Household appliance and method of operating a household appliance

Abstract

The invention in particular is directed to a household appliance, such as a washing machine or dishwasher, comprising a heat pump arrangement (3) with a heat pump (4, 5, 6) adapted to transfer heat to an operating medium (2) of the appliance (1, 3), with a closed storage tank (9) adapted to receive a phase change substance (10) and being heat exchangeably coupled with a process side (5) of the heat pump (4, 5, 6), with at least one sensor (11) adapted and arranged to detect an actual phase state of the phase change substance (10), and with a recovery unit (12) adapted and operable to actively recover the phase change substance (10) in dependence of a signal of the sensor (11).

Claims

1. Method of operating a household appliance which comprises a heat pump arrangement with a heat pump adapted to transfer heat to an operating medium of the appliance, with a closed storage tank adapted to receive a phase change substance and being heat exchangeably coupled with a process side of the heat pump, with a sensor adapted and arranged to detect an actual phase state of the phase change substance, and with a recovery unit adapted and operable to actively recover the phase change substance in dependence of a signal of the sensor, wherein the method comprises the steps of detecting an actual phase state of the phase change substance and operating the recovery unit for a selected time interval if a sensor signal is indicative of a predefined critical phase state of the phase change substance.

2. Method according to claim 1, wherein activating the recovery unit comprises activating a ventilator to impinge the storage tank, thus indirectly the phase change substance, with ambient air.

3. Method according to claim 1, wherein activating the recovery unit comprises activating a heating element to actively apply heat to the phase change substance.

4. Method according to claim 1, wherein activating the recovery unit comprises operating the heat pump in reversed mode to thereby transfer heat energy to the phase change substance.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) Embodiments of the invention will now be described in connection with the annexed figures. Note that the exemplary embodiments according to the figures will be described to the extent required for fully understanding the invention. In the figures,

(2) FIG. 1 shows a schematic representation of relevant components of a household appliance in a first configuration; and

(3) FIG. 2 shows a schematic representation of relevant components of a household appliance in a second configuration.

DETAILED DESCRIPTION

(4) FIG. 1 shows a schematic representation of relevant components of a household appliance in a first configuration. The household appliance in the present case is a dishwasher, but may also be implemented as a washing machine. The appliance comprises a tub 1 adapted to receive or hold dishes to be cleaned. The tub 1 is further adapted to receive an operating medium 2, such as a washing or cleaning liquid.

(5) During washing or cleaning cycles, the operational medium in most of the cases is heated up in order to obtain optimal washing or cleaning results. Heating up the operational medium may be done by using electrical heaters. However, in order to speed up heating and to optimize energy consumption of the household appliance, a heat pump arrangement 3 is provided which is adapted and implemented to transfer heat to the operational medium, and thereby reduce the energy consumption of the heaters.

(6) The heat pump arrangement 3 comprises a heat pump comprising at least a compressor 4, evaporator 5 and condenser 6, as well as interconnecting ducting and other elements (not shown). The heat pump is adapted and implemented to transfer heat from a heat reservoir 7 to the operating medium 2. In FIG. 1, heat transfer is indicated by arrows.

(7) During operation, heat pump circulating fluid takes up, in the evaporator 5, heat from the heat reservoir 7 and releases heat, in the condenser 6. This corresponds to the ordinary operation of a heat pump.

(8) Heat released in the condenser 6 in the present embodiment can or is transferred to the operational medium 2 via a heat exchanger 8. In this way, the operational medium 2 can be heated via action of the heat pump.

(9) The heat pump arrangement 3, in particular the heat reservoir 7, further comprises a storage tank 9 which is filled with a phase change substance 10, in the present case water or an aqueous mixture. As to the term phase change substance 10, reference is made to the description above. In particular it is pointed out, that a phase change substance 10 suitable for the present applications reveals a phase transition liquid-solid, wherein the phase transition is such that latent heat of the phase transition can be exploited or used in the sense of a heat reservoir.

(10) The storage tank 9 is a closed storage tank, which in particular shall mean that the phase change substance 10 is tightly enclosed in the storage tank 9.

(11) In the present embodiment, the evaporator 5 of the heat pump is arranged within the storage tank 9, such that the evaporator 5, representing a process side of the heat pump, is heat exchangeably coupled to the phase change substance 10.

