DE102015203682A1 - Dryer with a heat pump with variable refrigerant mass and method for its operation - Google Patents

Abstract

The invention relates to a dryer 1 with a drying chamber 2 for objects to be dried, a heat pump with a refrigerant circuit 7 in which a refrigerant circulates, comprising an evaporator 8, a condenser 9, an expansion device 10 and a compressor 11, and a process air duct 3, in which a fan 24 for conveying process air is arranged, wherein evaporator 8 and condenser 9 are thermally coupled to the process air duct 3, and wherein the refrigerant circuit 7, a refrigerant reservoir 12 is connected to the variation of a refrigerant mass in the refrigerant circuit 7. The invention also relates to a method of operating this dryer.

Description

The invention relates to a dryer with a heat pump and a method for operating this dryer. The invention particularly relates to a dryer having a drying chamber, in particular a drum, for objects to be dried, a heat pump with a refrigerant circuit in which a refrigerant circulates, comprising an evaporator, a condenser, an expansion device and a compressor, and a process air duct, in which Blower for conveying process air is arranged, wherein evaporator and condenser are thermally coupled to the process air duct. The invention also relates to a method suitable for operating this dryer.

In a dryer, air (so-called process air) is passed through a fan via a heater into a moist object, usually wet laundry, containing a drying chamber, usually a drum. The hot air absorbs moisture from the objects to be dried. After passing through the drying chamber, the then moist process air is passed into a heat exchanger, which can be preceded by a filter, in particular a lint filter, for filtering out dirt particles, in particular fluff in the case of a tumble dryer or washer-dryer.

This drying process is energy-intensive, because as a rule, the process air is energetically lost before the application of heat to the objects to be dried supplied with the cooling of the process air in the heat exchanger process. By using a heat pump, this energy loss can be significantly reduced. The heat pump can serve to extract heat from the process air flowing from the moist objects, which is supplied to a corresponding heat sink, and to conduct this heat by means of a suitable pumping device to a heat source, from which it arrives at the process air before it is to be dried Subjected objects. Alternatively, heat can also be removed from an environment of the dryer by means of the heat sink and fed to the process air via the heat source.

In a dryer equipped with a compressor-type heat pump (also referred to herein as a "compressor type"), the warm, moisture-laden process air is cooled essentially in a heat sink evaporator of the heat pump, where the heat transferred to evaporate a heat exchanger is used in the heat pump in a so-called refrigerant circuit circulating refrigerant. The vaporized refrigerant passes to the compressor (also referred to herein as a "compressor") and is compressed there. The circulating in the refrigerant circuit refrigerant is driven by the compressor, which provides the necessary energy to operate the pumping process. From the compressor, the refrigerant passes to the condenser, where it is liquefied with the release of heat. The heat released heats the process air. The liquefied refrigerant flows through an expansion device, e.g. a throttle, where its internal pressure is reduced, back to the evaporator, which the circuit is closed. The throttle is in particular executable as a valve, aperture or capillary. Frequently, the refrigerant circuit is operated capillary tube controlled. The condensed water is then generally collected in a condensate tray and collected in a suitable container.

A heat pump clothes dryer with a compressor-type heat pump generally has a closed process air circuit and a refrigerant circuit. If air, ie process air, is sent through the drum loaded with damp laundry, the process air is loaded with water vapor. A drying program or a drying process can generally be subdivided into three phases, namely a heating phase, a quasi-stationary drying phase and a transient drying phase, which are run through in succession. In the heating phase, process air and damp laundry items are usually heated up to a first maximum temperature value T _p . At this temperature, the laundry items are then dried during the quasi-stationary drying phase, in particular with regard to the surface water. During the quasi-stationary drying phase, the relative humidity of the process air at the outlet of the drum is particularly high. During the transition to and during the transient drying phase, the relative humidity decreases and in general the temperature of the process air increases. This is due in particular to the fact that the surface water of the wet laundry is essentially evaporated and the drying phase is dominated by so-called deep drying of the laundry.

In the various drying phases, the requirements for a heat pump are different. It is therefore desirable to adapt the operation of a heat pump to the actual drying phase.

To avoid overheating of the refrigerant circuit, such a tumble dryer often has a further heat exchanger and / or an additional fan. The auxiliary fan is generally rarely in operation, as it only serves to overheat the refrigerant circuit, especially at higher ambient temperatures can result in preventing. The auxiliary fan is generally controlled by a temperature sensor and reduces its temperature when the refrigerant overheats. This happens because air is sucked in at ambient temperature and passed past the compressor. The air heats up and then leaves the dryer again. During operation of the additional fan, therefore, existing heat energy in the dryer to the environment, generally a storage room of the dryer delivered. In order for such a loss of energy can be avoided, it would be desirable to be able to dispense with an additional heat exchanger and / or an additional fan when operating a dryer with a heat pump.

For the control of a heat pump various possibilities are known.

