WO2013143576A1

WO2013143576A1 - Washing machine and method of operating a washing machine

Info

Publication number: WO2013143576A1
Application number: PCT/EP2012/055390
Authority: WO
Inventors: Luigi Salerno
Original assignee: Electrolux Home Products Corporation N.V.
Priority date: 2012-03-27
Filing date: 2012-03-27
Publication date: 2013-10-03

Abstract

In a washing machine comprising a washing tub (10) for accommodating articles to be cleaned, a water-softening device comprising an ion exchanger (30) through which fresh water can be fed before being passed to the washing tub(10),and a drain line (22; 42) for removing water from the tub(10), it is suggested that the dishwasher further comprises means (32, 34, 36; 48; 54) for providing for an indirect heat-exchange between said ion exchanger (30) and said drain line(22; 42). Further, a method of operating a washing machine is suggested, which method comprises: -passing water via a water-softening device comprising an ion exchanger to a washing tub; -heating water that is passed to the washing tub either before or after it enters the washing tub; -removing heated water from the washing tub; and -providing for an indirect heat-exchange between heated water which has been removed from the washing tub and water that is passed to the washing tub via the water-softening device.

Description

Washing machine and method of operating a washing machine

The present invention relates to a washing machine, such as a dishwasher a clothes washer or a laundry machine, and to a method of operating a washing machine, wherein the present invention particularly is concerned with reducing the energy consumption of the washing machine.

While in the past several attempts have been made to utilize in washing machines the heat of the washing liquor used in a preceding washing step for the warming of the washing liquor to be used during a subsequent washing step, most of the prior art solutions are disadvantageous in several aspects.

One solution which has been suggested in several patent documents, such as in DE-B-27 30 489, DE-A-42 38 450, EP-A-0 205 788, GB-A-2 139 084, WO- A-2009/156332, WO-A-2009/156498 and US-A-2002/9179584, uses an intermediate tank which is in direct thermal contact with the washing tub. Fresh water to be used in a subsequent washing step is fed to the intermediate tank to be warmed therein by heat dissipated from the washing tub. This solution is disadvantageous not only in that the intermediate tank requires additional space which, since in most countries the overall size of washing machines is more or less standardized, requires that the washing tub has to be made smaller, but also is inefficient in that the direct thermal contact results in the water contained in the intermediate tank immediately absorbing heat as soon as the washing tub is heated, so that in practice not only the water fed into the tub for a the present washing step but also that for the following washing step which is contained in the intermediate tank will be heated. Thus rather than using waste heat, in effect the heat for the subsequent washing step is supplied together with the heat for the present washing step.

In an attempt to overcome these problems, it has been suggested in EP-B-2 039 281 to provide for an water container that is not in direct contact with tub but which is warmed on the one hand by the ambient atmosphere and further by radiant heat from the tub. This solution is rather inefficient, because providing for the suggested heat transfer renders it impossible to provide for a thermal insulation of the tub. Thus, while the warming of fresh feed water is effected in part by heat that has been taken from the atmosphere and by dissipation from the washing tub, a similar but negative heat transfer will be seen for the water to be used within the washing tub during a present washing step, which will loose a good part of its heat into the atmosphere and to the feed water for the subsequent step.

In DE-A-39 00 617, EP-A-2 108 299, US-A-4 529 032 and similarly in US-A-5 660 193 there is disclosed a dishwasher with an additional tank for receiving hot drain water from the tub and a heat exchanger for pre-warming fresh water to be used in a hot rinse step after further heating. While in this manner the heat exchange between the washing tub and the drain water can be decoupled, the additional tank adds to the complexity and thus to the costs of the dishwasher and further as in the solutions discussed above requires additional space which detracts from the space available for the washing tub.

Finally, in US 2010/0024844 there is disclosed a dishwasher in which an input line and a drain line are arranged in a heat exchange relationship, so as to enable heat from warm cleaning water that it passed through the drain line to heat feed water that is passed traveling through the input line. While in this solution the liquids participating in the heat exchange are both in a flowing condition, in order to provide for sufficient time for the heat exchange the lines along which the heat exchange is to be effected need to be of a sufficient length, so that a similar amount of space is required as in the solution discussed above that relies on an intermediate tank. On the other hand, if the lines are made shorter, only a small portion of the heat contained in the water passing through the drain line can be recovered.

