DE102022204025A1 - Method for determining the final residual moisture in a heat pump dryer and heat pump dryer suitable for this purpose - Google Patents

Abstract

The invention relates to a method for operating a dryer 1 with a drum 3 for receiving items of laundry to be treated, a drive motor 18 for the drum 3, a process air duct 2 for guiding process air, in which process air is moved by means of a blower 6, which is attached to a first end 8 is connected to an air outlet opening of the drum 3 and at a second end 12 to an air inlet opening 9 of the drum 3, a control unit 10, a heat pump arranged in the process air duct 2 with an evaporator 4, a condenser 5, an expansion unit 14 and a compressor 13, wherein a first thermometer 28 for measuring the inlet temperature T1 is arranged at the refrigerant inlet 19 of the evaporator 4 and a second thermometer 29 for measuring the outlet temperature T2 is arranged at the refrigerant outlet 20 of the evaporator 4, the control unit 10 being set up to prevent overheating SH, which can be calculated as the difference T2-T1, to determine a residual moisture H of the laundry items, the method comprising the following steps in a drying process: (a) measuring the inlet temperature T1 at the refrigerant inlet 19 of the evaporator 4 and the outlet temperature T2 at the refrigerant outlet 20 of the evaporator 4; (b) calculation of the superheat SH as the difference T2-T1; and (c) determining the residual moisture of the laundry items from the superheat SH by means of the control unit 10. The invention also relates to a heat pump dryer suitable for carrying out this method.

Description

The invention relates to a method for determining the final residual moisture in a heat pump dryer and a heat pump dryer suitable for this purpose. The invention relates in particular to a method for operating a dryer with a drum for receiving items of laundry to be treated, a drive motor for the drum, a process air duct for guiding process air, in which process air is moved by means of a fan, the process air duct having a first end an air outlet opening of the drum and is connected at a second end to an air inlet opening of the drum, a control unit, a heat pump arranged in the process air duct with an evaporator, a condenser, an expansion unit and a compressor, with a first thermometer for measuring the refrigerant inlet of the evaporator Input temperature T1 and a second thermometer for measuring the output temperature T2 is arranged at the refrigerant outlet of the evaporator, as well as a heat pump dryer suitable for carrying out this method.

Drying processes using the condensation process are based on the evaporation of moisture from laundry items using warm process air and dehumidification of the process air through condensation on a heat exchanger. In the drying process, cool process air is generally passed through a fan over a heater, which can be, for example, the condenser (condenser) of a heat pump. The dry, warm process air then enters the drum as a drying chamber, which contains the laundry items to be dried. The dry, warm process air absorbs the moisture from the laundry items. The warm, moist process air is then passed from the drum into a heat exchanger for dehumidification, for example into an air-air heat exchanger or the evaporator of a heat pump. The warm, moist process air is cooled in it, whereby the water it contains is condensed and collected in a so-called condensate tray, which is generally located below the heat exchanger. When a certain level is reached, the condensed water is usually pumped by a pump (also called a “condensate pump”) into a container for temporary storage (also called a “condensate tank”) or into a sewer.

The drying process is generally carried out until a certain final residual moisture content of the dried laundry items is reached. In general, the degree of moisture is determined by measuring the electrical resistance of the laundry items. For this purpose, a different number of electrodes is usually arranged at different positions in the dryer. Using these electrodes, the laundry resistance is measured using direct or alternating current methods. As the residual moisture in the laundry decreases, the resistance of the wet laundry decreases. This resistance is determined and correlated with the residual moisture in the laundry. With a specified laundry resistance as a so-called switch-off value, especially for heating the process air, the drying process is usually ended. These switch-off values depend on the load quantity and the initial moisture (also referred to as the “initial residual moisture” of the damp laundry items coming from a washing machine) of the laundry items, since, for example, with the same humidity, the relative humidity of the process air is greater for larger load quantities. It should also be taken into account that if the initial moisture is high, it may take longer for the drying to be effective even inside the laundry items. In order to improve the execution of a drying process, process steps are often carried out to determine the initial state, i.e. in particular the load and initial moisture of the laundry items. Based on such information, the switch-off limit can then be adjusted. Methods are also known that correlate several measured variables such as energy, in particular the total energy used so far for drying, electrical power, temperature and elapsed time, in order to improve the prediction accuracy.

A heat pump is characterized by two heat exchangers, namely a heat sink in which heat is absorbed, a heat source in which heat is released, and a pump device which transfers heat from the heat sink to the heat source, if necessary with a change in temperature. In a condensation dryer equipped with a compressor-type heat pump, the warm, moisture-laden process air is cooled essentially in the heat sink of the heat pump, also known as an evaporator, where the transferred heat is used to evaporate a refrigerant circulating in the pump device designed as a circuit . The refrigerant evaporated due to the heating is supplied in the pumping device via a compressor to the heat source, which is a condenser for the refrigerant, to the heat pump, where heat is released due to the liquefaction of the gaseous refrigerant. Behind the condenser, the then liquid refrigerant is expanded in a throttle of the pump device, whereby its internal pressure is reduced is set and finally returns to the evaporator.

