temperature sensor could already transmit at least as much latent heat to the coolant that moisture could condense out of the process air. Such an arrangement can be configured as a heat pump, in which a coolant flows through an evaporator. Also possible is an embodiment in a so-called condensation dryer, in which a coolant, for example tap water, is admitted as required into a heat sink.

The moisture determination device is preferably designed and / or programmed for determining the moisture content based on a temporal sequence by means of the temperature sensor measured temperatures.

In particular, the moisture determination device is designed and / or programmed for determining an inlet-side rise and / or an outlet-side drop in the temperature of the process air or the coolant over the time sequence of measured temperatures of the process air compared to a previous temperature plateau value of the process air or of the coolant. As long as the process air is led to the heat sink with a uniform moisture content, the heat sink draws an even amount of moisture from the process air. Accordingly, the measurable temperatures remain substantially constant. However, if the moisture content in the process air is reduced due to clothes becoming dry in the laundry drying machine, the process air no longer gives only latent but increasingly more sensible heat to the coolant. In the case of the measurement of the temperature of the process air can thus be concluded from a drop in temperature, in particular the outlet of the evaporator or heat sink over time to a reducing moisture content of the process air. In the case of measuring the temperature of the coolant, it can be concluded accordingly from an increase in the temperature over time to a reducing moisture content of the process air. Also, the temperature difference between the inlet-side temperature and the outlet-side temperature of the heat sink can be detected and used for determining a moisture content (degree of drying). This can preferably be done by reference to a temperature difference plateau value, but also in absolute terms of the temperature difference (eg by exceeding or falling below a temperature difference threshold value).

Due to device- and process-related fluctuations, the temperature-plateau value means an average value of a succession of individual successive measured values. Accordingly, threshold values can also be defined whose overshoot or undershoot is used as an indicator for a fall in the process air temperature or an increase in the coolant temperature.

The at least one temperature sensor can be arranged for measuring a temperature of the process air on the outlet side of the heat sink, and a further temperature sensor can be arranged for measuring an inlet temperature of the process air on the inlet side of the heat sink. The at least one temperature sensor may be arranged behind a coolant inlet of the heat sink downstream of a coolant inlet of the heat sink according to a further embodiment for measuring a temperature of a flowing through the cooling body coolant or a coolant located in the heat sink and a further temperature sensor may then for measuring an inlet temperature of the coolant inlet side of the Heat sink can be arranged. As a result, two measured values of the process air or of the coolant in the region of the inlet or in the region of the outlet of the heat sink are provided according to corresponding embodiments which can also be used in combination, the difference value of which provides a more accurate measure for determining the dehumidifying performance of the heat sink. Indirectly, it is accordingly also possible to more accurately conclude a moisture content of the process air flowing out of the laundry drum than in the case of only a single, in particular outlet-side, temperature sensor.

The heat sink is preferably dimensioned and / or a control device is preferably configured and / or programmed to flow through the heat sink with coolant such that not all of the moisture content is drawn from the process air up to the at least one temperature sensor.

The heat sink may be formed in particular by an evaporator of a heat pump.

The at least one temperature sensor is preferably a sensor of a heater controller for controlling a process air temperature. Thus, a usually already existing temperature sensor can be used particularly advantageously so that not only a humidity sensor can be dispensed with, but even an additional temperature sensor can not even be used in the simplest configuration.

An independent solution of the present task is according to the invention also methods for operating a laundry drying device, wherein a moisture content is determined by deducted from a laundry drum process air and the moisture is at least partially condensed out with a heat sink from the process air, the moisture determination by measuring at least one temperature for the heat sink flowing medium or a medium located in the heat sink and by evaluating the measured Temperature is determined in which method the medium is selected from the group containing the process air and a coolant, and in which method the moisture content by measuring an outlet temperature of the medium outlet side of the heat sink and by measuring an inlet temperature of the medium inlet side of the heat sink is determined.

For moisture determination, a temperature difference of a temperature measured on the outlet side of the heat sink and a temperature measured on the inlet side of the heat sink is preferably formed.