The publication DE 10 2008 043 176 A1 describes a dryer with a drying chamber for objects to be dried, a supply air duct, a process air duct, an exhaust duct and a heat pump with a heat sink and a heat source, wherein the supply air duct and the exhaust duct by means of a mechanism via a recirculating air duct for adjusting a proportion of recirculation and exhaust air can be interconnected in the dryer. The dryer has a first sensor, which is arranged between the drying chamber and the heat sink, for determining a process air temperature and a second sensor for determining a temperature and / or a humidity of an air in a storage room.

Another possibility is to use a heat pump dryer with a variable capacity. Heat pump dryer with a compressor with a variable capacity are known per se.

This is how the publication describes DE 10 2005 041 145 A1 a clothes dryer in which the warm air used to dry the laundry is heated using a heat pump heating system including a variable power compressor. In one embodiment, the tumble dryer includes a control unit that controls or regulates the performance of the compressor in response to the temperature outside the tumble dryer.

The publication EP 2 284 310 A1 describes a dryer with at least one heat pump system, the dryer a process air circuit with a drum for laundry to be dried, at least one cooling circuit, a compressor with a variable rotational speed, a first and a second heat exchanger for each thermal coupling between the process air circuit and the cooling circuit , a control unit for controlling the rotational speed of the compressor and at least one sensor for measuring at least one physical parameter of the process air flow, the coolant and / or the laundry as a function of time. A central control unit is arranged to evaluate the time evolution of the parameters and to reduce the rotational speed of the compressor in accordance with the evaluation of the time dependence of the parameters.

The publication EP 2 182 104 A1 describes a washer-dryer with a compressor-type heat pump containing a speed-controllable compressor motor, such as a DC brushless motor, and a temperature sensor for measuring the outside temperature. The construction of the washer-dryer is intended to ensure that the use of a tubular throttle valve with a fixed orifice prevents the formation of frost on the evaporator when the compressor motor is in a stopped state.

The publication EP 2 415 927 A1 describes a clothes dryer with a heat pump containing a variable speed compressor. This can be avoided that a temperature of the refrigerant in the refrigerant circuit of the heat pump is too high.

The publication DE 10 2007 016 078 A1 describes a condensation dryer with a drying chamber for objects to be dried, a process air circuit in which a heater for heating the process air and the heated process air is guided by means of a blower on the objects to be dried, an air-to-air heat exchanger, a heat pump and a Control unit, by which the condensation dryer is controllable and in which a plurality of selectable programs for controlling the condensation dryer are stored. The programs include phased activation of heat pump, air-to-air heat exchanger and / or heating.

The publication WO 2012/065916 A1 describes a dryer with a heat pump, which contains in its coolant circuit a controllable compressor and a temperature sensor, and a method for its operation, in which the power consumption of the compressor is different in different drying phases.

The publication WO 2011/072999 A2 describes a dryer with a variable restriction expansion device and a sensor for detecting a state of the heat pump, in particular a temperature sensor in Refrigerant circulation. The expansion device is in particular a thermostatic expansion valve.

Against this background, it was an object of the present invention to provide a clothes dryer (also abbreviated herein as a "dryer") with a heat pump, which allows a better adaptation of the operation of the heat pump to a drying process. In particular, an adaptation of the operation of the heat pump to the different phases of a drying process, i. Heating phase, quasi-stationary drying phase and unsteady drying phase, be possible. Preferably, different sized loads of items to be improved should be considered. The object of the invention was also to provide a method for operating this dryer.

The solution of this object is achieved according to this invention by a dryer and a method for operating a dryer with the features of the respective independent claim. Preferred embodiments of the method and the dryer according to the invention are listed in respective dependent claims and the following description, wherein preferred embodiments of the dryer according to the invention correspond to preferred embodiments of the method according to the invention and vice versa, even if this is not explicitly stated herein.

The invention thus relates to a dryer with a drying chamber for objects to be dried, a heat pump with a refrigerant circuit in which a refrigerant circulates, comprising an evaporator, a condenser, an expansion device and a compressor, and a process air duct, in which a blower for transport is arranged by process air, wherein the evaporator and the condenser are thermally coupled to the process air duct, and wherein the refrigerant circuit, a refrigerant reservoir for varying a refrigerant mass in the refrigerant circuit is connected.

In a particularly preferred embodiment of the dryer according to the invention, the refrigerant reservoir is connected to the refrigerant circuit for varying the refrigerant mass via a storage valve. Most preferably, the refrigerant reservoir is connected to the refrigerant circuit via a single pipeline in which the valve is arranged. The valve may be, for example, a two-way valve, a pressure valve, a solenoid valve or an electric control valve.

Alternatively or in addition thereto, the refrigerant reservoir is connected to the refrigerant circuit via at least one additional channel parallel to the refrigerant circuit, wherein the refrigerant mass in the additional channel can be separated from the refrigerant circuit by an upstream and a downstream storage valve.

