EP2006437A1 - Laundry drier with heating in heat pump circuit - Google Patents

Abstract

The dryer has a controller (8), and a drum (1) for accommodating clothes to be dried. A process circuit conducts heated process air through the drum for cooling the process air for dewatering and for reheating the process air. A heat pump circuit conducts a medium e.g. liquid medium, through a condenser (3), a throttle (5), an evaporator (6) and a compressor (2). The process air is heatable by the condenser and coolable by the evaporator. A heater (9) i.e. electric heater, is arranged in the heat pump circuit between the evaporator and the condenser.

Description

The invention relates to a tumble dryer according to the preamble of claim 1.

Dryers of this type, which are used for cooling and heating of the evaporator and the condenser of a heat pump cycle, are characterized by a high efficiency.

In EP 1 884 586 a device of this type is described, which is equipped with an additional heating in the process cycle, which allows it, especially in the starting phase, to raise the temperature quickly. However, additional heaters of this type are disadvantageous because they produce additional flow resistance in the process cycle, are susceptible to contamination and can even lead to ignition over flying lint.

Object of the present invention is therefore to provide a tumble dryer of this type, which avoids these disadvantages at least partially.

This object is achieved by the tumble dryer according to claim 1.

Accordingly, therefore, a heater is provided in the heat pump cycle. Thus, the system can therefore be supplied via the heat pump cycle energy, which in the process cycle no additional heating or only an additional heater lower power is required.

The medium in the heat pump cycle can be heated more easily than the air in the process cycle, as there are smaller flow cross sections in the heat pump cycle. In addition, the medium of the heat pump cycle is not burdened with lint and the like, so that the problem of clogging of the heating is not.

The heating in the heat pump cycle can also be constructed more compact and cheaper than one in the process cycle.

In a preferred embodiment, the heater is arranged in the heat pump cycle between the condenser and the evaporator. This is advantageous because there the medium is liquid, whereby a good heat transfer is achieved. Even more advantageous is the arrangement of the heater between the throttle body and the evaporator, i.a. since in this case directly evaporates refrigerant through the supplied heating power and so a large power can be introduced into the system.

The booster heater can be used by the controller of the device to raise the temperature in the heat pump cycle with the heater at the beginning of a drying process. Further, the controller may be configured to activate the heater in an operating phase, after the start phase, only if there is a risk that the compressor sucks in liquid medium.

Advantageously, in addition to the heating in the heat pump circuit, an additional heat exchanger is arranged, with which the heat pump cycle heat can be withdrawn.

• Fig. 1 ein Blockdiagramm der wichtigsten Komponenten einer ersten Ausführung des Wäschetrockners und
• Fig. 2 ein Blockdiagramm einer zweiten Ausführung des Wäschetrockners.

Further preferred embodiments will become apparent from the dependent claims and from the following description with reference to FIGS. These show:

• Fig. 1 a block diagram of the main components of a first embodiment of the tumble dryer and
• Fig. 2 a block diagram of a second embodiment of the tumble dryer.

The device after Fig. 1 has a drum 1 for receiving the laundry to be dried. It is a process cycle provided (which in Fig. 1 shown by solid lines), in which heated process air passed through the drum 1, then cooled and then reheated and fed back into the drum 1.

A blower 10 serves to pump over the process air.

Further, a heat pump cycle is provided (the path of the pumped by the heat pump cycle medium in Fig. 1 shown with dotted lines). The medium is conveyed by a compressor 2 to a condenser 3, from there to an additional heat exchanger 4, then via a throttle body 5, for example in the form of capillaries or an expansion valve, to an evaporator 6 and then back to the compressor 2 via a heater 9 The evaporator 6 serves to cool the process air and thereby remove water from it, while the condenser 3 serves to reheat the process air so that it can absorb new water.

How out Fig. 1 further seen, a fan 7 is provided, with which ambient air is passed through the additional heat exchanger 4 in order to cool it.