According to the design of the refrigeration circuit of a heat pump dryer, the refrigerant on the low-pressure side (in the evaporator) is overheated after complete evaporation. The temperature difference between the temperature of the superheated steam and the evaporation temperature is called superheating (SH). The SH changes as the heat absorption in the refrigerant changes. This occurs when the energy input into the evaporator changes, particularly when the energy in the air from the drum changes.

The phenomenon of overheating of a refrigerant in a heat pump has long been known, for example EP 2 468 945 B1 and EP 2 745 760 A1 known and also their importance for controlling a heat pump, whereby it is known in particular that the overheating fundamentally changes during operation of a heat pump due to the special features of a heat pump. That's how it describes EP 2 468 945 B1 that the air heating capacity at the condenser is always higher than the air cooling capacity at the evaporator. The condenser must also dissipate the heat generated by the refrigerant compression system itself. This results in a continuous increase in the temperature of the air supplied to the drum and a continuous increase in the refrigerant pressure and temperature on the discharge side of the refrigerant compressor. On the one hand, this behavior is useful at the beginning of the drying cycle as it speeds up the set-up phase, but on the other hand it becomes very negative when the hot air generator reaches the steady state operating state at full power. The EP 2 468 945 B1 also describes maintaining the output temperature from the evaporator in a specified temperature range by adjusting the flow rate or prior cooling of the refrigerant.

Against this background, the object of the present invention was to provide an improved method for operating a heat pump dryer, with which in particular its control by determining a residual moisture of laundry items to be treated therein is possible in an improved, in particular more precise manner, so that on the basis of this criterion the end of a drying process or the switching off of the heat pump dryer can be carried out as precisely as possible. The object of the invention was also to provide a heat pump dryer suitable for this purpose.

The solution to this problem is achieved according to this invention by a method for operating a heat pump dryer and a heat pump dryer suitable for carrying out this method with the features of the respective independent patent claims. Preferred embodiments of the method according to the invention and of the heat pump dryer according to the invention are listed in the respective dependent patent claims. Preferred embodiments of the method according to the invention correspond to preferred embodiments of the heat pump dryer according to the invention and vice versa, even if this is not explicitly stated herein.

1. (a) Messung der Eingangstemperatur T1 am Kältemitteleintritt des Verdampfers und der Ausgangstemperatur T2 am Kältemittelaustritt des Verdampfers;
2. (b) Berechnung der Überhitzung SH als Differenz T2-T1; und
3. (c) Bestimmung der Restfeuchte der Wäschestücke aus der Überhitzung SH mittels der Steuerungseinheit.

The subject of the invention is therefore a method for operating a dryer with a drum for holding items of laundry to be treated, a drive motor for the drum, a process air duct for guiding process air, in which process air is moved by means of a fan, the process air duct being at a first end with an air outlet opening of the drum and at a second end with an air inlet opening of the drum, a control unit, a heat pump arranged in the process air duct with an evaporator, a condenser, an expansion unit, for example a controllable expansion valve, and a compressor, wherein at the refrigerant inlet of the evaporator a first thermometer for measuring the inlet temperature T1 and a second thermometer for measuring the outlet temperature T2 is arranged at the refrigerant outlet of the evaporator, the control unit being set up to calculate from a superheat SH, which can and preferably is calculated as the difference T2-T1 to determine a residual moisture H of the laundry items, the method comprising the following steps in a drying process:

1. (a) measuring the inlet temperature T1 at the refrigerant inlet of the evaporator and the outlet temperature T2 at the refrigerant outlet of the evaporator;
2. (b) calculation of the superheat SH as the difference T2-T1; and
3. (c) Determination of the residual moisture of the laundry items from the superheat SH using the control unit.

According to the invention, it is particularly preferred that the determination of the residual moisture of the laundry items from the overheating SH is evaluated using the SH curve that decreases over time.

The drying efficiency of a dryer is particularly evaluated by the accuracy of the moisture sensing. Therefore, the residual moisture is of crucial importance, especially at the end drying, to be determined as precisely as possible.

This invention is based on the correlation between the residual moisture H in the laundry items and the superheat (SH) of the refrigerant in the evaporator.

The SH is a very sensitive variable in the refrigeration cycle. For example, it reacts to changes in the humidity of the process air. At the end of the drying process, the process air transports less and less water from the laundry items to the evaporator. This decrease in latent energy in the form of water vapor leads to a measurable change in superheat SH. At the end of the drying process, this change correlates directly with the decrease in water transport in the drum from the laundry items to the process air via evaporation, and thus from the process air to the evaporator, where the condensation of the water vapor takes place. The SH decreases because the specific enthalpy of the process air decreases due to the reduced amount of water, which results in a smaller amount of energy being supplied to the evaporator from the process air per unit of time.

Preferably, the method according to the invention is carried out in such a way that the superheat SH is measured continuously during the drying process at least over a predetermined period of time Δt _set and, if it is determined that the measured superheat SH is essentially constant in the period Δt _set , the measured SH is used as a reference value (threshold value ) SH _ref is used to determine the residual moisture. The speed of the fan and/or the speed of the compressor is preferably constant in the period Δt _set . If SH _ref is not reached, a final drying phase can advantageously be started, which is suitable for the end of the overall drying in order to achieve a final residual moisture of 0% as accurately as possible.

The load of the drum with laundry items should preferably be determined in a drying process in order to be able to adapt the drying process to the load, since different amounts of laundry items behave differently.