(12) The heat pump arrangement 3 further comprises a sensor 11 which is adapted to sense or detect an actual phase state of the phase change substance 10.

(13) The heat pump arrangement 3 in the present case further comprises an electric resistance heater 12, which in the present case is arranged within the storage tank 9 in order to directly apply heat energy to the phase change substance 10.

(14) The heat pump arrangement 3 of the present embodiment is adapted and implemented in such a way, that the heater 12 is activated in dependence of a signal of the sensor 11. In more detail, the heater 12 is activated, if the sensor 11 senses or detects a critical phase state of the phase change substance 10.

(15) During ordinary operation of the heat pump as set out above, heat can be transferred from the phase change substance 10 to the operating medium 2 at least as long as phase change substance 10 in the liquid phase exists. In transferring heat to the operating medium 2, the phase change substance 10, which consists of water or an aqueous mixture, is cooled down, and is gradually transferred from the initial liquid phase to the solid or frozen phase.

(16) If all, or essentially all, or at least a major part of the phase change substance 10 is in the solid state, heat transfer from the phase change substance 10 to the operating medium 2 becomes increasingly difficult or less efficient. For this reason, the heat pump arrangement 3 is implemented such that in case that the sensor detects or senses a critical phase state, which may correspond to a situation where all or essentially all of the phase change substance is in the solid phase, the heater 12 is activated to transfer solid phase change substance 10 to liquid phase change substance 10 again.

(17) The action of transferring solid phase change substance 10 to liquid phase change substance 10 is also called recovery in the sense of the present invention. It shall be noted that a critical phase state may be any state considered to involve inadequate operational performance and hence requiring recovery of the phase change substance 10. It shall be noted, that the recovery unit, in the present case the heater 12, in general can be activated at any time or in any state, in particular also if no critical phase state is present. There may be provided several threshold values indicative of critical phase stated, wherein the threshold values may be used as activation thresholds for the recovery unit. A respective threshold may be a fixed value set by the manufacturer, a value selected by a user and/or a value calculated or determined, in particular in a prospective manner, by the household appliance, in particular heat pump arrangement 3.

(18) Timely recovering the phase change substance 10 in particular may improve modes of continued operation of the household appliance. In particular, operational modes in which several subsequent washing or cleaning cycles can be conducted under essentially equal conditions may be possible. Actively recovering the phase change substance 10, in the present case via the heater 12, produces a considerable time advantage as compared to passive recovery and/or recovery by transferring residual heat of waste washing or cleaning liquid to the phase change substance 10.

(19) Instead or additional to using the heater 12 as a recovery unit, a ventilator or fan may be used, which is adapted to impinge ambient air to the storage tank 9 and thus to the phase change substance 10.

(20) FIG. 2 shows a schematic representation of relevant components of a household appliance in a second configuration. The second configuration differs from the first configuration in that the recovery unit is implemented in a different way.

(21) In the embodiment as shown in FIG. 2, the heat pump assembly 3, in more detail the recovery unit, comprises a valve assembly 13 which is adapted and arranged such that the heat pump can be operated in reversed mode. In so far, the heat pump in reverse operational mode can be regarded as the recovery unit.

(22) Operating the heat pump in reversed mode will lead to heat transfer to the phase change substance 10. In this way, the phase change substance 10 can be recovered, i.e. solid, frozen phase change substance 10 can be transferred to the liquid phase, i.e. recovered phase. Reversed operation of the heat pump in particular may be applied in a time span between subsequent washing or cleaning cycles. This in particular may be applied if residual waste heat from the tub 1 can be exploited and transferred to the phase change substance 10.

(23) The recovery unit of the second configuration has similar advantages as compared to the heater 12 described in connection with FIG. 1. In particular, it is also possible to obtain continued and uniform operation of the household appliance, in particular in subsequent operational cycles, i.e. washing or cleaning cycles.

REFERENCE SIGNS

(24) 1 tub 2 operating medium 3 heat pump arrangement 4 compressor 5 evaporator 6 condenser 7 heat reservoir 8 heat exchanger 9 storage tank 10 phase change substance 11 sensor 12 heater 13 valve assembly