The additional heat exchanger 4 serves to extract heat from the heat pump cycle and thus the entire system and to deliver it to the ambient air. Preferably, the amount of heat extracted is controlled depending on the temperature in the heat pump cycle (and / or depending on the temperature in the process loop), eg by operating the blower 7 at a higher power as the temperature rises. The function and operation of the additional heat exchanger are described in detail in EP 1 884 586 described.

The temperature T1 of the medium running in the heat pump cycle is preferably used after the additional heat exchanger 4 and before the throttle element 5 for controlling the blower 7. However, another temperature of the process cycle or heat pump cycle may be used, for example, that of the medium before the auxiliary heat exchanger 4.

For driving the fan 7, the device has a correspondingly designed controller 8 and suitable temperature sensors 40, 41. Preferably, at least the temperature T1 measured at the inlet of the throttle body 5.

The heater 9 is preferably configured as an electric heater (i.e., resistance heater) which is e.g. is arranged on the outside of the tube of the medium and this heats directly. It is activated by the controller 8 depending on the respective process phase and the process parameters.

The heater 9 has two tasks, which can be used individually or in combination in a specific embodiment of the device.

On the one hand, the heater 9 serves to supply thermal energy to the system in the starting phase. As a result, the temperatures required for efficient drying can be achieved more quickly, whereby the time required to dry the laundry can be reduced. The compressor thus works practically from the beginning in the optimum range. The heat, which is supplied from the heater 9 to the medium, is pumped by the compressor to a higher temperature level. Thus, the process circuit is heated by the condenser 3 from the beginning with full heating power.

On the other hand, the heater 9 serves to prevent in the operating phase, after the start phase, that the compressor 2 sucks liquid medium. A suction of liquid medium can lead to damage of the compressor and is therefore undesirable. Thus, an optimal overheating of the suction gas can always be ensured (no liquid). But the overheating reserve can be made small, since the heater 9 is able to raise the temperature T2 before the compressor 2, if necessary, quickly.

For supplying energy in the starting phase, the heater 9 is activated by the controller at the beginning of the process, whenever the temperature T2 of the medium entering the compressor 2 is below a predefined "intake temperature range". Of the "Intake temperature range" is the temperature range in which the temperature T2 is in the operating phase, ie after the end of the starting phase. Typically, the device is designed so that the intake temperature range is around 20 ° C to 45 ° C. In the condenser 3, the temperature in this case, for example, about 75 ° C and in the evaporator, for example, about 25 ° C, so that in the process cycle an efficient dehydration can take place.

The startup phase may take a fixed predetermined time, e.g. around 10 minutes. The starting phase can also be terminated in advance if a temperature in the process cycle or heat pump cycle has reached a threshold, in particular if the temperature T1 (or otherwise a temperature between the condenser 3 and the evaporator 6) has reached such a threshold. For the temperature T1, this threshold is e.g. at 60 to 70 ° C.

ein Mass für dieses Risiko ist. Insbesondere kann, wie in EP 1 884 586 erwähnt, die Temperaturdifferenz ΔT mit der Temperatur T2 verglichen werden. Deshalb vergleicht die Steuerung 8 vorzugsweise die Temperaturdifferenz ΔT mit der Temperatur T2 um zu entscheiden, ob die Heizung 9 aktiviert werden soll. Insbesondere kann sie die Heizung 9 immer und nur dann aktivieren, wenn die Bedingung T1 - T2 > k·T2 erfüllt ist, wobei k zwischen 0.1 und 10 liegt, vorzugsweise k = 1, und wobei T1 und T2 in °C angegeben sind.After the start phase, the heater 9 is activated by the controller 8 only if there is a risk that the compressor 2 sucks liquid medium. As in EP 1 884 586 By monitoring temperatures T1 and T2, it is possible to estimate this risk. In particular, it turns out that the temperature difference $$\mathrm{.DELTA.T}\mathrm{=}\mathrm{T}\mathrm{1}\mathrm{-}\mathrm{T}\mathrm{2}$$

a measure of this risk is. In particular, as in EP 1 884 586 mentioned, the temperature difference .DELTA.T be compared with the temperature T2. Therefore, the controller 8 preferably compares the temperature difference ΔT with the temperature T2 to decide whether the heater 9 should be activated. In particular, it can activate the heater 9 whenever and only if the condition T1-T2> k · T2 is satisfied, where k is between 0.1 and 10, preferably k = 1, and T1 and T2 are given in ° C.