It is an object of the present invention to overcome the problems with the prior art systems. In particular, the present invention aims at providing a washing machine in which the heat of washing liquor used in a preceding washing step is utilized for the warming of the washing liquor to be used during a subsequent washing step, wherein however less space is required for providing for the heat exchange than in prior solutions.

In a first aspect of the present invention this object is solved in that in a washing machine comprising a washing tub for accommodating articles to be cleaned, a water-softening device comprising an ion exchanger through which fresh water can be fed before being passed to the washing tub, and a drain line for removing water from the tub, the dishwasher further comprises means for providing for an indirect heat-exchange between the ion exchanger and the drain line.

In a second aspect of the present invention the above object is solved by a method of operating a washing machine, comprising:

passing water via a water-softening device comprising an ion exchanger to a washing tub; heating water that is passed to the washing tub either before or after it enters the washing tub;

removing heated water from the washing tub; and

providing for an indirect heat-exchange between heated water which has been removed from the washing tub and water that is passed to the washing tub via the water-softening device.

The present invention advantageously employs the ion exchanger of the water-softening device also for the heat exchange and thus recognizes that the ion exchanger, which is a component that anyway usually is provided in washing machines, and particularly usually is present in all dishwasher, has a sufficient volume capacity to provide for an efficient and effective heat exchange for heating the washing liquor to be used during a subsequent washing step by the waste heat of washing liquor that has been used in a preceding washing step and which is drained from the washing tub.

Preferred embodiments of the present invention are defined in the dependent claims.

Preferably, said means for providing for an indirect heat-exchange comprises a heat conductor which is arranged in thermal contact with the ion exchanger and the drain line, and which thus provides for a direct transfer of heat from heated water that is removed from the washing tub to fresh water that is passed through the ion exchanger. In order to provide for an efficient transfer of heat, the heat conductor preferably is made of a material exhibiting high thermal conductivity and preferably is made of copper, a copper-containing material, aluminum or an aluminum-containing material.

As in known water-softening devices, the ion exchanger can comprise a compartment that contains an ion exchange material through which fresh water can be fed before being passed to the washing tub, wherein in accordance with the present invention the heat conductor projects into such compartment so as to heat the fresh water by heat that has been removed from the water that is passed through the drain line. Based on the amount of warmed or pre- warmed water required for subsequent cleaning steps, the size of the ion exchanger compartment can be adapted

The ion exchange material can comprise an ion exchange resin, such as an organic polymer containing anionic functional groups to which sodium ions (Na⁺) are electrostatically bound and which can be readily replaced by those ions in the fresh water that are responsible for hardness, such as Ca²⁺ and Mg²⁺.

In order to provide for an efficient heat transfer from the water that is passed through the drain line, the heat conductor can project into the drain line or, in order to avoid that the heat conductor thus causes a higher flow resistance in the drain line, it can comprise a section of heat conducting tubing that is provided in the drain line.

In another preferred embodiment the heat conductor comprises a section of heat conducting tubing that forms part of the drain line and which extends within the ion exchanger. In such embodiment the drain line thus is arranged to extend through the ion exchanger, wherein in order to provide for an indirect heat-exchange between colder fresh water within the ion exchanger and the warmer water removed from the tub via the drain line, at least part of the portion of the drain line that extends through the ion exchanger is made of a heat conducting material. In embodiments wherein the washing machine comprises an intermediate tank arranged to temporarily accommodate water from the washing tub for later use, the drain line can be connected to the intermediate tank. Additionally or alternatively, the drain line can be connected to a waste line for removing water from the washing machine.

In the method of the present invention, the step of providing for an indirect heat-exchange preferably comprises passing heated water which has been removed from the washing tub via a drain line which is in thermal contact with the ion exchanger, wherein in a particularly preferred embodiment of such method prior to removing heated water via the drain line the ion exchanger is filled with fresh feed water, so as to make the most efficient use of the heat contained in the water flowing through the drain line.