The moisture content is preferably determined on the basis of a chronological sequence of measured temperatures or temperature differences. In particular, in the case of an inlet-side rise and / or an outlet-side drop in the temperature of the process air over the chronological sequence of measured temperatures or temperature differences of the process air relative to a previous temperature or temperature difference plateau value of the process air, a decreasing moisture content is indicated. Additionally or alternatively, even with an inlet-side drop and / or outlet-side rise in the temperature of the coolant over the chronological sequence of measured temperatures of the coolant with respect to a previous temperature plateau value of the coolant, a decreasing moisture content of the process air can be indicated.

Such a laundry drying apparatus or a method for operating a laundry drying apparatus with such method steps not only offers a reduction in costs through the use of inexpensive temperature sensors instead of moisture sensors. Surprisingly, a longer life of the device due to the higher life of the temperature sensors relative to humidity sensors can be achieved. Another advantage is that such temperature sensors, in contrast to moisture sensors do not need to be cooled, which further simplifies the construction and operating costs. Surprisingly, even greater accuracy is achievable when such indirect measurement is performed over measured temperatures rather than direct moisture measurement.

FIG 1

ein Wäschetrocknungsgerät mit Komponenten zum Ausbilden einer Feuchtigkeitsbestimmungseinrichtung auf Basis einer indirekten Temperaturmessung;

FIG 2

ein Diagramm zur Veranschaulichung eines Verhältnisses von Temperatur einer Prozessluft im Verhältnis zu deren Feuchtegehalt;

FIG 3

ein Diagramm mit einer Vielzahl von Temperaturkurven insbesondere von Prozessluft in einem Wäschetrocknungsgerät gemäß FIG 1 über der Zeit aufgetragen;

FIG 4

ein weiteres derartiges Diagramm bei Einsatz eines Wärmeaustauschers mit einem im Vergleich zu FIG 3 geringeren Wirkungsgrad; und

FIG 5

ein weiteres Diagramm, bei welchem Kurven einer Kühlmitteltemperatur über der Zeit aufgetragen sind.

Embodiments of the invention will be explained in more detail below with reference to the drawing. Show it:

FIG. 1

a laundry drying apparatus having components for forming a humidity determining device based on an indirect temperature measurement;

FIG. 2

a diagram illustrating a ratio of temperature of a process air in relation to their moisture content;

FIG. 3

a diagram with a variety of temperature curves in particular of process air in a laundry drying apparatus according to FIG. 1 applied over time;

FIG. 4

another such diagram when using a heat exchanger with a compared to FIG. 3 lower efficiency; and

FIG. 5

another diagram in which curves of a coolant temperature over time are plotted.

FIG. 1 schematically shows a laundry drying device 1 with a laundry drum 2, which is fluidically coupled to a recirculation or process air duct 3. In a drying process, process air a heated from the circulating air duct 3 into the laundry drum 2 is typically blown by means of a circulating air blower, not shown here. The process air absorbs moisture there by releasing heat and is again sucked out of the laundry drum 2 into the recirculating air duct 3 where it is initially cooled in order to at least partially condense out. To cool and condense the process air a, a heat sink 4 is coupled into the recirculating air duct 3, which is flowed out of the laundry drum 2 by means of the moist, warm exhaust air. For subsequent heating of the cooled process air, a heater 8 is coupled into the circulating air channel 3. After warming up, the dry-heat process air is blown back to the laundry drum 2.

In the embodiment shown, the heat sink is designed as an evaporator 4 and the heater is configured as a condenser 8 of a heat pump 6. The heat pump 6 also has a compressor 5 and a throttle 14, which are interconnected by means of a coolant c leading coolant line 7 as shown and basically known in a circuit. In the condenser 8, the refrigerant c is brought from a gaseous to a liquid state, wherein heat is discharged to the process air a. Subsequently, the coolant c is fed into the evaporator 4, in which the coolant c is evaporated. Accordingly, the evaporator 4 removes heat from the process air a, so that moisture condenses out of the process air a. Such condensed moisture is either removed from the device to the outside or collected in a condensate tank, not shown. Possibly. the heat pump or the condenser 8, a further heating, for. B. an electric heater, downstream (not shown).