In this case, T1 preferably corresponds to the temperature of the medium between the condenser 3 and the evaporator 6, in particular between the condenser 3 and the throttle body.

On the other hand, the temperature T2 is the temperature between heater 9 and compressor 2. In principle, however, another temperature value in the heat pump cycle between the evaporator 6 and the compressor 2 can be used.

1. a) Die Temperatur des Mediums ist zwischen dem Verdampfer 6 und dem Kompressor 2 gering, so dass das Medium dort effizient geheizt werden kann.
2. b) Droht das Risiko, dass der Kompressor 2 flüssiges Medium ansaugt, so kann die Temperatur des angesaugten Mediums direkt und schnell beeinflusst werden.

In the embodiment described so far, the heater 9 is located between the evaporator 6 and the compressor 2. This arrangement is advantageous for various reasons:

1. a) The temperature of the medium is low between the evaporator 6 and the compressor 2, so that the medium can be heated efficiently there.
2. b) If the risk of compressor 2 sucking in liquid medium threatens, the temperature of the aspirated medium can be directly and quickly influenced.

However, even more advantageous is the arrangement of the heater between the condenser and the evaporator, since this area, the medium is liquid, so that a more efficient heat transfer can take place, because the heat transfer coefficient of the liquid medium is greater than the suction gas.

Particularly advantageous is the arrangement, as in Fig. 2 is shown, in which the heater 9 is arranged between the throttle body 5 and evaporator 6, since in this area directly evaporated refrigerant with the heat supplied and so a greater power can be introduced into the system.

The suction gas temperature is in this embodiment (in contrast to the execution after Fig. 1 ) is not increased (at least not over the process air temperature) and thus the mass flow of the refrigerant is not reduced. There is even an increase in the evaporation pressure, which increases the mass flow of refrigerant can be. Thus, the tumble dryer can be brought to operating temperature faster.

In contrast, the execution according to Fig. 1 the disadvantage that the heating power is fed to the almost or already completely gaseous medium, which causes it to heat up strongly, but without absorbing very large amounts of energy (no phase change). The supplied power is limited in this case by the rapidly increasing gas temperature (relatively small heat capacity). At the same time, the mass flow of refrigerant decreases because the density of the suction gas decreases (the evaporation pressure can hardly be influenced in this variant).

In principle, however, an arrangement of the heater 9 between the compressor 2 and the capacitor 3 is conceivable. This arrangement has the advantage that the risk of overheating of the compressor 2 is lower. In this case, care should be taken that despite heating operation, the medium in the condenser 3 condenses out completely. For this purpose, one or more temperatures between the heater 9 and the additional heat exchanger 4 can be monitored. Preferably, the temperature difference between the condenser 3 and the medium after the condenser 3 and before the additional heat exchanger 4 is monitored: this temperature difference drops below a predetermined value of e.g. 3 ° K, this is an indication that there is no complete condensation, in which case the power of the heater is to be reduced.

Preferably, the power of the heater 9, as mentioned, is limited in the starting phase via the temperature T2 and the length of the starting phase is limited by the temperature T1 or the time. However, a limitation of the heater 9 via a different temperature in the heat pump cycle is also possible in principle. However, the limitation over the temperature T2 has the advantage that can be responded to impending overheating of the compressor nimble by the temperature T2 is compared by the controller 8 with an upper limit and, at Reaching the upper limit, activating the heater 9 is suppressed.

