Device and method for indirectly measuring the temperature of hot water in a storage tank

Abstract

The invention relates to a method for indirectly measuring the temperature of hot water in a water heater (1), the water heater comprising a tank (13) having a wall delimiting an internal cavity suitable for containing a volume of water to be heated, an insulating material casing (12) surrounding the tank (13), and a skin (11) surrounding the insulating material casing (12). The method comprises the steps of: - measuring a temperature Tp e of the skin (11) by means of a sensor (5) positioned in contact with an external surface of the skin (11), - determining the temperature of the water contained in the internal cavity as a function of the measured temperature Tp e of the skin (11) and an ambient air temperature T air around the water heater (1). (Shorthand figure: Figure 4)

Description

Description Title of the invention: Device and method for indirect measurement of the hot water temperature in a storage tank FIELD OF THE INVENTION

[0001] The invention lies in the field of energy management in buildings. More In particular, the invention relates to a method for indirect measurement of the tem- hot water temperature included in a water heater or storage tank. STATE OF THE ART

[0002] — A water heater (also called a hot water tank) generally includes, inside to outside, a tank, insulation generally formed of poly- injected urethane, and a skin that is usually formed of metal or plastic. As a general rule, obtaining an internal temperature of the tank requires the implementation of installation of temperature probes inside the tank or on the tank,

[0003] For existing tanks, the installation of such probes requires interventions on the hydraulic and electrical circuit of the balloon, and therefore the expertise of a professional, the user cannot carry out such operations by himself.

[0004] In addition, the installation of such probes requires intervention on the insulation, and therefore can create thermal bridges which compromise the thermal sealing of the tank.

[0005] There are recent water heaters which integrate internal sensors, arranged in the tank so as to measure the temperature of the water in the tank. However, this is of a minority of water heaters, and the majority of existing water heaters do not do not have such sensors.

[0006] Water heaters known from the state of the art are generally supplied with night or during off-peak hours, and only during these periods, so that in the event of a significant use of domestic hot water during the day, the planned stock may not Be sufficient, and the user may unexpectedly run out of water domestic hot water. Statement of the invention

[0007] An aim of the invention is to enable real-time evaluation of a tem- water temperature in a water heater or hot water storage tank, without the need to perform complex operations or degrade the structure of the water heater.