To control various functions of such a laundry drying device 1, this has a control device 9. The control device 9 is in particular configured and / or programmed to determine a moisture content in the process air a in order to control the further operation depending on the moisture content, in particular a heating of the process air and an operating time of a drying process.

In addition, the laundry drying device 1 is equipped with a moisture-determining device, to which at least one temperature sensor 11 or preferably two or more temperature sensors 10 - 13 belong here in addition to the appropriately designed and / or programmed control device 9. By means of the temperature sensors 10-13, a corresponding temperature Ta1, Ta2 of the process air a or a temperature Te1, Te2 of the coolant c is measured. More specifically, a first temperature sensor 10 is coupled into the recirculating air duct 3 on the inlet side (upstream) of the evaporator 4, which senses a temperature Ta1; a second temperature sensor 11 is coupled into the circulating air duct 3 on the outlet side (downstream) of the evaporator 4, which senses a temperature Ta2; If a third temperature sensor 12 is coupled into the coolant line 7 on the inlet side (upstream) of the evaporator 4, which senses a temperature Te1, and a fourth temperature sensor 13 is coupled into the coolant line 7 on the outlet side (downstream) of the evaporator 4, which senses a temperature Te2. The temperatures or corresponding temperature signals are supplied to the control device 9, so as to close by an indirect procedure from a temperature measurement on the moisture content of the process air a.

While these positions are particularly preferred for the temperature sensors 10, 11, in principle other positions within the evaporator 4 or in the air duct 3 may also be selected spaced from the evaporator 4, as long as between these temperature sensors 10,11 at least a portion of the evaporator condensing path 4 lies. Since usually at least one temperature sensor is arranged in the air duct 3 for measuring the temperature of the process air a to allow control of the drying cycle, only a further additional temperature sensor needs to be arranged accordingly in the circulating air duct 3, which is much cheaper than the provision of a moisture content direct measuring humidity sensor.

According to an alternative embodiment but with a somewhat less accurate measurement result, a measurement using only a single temperature sensor, namely here the temperature sensor 11 for measuring the temperature Ta2 of the process air a outlet side of the evaporator 4 can be performed.

The coolant temperature sensors 12, 13 may be used alternatively or additionally, as described in greater detail below.

FIG. 2 shows on the basis of a physiometric diagram, the ratio of moisture content F against a temperature T of the process air a. By way of example, a dew point of the process air a is shown. The higher the temperature T, the higher is the moisture content F when maximum humidity is assumed. When the process air a cools, it loses moisture accordingly, so that part of the moisture content is removed in accordance with the temperature reduction dT.

Accordingly, it can be determined in a laundry drying device based on at least one temperature measurement to what extent the moisture content in or on the heat sink 4 has been reduced.

If a clothes dryer with a heat pump 6 is used, for. B. after FIG. 1 , an indirect measurement of the moisture content in the process air a can advantageously be determined on the basis of the properties of such a heat pump 6 become. Two fundamentally different types of measurement are considered here.

When a drying process is started and the laundry in the laundry drum 2 is full of moisture, the process air a, which is introduced into the laundry drum 2, absorbs an amount of moisture, ideally a moisture amount up to the saturation limit, according to FIG FIG. 2 , Accordingly, the process air a leaves the laundry drum 2 with a high moisture content. This process air a with the high moisture content is led to the evaporator 4 of the heat pump 6 and cooled there. As a result of the cooling of the process air a at the evaporator 4, water or moisture must condense out of the process air a as soon as it reaches the dew point and accordingly there is saturation with the moisture.

When the process air a is further cooled along the dew point, a heat exchange takes place in or with the evaporator 4. The exchanged heat consists of latent heat to condense the water and sensitive heat to cool the temperature of the process air a or to heat the coolant c in the evaporator 4. At the beginning of a drying inflow, when the humidity in the process air a is high, is the latent heat in the evaporator 4 is much higher than the sensible heat. As the moisture in the process air a decreases, the percentage of sensible heat increases relative to the proportion of latent heat.

