DK2468949T3

DK2468949T3 - Dryer with temperature-controlled additional heat exchanger

Info

Publication number: DK2468949T3
Application number: DK11009967.8T
Authority: DK
Inventors: Roland Gerig
Original assignee: V Zug Ag
Priority date: 2010-12-24
Filing date: 2011-12-19
Publication date: 2016-09-12
Also published as: CH701685B1; EP2468949A3; PL2468949T3; EP2468949B1; AU2011265517A1; CH701685A2; CN102560988A; SI2468949T1; EP2468949A2

Description

Field of invention

The invention relates to a laundry dryer with a heat pump and an additional heat exchanger as well as to a method for its operation.

Background A laundry dryer with heat pump generally comprises a drum for receiving the laundry to be dried, which is arranged in a processing air circuit. In the processing air circuit warmed up processing air is led through the drum, then it is cooled down for extracting water therefrom, heated up again and led back to the drum. In addition to this, there is a heat pump circuit in which a fluid is fed through a condenser, an expansion member (expansion valve), an evaporator and a compressor back to the condenser. The processing air is heated up by means of the condenser and cooled down by means of the evaporator .

In CH 699 018 a laundry dryer is described, which has an additional heat exchanger arranged in its processing air circuit in order to remove heat from the system. The operation of the additional heat exchanger is controlled as a function of the temperature of the processing air.

In EP 1 983 095 a laundry dryer is described, which has an additional heat exchanger in its heat pump circuit in order to remove heat from the system. The operation of the additional heat exchanger is controlled as a function of the temperature of the heat pump circuit. DE 102008040853 describes in Fig. 3 a laundry drier with two additional heat exchangers of which the one cools the processing air circuit and the other one the heat pump circuit. Temperature sensors are provided in the heat pump circuit, the signal of which is used to control a blower for cooling the additional heat exchanger .

In both cases the additional heat exchanger serves to avoid an overheating of the system.

Short description of the invention

It is therefore an object to provide a laundry dryer and a method for its operation which combine a good efficiency with a high operation safety.

This object is achieved by the independent claims .

Accordingly, at least one temperature sensor is arranged in the heat pump circuit. Furthermore, the laundry dryer has a controller adapted to control, depending on the signal from the temperature sensor, the amount of heat which can be extracted from the processing air circuit by means of the additional heat exchanger.

The invention is based on the idea that it is advantageous to mount the additional heat exchanger in the processing air circuit because this allows to remove heat as well as humidity, at the same time, from the processing air by means of the additional heat exchanger, which improves the drying operation. On the other hand, the additional heat exchanger is, even though it is arranged in the processing air circuit, not controlled as a function of the temperature in the processing air circuit. It is rather controlled as a function of the temperature in the heat pump circuit. This is based on the understanding that, during an overheating of the system, the heat pump circuit is damaged first, such that the present solution provides an improved degree of safety.

In contrast to this, known devices having the additional heat exchanger arranged in the processing air circuit, control its operation as function of the temperature of the processing air circuit. On the other hand, conventional solutions having an additional heat exchang- er in the heat pump circuit control its operation as a function of the temperature of the heat pump circuit. In the present device the additional heat exchanger is arranged in the processing air circuit, but it is controlled as a function of the temperature of the heat pump circuit, which at the same time leads to a higher efficiency and a higher safety in the manner described above.

The invention also relates to a method for operating the laundry drier in this manner.

Short description of the drawings

Further embodiments, advantages and applications of the invention are disclosed in the dependent claims as well as in the following description, which description makes reference to the attached figure. The figure shows a block diagram of the most important components of a laundry dryer.

Detailed description of embodiments

The laundry dryer of Fig. 1 comprises a drum 1 for receiving the laundry to be dried. A processing air circuit is provided (which is shown in solid lines in Fig. 1), in which heated up processing air is led through drum 1, then cooled down and thereafter heated again and led back to drum 1.

In the processing air circuit, in particular before drum 1, an optional electrical heater (start up heater) 9 can be provided, which allows to feed heat to the processing air in a controlled manner, e.g. during start up of the device, or it can be used to generally raise temperature level in the processing air circuit. A blower 10 is provided for pumping the processing air.

Furthermore, a heat pump circuit (with the path of the fluid conveyed in the heat pump circuit being shown in dotted lines in Fig. 1) is provided. The fluid is fed by means of a compressor 2 to a condenser 3, then through an expansion member 5, e.g. a capillary or an expansion valve, to an evaporator 6 and then back to compressor 2. Evaporator 6 serves to cool down the processing air and to thereby extract water therefrom, while condenser 3 serves to heat the processing air up again such that it can take up new water.

As can further be seen from Fig. 1, an additional heat exchanger 4 is arranged in the processing air circuit. As mentioned above it serves to extract heat from the processing air circuit. Preferably, it is arranged between drum 1 and evaporator 6 because at this position it can also remove water from the processing air.