[0008] For this purpose, a method is provided for indirectly measuring a water temperature. hot in a water heater, the water heater comprising a tank comprising a wall delimiting an internal cavity suitable for containing a volume of water to be heated, a insulating material envelope surrounding the tank and a skin surrounding the envelope in insulating material, the method comprising steps of: - measure a 7p temperature of the skin using a sensor positioned in contact with an external surface of the skin, - determine the temperature of the water contained in the internal cavity as a function of the temperature Tp, measured from the skin and a temperature 7,; of the ambient air around the water heater. Thus, the invention makes it possible to estimate in real time the temperature of the hot water contained in the water heater, on all types of hot water tank and without requiring intrusive intervention or requiring particular expertise. According to one implementation of the method, the ambient air temperature T4; is measured by means of an ambient air probe. According to one implementation of the method, the volume of water contained in the internal cavity is modeled as a stack of several horizontal layers, and for each layer of a first subset of layers of the stack, a temperature of the layer is measured by means of a respective sensor placed in contact with the external surface of the skin, opposite the horizontal layer. According to one implementation of the method, for each layer of a second subset of layers distinct from the first subset of layers, the temperature of the water in the internal cavity is estimated by interpolation or extrapolation from the temperatures measured for the layers of the first set of layers. According to one implementation of the method, the temperature 7p; of the water in the internal cavity of the water heater or in a horizontal layer of the first set of layers is determined according to the equation: Tp,= k(Tp,-Tair)+Tp, where k is a coefficient determined for each sensor, Zp, is the temperature measured on the external surface of the skin and 7,, is the ambient air temperature. According to one implementation, the method comprises a calibration phase during which the coefficient k for each sensor is determined according to the following successive steps: - detection of a charged state of the water heater; - detection of water withdrawal when the temperature of domestic hot water leaving the tank Tzcs measured by the probe increases suddenly up to a predefined threshold temperature Tu; - obtaining a domestic hot water temperature coming out of the Trcs tank; - initiation of a recording of the temperatures Tp, measured by the sensors, and of the ambient air temperature 7,; around the water heater; - calculation of the coefficient k for each sensor using the equation: The Tres TP, = According to one implementation of the method, the water heater is considered to be in the loaded state when a loading of the water heater with hot water has been carried out for a period of time greater than a minimum time necessary for loading the water heater. The invention further relates to a method for estimating the volume of domestic hot water contained in a water heater containing a total volume of water, the volume of hot water being defined as the volume of water having a temperature greater than or equal to a Tru value, comprising the steps of: - estimating a water temperature value in each layer of a plurality of horizontal layers of the total volume of water, by means of the method for indirect measurement of hot water temperature according to the invention, - estimate the volume of domestic hot water in the water heater based on: i, of a volume of each horizontal layer comprising hot water having a temperature greater than or equal to the value Tu ii, of the estimated temperature of each horizontal layer comprising hot water having a temperature greater than or equal to the value 7 .ur iii. a cold water temperature entering the water heater. According to one implementation of the method, the volume of domestic hot water contained in the water heater is obtained using the equation: “ T-Trr V,= Lava where: and n represent, respectively, each horizontal layer and the total number of horizontal layers comprising hot water having a temperature greater than or equal to the value T,.…, Vi is the volume of water in the layer;, Ti is the temperature of the layer; and Tzr is a temperature of the cold water entering the water heater. The invention further relates to a method for analyzing the scaling of a water heater at a given time, comprising the following steps: - estimation of an initial time interval required to heat a volume of water in a water heater when the water heater is not scaled; - estimation of a second time interval necessary to heat the same volume of water in the water heater at the given time; - comparison of the first time interval and the second time interval, an increase in the time required to heat the volume of water being indicative of scaling of the water heater; each of the first and second time intervals corresponding to a time interval necessary for a temperature of the volume of hot water in the heater to water (1) estimated by means of the indirect hot water temperature measurement method according to the invention is greater than a predefined value T,.