Patent Application
20110289695
This application claims priority to European Application No. 10163744.5, filed on May 25, 2010
The invention relates to a laundry treatment apparatus having a heat pump system, and a method for operating the same. The laundry treatment apparatus may be a dryer or a washing machine having drying function.
If a heat pump system is not operated permanently as in a freezer or refrigerator, but it is operated temporarily when momentarily required, the heat transfer capability for transferring heat from the evaporator to the condenser is slowly increasing over time after starting the heat pump system. It is known to use such heat pump systems in condenser dryers. There are different conventional approaches to increase the initial heat transfer capability and/or to reduce the time required till full heat transfer capability.
For the dryer with heat pump system of DE 31 13 471 A1 it is proposed to heat the circulated drying air not only by a condenser of a heat pump but also by an electrical heater to heat up the evaporator and to dry the laundry.
EP 1 650 343 A1 suggests a dryer with a heat pump system in which the air in the air circulation path can be heated by an electric heater. The electric heater is used before starting the heat pump system to warm up the evaporator and to provide heat for drying the laundry.
In the dryer having a heat pump system of EP 0 999 302 B1 an additional evaporator external to the air circulation path is used which is heated or cooled by air sucked from the outside of the dryer.
An auxiliary evaporator arranged in a water storage tank is suggested in EP 1 983 094 A1. Alternatively it is suggested to open the air circulation path to introduce ambient air to heat up the evaporator in the initial stage of the drying operation.
In the dryer having a heat pump system of WO 2007/023510 A1 there is an external condenser for removing process heat out of the air circulation path on the one hand and on the other hand there is a heating element for additionally and permanently heating the air. The heating element is operated by electric power or by steam.
DE 10 2005 041 145 A1 suggests that the efficiency of the compressor is adapted by operating it at the start with a higher power and then to reduce the power or efficiency of the compressor.
It is an object of the invention to provide a laundry treatment apparatus having a heat pump system and a method of operating a laundry treatment apparatus, in which the time for the heat pump system to come to an elevated efficiency is shortened without the need for additional elements.
According to an aspect of the invention, a laundry treatment apparatus is operated having a storing compartment for storing laundry therein. The laundry treatment apparatus has at least one operation mode in which the laundry can be dried using a heat pump system. In a preferred embodiment the laundry treatment apparatus is a dryer that has a rotatable drum or is a washing machine having drying function in which the laundry is stored in a rotatable drum arranged in a tub. Laundry treatment can, however, also be performed in another type of apparatus, for example a cabinet for dry cleaning of laundry.
The heat pump system has an evaporator and a condenser, wherein the terms evaporator and condenser are used here in relation to the heat pump system. In other words, the evaporator in the laundry treatment apparatus is used normally as a condenser with respect to the air circulation path such that in normal operation of the evaporator the humidity circulated with the air is condensed at the evaporator. Correspondingly, in the condenser the coolant liquid is condensed, by deposit heat in the condenser which is heat exchanged to the air circulated on the outside surfaces of the condenser. The evaporator and the condenser are arranged in the air circulation channel which has at least a first and a second end each of which is fluidly and/or mechanically connected to the storing compartment. The heat pump system is used to dry the laundry wherein—as in the prior art—humidity is circulated in the air circulation path, the humidity condenses at the evaporator while cooling the air, then the air is heated up for drying at the condenser, and the heated air takes up humidity from the laundry.
The air circulation is powered by at least one blower that blows the air through the air circulation channel and the storing compartment. Preferably, at least the fan of the blower is arranged within the air circulation channel. The compressor of the heat pump system may be arranged within or partially within the air circulation channel or outside of the air circulation channel, preferably in an inner space of the laundry treatment apparatus.
