METHOD, COMPUTER READABLE MEDIUM AND HOUSEHOLD APPLIANCE FOR PERFORMING LIMESCALE DEPOSITION DETECTION BY THERMAL PULSE TECHNOLOGY

Abstract

A method controls a household appliance being or containing a water heater with regard to limescale deposition. The method includes generating at least one thermal pulse by operation of an electrical heating element of the water heater, and measuring a plurality of successive temperature values. The method further includes determining one or more parameter values of a measurement pattern arising from the plurality of successive temperature values and their respective time of measurement, and ascertaining a limescale deposition state of the water heater based on the determined parameter value. A household appliance contains a computer readable medium having stored thereon instructions configured to trigger, when executed, the household appliance to perform such a method.

Claims

1. A method of controlling a household appliance being or containing a water heater with regard to limescale deposition, the method comprises the steps of: generating at least one thermal pulse by operation of an electrical heating element of the water heater during a pulse time interval; measuring, during a measurement time interval containing the pulse time interval and by at least one temperature sensor, a plurality of successive temperature values; determining at least one parameter value of a measurement pattern arising from the plurality of successive temperature values and their respective time of measurement; and ascertaining a limescale deposition state of the water heater based on the at least one parameter value.

2. The method according to claim 1, wherein the limescale deposition state includes: a limescale accumulation percentage indicator reflecting a current value of a limescale accumulation percentage of the water heater with respect to a predefined maximum accumulation; and/or a decalcifying need indicator reflecting a stage contained in a predetermined graduation of needs for decalcifying the water heater.

3. The method according to claim 1, which further comprises providing a signal to a user based on the limescale deposition state.

4. The method according to claim 1, wherein the at least one parameter value contains: a maximum temperature occurring in the measurement pattern; a maximum temperature difference occurring, in the measurement pattern, between a measured temperature value and its antecedent measured temperature value; a minimum temperature difference occurring, in the measurement pattern, between a measured temperature value and its antecedent measured temperature value; a maximum value of a derivative of a function interpolating the measurement pattern; a minimum value of the derivative of the function interpolating the measurement pattern; and/or a value of a mathematical function applied to at least one of the maximum temperature, the maximum temperature difference, the minimum temperature difference, the maximum value and/or the minimum value.

5. The method according to claim 1, wherein the at least one parameter value includes a moving average of the plurality of successive temperature values over time, and/or a moving average of differences of the successive temperature values over time.

6. The method according to claim 1, wherein the ascertaining of the limescale deposition state is further based on at least one previous parameter value determined with regard to at least one former thermal pulse previously generated by means of the electrical heating element.

7. The method according to claim 1, wherein the thermal pulse has a duration of: at most 5 seconds; and/or at least 0.5 seconds.

8. The method according to claim 1, wherein the thermal pulse has a duration of: at most 4 seconds; and/or at least 1 second.

9. The method according to claim 1, wherein the thermal pulse has a duration of: at most 3 seconds; and/or at least 2 seconds.

10. The method according to claim 1, wherein during the measurement time interval, at least 10 and/or at most 100 of the successive temperature values are measured per second.

11. A non-transitory computer readable medium storing computer executable instructions configured to trigger, when executed, a household appliance being or comprising a water heater with an electrical heating element, at least one temperature sensor and a computer to perform a method of controlling the household appliance, the method comprises the steps of: generating at least one thermal pulse by operation of the electrical heating element of the water heater during a pulse time interval; measuring, during a measurement time interval containing the pulse time interval and by said at least one temperature sensor, a plurality of successive temperature values; determining at least one parameter value of a measurement pattern arising from the plurality of successive temperature values and their respective time of measurement; and ascertaining a limescale deposition state of the water heater based on the at least one parameter value.