…. The invention further relates to a water heater kit, comprising: - a case, - a sensor, the sensor being capable of measuring a temperature Tp, of the external surface of a skin of the water heater, the housing being capable of receiving measurements carried out by the sensor, the housing being further capable of implementing the method for estimating the temperature of the hot water according to the invention. According to one embodiment of the kit, the housing comprises a communication interface capable of transmitting a signal containing data representative of temperature values ​​measured by the sensor to a remote server so that the data can be analyzed and / or transmitted to a portable terminal. According to one embodiment of the kit, the housing is furthermore capable of sending a notification to the portable terminal when the volume of hot water available in the water heater falls below a predefined volume, and / or the housing is capable of receiving a remote command to start the water heater from the portable terminal. The invention further relates to an assembly comprising - a water heater including: 1, a tank, the tank comprising a wall delimiting an internal cavity suitable for containing a volume of water to be heated, li. an envelope of insulating material surrounding the tank and lii, a skin surrounding the envelope of insulating material; - a sensor placed in contact with an external surface of the skin and - a housing capable of receiving measurements taken by the sensor and of implementing the method for estimating the temperature of the hot water according to the invention. DESCRIPTION OF THE FIGURES We will now present an embodiment of the invention by way of non-limiting example in support of the drawings in which: [Fig.1] is a diagram showing a typical water heater structure. [Fig.2] is a diagram showing a sectional view of a water heater, showing data used in the proposed method. [Fig.3] is a diagram illustrating a modeling step of the hot water tank, according to an implementation of the proposed method. [Fig.4] is a diagram illustrating a particular implementation of the method, as well as a kit suitable for implementing the method. [Fig.5a] and [Fig.5b] illustrate an experimental setup and the results of the associated experiment, carried out by the inventors to demonstrate the reliability of the proposed method. DETAILED DESCRIPTION With reference to [Fig. 1], a water heater 1 comprises a tank 13 in which the stored water is placed, insulation 12 and a generally metallic skin 11. The tank is supplied with cold water at a temperature between 5 and 20°C by a water inlet 3 placed in the lower part of the water heater 1 and makes it possible to supply various devices via a water outlet 2 placed in the lower or upper part of the water heater 1, the devices thus supplied being able in particular to include taps, household appliances or shower heads. The hot water is produced by an electrical resistance 10 placed inside the tank 13 which heats all of the water contained in this tank 13 to a temperature between 45 and 80°C by consuming electricity from the network (power supply not shown in [Fig. 1]). With reference to [Fig. 3], the proposed method comprises a first step of measuring temperatures carried out using one or more sensors 5 arranged outside the water heater 1, on the external surface of the skin 11. The temperature T; of the water contained in the internal cavity can then be estimated from the temperatures Tp, measured by the sensors 5, as well as a temperature T;;, of the ambient air in the environment of the water heater. Such sensors 5 can be arranged on the external surface of the skin 11 on any water heater and by any user, the installation not requiring any specific skills in plumbing, measurement or electricity. In addition, it is not necessary to dismantle the tank or to make an opening in the insulation 12, which is necessary in the methods known from the state of the art in order to place sensors directly measuring a water temperature in the internal cavity of the tank 13. The sensors 5 may, without limitation, be chosen from thermistors, thermocouples, digital sensors capable of generating a usable signal without processing, Pt100 temperature probes (i.e. having a resistance of 100 Ohms at 0°C) or Pt1000 (resistance of 1000 Ohms at 0°C) sensors. Pt100 probes have the advantage of being precise, while thermistors provide less precise measurements but have a lower cost. Each sensor can be attached by a magnet, adhesive tape, strap, suction cup or any other suitable means of attachment. According to one implementation, the method uses two expressions to obtain a thermal power passing through the insulation of the tank. With reference to [Fig.2], we can define a thermal power @7z passing through the balloon according to the equation: = SIi-Tair Qu =s dt where S is the surface area of ​​the water heater wall considered; T4; is the temperature of the ambient air; 7; is the temperature of the water placed in the internal cavity of the tank 13, which is to be estimated; Tp. is the temperature of the external wall of the skin 11; Tp; is the temperature of the internal wall of the skin; h; is a convective exchange coefficient between the water placed in the tank 13 and the internal surface of the skin 11 and Δ, is a convective exchange coefficient between the ambient air and the external surface of the skin 11; e is a thickness of the insulation and