The refrigerant reservoir may be arranged in different places in the refrigerant circuit. Preferably, the device is arranged in the refrigerant circuit between the condenser and expansion device.

In the refrigerant reservoir, the refrigerant mass is preferably present in liquid form.

The compressor used in the dryer according to the invention may be, for example, an AC compressor or a variable-capacity compressor. Preferably, the compressor is a variable-power compressor, in particular a BLDC compressor.

A further improved control of the heat pump can be achieved in that an expansion valve is arranged in embodiments of the dryer according to the invention in the refrigerant circuit. The expansion device used preferably includes at least one electronic or thermodynamic expansion valve. Preferably, an electronic expansion valve is used.

In a further embodiment of the invention, the expansion device used includes at least two throttles connected in parallel. Each of these throttles is preferably associated with a valve.

A precise control of the heat pump in the dryer according to the invention is particularly possible if a temperature sensor S ^T _{KM is} arranged in the refrigerant circuit. Preferably, the temperature sensor S ^T _{KM is} arranged in the condenser, for example, on ¾ of the refrigerant line in the condenser.

In the dryer according to the invention, the refrigerant reservoir is preferably dimensioned so that it allows an increase in the refrigerant mass in the refrigerant circuit in the range of 20 to 50%, based on an average refrigerant mass in the refrigerant circuit.

The dryer according to the invention has a fan for conveying the process air through the process air duct and the drum. Separate drive motors can be used to drive the drum and blower. However, it has proved to be advantageous for the drive of the fan and drum a common Drive motor, preferably a variable-power drive motor to use. If available in the dryer, a separate drive motor is generally used for the variable-power compressor. The variable-power compressor is then in particular a screw compressor or rotary piston compressor, preferably a rotary piston compressor.

A drying program to be carried out in the dryer according to the invention can be monitored, for example using a conductivity sensor in the drum, so that an optimum refrigerant mass in the refrigerant circuit can be adjusted. In this case, the conductance L _{w of} the laundry items is preferably measured with the conductance sensor as a function of the time t and, for example, the transition from the quasi-stationary to the transient drying phase determined if a predetermined lower conductance L _W ^{min of} the laundry items and / or a predetermined minimum value (ΔL _W / Δt) _{min is reached} for the amount of the time decrease of the conductance L _w . The predefined lower conductance L _W ^{min of} the items of laundry could, for example, correspond to the condition "ironing".

The monitoring of a drying program and thus the determination of an optimum refrigerant mass can also be done using a humidity sensor at an outlet of the drying chamber or drum. In this case, a relative humidity F _rel of the process air leaving the drum is preferably measured with a humidity sensor.

It is preferable to measure a temperature T _KM of the refrigerant in the refrigerant circuit by means of a temperature sensor S ^T _KM and controlling the refrigerant mass in the refrigerant circuit so that the temperature T _KM within a predetermined range T _KM ¹ ≤ T _KM ≤ T _KM ^2. If a temperature T _{KM of} the refrigerant is measured with a temperature sensor S ^T _KM arranged in the refrigerant _circuit, the refrigerant _{mass in} the refrigerant circuit is preferably reduced when the maximum permissible refrigerant temperature T _KM ^{max is} reached or exceeded. If a variable-capacity compressor is used, this can be used in addition to the control of the temperature T _KM so that it is within the range T _KM ¹ ≤ T _KM ≤ T _KM ² .

The value of T _KM ^max depends on the type of the refrigerant and on the location of the mounting of the temperature sensor S ^T _KM in the refrigerant circuit. For example, T _KM ^{max may be} very close to a maximum temperature specified by the manufacturer of a refrigerant for efficient and safe use of the refrigerant. Another factor may be the maximum allowable coil temperature of the drive motor of the compressor. This is influenced by the insulation used and is for example 115 ° C. Another limiting factor that affects T _KM ^max is the lubricant used in the compressor. Too high temperatures can lead to decomposition, in particular carbonization, of the lubricant and thus to its failure and eventually to failure of the compressor. An important factor is also the pressure of the gaseous refrigerant behind the compressor to which the strength of the tubes used must be adapted.

If present in the dryer according to the invention, the temperature sensor or sensors preferably have an elongate body with a temperature-sensitive tip. A preferred temperature sensor is an NTC sensor. Advantageously, for example, a temperature sensor S ^T _KM inclined in the process air circuit in the direction of the evaporator.

The dryer according to the invention generally has a condensate tray for collecting the condensate occurring in the evaporator and optionally in another heat exchanger. From the condensate pan, the condensate is disposed of either by manual emptying or by pumping by means of a condensate pump in a condensate tank, which in turn can be emptied manually, or directly into a sewer system.

In the dryer according to the invention, a heat pump and an air-to-air heat exchanger can be used simultaneously. In this case, heat pump and air-air heat exchanger can complement the cooling of moist, warm process air, for example, the fact that the air-air heat exchanger is used in particular in the event of impending overheating of the refrigerant.