12. A household appliance being or comprising a water heater, the household appliance comprising: an electrical heating element; at least one temperature sensor; a computer, wherein the household appliance is configured to perform a method of controlling the household appliance, the method comprises the steps of: generating at least one thermal pulse by operation of said electrical heating element of the water heater during a pulse time interval; measuring, during a measurement time interval containing the pulse time interval and by said at least one temperature sensor, a plurality of successive temperature values; determining at least one parameter value of a measurement pattern arising from the plurality of successive temperature values and their respective time of measurement; and ascertaining a limescale deposition state of the water heater based on the at least one parameter value.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0034] FIG. 1 is a diagrammatic, perspective view of a configuration of a household appliance according to an exemplary embodiment of the present invention;

[0035] FIG. 2 is graph showing a correlation of parameter values of a measurement pattern and respective underlying limescale accumulation percentages, along with a graduation of corresponding needs for decalcifying the water heater;

[0036] FIG. 3A is a graph of a function interpolating correlations of time values to respectively measured successive temperature values, and an underlying heat pulse entailing the temperature values;

[0037] FIG. 3B is a graph showing a derivative of the function of FIG. 3A, along with the underlying heat pulse; and

[0038] FIG. 4 is a flow chart showing steps of a method according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0039] Referring now to the figures of the drawings in detail and first, particularly to FIG. 1 thereof, there is shown an exemplary household appliance 1 according to an embodiment of the present invention is schematically depicted. The household appliance 1 is a water heater, which is depicted as filled with water W. For illustration, the various layers of the water heater as well as a currently present limescale accumulation layer L are shown incomplete, such that an insight in the structure is provided.

[0040] In the example depicted, the household appliance 1 is embodied as a receptacle such as an electric kettle. It contains a body structure 11, an electrical insulation layer 12 and an electrical heating element 13 which in the present case is formed as a laminar layer of the water heater, in particular of its wall. As is to be understood, additionally or alternatively, a bottom area of the water heater may contain at least a part of the/an electrical heating element. housing layer preferably further comprised by the household appliance 1, covering the electrical heating element 13 and insulating it outwardly, is omitted in FIG. 1.

[0041] The household appliance 1 is configured to perform a method according to an embodiment of the present invention. To this end, the household appliance contains a temperature sensor 14 connected to the electrical heating element 13 and to the body structure 11, and a computer unit 15 configured to receive a plurality of temperature values measured by the temperature sensor 14, to determine one or more parameter value/s of a measurement pattern arising from the plurality of successive temperature values and their respective time of measurement, to ascertain a (current) limescale deposition state of the water heater based on the determined parameter value/s, and to cause a gauge 16 further comprised by the household appliance 1 to provide a signal based on the ascertained limescale deposition state. Additionally or alternatively to the analogue gauge 16 shown in FIG. 1, for providing such signal, the household appliance might comprise a digital display, at least one indicator lamp and/or an acoustic signalling means such as a beeper (not shown in FIG. 1).

[0042] In FIG. 2, a correlation of parameter values v of a measurement pattern and respective underlying limescale accumulation percentages is depicted along with a graduation G of corresponding needs for decalcifying the water heater. In the exemplary case depicted, the graduation contains three stages g.sub.1, g.sub.2, g.sub.3: If a limescale accumulation percentage is between 0% and 20%, which in the exemplary diagram of FIG. 2 is derived from parameter values v being in the range from about 3.2 to 4, the stage g.sub.1 indicates a low need for decalcifying the water heater. By contrast, if the parameter values v are in the range from about 1.95 to about 3.2, they indicate a limescale accumulation percentage from 20% to 50%, which means a medium need for decalcification of the water heater, as indicated by the stage g.sub.2. A limescale accumulation percentage higher than 50% can be concluded from parameter values smaller than about 1.95 and requires decalcifying the water heater for maintaining its safe operability, which is reflected by a stage g.sub.3.

[0043] FIG. 3A exemplifies steps carried out according to a method subject to the present invention: Therein, an interrelation between a generated thermal pulse P and a measurement pattern Q arising from successively measured temperature values is illustrated by graphs showing the respective progressions during a measurement time interval I.

[0044] Indeed, the lower graph in FIG. 3A indicates a thermal pulse generated during a pulse time interval D contained by the measurement time interval I. Therein, the ordinate specifies a voltage ratio for the electrical heater element as compared to a standard operating voltage thereof, and the abscissa specifies the progress in time.