Δ is a thermal conductivity of the insulation. The thermal power passing through the balloon insulation can also be expressed as a function of the layers it passes through, according to the equation: Qrh=h,S (Tp,-Tair)= #2 (Tp,-Tp,) Thus, a comparison of equations 1 and 2 leads to the equation: Tp,= $he(Tp,-Tair)+Tp, Taking into account the heat exchanges present in the tank, it can be estimated that h; is much greater than h,, so that the internal temperature T, and the temperature of the internal wall Tp; of the tank 11 are identical. When the tank is completely charged, that is to say when all the water contained in the tank 13 is hot, these temperatures are equal to the temperature Tzcs of the water leaving the tank through the water outlet 2: Tp,= Ti=T ECS Using this assumption in equation 3, we obtain: Very-TP, at cr FE Tp Fair Or [Math 6] &=5 x he. This coefficient k therefore makes it possible to define a single unknown comprising all the unknowns of equation 3, namely the exchange coefficient h, and the characteristics relating to the insulation e and A. Once this coefficient k is known, in particular thanks to a calibration process which will be defined later, the temperature of the water inside the tank can be calculated according to the equation: Ti=Tp,=k(Tp,-Tair)+Tp, According to one implementation, an ambient air sensor 6 will be placed in the environment of the hot water tank 1, which will allow the temperature of the ambient air 7 to be measured in real time. The ambient air sensor 6 can advantageously be placed high up, close to the water heater 1 — for example along a wall along which the water heater is installed. When the water heater is placed in a cupboard, the ambient air sensor 6 can be placed inside the cupboard. The ambient air sensor 6 should ideally be placed away from any obstacle. [Fig. 3] illustrates a phenomenon called "stratification": in a water heater 1, the density of the water decreases with the temperature, so that the hot and cold waters are positioned separately in a plurality of layers in a vertical direction, going from the coldest layers at the bottom of the water heater to the hottest layers at the top of the tank. At the interface between two adjacent layers, the temperature gradient is very high, so that there is an abrupt temperature transition from one layer to the other. Thus, in order to represent this physical phenomenon more faithfully to reality, the method comprises, according to a particular implementation, a modeling of the volume of water contained in the internal cavity arranged in the tank 13 in several horizontal layers. For a first set 21 of horizontal layers, the temperature of each layer is measured by means of a respective sensor 5, placed in contact with the external surface of the skin 11 opposite the corresponding horizontal layer. In order to obtain an accurate measurement of the temperature of the external surface of the skin 11 for each layer, it is possible to provide that the first set 21 comprises all the horizontal layers, that is to say that each defined horizontal layer is associated with a separate sensor 5 measuring its temperature. Alternatively, and in order to reduce the number of sensors required for the measurement step and the number of measurements to be made, a second set 22 of horizontal layers can be defined, distinct from the first set 21. In this implementation, each horizontal layer of the first set 21 is associated with a distinct sensor 5, and the horizontal layers of the second set 22 are not associated with any sensor. According to the non-limiting example of [Fig. 3], layers 2, 5 and 8 belong to the first set 21 and layers 1, 3, 4, 6, 7, 9 and 10 belong to the second set 22 of horizontal layers. The temperatures of each layer of the second set 22 are then obtained: - either by interpolation, when said layer of the second set 22 is arranged between at least two layers of the first set 21. According to the example illustrated in [Fig.3], this is the case for layers 3, 4, 6 and 7; - either by extrapolation, when said layer of the second set 22 is arranged vertically above the highest layer of the first set 21, or vertically below the lowest layer of the first set. According to the example illustrated in [Fig.3], this is the case for layers 1, 9 and 10. According to an implementation of the method, the interpolation and / or extrapolation is a linear interpolation and / or extrapolation. Alternatively, a polynomial interpolation and / or extrapolation, or any other type of interpolation and / or extrapolation, may be provided. As mentioned previously, according to one implementation, the proposed method comprises a calibration phase of the coefficient k presented in equation 5. This calibration phase is carried out following the steps of measuring a temperature of the skin 11 and determining a temperature of the water contained in the internal cavity of the tank 11 of the method. For this phase, it is necessary to obtain a temperature Tzcs of the hot water leaving the water heater 1 through the water outlet 2. For this purpose, an outgoing water probe 7 can be provided along the water outlet 2 in order to measure this temperature Tzcs. This gives an accurate estimate of the temperature of the water leaving the water heater 1. The calibration phase includes the following successive steps: - detection of a charged state of the water heater; - detection