The laundry treatment apparatus has a steam generator which is arranged within the body of the laundry treatment apparatus. The steam generator is nowadays a common element of a laundry treatment apparatus that provides laundry processing by using steam supplied to the laundry. Preferably the method of operating the textile treatment apparatus comprises at least one steam treatment mode or cycle for steam treatment of the laundry stored in the storing compartment. The steam generator is adapted to supply steam into the air circulation channel and/or into the storing compartment for laundry treatment. The steam supplied by the steam generator is allowed to contact the laundry stored in the storing compartment for steam treatment. For at least an overlapping period or for overlapping periods, the steam generator is generating and supplying steam into the air circulation channel and/or the storing compartment while at the same time the heat pump system is operated. Preferably at least in the initial phase or during an initial phase after starting the operation of the compressor of the heat pump system steam is supplied by the steam generator.
In the initial phase or start-up phase of operating the compressor the purpose or main purpose of the supplied steam is to heat up the evaporator to come to working temperature. However, it is also possible to start operation of the heat pump system, i.e. to operate the compressor thereof, while the laundry is still processed in a steam treatment mode or cycle. The steam is hot steam (at the origin of supply preferably the steam temperature is higher than 70° C., 80° C., 90° C. or 95° C.) and/or preferably the steam is pure water steam. Alternatively, the steam is essentially water steam (more than 60%, 70% or 80% of volume) to which additives are added. Additives could be a disinfectant agent, a bleaching agent, deodorizing agent, an impregnant agent, a softener agent or others.
In an embodiment the steam is generated by the steam generator and supplied to the air circulation channel and/or the storing compartment for a predefined period since or after starting the operation of the heat pump system and then after the predefined period the steam generation and supply is stopped. By this overlap of the operation of the heat pump system and the steam generator the intermediate effect of additional energy consumption by the steam generator is limited and in total the result of this additional energy consumption and humidification of the laundry is more than counterbalanced by the acceleration of the equilibration process for the heat pump system to come to high efficiency in the drying cycle.
According to another embodiment steam is generated during an initial operation of the heat pump system, for example the steam generation by the steam generator is started when starting the operation of the heat pump system. Steam generation and supply of steam is continued until it is stopped in dependency of one or more predefined parameters. Thus, the duration of steam generation by the steam generator is for example dependent on one or more parameters indicating or being a measure that the heat pump system has arrived at a predefined operation efficiency.
A predefined parameter or one of the predefined parameter(s) is (are) the temperature and/or the pressure of the working fluid circulating in the heat pump system or the temperature of one of the elements of the heat pump system, in particular the temperature of the compressor, the evaporator or the condenser.
Parameters, which are monitored and used to decide whether steam generation can be stopped and/or whether the predefined working efficiency of the heat pump system is effected, are for example the temperature of the working fluid in the heat pump system or a temperature difference of a working fluid measured at different locations in the heat pump system, for example at the inlet/outlet of the evaporator. For example the temperature difference is taken from the temperature of the condenser and the temperature of the evaporator, which for example are measured with a temperature sensor in contact with the evaporator and condenser. The temperature can also be measured at a fluid conduit coming or going to these elements.
A predefined or sufficient working efficiency has for example been reached when the temperature difference between condenser and evaporator is more than or equal to 5° C., 10° C., 15° C. or 20° C.
Alternatively or additionally one or more of the parameters are the pressure and/or temperature of the working fluid in the evaporator (for example measured at the inlet/outlet thereof), the condenser and/or the compressor. For example, the pressure within the evaporator is measured which indicates the pressure of the working fluid (or cooling fluid), wherein a sufficient pressure limit has to be achieved before the compressor and thus the heat pump system can operate efficiently.
Additionally or alternatively, the power consumption of the heat pump system, for example the current to the compressor, is a parameter indicating when an efficient working condition of the heat pump system is achieved.
Alternatively or additionally, one or more of the parameters is the temperature at a specific location in the air circulation channel and/or a temperature difference between two different locations in the air circulation channel, for example inlet/outlet of the drum. Then these parameters can be monitored as a parameter for determining when the steam generation is to be stopped.