The degree of moisture of the laundry items, i.e. the moisture or residual moisture, changes during a drying process because first surface water and finally pore and capillary water evaporate from the fabric of the laundry items. Depending on the moisture of the laundry items at the beginning of the drying process and the type of fabric, the course of a moisture level in a drying process is different and a continuous and precise determination of a moisture level is therefore advantageous for gentle and energy-efficient drying of the laundry items, as well as precise control of the final residual moisture with respect to a predetermined Value such as “iron dry”.

A drying process is therefore influenced by the proportions of surface water and water present inside the laundry items, with the latter only being removed relatively slowly from the laundry items. A drying process therefore also depends on the load of laundry items.

In order to specify a residual moisture H ^set , it is in any case advantageous if the amount of laundry loaded into the drum and/or the initial moisture content of the laundry items can be taken into account.

In a preferred embodiment of the method according to the invention, a load W of the drum with laundry items is therefore taken into account for determining the predetermined residual moisture H ^set , a relationship between the load W and the residual moisture H ^set stored in the control unit being used.

The load amount and/or initial moisture content can be set by a user or preferably determined by the dryer. Various procedures are possible for this. A determined load quantity refers to the dry mass of the items of laundry placed in the drum to be dried. However, at the beginning of the drying process, laundry items have a moisture content, based on the dry matter of the laundry items, of approximately 60%, for example, after a washing process and a spin cycle at 1200 rpm. In addition, different load quantities behave differently in a drying process. For example, a drying process with a full load can take longer than a drying process with a half load. The duration of the individual phases in the drying process can also vary.

The method of determining the load W of the drum with items of laundry is not restricted according to the invention. For example, the load can be determined by input from the user. In general, however, the loading of the drum is determined by the dryer, for example by weighing the drum and/or by evaluating a motor current and/or an electrical power of the electric drive motor.

The loading is preferably determined by evaluating a motor current and/or an electrical power of the electric drive motor. For example, if the power delivered to the electric drive motor is kept constant, the dependence of the motor current on a load of the electric drive motor can be used to determine the loading state of the drum. In particular, a course of the current can be tracked within a predetermined period of time, for example when the drum is running up. It is possible to draw conclusions about the load based on the dependence of the torque of the electric drive motor on the loading condition of the drum and on the basis of the dependence of the torque on the motor current.

According to the invention, a method is therefore preferred in which the drive motor is a BLDC electric motor and its drive power is evaluated with regard to loading the drum with laundry items.

The dryer used in the method preferably has at least one sensor for determining measured values of the process air and the control unit will link the measured values of the process air and/or calculation variables calculated therefrom with model parameters determined from a prediction model to determine the residual moisture.

• (d) Vergleichen der bestimmten Restfeuchte H mit einer vorgegebenen Restfeuchte H^set _; und
• (e) Beenden des Trocknungsprozesses bei Erreichen oder Unterschreiten der vorgegebenen Restfeuchte H^set umfasst.

The process according to the invention preferably contains the process steps in addition to the process steps (a) to (c) mentioned therein

• (d) comparing the determined residual moisture H with a predetermined residual moisture H ^set _; and
• (e) Ending the drying process when the specified residual moisture H ^set is reached or falls below.

The superheat SH can be kept at a constant value through process control, e.g. by means of an expansion valve, or by having a speed-controllable compressor regulate this temperature difference. In such cases, a control deviation (e = actual value - target value) could be viewed as an indirect measure or substitute variable for the SH. The changes in SH or the control deviation can provide information about the residual moisture in the laundry using a suitable algorithm. The signal (values) coming from the algorithm could be used in addition to measuring the conductance signal, or for direct use of the process control variable (residual moisture in the laundry).

In general, an SH of 0 K or just above is particularly energy efficient. An SH > 0 K may be necessary to prevent liquid refrigerant from hitting the compressor. An SH > 0 K is a kind of safety factor to ensure that no liquid refrigerant hits the compressor.

1. (a) Messen einer relativen Feuchtigkeit H_rel der Prozessluft mit dem Feuchtesensor;
2. (b) Messen einer Temperatur T_P der Prozessluft mit einem Temperatursensor;
3. (c) Ermitteln einer absoluten Wasserbeladung Lw der Prozessluft aus der relativen Feuchtigkeit H_rel unter Berücksichtigung der Temperatur T_P, wobei ein in der Steuerungseinheit vorzugsweise hinterlegter Zusammenhang zwischen einer maximalen Wasserbeladung L_W ^max und der Temperatur T_P herangezogen wird;
4. (d) Verfolgen des zeitlichen Verlaufs der Wasserbeladung L_W;
5. (e) Heranziehen des zeitlichen Verlaufs der Wasserbeladung L_w zur Bestimmung einer Restfeuchte H in den Wäschestücken;
6. (f) Vergleichen der Restfeuchte H mit einer vorgegebenen Restfeuchte H^set; und
7. (g) Beenden des Trocknungsprozesses bei Erreichen oder Unterschreiten der vorgegebenen Restfeuchte H^set.