Additional heat exchanger 4 is an air-air-heat exchanger, through which the processing air as well as environmental air are passing, with the processing air and the environmental air being preferably spatially separated such that they cannot mix. Furthermore, a blower 7 is provided by means of which environmental air can be fed through additional heat exchanger 4 in order to cool the same.

The amount of heat extracted from the processing air circuit by the additional heat exchanger 4 is controlled by the speed of rotation of blower 7. This speed of rotation is controlled by a controller 8 of the device depending on at least one temperature in the heat pump circuit. For this purpose a temperature sensor 11 is arranged in the heat pump circuit. Controller 8 is adapted and structured to control the speed of blower 7 as a function of the signal form temperature sensor 11, e.g. by operating blower 7 with higher speed when the temperature increases. For example, blower 7 can only be switched on if the temperature in the heat pump circuit exceeds a given threshold value. Preferably, however, the speed of blower 7 is increased by controller 8 continu ously or at least in several steps when said temperature increases .

The temperature-dependent controlling of blower 7 allows to quickly feed heat to the processing air circuit during start up, such that the processing temperature is reached quickly, whereafter, in normal operation, an overheating of the heat pump circuit is prevented.

Preferably, the temperature of the fluid in the heat pump circuit is measured at the location where this temperature is approximately equal to the condensation temperature of the fluid. This is the case between condenser 3 and expansion member 5, or at the exit of condenser 3 or at the input of expansion member 5.

The present invention can be used independently of the type of fluid used in the heat pump circuit. It can, e.g., be used with heat pump circuit carrying R134a or CO2.

The following table shows, by way of example, the amount of cooling air or the relative operating power of blower 7 as a function of the temperature T1 at temperature sensor 11 for a heat pump having a fluid of type Rl34a:

Temperature T1 Amount of cooling air 64 - 65°C 51% 65 - 66°C 72% 66 - 67 °C 85% 67 - 68 °C 93% 68 - 69°C 100%

As can be seen starting from a reference temperature TO = 64°C the power of blower 7 is increased. For lower temperatures, blower 7 can be switched off or it can be run with low power. The table shows the flow of cooling air in percent of the volume flow of the transported air quantity relative to the maximum flow of cooling air that can be delivered by blower 7. The above table is to be understood as an example. In particular, depending on the maximum capacity of blower 7, depending on the fluid in the heat pump circuit as well as depending on other device parameters, other values may be used. The seguence can be coarser or finer, or a continuous dependence between blowing power and temperature can be used. A dependence in several steps or a continuous dependence allows a finer control of the energy extraction as compared to a "binary" on-off-control.

If temperature T1 falls, the amount of cooling air is reduced. In order to prevent quick switching, step changes are not carried out in an arbitrary fast way but are e.g. one per minute.

It is also conceivable that the power of blower 7 can also be controlled depending on further temperatures, such as it is e.g. illustrated in Fig. 6 of EP 1 884 586.

While the present application describes advantageous embodiments of the invention, it is clearly to be understood that the invention is not limited thereto and also be carried out in different manner within the scope of the following claims.

Claims

1. Dryer with a drum (1) for receiving laundry to be dried, a process air circuit for passing heated process air through the drum (1), for cooling the process air by water extraction and for reheating the process air, a heat pump circuit for conducting a medium through a capacitor (3), a throttle member (5), an evaporator (6) and a compressor (2) back to the capacitor (3) where the process air can be heated with the capacitor (3) and the process air can be cooled with the evaporator (6) ), a fan (7) wherein an additional heat exchanger (4) is provided which is cooled by the fan (7), wherein the additional heat exchanger (4) is arranged in the process air circuit and is designed to extract heat from the process air circuit, and wherein the fan (7) is configured to blow on the additional ambient air heat exchanger (4) and wherein the control unit (8) is configured to control a fan speed (7) depending on the signal from a temperature sensor (11), temp the erature sensor (11) is arranged in the heat pump circuit and the dryer has a control unit (8) with which a heat effect which can be extracted from the process air circuit by the additional heat exchanger can be controlled depending on the signal from the temperature sensor (11), characterized in that is provided precisely an additional heat exchanger (4) which is cooled by the fan (7).

A dryer according to claim 1, wherein the additional heat exchanger (4) is arranged between the drum (1) and the evaporator (6).

Dryer according to one of the preceding claims, wherein the temperature sensor (11) is arranged between the capacitor (3) and the throttle member (5) or on the output side of the capacitor (3) or on the input side of the throttle member (5) ·

Dryer according to one of the preceding claims, wherein the control unit (8) is designed to increase the speed of the fan (7) at an increasing temperature continuously or in several stages.

A method of operating a dryer according to one of the preceding claims, wherein the heat output drawn from the process air circuit by the auxiliary heat exchanger (4) is controlled depending on a signal from the temperature sensor (11).