[0045] The upper graph in FIG. 3A illustrates a plurality of temperature values measured during the measurement time interval I. In the figure, to improve clearness of the picture, only temperature values T.sub.n−1, T.sub.n and T.sub.k are referenced.

[0046] To visualise the correlation of the thermal pulse P and the measurement pattern Q, the abscissa of this graph coincides with that of the lower graph, whereas the ordinate specifies the respective temperature T.

[0047] The respective limescale accumulation on a surface of the water heater may significantly change the thermal transient condition on the heater surface. This may have considerable influence on the measurement pattern Q under non-equilibrium thermal state, generated by the (short) thermal pulse. However, the measurement pattern Q may typically depend on heat propagation through the structure of the water heater, on heater-water transient parameters and/or on heat convection around heater structure caused by flowing (surrounding) water. Therefore, any change in those parameters may have its mirroring response in the measurement pattern Q.

[0048] As can be seen in FIG. 3A, during a pre-monitoring time interval temperature values are measured before the thermal pulse P is generated. In the present exemplary case, a temperature tightly above 0° C. is measured. The thermal pulse P is then generated during the pulse time interval D (and lasting this interval D), which in the present case has a duration of about 3 seconds. During the pulse time interval D, the respectively measured temperature values increase. At an end of the thermal pulse, a maximum temperature M.sub.t is measured. Thereafter, in a subsequent time interval i.sub.2, the measured temperature values decrease over time.

[0049] The maximum temperature M.sub.t may be determined as a parameter value of the measurement pattern Q, based on which a (current) limescale deposition state of the water heater may be ascertained.

[0050] Additionally or alternatively, further characteristics of the measurement pattern may be considered to ascertain the limescale deposition state. For instance, a plurality of temperature differences between subsequent (neighboured) measured temperature values may be calculated, such as the difference Δ.sub.n=T.sub.n−T.sub.n−1. These differences may be compared with each other. For instance, a maximum and/or a minimum temperature difference occurring, in the measurement pattern Q, between a measured temperature value and its antecedent measured temperature value may respectively be determined as a parameter value, based on which a current limescale deposition state of the water heater may be ascertained.

[0051] Similarly, a derivative of a function interpolating the measurement pattern Q may (additionally or alternatively) be considered, as illustrated in the upper graph shown in FIG. 3B. Therein, the above-described graph representing the thermal pulse P is again reproduced, as a lower graph, so as to visualise the correlation of the derivative and the thermal pulse P.

[0052] A maximum value M.sub.d and/or a minimum value m.sub.d of the derivative may respectively be determined as a parameter value, based on which a current limescale deposition state of the water heater may be ascertained.

[0053] FIG. 4 depicts various steps of a method M according to a possible embodiment of the present invention. To increase intelligibility, in the following the steps are described with further reference to FIG. 3A.

[0054] In a step S.sub.1, a water heater of a household appliance is filled with water (e.g., with tap water), preferably up to a predefined operating level of the water heater.

[0055] Thereafter, in a step S.sub.2, a water temperature is pre-monitored during a pre-monitoring time interval i.sub.1 as indicated in FIG. 3A; if included in the household appliance, a circulation pump of the household appliance may further be run.

[0056] A step S.sub.3 then comprises generating a thermal pulse P by operating an electrical heating element of the water heater. The operating the electrical heating element may be performed with a standard operating voltage of the electrical heating element or with a voltage which is reduced in comparison with the standard operating voltage; the latter reduced voltage may be protective and thus advantageous in particular in case of a possible heavy limescale accumulation.

[0057] In a step S.sub.4, successive temperature values T.sub.n−1, T.sub.n, T.sub.k resulting from the thermal pulse are measured during the duration thereof.