To improve the evaluation of the SH, further measurements can be carried out during the drying process and used as part of a multivariate analysis:

1. (a) measuring a relative humidity H _rel of the process air with the humidity sensor;
2. (b) measuring a temperature T _P of the process air with a temperature sensor;
3. (c) determining an absolute water load Lw of the process air from the relative humidity H _rel , taking into account the temperature T _P , using a relationship between a maximum water load L _W ^max and the temperature T _P , which is preferably stored in the control unit;
4. (d) tracking the time course of the water loading L _W ;
5. (e) using the time course of the water load L _w to determine a residual moisture H in the laundry items;
6. (f) comparing the residual moisture H with a predetermined residual moisture H ^set ; and
7. (g) End the drying process when the specified residual moisture H ^set is reached or falls below.

As already mentioned, the water load can be determined via the power consumption of a variable (BLDC) electric motor.

The start of the process according to the invention generally takes place at the same time as the initiation of a drying program. In this case, a usually additionally used electric heater and the fan are generally switched on in order to direct heated process air into the drum for drying damp laundry items.

In a preferred embodiment of the method according to the invention, a temperature sensor and a humidity sensor are arranged in the process air duct before and after the drum, the relative humidity H _rel being then used for multivariate analysis in conjunction with the measured SH as relative humidity H _rel ^before and as relative Humidity H _rel is measured ^after the drum; the temperature T _P of the process air as the temperature T _P ^before the process air before and as the tem temperature T _P is measured ^after the process air after the drum; and from the relative humidities H _rel ^after and H _rel ^before , taking into account the temperatures T _P ^after and T _P ^before , an absolute water load L _W ^after the process air after the drum and an absolute water load L _W ^before in front of the drum is calculated, and from this one Difference ΔLw = L _W ^after - L _W ^before is calculated. The time course of the difference ΔL _W of the water load Lw can be followed; and the time course of the difference ΔL _W of the water load Lw of the process air can also be used to determine the residual moisture Rw in the laundry items by evaluating the SH.

The optionally used temperature sensors and humidity sensors are not restricted as long as they can be used to measure a temperature or relative humidity of the process air. However, it is advantageous to use sensors that can measure the temperature and relative humidity of the process air at the same time. In a preferred embodiment of the invention, a dual sensor is used as the temperature sensor and as the humidity sensor, with which the temperature T _P and the relative humidity H _rel of the process air can be measured at the same time. Even more preferred is the use of a triple sensor, with which the pressure P _P of the process air can also be determined.

When determining the residual moisture according to the invention via the absolute loading of the process air with water, the influence of the air pressure is advantageously taken into account.

In a preferred embodiment of the method according to the invention, at least one pressure sensor is present in the process air duct, which measures the pressure P _P of the process air, which is then used to determine the water load Lw, with a relationship stored in the control unit between the pressure P _P , a maximum water load L _W ^max and the temperature T _P is used.

A triple sensor is preferably used as the pressure sensor, with which the relative humidity H _rel and the temperature T _P can also be measured at the same time.

A drying process in the dryer according to the invention is influenced in particular by an air flow of the process air, since the size of the air flow determines how long a certain amount of air can be in contact with damp laundry items.

In a preferred embodiment of the method according to the invention, the air flow _AP of the process air is therefore set or measured and taken into account for determining the predetermined residual moisture H ^set , a relationship between the air flow _AP and the residual moisture H ^set stored in the control unit being used. A speed or power consumption of the fan can be viewed as a measure of the air flow A _P of the process air. However, an actual air flow of the process air can also be measured using a flow meter and then viewed as the air flow A _P of the process air.

The measured SH values and preferably also the measured values of the process air and/or calculation variables calculated therefrom are preferably linked to model parameters determined from a prediction model, with different groups of model parameters being used for different humidity ranges. Due to the different groups of model parameters, an accuracy in determining the degree of moisture can be flexibly adapted to different sections of a drying process - and in particular to target values that change during a drying process.

The fact that the measured values and/or calculation variables calculated therefrom are linked to predetermined model parameters can include only measured values, only calculation variables or any combination of at least one measurement variable and at least one calculation variable being linked to predetermined model parameters. A calculation variable can be a variable derived or calculated from one measured variable or from several measured variables of a sensor or several sensors. A calculation quantity can, for example, be a mathematical product or a quotient of at least one “directly” measured measured value and/or a quantity calculated by applying at least one mathematical function (root, power, exponent, logarithm, etc.) to at least one measured value. In addition, a calculation variable can be formed by forming the difference and/or averaging several measured values (one or more sensors).

A moisture range is understood to mean, in particular, a range of a moisture level of the laundry.

In a preferred embodiment of the invention, each input parameter (i.e., a measured value or a calculation variable) is linked to a respective model parameter. Furthermore, it is preferred that the measured values are recorded continuously with a particularly constant acquisition rate.

A “model parameter” can be understood in particular as a value - for example determined experimentally and/or numerically - which is used to link with at least one measured value in order to determine the moisture level of the laundry. Multiple model parameters can be grouped in a vector (“parameter vector”) or in a matrix (“parameter matrix”). A single model parameter can be a constant, a variable, or a formula. The at least one model parameter used in the method can result, for example, from a previously carried out "learning" - for example at the factory - of the associated - in particular multivariate - prediction model. In particular, those model parameters (values) are used that previously gave the best match between the calculated moisture value and a directly measured moisture value, for example.

According to the invention, it is preferred that the degree of moisture is calculated by means of a vector multiplication of a vector of the measured values or calculation variables (“measurement vector”) with a parameter vector. The parameter vectors can be stored in the laundry drying device.