At the beginning of a drying process, the process air is warmed up over time. Accordingly, the moisture content of the process air increases with increasing time until an equilibrium is established and a substantially constant temperature can be measured at various positions of the circulating air channel 3 until the laundry to be dried dries and delivers less moisture to the process air a. If the process is stable and a constant air flow of the process air a and a constant heat exchange in the evaporator 4 are achieved, the temperature exchange of the process air a in the evaporator 4 is higher, while the sensible heat is high or increases, until finally the moisture or the moisture content in the process air a at the outlet of the laundry drum 2 decreases.

Accordingly, by measuring the temperature of the process air a at the inlet and at the outlet of the evaporator 4, an indirect measurement of the moisture content of the process air a, when it leaves the laundry drum 2, can be carried out. By determining corresponding temperature values, the control device 9 can close the moisture content of the process air a and control the drying cycle of the cooling drying device 1 in a coordinated manner.

In the embodiment of FIG. 1 With the two temperature sensors 10, 11 on the inlet side or outlet side of the evaporator 4, a comparison is carried out by the control device 9 as to whether and / or by what amount the temperature Ta1 measured on the inlet side of the evaporator 4 is smaller than the temperature Ta2 measured on the outlet side, and it becomes a difference between these values is determined or evaluated. Sufficient drying can then be detected, for example, by exceeding a predetermined differential temperature threshold (absolute size) or by a change in the differential temperature with respect to the differential temperature at a plateau p over time exceeding a certain level (relative size).

On the other hand, in the alternative second embodiment, the control device 9 with the only one temperature sensor 11 preferably checks to what extent a temperature Ta2 (t) of the process air a develops over time and can be sufficiently dried, for example, from exceeding a previously time-averaged plateau value to determine a certain amount. Namely, when the moisture content decreases after a time of conditions holding the values constant, less latent heat is absorbed by the process air a in the evaporator 4 and more sensible heat is absorbed. Accordingly, the temperature of the process air in the evaporator 4 then decreases more and more. Accordingly, by means of the control device 9 it can be detected by suitable programming that the temperature Ta2 (t) of the process air a on the outlet side of the evaporator 4 decreases over time and thus the moisture content of the process air a decreases. In comparison to the first embodiment, however, this effect can not be determined so precisely, since process and environmental changes are not easily compensated. Thus, during the decrease of the moisture content in the process air a at the same heating power for the subsequent heating of the process air a this occurs with a reduced temperature in the laundry drum 2 and can correspondingly less Take moisture from the already partially dried laundry. With appropriate countermeasure can be achieved that with decreasing moisture content in the process air and the proportion of heat that is transferred by the process air a to the partially dried laundry changes, which ultimately during the drying cycle, the temperature of the process air a at the outlet of the laundry drum 2 increase. This can in turn be compensated by a more sensitive cooling in the evaporator 4 with reduced moisture content.

FIG. 3 shows an example of a drying cycle in a laundry drying apparatus 1 according to FIG. 1 , wherein temperature profiles of the process air a are shown at different points in the air duct 3. The respective temperature T is plotted over the course of time t. Since 2 temperature sensors were used at the respective measuring points for experimental purposes, 2 measured curves for the respective temperature value are correspondingly shown in a single position. The highest temperature values are reached by curves k1 at the inlet of the laundry drum 2 and the outlet of the condenser 8. After the start of the drying cycle, the process air a is still relatively cold during the first 40 to 50 minutes, for example, and is passed through the condenser 8, and possibly another, Heating device, not shown, increasingly heated until a plateau value is reached in the region of a plateau p under constant operating conditions. The plateau p extends over a period of about 40 to 50 minutes to over 90 minutes and corresponds to the length of time during which about constant conditions prevail in the laundry dryer, since a uniform amount of moisture is released from the laundry to the process air a and a uniform amount of moisture in the evaporator 4 is withdrawn from the process air a. In the subsequent period in which due to an increasing drying of the laundry less moisture is discharged to the process air a, the laundry absorbs correspondingly more heat, so that the temperature k1 at the entrance of the laundry drum 2 gradually decreases until the drying cycle is completed.

