EP1983095B1 - Laundry drier with a heating in the heat pump circuit - Google Patents

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.

In EP 1 650 343 a device is described which comprises a heater between the evaporator and compressor, which serves to prevent the suction of liquid medium by the compressor at the beginning of the process.

Object of the present invention is therefore to provide a tumble dryer of this type, which also prevents the suction of liquid medium well.

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, since smaller flow cross sections are present in the heat pump cycle. In addition, the medium of the heat pump cycle not burdened with fluff and the like, so that the problem of blockage of the heating does not arise.

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

According to the claim, the controller is configured to activate the heater in response to a temperature difference ΔT, where ΔT = T1-T2, where T1 is a temperature of the medium between the condenser and the evaporator, and T2 is a temperature of the medium between the evaporator and the compressor is.

In a preferred embodiment, the heater is arranged in the heat pump cycle between the evaporator and the compressor. This is advantageous because there the medium has a relatively low temperature, so that it can be heated efficiently.

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.

Further preferred embodiments will become apparent from the dependent claims and from the following description with reference to FIG. This shows a block diagram of the most important components of an embodiment of the tumble dryer.

The device 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 from 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 an evaporator 6 and then via a heater 9 back to the compressor 2. The evaporator 6 serves to cool the process air and their water in this way to withdraw, while the condenser 3 serves to reheat the process air so that they new Can absorb 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 configured controller 8 and suitable temperature sensors 40, 41. Preferably, at least the temperature T1 at the inlet of the throttle body 5 is measured.

The heater 9 is preferably designed as an electric heater (ie resistance heating), which is arranged for example 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". 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 the heater 9 and the compressor 2. In principle, however, another temperature value can also be used in the heat pump cycle be used between the evaporator 6 and the compressor 2.

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.

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 (14)

1. Laundry 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 removing water and for reheating the process air,
   a heat pump circuit for guiding a medium through a condenser (3), a throttling device (5), an evaporator (6) and a compressor (2) back to the condenser (3), wherein the process air is heatable by means of the condenser (3) and the process air is cooled by means of the evaporator (6),
   wherein a heater (9) is arranged in the heat pump circuit and wherein the controller (8) is adapted to activate the heater (9) when there is a risk that the compressor (2) sucks liquid medium,
   characterized in that the controller (8) is adapted to activate the heater (9) depending on a temperature difference ΔT, wherein ΔT = T1 - T2, wherein T1 is a temperature of the medium between the condenser (3) and the evaporator (6) and wherein T2 is a temperature of the medium between the evaporator (6) and the compressor (2).
2. Laundry dryer according to claim 1,
   wherein the heater (9) is arranged between the evaporator (6) and the compressor (2) in the heat pump circuit.
3. Laundry dryer according to claim 2,
   wherein the heater (9) is regulated or controlled in such a way that it heats up the medium entering the compressor, at least in a start phase of the laundry dryer, to 20 to 45°C.
4. Laundry dryer according to claim 1,
   wherein the heater (9) is arranged between the compressor (2) and the condenser (3) in the heat pump circuit.
5. Laundry dryer according to one of the preceding claims, wherein an additional heat exchanger (4) is arranged in the heat pump circuit, additionally to the heater (9), by means of which heat is removed from the heat pump circuit.
6. Laundry dryer according to claim 5,
   wherein the additional heat exchanger (4) is arranged between the condenser (3) and the throttling device (5).
7. Laundry dryer according to one of the preceding claims, wherein T1 is a temperature between the condenser (3) and the throttling device (5).
8. Laundry dryer according to claim 6,
   wherein T1 is a temperature between the additional heat exchanger (4) and the throttling device (5).
9. Laundry dryer according to one of the preceding claims, wherein T2 is a temperature of the medium between the heater (9) and the compressor (2).
10. Laundry dryer according to one of the claims 7 to 9, wherein the controller (8) is adapted to compare ΔT with the temperature T2 in order to determine if the heater (9) has to be activated, and particularly, if the controller is adapted thereto, to activate the heater (9) when the condition T1 - T2 > k·T2 is fulfilled, with T1 and T2 in °C and k = 0.1 to 10, particularly k = 1.
11. Laundry dryer according to one of the preceding claims, wherein the controller (8) is adapted
    to increase the temperature of the medium in the heat pump circuit by means of the heater (9) in the start phase at the beginning of a drying process and
    to activate the heater (9) only when there is the risk that the compressor (2) sucks liquid medium in the operation phase after the start phase.
12. Laundry dryer according to claim 11,
    wherein the device is adapted to end the start phase after a fixed preset time and/or to end it latest when a temperature in the process circuit or the heat pump circuit has reached a threshold value, particularly when a temperature of the medium between the condenser (3) and the evaporator (6) surpasses a threshold value between 60 to 70°C.
13. Laundry dryer according to one of the preceding claims, wherein the heater (9) is an electric heater.
14. Laundry 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 a maximum value and to inhibit an activation of the heater (9) when the maximum value has been reached.

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