Furthermore, an embodiment is preferred in which the different groups are assigned to successively narrower moisture ranges and the accuracy of determining the degree of moisture is higher the narrower the moisture range used. In other words, the model parameters of a first group can be used for a first moisture range, the model parameters of a second group for a second moisture range, etc. Since a moisture range that successively follows in relation to a drying progress is narrower, it can determine the degree of moisture of the laundry more precisely there or predict than the previous humidity range. Successively narrower moisture ranges can in particular be understood to mean moisture ranges that are used one after the other for increasingly narrower or narrower moisture ranges.

It is also an embodiment that the degree of humidity is calculated using a “hierarchical” use of the groups of model parameters. This means that at the beginning of a drying process the first group of model parameters is used, which has sufficient accuracy for its first moisture range, then from a predetermined first transition value the second group of model parameters is used, which has a higher accuracy for its second moisture range.

According to the invention, it is particularly preferred that the prediction models are or have been generated using multivariate algorithms. These algorithms can in particular determine a maximum variance in the measured values or calculation variables during a drying process (e.g. using PCA and/or PLS). The prediction models can be in the form of matrices that are multiplied by measurement vectors. The prediction models or algorithms may have been adapted or trained based on experimental drying processes. In particular, a model can recognize a dynamic behavior of the measured values or calculation variables, which is determined by the physical drying and the drying process.

Preferably, the model parameters of all groups are calculated using a same basic model and input parameters (i.e. measured values and/or calculation variables) of the respective moisture ranges are used for different groups to adapt the basic model. This enables particularly low effort to determine the model parameters. In particular, the input parameters temperature, water load, specific enthalpy, relative humidity and the differences between pressure, humidity, temperature, water load and specific enthalpy can be made available alone or in any combination to adapt the basic model.

The fact that input parameters of the respective humidity ranges are used for different groups to adapt the basic model can include that only input parameters from the respective humidity ranges are used. Alternatively, input parameters from larger ranges than the respective humidity range can be used. In particular, input parameters can be used that extend beyond the respective humidity range down to 0%.

The adaptation or training of the model and thus the calculation of the model parameters for a specific humidity range can advantageously be carried out in such a way that a (not yet adapted) basic model or its algorithms is trained or adapted using experimentally determined input parameters that are suitable for this humidity range. Customizing may include setting parameters of the algorithms. In principle, the model parameters of a group can be determined based on a fitted model or based on a combination of several fitted models.

In general, different basic models can be used for at least two different moisture ranges, for example using different types of algorithms.

It is also preferred that the measured values include at least one relative humidity, a temperature and/or a pressure in addition to the superheat SH. Measuring these measurements enables a particularly precise prediction of the moisture level of the laundry. In particular, the calculation of the degree of humidity can only be carried out using the relative humidity and the temperature, or possibly only based on the temperature.

In one embodiment, the calculation variable includes a humidity difference, a temperature difference, a water load and/or an enthalpy. These calculation variables enable a particularly precise prediction of the moisture level of the laundry. The differences can be derived, for example, from measured values recorded in front of and behind the drum.

To calculate or predict the moisture level of the laundry items, combinations of measured values and calculation variables derived from each other can also be used. In one variant, the degree of humidity can be determined based on the input parameters: superheat SH; temperature or temperature difference; relative humidity or humidity difference; and water loading or difference in water loading can be calculated, whereby the water loading can be calculated from the temperature and the relative humidity. Instead of or in addition to the water loading, the enthalpy can be used, which can also be calculated from temperature, relative humidity, possibly pressure or differences thereof.

In a further embodiment, the determined moisture level of the laundry is compared with a target value, the target value corresponding to a point on a curve of a moisture level of a characteristic drying process. If the material moisture determined by the models is within a tolerance range associated with the target value, the drying process is stopped. This has the advantage that the influence of disturbances such as winders can be further reduced. Alternatively, the drying process can be stopped when the specific moisture level has reached an associated target or setpoint.

The invention also relates to a dryer with a drum for holding items of laundry to be treated, a drive motor for the drum, a process air duct for guiding process air, in which process air is moved by means of a fan, the process air duct having an air outlet opening at a first end Drum and is connected at a second end to an air inlet opening of the drum, a control unit, a heat pump with an evaporator, a condenser, an expansion unit and a compressor, with a first thermometer for measuring the inlet temperature T1 at the refrigerant inlet of the evaporator and at the refrigerant outlet of the A second thermometer for measuring the initial temperature T2 is arranged on the evaporator, and the control unit is set up to determine a residual moisture H of the laundry items from a superheat SH, which can be calculated as the difference T2-T1 and is preferably calculated therefrom.

According to the invention, a dryer is preferred in which the control unit is set up so that, in order to determine the residual moisture, the superheat SH and/or calculation variables calculated therefrom are linked to model parameters determined from a prediction model.

In a particularly preferred embodiment of the invention, the dryer has at least one sensor for determining measured values of the process air and the control unit is set up to link the measured values of the process air and/or calculation variables calculated therefrom with model parameters determined from a prediction model in order to determine the residual moisture . Preferably, the at least one sensor for determining measured values of the process air comprises a temperature sensor and/or a humidity sensor. A dual sensor or triple sensor is preferably used as the temperature sensor and as the humidity sensor, which can simultaneously measure the temperature T _P and the relative humidity H _rel of the process air. A triple sensor is preferably used as the temperature sensor and as the humidity sensor, with which, in addition to the temperature T _P and the relative humidity H _rel , an air pressure P _P of the process air can also be measured.