For more rapid heating of the process air, an electric heater may additionally be present in the dryer according to the invention. If the dryer comprises an additional electric heater in one embodiment, a faster heating of the process air and thus a faster drying process in the dryer are possible. However, this would affect a possible energy savings.

The dryer of the invention preferably also comprises an optical and / or acoustic display device which allows the user of the dryer to view e.g. Operating parameters and / or an expected duration of the drying process allows.

• (a) Durchführung eines Trocknungsprogrammes, bei dem zeitlich hintereinander eine Aufheizphase, eine quasistationäre Trocknungsphase und eine instationäre Trocknungsphase durchlaufen werden; und
• (b) Variation der Kältemittelmasse im Kältemittelkreislauf in Abhängigkeit davon, ob eine Aufheizphase, eine quasistationäre Trocknungsphase und eine instationäre Trocknungsphase durchlaufen wird.

The invention also provides a method for operating a dryer with a drying chamber for articles to be dried, a heat pump having a refrigerant circuit in which a refrigerant circulates, comprising an evaporator, a condenser, an expansion device and a compressor, and a process air passage in which a blower for conveying process air is arranged, wherein the evaporator and condenser are thermally coupled to the process air duct and wherein a refrigerant reservoir for varying a refrigerant mass in the refrigerant circuit is connected to the refrigerant circuit, comprising the steps of:

• (A) carrying out a drying program in which a heating phase, a quasi-stationary drying phase and a transient drying phase are passed through one after the other; and
• (B) Variation of the refrigerant mass in the refrigerant circuit depending on whether a heating phase, a quasi-stationary drying phase and a transient drying phase is passed.

In a preferred embodiment of the method, the refrigerant mass in the refrigerant circuit is dependent on the load of the dryer with laundry, wherein in the control unit, a relationship between the refrigerant mass in the refrigerant circuit and the load is deposited. The loading may be entered manually by a user of the dryer, or may be entered automatically by an optional suitable measuring device in the dryer, e.g. a scale, to be determined. Moreover, if a conductivity sensor is present in the drying chamber, the loading can also be determined by measuring the conductivity at the beginning of a drying process.

It is preferred that the refrigerant mass in the refrigerant circuit decreases from the heating phase to the transient drying phase. In particular, it is advantageous if the refrigerant mass in the refrigerant circuit in the heating phase is greatest, is smaller in the stationary drying phase and smallest in the transient drying phase. The reduction of the refrigerant mass at the transitions between heating phase and quasi-stationary drying phase and between the quasi-stationary and the transient drying phase is greater than the variation of the refrigerant mass in the refrigerant circuit during a drying phase.

In a preferred embodiment of the method, the refrigerant storage is connected via a valve to the refrigerant circuit and the filling and emptying of the refrigerant storage takes place with the valve open by generating a pressure gradient between the refrigerant reservoir and the refrigerant circuit by changing the power consumption of the compressor. For example, if it is intended to reduce the refrigerant mass in the refrigerant circuit, a variable-capacity compressor can be operated so that the pressure of the refrigerant in the refrigerant circuit upstream of the valve is greater than in the refrigerant storage. When the valve is open, a flow of refrigerant then flows into the refrigerant reservoir. Accordingly, a variable-capacity compressor in the refrigerant circuit can also be operated so that a reverse pressure gradient is generated, the refrigerant is therefore in the refrigerant reservoir at a higher pressure than in the refrigerant circuit. Then, a flow of refrigerant from the refrigerant storage takes place in the refrigerant circuit. The variable-power compressor is preferably a BLDC compressor.

It is also conceivable to influence the pressure gradient, for example by heating the refrigerant reservoir.

In embodiments of the invention, a self-regulating refrigerant circuit may be provided. A valve between the refrigerant reservoir and the refrigerant circuit may then be unnecessary if necessary. Thus, when using an AC compressor during a drying process in the refrigerant circuit rise the temperature and thus the pressure. This pressure increase can be used to increasingly fill a refrigerant reservoir with a refrigerant during a drying process. Thus, the amount of refrigerant in the refrigerant circuit can be reduced in a desired manner with increasing drying progress in an automatic manner. Due to the reduced amount of refrigerant in the refrigerant circuit decreases in this case, the compressor power. On the other hand, the refrigerant in a refrigerant storage at the beginning of a drying process is at a higher pressure than the refrigerant in the refrigerant cycle. This pressure difference can be used to increase the refrigerant mass in the refrigerant circuit at the beginning of a drying process by at least a portion of the refrigerant mass passes from the refrigerant storage in the refrigerant circuit.