Additionally or alternatively, one or more of the parameters is the humidity of the circulated air, which can be detected at the air inlet or air outlet of one of the following elements: the evaporator, the condenser, the air circulation channel and the storing compartment.
The dependency of the one or more parameters may be a temporal behaviour of the one or more parameters wherein a temporal gradient or change is used to determine the time for stopping the steam generator. In addition or alternatively to the temporal changes or gradients, local changes or gradients can be determined on which the decision to stop steam generation is based.
In a preferred embodiment the steam generated by the steam generator is first supplied into the storing compartment, i.e. the steam is not supplied to the storing compartment via the air circulation channel, but it is directly supplied from the generator into the laundry storing compartment. For example the steam generator is a steam generator within the body of the laundry treatment apparatus, but is arranged external to the storing compartment and the air circulation channel. Then a duct or connection provides steam from the steam generator into the storing compartment which is for example a drum of a washing machine or a dryer.
In another arrangement the steam generator is arranged within a tub in which the storing compartment is arranged, preferably a rotatable drum. For example the steam generator is the electrical heater element of the washing machine arranged in the sump of the tub and the steam generator heats water in the sump to generate the steam. In this embodiment preferably only a small amount of water is provided in the sump such that the water level is below the storing compartment (rotatable drum) and not in contact with the laundry stored in the storing compartment.
Preferably, the laundry treatment apparatus provides that the amount and/or time and/or temperature of steam supplied by the steam generator depends on a user selection input at a control unit of the laundry treatment apparatus. If for example delicate laundry, which is not appropriate for steam treatment, is stored in the storing compartment, the user can suppress steam generation during operation of the heat pump system to avoid damage to the laundry. Alternatively or additionally, the temperature of the steam is reduced by a corresponding user selection when the laundry is sensitive to hot steam. The user selection may be a dedicated selection for reducing steam supply to the laundry or it may be an indirect selection by selecting the type of laundry and/or type of laundry treatment preceding the drying cycle. The amount of steam to be supplied from the steam generator may for example depend on the amount of laundry stored in the storing compartment and/or its humidity. If for example the stored amount of laundry is high and the laundry has a high humidity, then a higher amount of steam is required for bringing up the working temperature of the evaporator. In this case the temperature of the laundry in the compartment has to be increased at the same time with the evaporator's temperature.
The laundry treatment apparatus according to the invention comprises a steam generator arranged within the body of the laundry treatment apparatus and is designed to supply steam into the storing compartment and/or to the air circulation channel. In other words, the steam generator is in fluid connection with the interior of the storing compartment and/or air circulation channel such that the steam generated by the steam generator is available for laundry processing or treatment.
Preferably, the laundry treatment apparatus has embodiments and configurations as described above in connection with the method. All features mentioned above are applicable individually or in any combination as will be readily understood by the skilled person to be a meaningful contribution. The embodiments and their features described below in connection with the laundry treatment apparatus are also applicable individually or in any combination to the laundry treatment apparatus that is operated in the method.
According to a preferred embodiment the control unit of the laundry treatment apparatus is adapted to operate the heat pump system and the steam generator at the same time at least for one or a plurality of overlapping periods, preferably during the initial phase of the operation of the heat pump system such that the evaporator is heated in the start-up phase of the heat pump system. Thereby the working temperature of the evaporator and the coolant liquid therein is increased to increase the evaporation of the coolant liquid within the evaporator. This increases the efficiency of the compressor by providing coolant liquid vapour to be compressed.
In an embodiment the steam generator is arranged within the storing compartment, in particular within a tub surrounding the storing compartment, or is arranged in the air circulation channel. In this configuration no steam supply line is required to convey the steam generated by the steam generator into the storing compartment and/or the air circulation channel. In another embodiment the steam generator is arranged within the body of the laundry treatment apparatus, but outside the storing compartment and the air circulation channel and a steam supply line and/or an opening between steam generator and the storing compartment and/or the air circulation channel is provided.