Furthermore, the temperature Ta1 of the process air a is shown on the inlet side of the evaporator 4 or on the outlet side of the laundry drum 2. Until the constant operating conditions or the plateau p are reached, this temperature Ta1 gradually increases. At the plateau p it reaches a more or less constant temperature plateau value Ta1p. At the end of the plateau p or in particular behind the plateau p, the temperature Ta1 increases with increasing degree of drying of the clothing the laundry drum 2 and correspondingly less moisture absorption of the process air a gradually increases. The temperature plateau Ta1p is in the example shown in a range between just under 40 ° C and 5 ° C.

Typically, no constant fixed temperature plateau values are specified or determined, since a different amount of moisture is always transferred to the process air a by the amount of clothes to be dried in the laundry drum 2 and their uneven rotation. Accordingly, threshold values surrounding such plateau values are preferably determined and considered by the control device 9 in order to take account of these natural conditions.

Also shown is the temperature Ta2 of the process air a measured at the evaporator 4 on the outlet side. At the beginning of a drying cycle, when the process air has not absorbed any appreciable moisture, the process air a is strongly cooled by the evaporator 4 and takes only a few minutes continuously until reaching the plateau p temperature. A temperature plateau Ta2p this temperature Ta2 outlet side of the evaporator 4 is about 25 - 30 ° C. If the laundry increasingly emits less moisture to the process air a, the process air a is increasingly cooled by the evaporator 4 again, so that the temperature Ta2 of the process air a on the outlet side of the evaporator 4 after the end of the plateau p falls again or assumes lower values ,

Accordingly, an analysis of both the inlet-side and the outlet-side temperatures Ta1 and Ta1 of the process air a at the evaporator 4 or heat sink 4 is preferably carried out. By the controller 9 much more prominent than the analysis of the individual temporal temperature curves Ta1 (t), Ta2 (t) can be evaluated according to their difference. During the duration of the plateau p, a temperature difference dT1 between the inlet and outlet side temperatures Ta2-Ta1 is significantly lower than a temperature difference dT2 between these temperature values after the plateau p. The two temperature differences dT1, dT2 are illustrated by arrows in the diagram.

The described effects also depend to a great extent on the quality of the heat exchanger or heat pump 6. When working with a heat exchanger with low efficiency, the evaporator 4 from the Process air a do not remove sufficient moisture content, whereby the moisture content during the drying cycle is more stable. In addition, if part of the moisture content can escape into the environment, the effects on the temperatures in the area of the evaporator 4 are further reduced, so that detection by the control device 9 is made more difficult. Exemplary is based FIG. 4 illustrates such a situation. Accordingly, a laundry drying apparatus with a cooling body or evaporator 4 that is as effective as possible is preferably able to recognize the detection of the temperature variations over time or the temperature differences over time as well as possible. In FIG. 4 are the same reference numerals as in FIG. 3 so that with regard to explanations to the explanations to FIG. 3 is referenced. Visible is unlike FIG. 3 in that the temperature differences are less pronounced and that the temperatures in the plateau region are slightly different from those according to FIG. 3 differ.

According to a further aspect, a heat exchange efficiency in the heat pump also depends on the relative moisture content of the process air a conducted through the evaporator 4. In the case of an exemplary heat exchanger or its evaporator 4, the process air a with a higher moisture content has a better heat exchange efficiency. When the moisture content becomes lower during the drying cycle, the heat exchanger or heat pump has a decreasing heat exchange performance.