The variation of the refrigerant mass in the process according to the invention can be carried out on the basis of various criteria predetermined by a user of the dryer. For example, it may be predetermined that a drying program should be carried out as energy-optimally and / or gently as possible for the items of laundry. On the other hand, it can also be specified by a user that a drying program should be completed as quickly as possible. In addition, other settings can be made by a user. In any case, an optimal variation of the refrigerant mass in the refrigerant circuit can be performed for each desired program.

When operating a dryer, it makes sense to protect the dryer as well as the laundry items to be dried therein that the temperature of the process air is not too high. Therefore, a temperature T _PL is preferably measured of the process air and, on reaching a predetermined maximum process air temperature T _PL ^max, the power P of the compressor is reduced to a maximum of 0.1 P _max process of the invention by means of an arranged in the process air circuit temperature sensor S ^T _PL. Preferably, the compressor is switched off when a critical process air temperature T _PL ^crit > T _PL ^{max is} reached or exceeded. When present, the temperature sensor S ^T _KM is preferably arranged between the drum and the evaporator.

Preferably, the load of the drum with laundry is taken into account for carrying out the method. In particular, the loading of the drum with laundry items by the control unit is taken into account by storing in the control unit a relationship between a refrigerant mass, a temperature of the refrigerant and a load of laundry items.

In the method according to the invention, the outside temperature T _R can advantageously be taken into account in an installation room of the dryer. The waste heat losses of the dryer are dependent on the ambient temperature, wherein at a high ambient temperature, the temperature difference between the heat-emitting surfaces in the dryer, which can also be referred to as convection surfaces, such as the drum, is lower to the ambient temperature, so that there are lower energy losses due to convection , This leads to a higher end temperature in the refrigerant circuit, which can be critical and could require the switching on of a fan or another heat exchanger, if present in the dryer. In the prior art, the amount of heat dissipated by the process air is usually controlled via an additional fan. However, this would increase the waste heat losses.

In a preferred embodiment, therefore, the inventive method is adapted to the outside temperature of a room installation of the dryer by using a temperature sensor S ^T _AR a temperature T _{R is} measured in the installation room and the refrigerant mass in the refrigerant circuit is varied such that it additionally depends on the measured temperature T _R is so that the temperature of a refrigerant in the refrigerant circuit within a predetermined range T _KM ¹ ≤ T ≤ T _{KM KM} ^2. If present in the dryer according to the invention, preferably also a power consumption of the variable-power compressor is taken into account. Preferably, a speed-controlled compressor is then used as a power-dependent compressor whose speed ω _{K is} varied as a function of the measured temperature T _R.

If it is to be taken into account in the method according to the invention, the temperature T _R in the installation room is measured with a temperature sensor S ^T _AR , which can be arranged at different locations on the dryer, eg in contact with the installation room or inside the dryer. In the latter case, however, it should be ensured that a heat-generating and thus the temperature-increasing operation of the dryer is sufficiently long ago or due to a suitable thermal insulation, the measurement of the temperature T _R can not or hardly influence. Then a temperature measured inside the dryer can be used as a measure of the temperature T _R.

In a preferred embodiment of the method according to the invention, therefore, the outside temperature T _{R is} measured in the installation room with a arranged in the process air circuit temperature sensor S ^T _PL , if a predetermined period of time t _{set has} passed since the implementation of a last drying process and the measurement of the temperature of the process air.

In a drying process, the temperature of the process air rises gradually. As already mentioned, in the heating phase process air and damp laundry items are generally heated up to a first maximum temperature value T _p . In order for this increase in temperature to occur as rapidly as possible, in a preferred embodiment of the method _according to the invention, a possibly present speed-dependent compressor is reached until a predetermined temperature T _qus at which the time increase of the temperature T _{PL of} the process air has dropped to a minimum value power consumption is within the range of 0.9 to 1p _max p, operated. Here, p _{max is} the maximum power consumption of the compressor. According to the invention, this is preferably carried out in connection with a simultaneously increased refrigerant mass in the refrigerant circuit.

The invention has numerous advantages. Thus, the invention allows a flexible adaptation to the wishes of a user of the dryer. In particular, an increased energy efficiency is possible because an improvement in the energy efficiency in the operation of the dryer can be achieved by changing the refrigerant mass in the refrigerant circuit. By changing the refrigerant mass in the refrigerant circuit, in particular a dynamic change, a drying process can optimally to different boundary conditions as well be adapted to different drying targets, ie desired residual moisture and / or drying times. This also allows in particular an increased flexibility with respect to different operating points of the heat pump.

A dryer can always be operated in the energetically optimal operating point, without unnecessarily dissipating heat energy to the surroundings of the dryer, with overheating of the refrigerant circuit being avoided by reducing the refrigerant mass in the refrigerant circuit. In embodiments of the invention this can additionally be assisted by a regulation and in particular reduction of the power introduced into the compressor.

The dryer according to the invention also has the advantage that it allows an energy-efficient and safe implementation of a drying process, wherein in embodiments different installation conditions and different weather conditions and seasons can be optimally taken into account by an outdoor temperature in the installation room of the dryer is taken into account. The invention enables the energy-optimized operation of a dryer with a heat pump without the need for an additional fan in all environmental conditions.