The steam generator of the laundry treatment apparatus is provided for laundry processing or treatment in respective laundry treatment apparatus operation modes or cycles. Thus the steam generator does not represent an additional element of the laundry treatment apparatus solely for shortening the start-up phase of the heat pump system having the compressor, condenser and evaporator. Laundry treatment processes or cycles in which steam is used for laundry treatment are for example, but not limited to: providing steam to the laundry for anti-wrinkle purposes, providing steam to the wash liquid for heating up the washing liquid, providing steam for sterilisation, and providing steam for dry cleaning.
According to an embodiment, the laundry treatment apparatus has a storing compartment, in particular a rotatable drum, that is enclosed by a tub or container and a sump arranged in the tub below the storing compartment (e.g. rotatable drum). A heating element arranged in or at the sump is configured to heat up water contained in the sump to generate steam and to supply it to the storing compartment. Preferably, the storing compartment has a plurality of openings connecting its interior and the outer volume within the tub, so that the steam can permeate into the storing compartment for laundry processing.
According to a preferred embodiment the blower has an operation mode with reduced or zero air conveying power. For example, an operation mode in which the blower is de-energized or stopped or in which the power provided to the blower is reduced. Then the control unit of the treatment apparatus is adapted to control the steam generator to generate and supply steam while the blower is de-energized or operating with a reduced air amount conveying power at least partially during the initial phase of operating the heat pump system. In case of reduced air conveying, the hot steam is first provided to the evaporator to heat up the evaporator and the reduced air circulation speed causes the heat exchange time (dwell time) between steam and evaporator to be extended. In case of de-energizing the blower the steam can diffuse to the evaporator and deposit the heat energy there. In particular, when the evaporator is arranged at an upper level within the body of the treatment apparatus, the hot steam will ascend and collect at the evaporator to heat it up. This chimney effect is improved when the laundry treatment apparatus is configured such that the evaporator is arranged above an inlet area or steam generation area for supplying the steam into the storing compartment and/or air circulation channel.
According to an embodiment the compressor is arranged in the air circulation channel, preferably downstream from the evaporator. The terms ‘downstream’ and ‘upstream’ as well as ‘forward air flow’ and ‘backward air flow’ relate to the normal operation mode of the heat pump system and blower. In the normal operation mode the laundry treatment apparatus operates as a condenser dryer in which the humidity-laden air from the storing compartment is sucked into the air circulation channel at the first end of the channel by the operation of the blower and first contacts the evaporator in the air channel for condensing water there. Downstream from the evaporator the condenser is arranged to heat up the air that has a reduced humidity after passing the evaporator. The condenser heats up the air before flowing the warm air into the storing compartment through the second end of the air circulation channel.
Reference is made in detail to preferred embodiments of the invention, examples of which are illustrated in the accompanying figures, which show:
The heat pump system 10 of the washing machine 2 shown in
The heater 8 is arranged at the bottom of the tub 6 in a sump. The heater 8 is used during washing cycles for heating the washing liquid. Further, heater 8 is used to generate steam 9 for steam treatment of the laundry stored in the drum 7 of the washing machine. Laundry steam treatment processes are for example refreshment processes, anti-wrinkle processes, washing process, sterilisation, deodorisation and so on. The steam which is indicated by the arrows 9 distributes around the drum 7 within the tub 6 and penetrates through openings provided in the periphery or sidewalls of the drum 7.