Preferred embodiments of the present invention are described below in detail by reference to the attached drawings. While below the present invention is described in further detail by reference to a dishwasher, as noted above, the present invention is not restricted to dishwashers but can be applied with advantage to any kind of washing machine such as commercial or domestic dishwashers, or commercial or domestic clothes washers or laundry machines. In the accompanying drawings:

Fig. 1 is a schematic drawing of a dishwasher made in accordance with the present invention; and

Fig: 2 illustrate a modified embodiment of the dishwasher of figure 1.

The dishwasher shown in figure 1 comprises a washing tub 10 for accommodation of articles to be cleaned. At its lower end, washing tub 10 comprises a sump 12 for collecting any water that has been passed towards the articles to be claimed by means of a rotating spray arm 14 which is fed with water by means of a circulation pump 16. Circulation pump 16 thus draws in, via a filter 18, water that has collected at the bottom of the washing tub, as well as fresh water which is fed to sump 12 via a line 20. At the bottom of sump 12 there further is connected a drain line 22 via which water that no longer shall be used for a further washing step can be removed from the dishwasher via a drain pump 24. Fresh water from a feed line 26 that can be connected to a tap is fed via a water inlet valve 28 to a water softening device of which there is shown in figure 1 only an ion exchanger 30 which in the conventional manner contains an ion exchanger material, such as an ion exchanger resin. The water softening device further typically comprises a salt container (not shown) which is used for regenerating the ion exchanger material within ion exchanger 30.

While the water that is fed to the dishwasher via feed line 26 typically is cold, the water that is drained from sump 12 via drain line 22 typically is warmer, especially in washing cycles that use heated water. Thus, in a typical domestic dishwasher after the main washing step on average an amount of 4 liters of water at a temperature of 40 °C are drained. Assuming that the feed line 26 is connected to a domestic tap which provides fresh water at a temperature of 15 °C, the usable energy content can be calculated by the following formula:

E = mass · specif ic heat capacity of the water · temperature difference In the above example the usable energy content thus can be calculated as:

418,1 kj

E = A kg - 4,181 -^- · (313 K - 288 ΛΓ) = 418.1 kj = kWh = 0,116 kWh

9 ^K 3600

Considering that for example in accordance with the energy label normative applicable in Germany a dishwasher is denoted as "class A" if it has a consumption of l,08kWh, whereas it is denoted "class A+" if it has a consumption of 1 ,02kWh, the difference between A and A+ is only 0.06kWh. That is, if only half of the heat contained in the water used during the main washing step can be recovered, this saving in energy will result in the machine qualifying for a higher energy consumption class.

In order to recover the heat contained in the water to be drained, the dishwasher shown in Fig. 1 further comprises a heat exchanger means which thermally couples drain line 22 to ion exchanger 30. In the embodiment shown in Fig. 1, drain line 22 is arranged to extend in proximity to ion exchanger 30 and comprises a section 32 that is made of heat conducting tubing, such as copper. Within ion exchanger 30 there is provided a heat exchanger plate 34 which is thermally coupled to the heat conducting section 32 via a plurality of heat conductors

36.

While in conventional dishwashers any water that is required for a certain washing step usually is introduced into the dishwasher at the time when such washing cycle shall begin, in the washing machine suggested herein, feed water to be used in a subsequent washing cycle preferably is stored in advance in the ion exchanger, so that such water can be pre-warmed by heat that is removed from water that is removed from the washing tub 10 via waste line 22. In case that a higher temperature is required for a certain washing cycle, the water can be further heated for example by an electric heating means, not shown herein.

In Fig. 2 there is shown a further embodiment of a dishwasher made in accordance with the present invention which in addition to the components of the dishwasher shown in Fig. 1 further comprises an intermediate tank 40 within which water that has been used in a first washing step can be temporarily stored for later use in a subsequent washing step. Thus, if water that has been used within washing tub 10 shall be temporarily stored for later use in a subsequent washing step, such water is drained via a further drain line 42 which is connected via a pump 44 to intermediate tank 40. In order to make use of the heat contained in the water removed from tub 10 via a drain line 42 there is provided for a heat exchanger means 48 between drain line 42 and ion exchanger 30 similarly as it was explained by reference to figure 1. Fresh water that is fed to the dishwasher from feed line 26 via the ion exchanger 30 thus can be warmed within the ion exchanger 30 by heat that has been withdrawn from drain line 42, wherein the feed water then is passed to sump 12 via a feed line 50 which is connected to the ion exchanger 30 via a three-way valve 52. Any water that is not presently required can be fed via three-way valve 52 to intermediate tank 40.