In addition, it is possible to take into account the sensitivity of items of laundry such as wool, silk or lace, by an improved control of the heat pump, the temperature of the process air can be better adapted to the type of laundry. This can be done by changing the refrigerant mass in the refrigerant circuit and in embodiments of the invention additionally by changing the power consumption of a variable-power compressor by, for example, a suitable upper temperature of the refrigerant is set and regulated.

Further details of the invention will become apparent from the following description of non-limiting embodiments of a dryer according to the invention, in which a method according to the invention can be carried out. Reference is made to the 1 to 3 ,

1 shows a vertical section through a dryer according to a first embodiment.

2 shows a vertical section through a dryer according to a second embodiment.

3 shows a vertical section through essential to the invention parts of a third embodiment.

The 1 shows a vertical section through a dryer according to a first embodiment, in which a method to be described below can be performed. Other embodiments are conceivable.

The Indian 1 illustrated dryer 1 has a drum rotatable about a horizontal axis 2 as a drying chamber, within which (laundry) driver 14 are attached to the movement of laundry items, not shown here during a drum rotation. Process air is achieved by means of a blower 24 through the drum 2 in a process air cycle 3 guided. After passing through the drum 2 is the moist, warm process air in the evaporator 8th a heat pump 8th . 9 . 10 . 11 which also has a variable speed compressor 11 , an expansion device 10 , eg one or more throttles, and a condenser 9 having. The in the 1 arrows shown indicate the flow direction of the air or a refrigerant.

That in the evaporator 8th evaporated refrigerant of the heat pump 8th . 9 . 10 . 11 is via the variable speed compressor 11 in the refrigerant circuit 7 to the liquefier 9 directed. In the liquefier 9 the refrigerant liquefies under heat to those in the process air circuit 3 flowing process air. The now in liquid form refrigerant is about as a throttle 10 turn to the evaporator 8th passed, whereby the refrigerant circuit is closed. A temperature sensor S ^T _KM 6 between evaporator 8th and compressors 11 measures the temperature T _{K of} the refrigerant in this embodiment.

One in the dryer 1 in the process air circuit 3 between drum 2 and evaporator 8th mounted temperature sensor S ^T _PL 5 is used to measure the temperature T _{PL of} the process air or, if the dryer has been switched off for a sufficiently long time 1 for measuring the temperature T _R in the installation room, which can also be used in this embodiment for controlling the dryer or its heat pump.

When in the 1 embodiment shown is also an electric heater 13 present, which can be used for a more rapid heating of the process air. In other embodiments of the invention may be applied to the electric heater 13 be waived.

In the dryer 1 of the 1 is from the liquefier 9 or the electric heater 13 heated air from the rear, ie from the one of the filling port closing access door 17 opposite side of the drum 2 through whose perforated bottom into the drum 2 passed, comes with the not shown here, to be dried Laundry items in contact and flows through the filling opening of the drum 2 to a lint filter 21 inside the access door 17 , Subsequently, the process air flow in the access door 17 deflected downwards. The process air is in the process air cycle 3 the evaporator 8th fed, in which the warm, laden with moisture process air is cooled. The separated moisture is in a condensate tray 25 collected from where it can be removed, for example, by pumping, for example, in a condensate tank, not shown here.

The drum 2 will be at the in the 1 shown embodiment on the rear floor by means of a pivot bearing and front by means of a bearing plate 18 stored, with the drum 3 with a brim on a sliding strip 19 on the bearing plate 18 rests and is held at the front end. The control of the condensation dryer 1 via a control unit 4 by the user via a control unit 20 can be regulated.

A refrigerant reservoir 12 allows the variation of the refrigerant mass in the refrigerant circuit 7 ,

An optical / acoustic display device 16 allows the user of the dryer the display of eg operating parameters and / or an expected duration of the drying process.

In the process of operation, process air is repeated through the process air cycle 3 circulates until preferably a desired degree of drying of the laundry items is reached. The dryer of the 1 made possible by varying the refrigerant mass in the refrigerant circuit 7 a precise control of the operation of the heat pump and in particular the temperature of the refrigerant, so that a drying phase can be controlled efficiently. In addition, the blower 24 and the variable-power compressor 11 be controlled so that a predetermined maximum temperature T _{max is} not exceeded for the temperature of the process air. Overall, an energy-efficient operation of the dryer is achieved.

In the embodiment shown here, the drum 2 and the fan 24 through a common, in the 1 not shown, power variable electric motor, here a BLDC motor, driven. Another, also in the 1 Not shown, power variable electric motor is used to drive the variable-power compressor 11 ,

In this method, by evaluating sensor signals of a sensor, a transition between the individual drying phases, for example, from the quasi-stationary to non-stationary drying phase, determined so that the refrigerant mass in the refrigerant circuit 7 can be set optimally.