The evaporator 14 and the condenser 16 are arranged at least partially within air circulation channel 20 which has a first end connected to an inlet 22 of the tub 6 and a second end connected to an outlet 24 of the tub 6. The air circulation channel 20 and the tub 6 form a closed channel system for circulating the air, for example during steam laundry treatment cycles and drying cycles of the washing machine. At least the fan of a blower 26 is arranged within the air circulation channel 20 that forcibly circulates the air within the channel system, i.e. the air is blown from the air circulation channel 20 through inlet 22, through the tub 6 and out of the tub 6 through the outlet 24 back into the air circulation channel 20 at the second end thereof
In the embodiment of
When the heat pump 10 has developed full or nearly full working efficiency after the start-up phase, the normal operation of the drying cycle is achieved in which the blower 26 circulates the air through the channel 20 and tub/drum 6/7. The circulated air is cooled at the evaporator 14 so that the humidity-laden air condenses water at the surfaces of the evaporator 14. The condensed water is collected and guided to a tank (not shown) where it can be removed by the user from time to time. Downstream from the evaporator 14 the circulated air passes over the surfaces of the condenser 16 where it is heated by the heat of the condenser 16. The heated air with reduced humidity is blown into the tub/drum through inlet 22 where it then passes over the laundry in drum 7. The drum 7 is rotated so that during the drying cycle the laundry is agitated in tumbling mode. The heated air takes humidity from the laundry and carries it out of the drum/tub through outlet 24 towards the evaporator 14 arranged within the air circulation channel 20.
As in prior art, when starting the heat pump system 10 under the control of a control unit of the washing machine 2 and when the evaporator 14 and compressor 12 have nearly the same temperature after an extended duration of non-operation of the heat pump system, the heat pump system 10 has an extended initial phase in which the operation efficiency is low. Mainly, the efficiency is low as there is no or little coolant liquid vapour within the evaporator 14 which has a low starting temperature. For accelerating the start-up or initial phase of the heat pump system 10, i.e. for shortening the time until full operation or efficient operation of the heat pump system 10, at least during a period during the initial phase of the heat pump system 10, the control unit controls heater 8 to heat water stored in the sump of tub 6 to generate steam. The steam 9 generated in the tub 6 also distributes into the drum 7 and can be sucked in through outlet 24 to the air circulation channel 20 to be flown over evaporator 14. Thus, the hot steam 9 generated in the tub 6 provides additional heat to heat up evaporator 14. An increase in the coolant liquid vapour pressure within the evaporator 14 is achieved much faster than without additional heat from the steam 9. Consequently the duration of the initial phase is shorter than without producing steam.
The power supplied to heater 8 (or steam generator 30) is switched off or reduced when a temperature/pressure detected at the evaporator 14 reaches a predefined level which corresponds to a reference efficiency level Eref of the heat pump system 10. When stopping or reducing the power to the heater 8 (steam generator) at time T1′ steam supply by residual heat capacity is sufficient to result in an increase of the temperature of the evaporator 14 to overcome the critical efficiency level EC of the heat pump system 10. The relation Eref/T1′ and EC/T2 is known from empirical data of the respective washing machine 2 such that Eref or the temperature associated therewith is the trigger for energy stop or reduction at the steam generator 8/30. Thus
The steam treatment cycle is started at time T5, i.e. prior to time T6 as shown. In another embodiment it can be provided that the steam treatment starts at time T6 or after T6 such that the steam treatment cycle fully overlaps with the initial phase (time period T6 to T7) of the heat pump system after starting the heat pump system 10 at time T6. Here the energy of the steam that is supplied for laundry steam processing is used at the same time for heating up the evaporator 14. In this case not only the time duration required for the drying cycle is reduced by the supply of steam energy, but additionally the time duration is reduced in that the initial phase or start up phase of the heat pump system is overlapping the steam treatment cycle. In effect, energy and time are saved by at least partially overlapping heat pump operation period and steam treatment cycle.
The processes of
Returning to the embodiment of a washing machine 2′ in
Different from
When steam is supplied from the generator 30 during the initial or start-up phase of the heat pump system 10′—for example during processes as shown in
In particular if the blower 26′ is switched off, the hot steam or the hot air heated by the steam is ascending due to convection. As the arrangement and geometry of tub 6′ (and/or drum 7), channel 20′ and evaporator 14′ is designed such that the ascending air or steam preferably reaches the evaporator, the evaporator is the element of the heat pump system that will be primarily heated up. Thus shortening of the initial phase of the heat pump system can be achieved easily.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10163744.5 | May 2010 | EP | regional |