[0058] In a step S.sub.5, further successive temperature values resulting from the thermal pulse are measured in a subsequent time interval i.sub.2 following an end of the thermal pulse P. The time interval I during which the plurality of successive temperature values are measured in accumulated steps S.sub.2, S.sub.4 and S.sub.5, thus exceeds an end of the thermal pulse P by the subsequent time interval i.sub.2. During the time interval i.sub.2, the temperature values preferably reduce to at most a half or a third of the maximum temperature M.sub.t (being a peak value of the measured temperature values). Preferably, the length of the subsequent time interval i.sub.2 is at least as long as the duration of the thermal pulse, as indicated in FIG. 3A.

[0059] In a step S.sub.6, one or more parameter value/s of a measurement pattern Q containing the plurality of successive temperature values are determined. The parameter value/s may further be stored in a data memory. It/they may comprise a maximum temperature M.sub.t occurring in the measurement pattern, a maximum and/or a minimum temperature difference respectively occurring, in the measurement pattern Q, between a measured temperature value and its antecedent measured temperature value, and/or a value of a mathematical function applied to one or more of the values. In particular, the one or more parameter value/s may comprise a moving average of the plurality of measured successive temperature values T.sub.n−1, T.sub.n, T.sub.k over time, and/or a moving average of differences of measured successive temperature values over time.

[0060] A step S.sub.7 then includes ascertaining a (current) limescale deposition state of the water heater based on the determined parameter value/s. The such ascertained limescale deposition state may comprise one or more indicators, such as a limescale accumulation percentage indicator reflecting a current value of a limescale accumulation percentage of the water heater with respect to a predefined maximum accumulation. Additionally or alternatively, the ascertained limescale deposition state may comprise a decalcifying need indicator reflecting a respective current degree of need for decalcifying the water heater, as contained in a predetermined graduation (see FIG. 2).

[0061] The ascertaining may be further based on one or more previous parameter value/s determined (and stored) with regard to at least one former thermal pulse previously generated by means of the electrical heating element, based on a frequency of utilization of the water heater and/or based on a duration a last decalcification of the water heater dates back.

[0062] In step S.sub.8, based on the ascertained limescale deposition state, a signal is provided to a user, such as by means of an analogue and/or digital gauge (which may, for instance, indicate a respective (current) limescale accumulation percentage) and/or by a graded indication of a degree of need for decalcifying the water heater (such as by means of at least one indicator lamp and/or an acoustic identification).

[0063] Disclosed is a method M of controlling a household appliance 1 being or containing a water heater with regard to limescale deposition. The method includes generating at least one thermal pulse P by operation of an electrical heating element 13 of the water heater, and measuring a plurality of successive temperature values T.sub.n−1, T.sub.n, T.sub.k. The method further contains determining one or more parameter value/s p of a measurement pattern Q arising from the plurality of successive temperature values T.sub.n−1, T.sub.n, T.sub.k and their respective time of measurement, and ascertaining a limescale deposition state of the water heater based on the determined parameter value/s p.

[0064] Further disclosed are a household appliance 1 configured to perform such a method M, and a computer readable medium having stored thereon instructions configured to trigger, when executed, a household appliance to perform such a method M.

[0065] The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention: [0066] 1 household appliance [0067] 11 body structure [0068] 12 electrical insulation layer [0069] 13 electrical heating element [0070] 14 temperature sensor [0071] 15 computer unit [0072] 16 gauge [0073] D pulse time interval [0074] Δ.sub.n difference between subsequent measured temperatures [0075] g.sub.1, g.sub.2, g.sub.3 stage [0076] G predetermined graduation [0077] i.sub.1 pre-monitoring interval [0078] i.sub.2 subsequent time interval [0079] I measurement time interval [0080] L limescale accumulation layer [0081] M method [0082] m.sub.d minimum value of the derivative of a function interpolating the measurement pattern Q [0083] M.sub.d maximum value of the derivative of a function interpolating the measurement pattern Q [0084] M.sub.t maximum temperature [0085] p parameter value [0086] P thermal pulse [0087] Q measurement pattern [0088] S.sub.1-S.sub.8 method steps [0089] T temperature [0090] T.sub.k, T.sub.n−1, T.sub.n measured temperature value [0091] W water