The heater 9 may be single-stage, multi-stage or continuously (analog) controlled. It can also be operated clocked. It is dimensioned so that it is able to supply the system with sufficient heat output. For example, it may have a maximum power of 1000 watts compared to the compressor power of e.g. 700 - 1000 watts.

The present invention can be used independently of the medium used in the heat pump cycle. The embodiment described here works, for example, with R134a, the same principle can be used with appropriate dimensioning but also eg in a CO ₂ cycle.

Claims (16)

Tumble dryer with
a controller (8),
a drum (1) for receiving laundry to be dried,
a process circuit for guiding heated process air through the drum (1), for cooling the process air for the purpose of dehydration and for reheating the process air,
a heat pump circuit for guiding a medium through a condenser (3), a throttle body (5), an evaporator (6) and a compressor (2) back to the condenser (3), wherein the condenser (3) the process air heated and with the Evaporator (6) the process air can be cooled,
characterized in that in the heat pump cycle, a heater (9) is arranged. Clothes dryer according to claim 1, wherein the heater (9) in the heat pump cycle between the condenser (3) and the evaporator (6) is arranged. Laundry dryer according to one of the preceding claims, wherein the heater (9) in the heat pump cycle between the throttle body (5) and the evaporator (6) is arranged. The tumble dryer according to claim 1, wherein the heater (9) is disposed in the heat pump cycle between the evaporator (6) and the compressor (2), and in particular wherein the heater (9) is controlled to control the medium entering the compressor at least in a start phase of the clothes dryer heats up to 20 to 45 ° C. Clothes dryer according to claim 1, wherein the heater (9) is arranged in the heat pump cycle between the compressor (2) and the condenser (3). Laundry dryer according to one of the preceding claims, wherein in the heat pump cycle in addition to the heater (9) an additional heat exchanger (4) is arranged, with which the heat pump cycle heat is withdrawn. Clothes dryer according to claim 6, wherein the additional heat exchanger (4) between the condenser (3) and the throttle body (5) is arranged. Clothes dryer according to one of the preceding claims, wherein the controller (8) is adapted to activate the heater (9) when there is a risk that the compressor (2) sucks in liquid medium. The tumble dryer of claim 8, wherein the controller (8) is configured to activate the heater (9) in response to a temperature difference ΔT, where ΔT = T1-T2, where T1 is a temperature of the medium between the condenser (3) and the evaporator (6), in particular between the condenser (3) and the throttle body (5), and wherein T2 is a temperature of the medium between the evaporator (6) and the compressor (2). Laundry dryer according to claims 6 and 8, wherein T1 is a temperature of the medium between the additional heat exchanger (4) and the throttle body (5). A tumble dryer according to any one of claims 9 or 10, wherein T2 is a temperature of the medium between the heater (9) and the compressor (2). A clothes dryer according to any of claims 9 to 11, wherein the controller (8) is adapted to compare ΔT with the temperature T2 to determine if the heater (9) is to be activated, and in particular when the controller (8) is arranged thereto is to activate the heater (9) when the condition T1 - T2> k · T2 is satisfied, with T1 and T2 in ° C and k = 0.1 to 10, in particular k = 1. Dryer according to one of claims 8 to 12, wherein the controller (8) is designed to
in a starting phase at the beginning of a drying process, raise the temperature of the medium in the heat pump cycle with the heater (9) and
in an operating phase, after the start phase has elapsed, only activate the heater (9) if there is a risk of the compressor (2) sucking in liquid medium. Dryer according to claim 13, wherein the device is designed so that the start phase is terminated after a fixed predetermined time and / or at the latest when a temperature in the process cycle or heat pump cycle has reached a threshold, especially if a temperature of the medium between the Capacitor (3) and the evaporator (6) exceeds a threshold between 60 to 70 ° C. Laundry dryer according to one of the preceding claims, wherein the heater (9) is an electric heater (9). Clothes dryer according to one of the preceding claims, wherein the controller (8) is adapted to compare a temperature (T2) between the heater (9) and the compressor (2) with an upper limit and activating the heater (9) upon reaching the Suppress upper limit.

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