Finally, according to the invention, a dryer is also preferred which has a conductivity sensor in the drum and in which the control unit is set up to determine the residual moisture in order to link the moisture value measured with the moisture sensor in the drum with model parameters determined from a prediction model.

As already mentioned, it is advantageous to evaluate the current and/or power consumption of an optionally used BLDC electric motor, for example wise with regard to loading the drum. In addition, the change in the residual moisture of the laundry items can be observed during the drying process. In a preferred embodiment of the dryer, the control unit is therefore set up to infer a moisture content H of the laundry items in the drum from the measured current of the drive motor.

In a further preferred embodiment of the dryer according to the invention, it has a controllable expansion valve in the heat pump and the control unit is set up to keep the superheat SH in a predetermined temperature range ΔT _SH by regulating the expansion valve.

According to the invention, a condensation dryer is preferred in which a temperature sensor and a humidity sensor are arranged in the process air duct before and/or after the drum.

In general, in the condensation dryer according to the invention, a condensate pump is arranged in a condensate trough or a condensate channel connected to the condensate trough. The condensate pan is generally connected via a so-called condensate channel to a container for temporarily storing the condensate, i.e. a condensate container, or to a wastewater pipe for disposing of the condensate.

The dryer according to the invention preferably has an electric heater or a gas heater, with an electric heater being preferably used. The heater is used to warm the process air before it is introduced into the drum of the heat pump dryer, especially at the beginning of a drying process.

The dryer according to the invention is in particular a tumble dryer per se or a washer-dryer. A washer-dryer is a combination device that has a washing function for washing laundry and a drying function for drying damp laundry.

The dryer according to the invention advantageously preferably has an optical and/or acoustic display device for different states of the heat pump dryer. An optical display device is preferably used. The display device can, for example, provide information about the operation of the dryer by outputting a text or by lighting up different colored LEDs, for example about the course of the absolute water load Lw and / or the residual moisture H of the laundry items, about the overheating SH, about the load quantity, the phase of the Drying process, for example heating phase, stationary phase, unsteady phase, or the remaining running time of a drying process.

Methods and heat pump dryers of the invention have several advantages. Advantages of the invention are in particular that a desired residual moisture of laundry items can be adjusted in an improved manner in a drying process, so that the end of a drying process can also be carried out in an optimized manner. In embodiments of the invention, laundry properties such as load and moisture level can be determined precisely by evaluating the superheat SF. An improvement in moisture sensing in the laundry items is possible by using temperature signals that are easy to determine. The invention offers the possibility of using the measured overheating in combination with existing conductance technology, or with alternative methods for determining the residual moisture in the laundry, e.g. using algorithms from multivariate data analysis as mentioned herein, in which the SH signal is combined with the signals from the Combined conductivity technology can be used. In embodiments of the invention, measured values of the process air, such as temperature, relative humidity and pressure, can also be advantageously used. Going through the individual phases of a drying process and in particular controlling a drying process to achieve a predetermined residual moisture content of the laundry items are possible in embodiments of the invention for each individual loading of the drum with laundry items. The method according to the invention and the dryer according to the invention thus allow an individual, energy-efficient and laundry-friendly implementation of a drying process adapted to the user's requirements.

Due to the present invention, the connection between the degree of dryness of the laundry, i.e. residual moisture, and the difference in water load can serve as an improved switch-off criterion for heating the process air and thus terminating the drying process. This switch-off criterion is generally dependent on the load and the process air volume flow, but is almost independent of the initial residual moisture, with these influencing factors being taken into account in embodiments of the invention.

In addition, this process is robust and inexpensive to implement. It is largely independent of the position or entanglement of the laundry items in the drum. Additionally, the process is fast and can provide calculated moisture levels in virtually real time. Appropriate applies to the dryers described herein that are suitable for carrying out the process.

• 1 einen Trockner gemäß einer nicht eingeschränkten Ausführungsform eines erfindungsgemäßen Trockner;
• 2 einen den Bereich des Verdampfers der im erfindungsgemäßen Trockner eingesetzten Wärmpumpe;
• 3 den Verlauf der Überhitzung SH (Superheating) während eines Trocknungsprozesses;
• 4 den Verlauf der gemessenen Wasserbeladung (Evap in) der Prozessluft am Eingang des Prozessluftkanals in den Verdampfer während eines Trocknungsprozesses; und
• 5 den berechneten Verlauf der spezifischen Enthalpie der Prozessluft während eines Trocknungsprozesses

zeigen.Further details of the invention are provided below with reference to the attached 1 until 5 explained, of which

• 1 a dryer according to a non-limited embodiment of a dryer according to the invention;
• 2 one the area of the evaporator of the heat pump used in the dryer according to the invention;
• 3 the course of superheating SH (superheating) during a drying process;
• 4 the course of the measured water loading (Evap in) of the process air at the inlet of the process air duct into the evaporator during a drying process; and
• 5 the calculated course of the specific enthalpy of the process air during a drying process

show.