of water withdrawal. When water is withdrawn, the temperature of the water leaving the water heater increases suddenly. A threshold temperature T sui is defined, for example but not limited to 40°C, beyond which the water is considered hot. Thus, water withdrawal is detected when the water increases suddenly so as to pass to a temperature higher than the threshold temperature 7... for example but not limited to in less than 30 seconds; - obtaining the temperature Tzcs of outgoing domestic hot water measured by probe 7, according to one of the two implementations defined above; - an initiation of a recording of the temperatures 7p, measured by each sensor 5, and of the temperature T,;, measured by the probe 6 of the ambient air around the water heater 1; - a calculation, for each sensor, of a coefficient k using equation 5. When the use of an outgoing water probe 7 is intended to measure the outgoing water temperature Tzcs, it is possible to regularly renew the calibration phase, for example once a month, so as to update the coefficient k, the outgoing water temperature Tzcs being able to vary over time. This ensures that, at all times, an accurate estimate of the coefficient k is available despite such variations. According to one implementation of the method, a minimum time required for loading the water heater 1 is known prior to the calibration phase, for example following the performance of tests. A loaded state of the water heater 1 is then detected when the time elapsed since the initiation of loading exceeds this minimum time required. This implementation allows in particular the detection of a loaded state of the water heater 1 when a single sensor 5 is placed on the external surface of the skin 11. Alternatively, and only when at least two sensors 5 have been placed on the external surface of the skin 11, a maximum difference in measured temperature can be defined, so that any difference between two temperatures Tp, measured by any two sensors is less than this predefined maximum difference. Indeed, when the water heater is in its fully loaded state, the temperatures Tp, measured by the different sensors are necessarily close. The invention further relates to a method for estimating a volume of domestic hot water V; contained in a water heater 1 containing a total volume of water. According to a convention known to those skilled in the art, it is common to define such a volume of hot water as being the total volume of water whose temperature is greater than a predefined threshold value 7. In the loaded state of the water heater 1, this volume of hot water V, is equivalent to or greater than the total volume contained in the water heater 1. The method for estimating a volume of domestic hot water comprises a first step of implementing the temperature estimation method defined above, so as to estimate a temperature value T; of the water in a plurality of horizontal layers of the total volume contained in the water heater. Thus, certain layers will have a temperature 7; estimated greater than or equal to the threshold value Tru and other layers will have a temperature 7; estimated lower than the threshold value T;ruit- The method includes a second step, during which the volume V7 of domestic hot water is estimated only based on the layers whose temperature 7; is greater than or equal to the threshold value Ti. More specifically, the volume V, of domestic hot water is estimated using a weight function (or weighted sum) in which the volumes of the layers whose temperature is greater than or equal to the threshold value T,… are added together, assigning them a coefficient that increases with their temperature. This translates into mathematical terms the fact that hot water, for example at 40°C, defined as water at the threshold temperature T,eui, is obtained by mixing cold water, for example at 20°C, and hot water, for example at 65°C, from one of the layers whose temperature is greater than Tu. Thus, for two layers C1 and C2 of the same volume and respective temperatures T / and T2 where T12T can T22 T threshold T1>72 A greater volume of hot water will be obtained from layer C1 than from layer C2. The use of a weighted sum thus allows an estimation of the volume of domestic hot water which takes into account the actual use that a user will make of it. According to a particular implementation of the method, the volume of domestic hot water contained in water heater 1 will be obtained by means of the following weight function: to T-Ter V,= Davos where ; and n represent, respectively, each horizontal layer and the total number of horizontal layers comprising hot water having a temperature greater than or equal to the value T,.