This is the second type of measurement justified. This effect is particularly evident in the area of the evaporator 4, since it operates closest to the dew point of the process air a. In the evaporator 4, the coolant c is transferred from the liquid to the gaseous phase. At the outlet of the evaporator 4, there must always be a gaseous phase without liquid fractions. During the actual phase change, the temperature of the coolant c remains constant, as long as no conductive effects can be detected in the coolant or a large pressure drop occurs. As soon as the coolant c has completely evaporated, its temperature begins to rise. Accordingly, by detecting the temperature Te1 of the refrigerant c on the inlet side of the evaporator and the temperature Te2 of the refrigerant c on the outlet side of the evaporator 4, or preferably at a point along the evaporator 4, heat exchange efficiency can be determined. This efficiency changes according to the above statements during the drying cycle.

Accordingly, the temperature sensors 12, 13, which are used for detecting the temperature Te1 or Te2 of the coolant c on the inlet side or outlet side of the evaporator 4, spaced from each other at the tube of the evaporator 4 or a corresponding connecting tube spaced from each other, wherein the distance is preferably less is than the length of the effective area of the tube of the evaporator 4. Of course, here again instead of an evaporator another equivalent usable heat sink can be considered.

With decreasing moisture content of the process air a during the drying cycle, the heat exchange or its efficiency deteriorates, so that the coolant takes longer, d. H. a longer distance must flow through the evaporator 4 to completely evaporate. Accordingly, the temperature difference or the temperature difference between a temperature sensor arranged on the inlet side and a specific point of a temperature sensor 13, which is arranged at a distance on the outlet side or from the inlet-side temperature sensor 12, decreases. This can be taken as a measure of the moisture content of the process air a or of the laundry still to be dried.

Accordingly, according to the preferred arrangement, a number of two temperature sensors 12, 13 are arranged on the cooling circuit, since an in FIG. 5 sketched difference formation dTc1, DTc2 of the temperatures Te2 - Te1 of the coolant c on the outlet side or inlet side of the evaporator 4 has a higher significance than a single over the time t considered temperature value. An application of two temperature sensors is still much cheaper in terms of design and cost than providing a humidity directly measuring humidity sensor. According to a less preferred embodiment, however, the measurement with only a single temperature sensor 13 in the region of the evaporator 4 or the condenser 8 can be implemented.

Also in these embodiments, in which the temperature of the coolant c is used as a criterion for the moisture content of the process air a, the use of a laundry drying device 1 is preferred, which has a heat pump 6 as effective as possible. If the vaporization power in the evaporator 4 became too low, the coolant c would assume a temperature very close to the temperature of the process air, so that the effects would be hidden. FIG. 5 shows an example of a diagram comparable to the diagrams FIG. 3 and FIG. 4 , However, temperature profiles of the temperature T of the coolant c over the time t are shown. Recognizable are again plateaus p in a range in which constant operating conditions are set. However, with the end of the plateau p, the individual temperature profiles are increasing or decreasing. The temperature difference dTc2 on the outlet side is again clearly visible on the inlet side compared to the temperature difference dTc1 on the inlet side. However, considering the temperature of the refrigerant c, the criterion for a drying laundry is not an increase in the temperature differences dTc1, dTc2 but a decrease in the temperature differences dTc1, dTc2.

A temperature Te1 of the coolant c on the inlet side of the evaporator is with the first of these in FIG. 1 sketched temperature sensors 12, which detects the coolant temperature on the inlet side or in front of the evaporator 4. The second of these temperature sensors 13 for determining the temperature differences dTc1, dTc2 is arranged on a three-quarter length of the evaporator 4 or its effective evaporator length.

Other exemplary temperatures shown are: a temperature Cp_OUT measured at the outlet of the compressor 8, temperatures Cd_3 / 4, Cd_7 / 8 at three quarters and seven-eighths of the length of the condenser and a temperature Cd_OUT at the outlet of the condenser 8. For experimental purposes was also a circulating air temperature Cd_air_OUT at the outlet of the condenser, a temperature Cd_IN at the inlet of the compressor, an outlet side temperature Ev_OUT at the evaporator and an ambient temperature K2 measured and outlined.