The 1 shows a vertical section through an embodiment of a dryer 1 according to the invention, which is designed as a condensation dryer with a heat pump, comprising a condenser and an evaporator. In 1 The long arrows indicate the flow direction of the process air. The short arrows with a blank arrowhead indicate the flow direction of the heat pump's refrigerant.

The in 1 Dryer 1 shown contains a drum 3 which can be rotated about a horizontal axis 12 as a drying chamber for receiving moist laundry items (not shown here), as well as a heat pump 4, 5, 13, 14, having an evaporator 4, a condenser 5, a compressor 13 and a throttle valve 14. Laundry drivers 25 are attached within the drum 3 for moving laundry items during rotation of the drum.

The process air is guided through the drum 3 in the process air duct 2 by means of a fan 6. In the embodiment shown here, in addition to heating the process air by the heat pump, it is also possible to heat the process air by an electrical heating device 21, which can be switched on, for example, for particularly rapid heating of the process air. The heated air is passed from behind, i.e. from the side of the drum 3 opposite a door 22 closing the filling opening, through its perforated bottom into the drum 3. The heated process air thus reaches the drum 3, where moisture is removed from the moist laundry items not shown in the figure.

The warm, moist process air leaves the drum 3 via a lint filter 16 inside the door 22, is diverted downwards and flows in the process air duct 2 to the evaporator 4 of the heat pump, where it is cooled. In the evaporator 4, a refrigerant circulating in the heat pump circuit 4, 5, 13, 14 is evaporated and fed via a compressor 13 to the condenser 5, where the refrigerant returns to the liquid state by releasing heat to the cooled and dehumidified process air flowing in the process air duct 2. The refrigerant, which is in liquid form, is directed to the evaporator 4 via a throttle valve 14, whereby the refrigerant circuit is closed. As a result of cooling, the moisture absorbed from the laundry items by the process air condenses in the evaporator 4 and is collected in a condensate tray 7, from which it can be pumped out for storage or disposal (not shown here). 23 means condensation.

The dryer 1 is controlled via a control unit 10, which can be regulated by the user via an operating unit 24. The dryer 1 also has an evaluation unit 11 in the control unit 10, which evaluates the measured values measured by the sensors.

The heat pump dryer 1 is suitable for carrying out the method according to the invention, in particular the control unit 10 being set up to carry out the method according to the invention.

An optical and/or acoustic display device 17 enables the display of a remaining running time of the drying process with regard to a residual moisture value selected by the user, for example iron dry, or the display of the determined load or other states of the dryer or the display of the status of the drying process, for example in a differentiated color Shape.

At the in 1 In the embodiment shown, the fan 6 and the drum 3 are driven by a common drive motor 18, which in this embodiment is a brushless direct current motor (BLDC).

Two triple sensors 26, 27, namely a triple sensor 27 at the first end 8 of process air duct 2 and a triple sensor 26 at the second end 9 of process air duct 2, are connected to the control unit 8, in particular the evaluation unit 11 contained therein. The triple sensors 27, 28 can each measure a relative humidity, a temperature temperature and the air pressure of the process air and thus provide the measured values that are advantageous for the method according to the invention, so that the residual moisture H of the laundry items and in particular also a load of the drum 3 with laundry items can be determined.

In the drum 3 there is a conductivity sensor 15, which is arranged on a laundry carrier 25, for the additional determination of the laundry moisture.

2 shows the area of the evaporator 4 of the heat pump used in a dryer according to the invention. A first thermometer 28 for measuring the refrigerant temperature T1 is arranged at the refrigerant inlet 19 and a second thermometer 29 for measuring the refrigerant temperature T2 is arranged at the refrigerant outlet 20. The evaporator 2 is in contact with the process air duct 2 in order to dehumidify the warm, moist process air contained therein. The thick solid arrows show the flow direction of the process air and the thin dashed arrows show the flow direction of the refrigerant.

3 shows the course of superheating SH (superheating) during a drying process. You can clearly see that SH initially increases and then decreases towards the end of the drying process, i.e. as time increases. It is this falling part of the SH curve that can be used particularly advantageously for determining residual moisture. This part is highlighted by a dotted tangent.

4 shows the course of the measured water load (Evap in) of the process air at the inlet of the process air duct into the evaporator during a drying process. According to the change of in 3 As shown in the curve shown, the curve of the water load also drops down, which is highlighted by a dotted straight line.

5 shows the calculated course of the specific enthalpy of the process air during a drying process and therefore corresponds in particular to the course of the SH curve in 3 .