… Vi is the volume of water in the layer;, Ti is the temperature of the layer; and Tyy is a temperature of the cold water entering the water heater 1. For this purpose, one can: - either take a measurement of the cold water temperature Tz using a cold water probe (not shown in the figures) placed on the water inlet 3. This has the advantage of ensuring an accurate estimate, at any time, of the cold water temperature Ter - either take a measurement of the temperature 7z= of cold water by means of one of the sensors 5 arranged on the external surface of the skin 11. We thus implement the hypothesis according to which the temperatures Tp, measured by the sensors 5 are equal to the temperature of the incoming cold water 7;#when the water heater 1 before the initiation of a loading of the water heater 1. - either estimate the temperature of the cold water 7, for example based on time and date data and / or geographical coordinates of the location of the water heater 1. This eliminates the need to use an additional probe to measure the temperature of the cold water Ter. The total volume of the water heater is generally known depending on the water heater model concerned. When this is not the case, the user can measure the perimeter and height of the water heater in order to estimate its volume. If necessary, a human-machine interface 14 can be provided allowing the user to specify such data. The invention further relates to a method for analyzing the scaling of a water heater | at a given time. Scaling of a water heater 1, corresponding to the formation of a limescale deposit in the lower part of the tank 13, on the electrical resistance 10 and on the internal wall of the tank 13, by solidification, under the effect of heat, of mineral salts contained in the drinking water - in particular calcium and magnesium. Scaling reduces the volume of the internal cavity of the tank 13 available for storing domestic hot water, and increases the time required for the tank during loading to reach the fully loaded state because it adds thermal resistance between the electrical heating resistance and the water in the tank. It is therefore possible to highlight scaling by identifying a drift in the necessary loading time. For this purpose, the proposed method for analyzing the scaling of a water heater at a given time includes the following steps: - estimation of a first time interval necessary to heat a volume of water in water heater 1 when the water heater is not scaled; - estimation of a second time interval necessary to heat the same volume of water in water heater 1 at the given time; - comparison of the first time interval and the second time interval; each of the first and second time intervals corresponding to a time interval necessary for a temperature of the volume of hot water in the water heater 1 estimated by means of the temperature estimation method according to the invention to be greater than a predefined value T,.…. It is possible, for an existing water heater, not to be able to estimate a first time interval necessary for loading before scaling, if the water heater 1 is already scaled. In this case, a plurality of measurements of a real time period necessary for loading the water heater 1 can be carried out, for example a given number of measurements per day over several days, then the increase in loading time can be studied. A significant increase in the time necessary for loading will thus make it possible to characterize scaling of the water heater 1. In particular, it will be possible to define a difference in loading time beyond which it is considered that scaling of the water heater 1 is characterized. The invention further relates to a kit for a water heater, comprising a housing 4 and at least one sensor 5, the sensor 5 being capable of measuring a temperature Tp, of the external surface of the skin 11 of the water heater 1 and of receiving measurements carried out by the sensor 5. According to one embodiment, the housing 4 comprises the human-machine interface 14 allowing the user to enter data relating to the water heater 1, such as, but not limited to, the measured perimeter and height of the water heater 1 necessary for a volume calculation according to the proposed method or the volume of the tank 13 when this value is known. According to one embodiment, the housing 4 is capable of implementing the method for estimating the temperature of the domestic hot water according to the invention. The housing 4 may comprise a communication interface capable of transmitting a signal containing data representative of temperature values ​​measured by the sensor 5 to a remote server 8. Thus, this data may be processed and / or transmitted to a portable terminal 9, for example but not limited to a computer, a mobile phone or a tablet. The housing 4 may also comprise a local memory capable of storing, at least temporarily, the data representative of temperature values ​​measured by sensor 5. According to one embodiment, the housing 4 may also be able to send a notification to the portable terminal 9. Such a notification may in particular be sent to alert a user that the volume of hot water available in the water heater 1 falls below a predefined volume. Thus, a user located far from his home or in a room not including the water heater 1 may be alerted that he risks running out of domestic hot water. According to one embodiment, advantageously complementary to the previous one, the box 4 is able to receive a signal from the portable terminal 9, in particular a start and / or stop command. Thus, the user will be able to initiate a loading of the water heater 1 remotely, in particular after receiving a notification from the box 4 informing him that the remaining volume of hot water is below a predefined threshold. A user who will leave his home for one or more days will thus be able to ensure that he has sufficient domestic hot water upon his return for the urgent uses that he wishes to make of it, According to one embodiment, the portable terminal 9 comprises an application capable of managing communications with the box 4. The portable terminal 9 may then comprise