In the embodiment shown in Fig. 2 not only drain line 42 is in a heat exchange relationship with ion exchanger 30 but also drain line 22 via which water can be withdrawn from the washing tub 10 by the action of a drain pump 24 so as to be passed to waste. In the embodiment shown in Fig. 2 drain line 22 is arranged to extend through the ion exchanger 30. In order to provide for an efficient transfer of heat from drain line 22 to ion exchanger 30 the drain line 22 comprises a section 54 which is located within the ion exchanger 30 and which is made of a material having a high thermal conductivity, such as copper or a copper containing material. It should be understood that instead of employing heat exchanger means 48, the heat exchange between drain line 42 and ion exchanger 30 also could be effected by arranging providing drain line 42 with a section made of a material having a high thermal conductivity which passes through the ion exchanger 30.

By the measures suggested herein substantial energy savings can be accomplished at relatively low costs. Thus, for example in a dishwasher that is designed for domestic use, energy savings are expected in a range of about 40 to 60 Wh.

Claims

A washing machine comprising:

a washing tub (10) for accommodating articles to be cleaned;

a water-softening device comprising an ion exchanger (30) through which fresh water can be fed before being passed to the washing tub (10); and

a drain line (22; 42) for removing water from the tub (10);

characterized in that the washing machine further comprises

means (32, 34, 36; 48; 54) for providing for an indirect heat-exchange between said ion exchanger (30) and said drain line (22; 42).

The washing machine of claim 1, wherein said means (32, 34, 36; 48; 54) for providing for an indirect heat-exchange comprises a heat conductor which is arranged in thermal contact with the ion exchanger (30) and the drain line (22; 42).

The washing machine of claim 2, wherein said heat conductor (32, 34, 36; 48; 54) is made of a material exhibiting high thermal conductivity.

The washing machine of claim 3, wherein said heat conductor (32, 34, 36; 48; 54) is made of copper, a copper-containing material, aluminum or an aluminum-containing material.

The washing machine of any one of claims 2 to 4, wherein said ion exchanger (30) comprises a compartment containing an ion exchange material through which fresh water can be fed before being passed to the washing tub (10), wherein said heat conductor (30) projects into said compartment.

The washing machine of claim 5, wherein said ion exchange material comprises ion exchange resin.

The washing machine of any one of claims 2 to 6, wherein said heat conductor projects into the drain line.

The washing machine of any one of claims 2 to 6, wherein said heat conductor comprises a section of heat conducting tubing (32, 54) that is provided in the drain line (22; 42) .

9. The washing machine of any one of claims 2 to 4, wherein said heat conductor comprises a section of heat conducting tubing (54) that forms part of the drain line (22) and which extends within the ion exchanger (30).

10. The washing machine of any one of the preceding claims, further comprising an intermediate tank (40) arranged to temporarily accommodate water from the washing tub (10) for later use, wherein said drain line (42) is connected to the intermediate tank.

11. The washing machine of any one of claims 1 to 9, wherein said drain line (22) is connected to a waste line for removing water from the washing machine.

12. The washing machine of any one of the preceding claims, which is a dishwasher, a clothes washer or a laundry machine.

13. A method of operating a washing machine, comprising:

passing water via a water-softening device comprising an ion exchanger to a washing tub;

heating water that is passed to the washing tub either before or after it enters the washing tub;

removing heated water from the washing tub; and

14. The method of claim 13, wherein the step of providing for an indirect heat-exchange comprises passing heated water which has been removed from the washing tub via a drain line which is in thermal contact with the ion exchanger.

15. The method of claim 14, in which prior to removing heated water via said drain line the ion exchanger is filled with fresh feed water.