REFERENCE SYMBOL LIST

1

Heat pump dryer

2

Process air duct

3

drum

4

Evaporator (of the heat pump)

5

Condenser (condenser) (of the heat pump)

6

fan

7

Condensate pan

8th

First end of the process air duct

9

Second end of the process air duct

10

Control unit

11

Evaluation unit in the control unit

12

Horizontal (rotational) axis

13

compressor (of the heat pump)

14

Expansion unit, expansion (throttle) valve

15

Conductivity sensor in the drum

16

Lint trap

17

Display device, optical and/or acoustic evaluation unit

18

Fan and drum drive motor, BLDC motor

19

Refrigerant inlet at the evaporator

20

Refrigerant leak at the evaporator

21

(electric) heating device

22

door

23

condensation

24

Control unit

25

Laundry take-out

26

First triple sensor (temperature, relative humidity, pressure)

27

Second triple sensor (temperature, relative humidity, pressure)

28

First thermometer (in the refrigerant circuit before the evaporator)

29

Second thermometer (in the refrigerant circuit after the evaporator)

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2468945 B1 [0006]
• EP 2745760 A1 [0006]

Claims (15)

Method for operating a dryer (1) with a drum (3) for holding items of laundry to be treated, a drive motor (18) for the drum (3), a process air duct (2) for guiding process air, in which process air is supplied by means of a fan ( 6) is moved, which is connected at a first end (8) to an air outlet opening of the drum (3) and at a second end (12) to an air inlet opening (9) of the drum (3), a control unit (10), a heat pump arranged in the process air duct (2) with an evaporator (4), a condenser (5), an expansion unit (14) and a compressor (13), with a first thermometer (28) at the refrigerant inlet (19) of the evaporator (4). the measurement of the inlet temperature T1 and a second thermometer (29) for measuring the outlet temperature T2 is arranged at the refrigerant outlet (20) of the evaporator (4), characterized in that the control unit (10) is set up to avoid overheating SH, which can be calculated as the difference T2-T1 to determine a residual moisture H of the laundry items, the method comprising the following steps in a drying process: (a) measuring the inlet temperature T1 at the refrigerant inlet (19) of the evaporator (4) and the outlet temperature T2 at Refrigerant outlet (20) of the evaporator (4); (b) calculation of the superheat SH as the difference T2-T1; and (c) determining the residual moisture of the laundry items from the superheat SH by means of the control unit (10). Procedure according to Claim 1 , characterized in that the superheat SH is measured continuously during the drying process at least over a predetermined period of time Δt _set and if it is determined that the measured superheat SH is essentially constant in the period Δt _set , the measured SH is used as a reference value SH _ref for determining the residual moisture is used. Procedure according to Claim 2 , characterized in that in the period Δt _set the speed of the fan (6) and / or the speed of the compressor (13) is constant. Procedure according to one of the Claims 1 until 3 , characterized in that the drive motor (18) is a BLDC electric motor and its drive power is evaluated with regard to loading the drum (3) with laundry items. Procedure according to one of the Claims 1 until 4 , characterized in that the dryer (1) has at least one sensor for determining measured values of the process air and the control unit for determining the residual moisture links the measured values of the process air and / or calculation variables calculated therefrom with model parameters determined from a prediction model. Procedure according to Claim 5 , characterized in that a dual sensor (26,27) is used as a temperature sensor and as a humidity sensor, which can simultaneously measure the temperature T _P and the relative humidity H _rel of the process air. Procedure according to one of the Claims 1 until 6 , characterized in that it additionally includes the method steps (d) comparing the determined residual moisture H with an upper limit value of the residual moisture H ^set ; and (e) ending the drying process when the specified residual moisture H ^set is reached or falls below. Dryer (1) with a drum (3) for holding items of laundry to be treated, a drive motor (18) for the drum (3), a process air duct (2) for guiding process air, in which process air is moved by means of a fan (6). , wherein the process air duct (2) is connected at a first end (8) to an air outlet opening of the drum (3) and at a second end (12) to an air inlet opening (9) of the drum (3), a control unit (10), a heat pump with an evaporator (3), a condenser (5), an expansion unit (14) and a compressor (13), with a first thermometer (28) for measuring the inlet temperature T1 at the refrigerant inlet (19) of the evaporator (3). and a second thermometer (29) for measuring the output temperature T2 is arranged at the refrigerant outlet (20) of the evaporator (3), and the control unit (10) is set up to calculate from a superheat SH, which can be calculated as the difference T2-T1 to determine the residual moisture of the laundry items. dryer (1). Claim 8 , characterized in that the control unit (10) is set up so that to determine the residual moisture, the superheat SH and / or calculation variables calculated therefrom are linked to model parameters determined from a prediction model. dryer (1). Claim 8 or 9 , characterized in that it has at least one sensor (26,27) for determining measured values of the process air and the control unit (10) is set up to determine the residual moisture, the measured values of the process air and / or to link calculation variables calculated from this with model parameters determined from a prediction model. dryer (1). Claim 10 , characterized in that the at least one sensor (26,27) for determining measured values of the process air comprises a temperature sensor and/or a humidity sensor. dryer (1). Claim 11 , characterized in that a dual sensor or triple sensor is used as a temperature sensor and as a humidity sensor (26,27), which can simultaneously measure the temperature T _P and the relative humidity H _rel of the process air. Dryer (1) according to one of the Claims 8 until 12 , characterized in that it has a conductivity sensor (15) in the drum (3) and the control unit (10) is set up to determine the residual moisture in order to link the moisture value measured with the moisture sensor in the drum with model parameters determined from a prediction model. Dryer (1) according to one of the Claims 8 until 13 , characterized in that the control unit (10) is set up to infer a moisture content H of the laundry items in the drum (3) from the measured current of the drive motor (18). Dryer (1) according to one of the Claims 8 until 14 , characterized in that it has a controllable expansion valve (14) in the heat pump and the control unit (10) is set up to keep the superheat SH in a predetermined temperature range ΔT _SH by regulating the expansion valve (14).

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