At the in 1 shown embodiment of a suitable for carrying out the process dryer can for this purpose a conductivity sensor 22 in the drum 2 be used, with the conductance sensor 22 the conductance L _w in the 1 Laundry items not shown as a function of the time t is measured. The transition from, for example, the quasi-stationary to the transient drying phase is determined when a predetermined lower conductance L _W ^{min of} the laundry items and / or a predetermined minimum value (ΔL _W / Δt) _{min has been reached} for the amount of time reduction of the conductance L _w .

At the in 1 shown dryer is also at an output of the drum 2 a humidity sensor 23 for measuring a relative humidity F _rel of the drum 2 leaving the process air. By measuring the relative humidity F _rel , the course of a drying program and, in particular, a transition between heating phase, quasi-stationary drying phase and transient drying phase can be monitored, so that the refrigerant mass in the refrigerant circuit can be optimally adapted to the drying progress.

2 shows a vertical section through a dryer according to a second embodiment.

In a process air duct 3 becomes process air by means of a blower 24 led in a circle. After heating the process air in the condenser 9 A heat pump brings the heated process air into the drum 2 in which moist laundry items, not shown here, are dried by means of the heated process air. The drum 2 is rotatably mounted. Damp-warm process air then leaves the drum 2 and gets to the evaporator 8th the heat pump in which it is cooled. The condensing moisture is in a condensate tray 25 collected. Subsequently, the cooled and dehumidified process air in the condenser 9 the heat pump is reheated and returned to the drum 2 directed. Evaporator 8th and liquefier 9 are in a refrigerant circuit 7 arranged in which in this embodiment, a variable-power compressor 11 and an expansion device 10 are located. The expansion device 10 consists of an electric expansion valve. Parallel to the refrigerant circuit 7 are two additional channels 27 arranged, in each of which a refrigerant storage 12 located. In front and behind the refrigerant storage tanks 12 are storage valves 26 . 26 ' . 26 '' and 26 ''' arranged, with which in the refrigerant storage 12 stored refrigerant can be separated from the refrigerant circuit. The refrigerant mass in the refrigerant storage tanks 12 can with at least partially opened storage valves 26 . 26 ' . 26 '' and 26 ''' at an existing overpressure in the refrigerant circuit 7 promoted become. Conversely, at a negative pressure in the refrigerant storage 12 the refrigerant mass in the refrigerant circuit 7 be reduced by adding these to the refrigerant storage 27 is transported. In this way, the operation of the heat pump can be precisely controlled and adapted to a drying phase. 4 means a control unit of the dryer.

3 shows a vertical section through essential parts of a third embodiment of a dryer.

This is only part of a refrigerant circuit 7 shown. In the refrigerant circuit 7 refrigerant (indicated by a closed arrow) flows from the condenser 8th via an expansion device 10 to the evaporator 8th , To the refrigerant circuit 7 is via an adjustable storage valve 26 a refrigerant reservoir 12 connected, with a refrigerant mass in the refrigerant circuit 7 can be varied. In the embodiment shown here, the special configuration of the expansion device allows an additional possibility for the control of the heat pump and thus of the dryer. The expansion device 10 includes namely in the in 3 shown embodiment connected in parallel with an expansion valve 28 , which is in particular an electronic expansion valve, and a throttle 29 , which in the flow direction of the refrigerant, a valve 15 (also referred to herein as "throttle valve") upstream.

The 3 serves only to illustrate possibilities of additional influence on the refrigerant circuit 7 , So also two chokes can be connected in parallel.

LIST OF REFERENCE NUMBERS

1

 dryer

2

Drum, drying chamber

3

 Process air circuit

4

 control unit

5

Temperature sensor S ^T _PL ; for measuring the temperature T _{PL of} the process air in the process air circuit between the drum and the evaporator

6

Temperature sensor S ^T _KM; in the refrigerant circuit for measuring a temperature T _{K of} the refrigerant

7

 Refrigerant circulation

8th

 Evaporator

9

 condenser

10

 Expansion device, e.g. one or more throttles

11

 Compressor, variable-capacity compressor, variable-speed compressor

12

 Refrigerant storage

13

 Electric heater

14

 laundry agitator

15

 Adjustable valve before throttle, throttle valve

16

 optical / acoustic display device

17

 access door

18

end shield

19

lubricating strip

20

operating unit

21

lint

22

 Conductance sensor (in the drum)

23

 Humidity sensor (to determine relative humidity)

24

 fan

25

Drain pan

26, 26 ', 26' ', 26' ''

memory valve

27

 additional channel

28

 Expansion valve, thermodynamic or electronic

29

 throttle

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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