Of course, the present invention is not limited to the described embodiment. Thus, a detection of the degree of drying by means of temperature sensing is also suitable for exhaust air dryer. The method is also applicable to both separate tumble drier and washer-dryer.

LIST OF REFERENCE NUMBERS

1

Laundry drying device

2

washing drum

3

air duct

4

heatsink

5

Evaporator

6

heat pump

7

Coolant line

8th

condenser

9

control device

10-13

temperature sensors

14

throttle

a

process air

c

coolant

CD_IN

Coolant temperature inlet side of the compressor

Cp_OUT

Coolant temperature outlet side of the compressor

Cd_OUT

Coolant temperature at the condenser outlet

CD_3 / 4

Coolant temperature to 3/4 length of the condenser

Cd_7 / 8

Coolant temperature to 7/8-length of the condenser

Cd_air_OUT

Convection temperature at the condenser

dT

temperature reduction

dT1

Process air temperature difference on inlet side

dT 2

Process air temperature difference on outlet side

DTC1

Coolant temperature difference inlet side

DTC2

Coolant temperature difference on outlet side

Ev_OUT

Coolant temperature on the outlet side of the evaporator

F

moisture content

p

plateaus

t

Time

T

temperature

Ta1

Temperatures of the process air inlet side

ta2

Temperatures of the process air on the outlet side

Ta2 (t)

Temperature of process air over time

Ta1p

Temperature plateau value of the process air inlet side

Ta2p

Temperature plateau value of the process air on the outlet side

Te1

Temperatures of the coolant inlet side

Te2

Temperatures of the coolant on the outlet side

Te2 (t)

Temperature of the coolant over time

k1

Temperature values at the entrance of the laundry drum

k2

ambient temperature

Claims (18)

1. Laundry drying apparatus (1) with a laundry drum (2), a moisture determining device (9, 10-13) for determining a moisture content of process air (a) discharged from the laundry drum (2) and a cooling body (4) for cooling the process air (a), wherein the moisture determining device (9, 10-13) comprises at least one temperature sensor (10-13) and the at least one temperature sensor (11) is arranged behind an inlet of the cooling body (4) for a medium (a, c) flowing through the cooling body (4) or a medium (c) present in the cooling body (4), characterised in that the medium (a, c) is either the process air (a) or a coolant (c) and that the at least one temperature sensor (11) is arranged for measuring an exit temperature (Ta2, Te2) of the medium (a, c) at the outlet side of the cooling body (4) and a further temperature sensor (10) is arranged for measuring an entry temperature (Ta1, Te1) of the medium (a, c) at the inlet side of the cooling body (4).
2. Laundry drying apparatus (1) according to claim 1, characterised in that the at least one temperature sensor (11) is arranged for measuring a temperature (Ta2) of the process air (a) at the outlet side of the cooling body (4).
3. Laundry drying apparatus (1) according to claim 1, characterised in that the at least one temperature sensor (13) is arranged behind a coolant inlet of the cooling body (4) for measuring a temperature (Te2) of a coolant (c) flowing through the cooling body (4) or a coolant (c) present in the cooling body (4).
4. Laundry drying apparatus (1) according to any one of the preceding claims, characterised in that the moisture determining device (9, 10-13) is designed and/or programmed for determination of the moisture content on the basis of a time sequence of temperatures (Ta1 (t); Ta2(t); Te1 (t); Te2(t)) measured by means of at least one such temperature sensor (11; 13).
5. Laundry drying apparatus (1) according to claim 4, characterised in that the moisture determining device (9, 10-13) is designed and/or programmed for determination of an increase in the entry temperature (Ta1) and/or a drop in the exit temperature (Ta2) of the process air (a) over the time sequence of measured temperatures (Ta 1 (t); Ta2(t)) of the process air (a) relative to a previous temperature
   plateau value (Ta2p) of the process air (a).
6. Laundry drying apparatus (1) according to one of claims 4 and 5, characterised in that the moisture determining device (9, 13) is designed and/or programmed for determination of a drop in the entry temperature (Te1) and/or the exit temperature (Te2) of the coolant (c) over the time sequence of measured temperatures (Te2(t)) of the coolant (c) relative to a previous temperature value plateau value (Te2p) of the coolant (c).
7. Laundry drying apparatus (1) according to any one of the preceding claims, characterised in that the at least one temperature sensor (11) is arranged for measuring an exit temperature (Ta2) for the process air (a) and a further temperature sensor (10) is arranged for measuring an entry temperature (Ta1) of the process air (a).
8. Laundry drying apparatus (1) according to any one of the preceding claims, characterised in that the moisture determining device (9, 10-13) is designed and/or programmed for determining a temperature difference of the entry temperature (Ta1; Te1) and the exit temperature (Ta2; Te2) of the medium (a, c), particularly relative to a temperature difference plateau value of the coolant (c).
9. Laundry drying apparatus (1) according to any one of the preceding claims, characterised in that the at least one temperature sensor (13) is arranged for measuring an exit temperature (Te2) of the coolant (c) behind a coolant inlet of the cooling body (4) and in addition an additional temperature sensor (12) is arranged for measuring an entry temperature (Te1) of the coolant (c).
10. Laundry drying apparatus (1) according to any one of the preceding claims, characterised in that the cooling body (4) is dimensioned and/or a control device is designed and/or programmed to flow through the cooling body with coolant (c) in such a manner that up to the at least one temperature sensor (11, 13) the entire moisture content is not extracted from the process air (a).
11. Laundry drying apparatus (1) according to any one of the preceding claims, characterised in that the cooling body is constructed by an evaporator (4) of a heat pump (6).
12. Laundry drying apparatus (1) according to any one of the preceding claims, characterised in that the at least one temperature sensor (10-13) is a sensor of a heating device control for controlling a process air temperature.
13. Method of operating a laundry drying apparatus (1), in which a moisture content is determined from process air (a) discharged from a laundry drum (2) and the moisture is at least partly condensed from the process air (a) by a cooling body (4), wherein the moisture determination is determined by measuring at least one temperature (Ta2; Te2) for a medium (a, c) flowing through the cooling body (4) or a medium (c) present in the cooling body (4) and by evaluation of the measured temperature (Ta2; Te2), characterised in that the medium (a, c) is either the process air (a) or a coolant (c) and that the moisture content is determined by measuring an exit temperature (Ta2) of the medium (a, c) at the outlet side of the cooling body (4) and by measuring an entry temperature (Ta1; Te1) of the medium (a, c) at the entry side of the cooling body (4).
14. Method according to claim 13, characterised in that the moisture content is determined on the basis of a time sequence of the measured temperatures (Ta2(t); Te2(t); Ta1 (t); Te1 (t)).
15. Method according to one of claims 13 and 14, characterised in that a temperature difference of the exit temperature (Ta2; Te2) and the entry temperature (Ta1 or Te1) is formed for the moisture determination.
16. Method according to claim 14, characterised in that in the case of a rise in the entry temperature (Ta1) or a drop in the exit temperature (Ta2) of the process air (a) over the time sequence of measured temperatures (Ta2(t)) of the process air (a) relative to a previous temperature plateau value (Ta2p) of the process air (a) a decreasing moisture content is indicated.
17. Method according to one of claims 14 and 16, characterised in that in the case of a drop in the entry temperature (Te1) or a rise in the exit temperature (Te2) of the coolant (c) over the time sequence of measured temperatures (Te1 (t); Te2(t)) of the coolant (c) relative to a previous temperature plateau value (Te2p) of the coolant (c) a decreasing moisture content of the process air (a) is indicated.
18. Method according to any one of claims 14, 15 and 17, characterised in that in the case of a rise in a temperature difference between the exit temperature (Ta2) and the entry temperature (Ta1) of the process air (a) or in the case of or at a drop in a temperature difference between the exit temperature (Te2) and the entry temperature (Te1) of the coolant (c) over the time sequence of respectively measured temperature differences relative to a previous temperature difference plateau value a decreasing moisture content is indicated.

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