• DE 102008043176 A1 [0009]
• DE 102005041145 A1 [0011]
• EP 2284310 A1 [0012]
• EP 2182104 A1 [0013]
• EP 2415927 A1 [0014]
• DE 102007016078 A1 [0015]
• WO 2012/065916 A1 [0016]
• WO 2011/072999 A2 [0017]

Claims (15)

Dryer ( 1 ) with a drying chamber ( 2 ) for objects to be dried, a heat pump with a refrigerant circuit ( 7 ) in which a refrigerant circulates, comprising an evaporator ( 8th ), a liquefier ( 9 ), an expansion device ( 10 ) and a compressor ( 11 ), as well as a process air channel ( 3 ), in which a blower ( 24 ) is arranged for the transport of process air, wherein evaporator ( 8th ) and liquefier ( 9 ) thermally with the process air channel ( 3 ), characterized in that to the refrigerant circuit ( 7 ) a refrigerant storage ( 12 ) for varying a refrigerant mass in the refrigerant circuit ( 7 ) connected. Dryer ( 1 ) according to claim 1, characterized in that the refrigerant reservoir ( 12 ) for varying the refrigerant mass via a storage valve ( 26 . 26 ' . 26 '' . 26 ''' ) to the refrigerant circuit ( 7 ) connected. Dryer ( 1 ) according to claim 1 or 2, characterized in that the refrigerant reservoir ( 12 ) to the refrigerant circuit ( 7 ) via at least one to the refrigerant circuit ( 7 ) parallel additional channel ( 27 ), wherein the refrigerant mass in the additional channel ( 27 ) by an upstream and a downstream storage valve ( 26 . 26 ' . 26 '' . 26 ''' ) from the refrigerant circuit ( 7 ) can be separated. Dryer ( 1 ) according to one of claims 1 to 3, characterized in that the refrigerant reservoir ( 12 ) in the refrigerant circuit ( 7 ) between condenser ( 9 ) and expansion device ( 10 ) is arranged. Dryer ( 1 ) According to one of claims 1 to 4, characterized in that the compressor ( 11 ) is a variable-power compressor. Dryer ( 1 ) according to claim 5, characterized in that the compressor ( 11 ) is a BLDC compressor. Dryer ( 1 ) according to one of claims 1 to 6, characterized in that the expansion device ( 10 ) at least one electronic or thermodynamic expansion valve ( 28 ) includes. Dryer ( 1 ) according to one of claims 1 to 7, characterized in that the expansion device ( 10 ) at least two reactors connected in parallel ( 29 ) includes. Dryer ( 1 ) according to one of claims 1 to 8, characterized in that in the refrigerant circuit ( 10 ) a temperature sensor S ^T _KM ( 6 ) is arranged. Dryer ( 1 ) according to claim 9, characterized in that the temperature sensor S ^T _KM ( 6 ) in the liquefier ( 9 ) is arranged. Dryer ( 1 ) according to one of claims 1 to 10, characterized in that the refrigerant reservoir ( 12 ) is dimensioned so that it increases the refrigerant mass in the refrigerant circuit ( 7 ) in the range of 20 to 50%, based on a mean refrigerant mass in the refrigerant circuit ( 7 ). Method for operating a dryer ( 1 ) with a drying chamber ( 2 ) for objects to be dried, a heat pump with a refrigerant circuit ( 7 ) in which a refrigerant circulates, comprising an evaporator ( 8th ), a liquefier ( 9 ), an expansion device ( 10 ) and a compressor ( 11 ), as well as a process air channel ( 3 ), in which a blower ( 24 ) is arranged for the transport of process air, wherein evaporator ( 8th ) and liquefier ( 9 ) thermally with the process air channel ( 3 ) and to the refrigerant circuit ( 7 ) a refrigerant storage ( 12 ) for varying a refrigerant mass in the refrigerant circuit ( 7 ), comprising the steps; (A) carrying out a drying program in which a heating phase, a quasi-stationary drying phase and a transient drying phase are passed through one after the other; and (b) variation of the refrigerant mass in the refrigerant circuit ( 7 ) depending on whether a heating phase, a quasi-stationary drying phase and a transient drying phase is passed through. A method according to claim 12, characterized in that the refrigerant mass in the refrigerant circuit ( 7 ) depends on the load of the dryer ( 1 ) with laundry items, whereby in the control unit ( 4 ) a relationship between the refrigerant mass in the refrigerant circuit ( 7 ) and the load is deposited. A method according to claim 12 or 13, characterized in that the refrigerant mass in the refrigerant circuit ( 7 ) decreases from the heating phase to the transient drying phase. Method according to one of claims 12 to 14, characterized in that the refrigerant reservoir ( 12 ) via a storage valve ( 26 ) with the refrigerant circuit ( 7 ) and the filling and emptying of the refrigerant storage with open storage valve ( 26 ) by generating a pressure gradient between the refrigerant reservoir ( 12 ) and refrigerant circuit ( 7 ) by changing the Power consumption of a variable-power compressor ( 11 ) he follows.

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