a second human-machine interface 14', either when the box 4 does not comprise a human-machine interface, or in addition to the human-machine interface 14 of the box 4. The user may therefore benefit from a fluid human-machine interface when receiving data from the box 4 and / or sending a signal to the box 4 from the portable terminal 9. The invention further relates to an assembly comprising: - a water heater 1 comprising: 1, a tank 13, the tank comprising a wall delimiting an internal cavity suitable for containing a volume of water to be heated, li. an envelope 12 made of insulating material surrounding the tank 13 and lii, a skin 11 surrounding the envelope 12 made of insulating material; - a sensor 5 placed in contact with an external surface of the skin 11 and - a housing 4 capable of receiving measurements taken by the sensor 5 and of implementing the method for estimating the temperature of the domestic hot water according to the invention. Additionally, the water heater 1 may comprise an actuator 15 capable of providing authorization and / or prohibition of charging of the water heater 1. This makes it possible to provide automated authorization of charging, in particular when the volume of hot water calculated in the tank is low and a shortage of hot water is anticipated. This also makes it possible to provide a prohibition of charging, in particular when the electrical network is saturated and it is necessary to reduce the consumption of users. lizers. Consumption can then be shifted and automatic charging authorization can be provided for later in the day, in which case the actuator 15 can be controlled by a programming clock. The actuator 15 can also perform a charging prohibition in order to avoid losses due to energy consumption to maintain the hot water temperature, so-called maintenance consumption, after detection of saturation of the tank charge. The invention finds other applications allowing the improvement of the services available to the user. A non-exhaustive list of these applications includes: - detection of a hot water draw-off, by calculating the temperature of the water in the internal cavity of the tank 13 and highlighting a sudden increase up to a value greater than a predefined threshold value 7,.,; - a periodic calculation, for example daily, of a volume of domestic hot water consumed; - a thermal loss assessment, by comparing the energy consumption of water heater 1 with the effective energy calculated as a function of the volume of domestic water heated and the increase in the temperature of this volume; - management of the recharging of the water heater in order to leave a predefined capacity for the storage of hot water heated using non-storable electrical energy. For example, a user generating his own electrical energy using photovoltaic panels can thus ensure that he does not lose energy by using it to heat a volume of water that can be stored in the water heater 1. It may then be interesting to provide that the actuator 15 authorizes an automatic charging of the water heater 1 when it is necessary to store electrical energy. - an alert to the user when the temperature of the domestic hot water contained in the water heater | is higher than a value required by the user, so as to avoid unnecessary energy expenditure for heating the water. Figures 5a and 5b respectively illustrate an experimental setup and the associated results, corresponding to an experiment carried out by the inventors to confirm the operation and reliability of the temperature calculation method according to the invention. 'Three sets of sensors 31-33 were positioned on the outer surface of the skin of an electric water heater, respectively at three heights. The water heater included a 200L tank. Each set of sensors 31-33 included three sensors placed at 120° intervals along the perimeter of the water heater. With reference to equation 3, the temperatures 7p; calculated on the basis of the measurements Tp. made by the sensors 31-33 were compared to temperatures recorded using several probes 35 pre-installed on the inner wall of the tank, thus making it possible to measure the temperatures Tp; of the inner wall. In [Fig.5b], curves I-III represent the internal temperature measurements Tp; carried out directly by the probes 35, respectively for the probes 35 arranged opposite the series of low 31, intermediate 32 and high 33 sensors. Curves i-iii represent the temperatures Zpi calculated on the basis of the measurements Tp, carried out by the sensors 31-33. The experiment thus carried out showed that sensors 31-33 provided a reliable image of the internal temperature of the tank, and also made it possible to identify hot water withdrawal events.

Claims

Claims

1. Method for indirectly measuring a hot water temperature in a water heater (1), the water heater comprising a tank (13) comprising a wall delimiting an internal cavity capable of containing a volume of water to be heated, an envelope (12) of insulating material surrounding the tank (13) and a skin (11) surrounding the casing (12) made of material insulator, the method comprising steps of: - measure a temperature (7p,) of the skin (11) by means of a sensor (5) positioned in contact with an external surface of the skin (11), - determine the temperature of the water contained in the internal cavity by function of the measured skin temperature (Tp,) (11) and a tem- temperature (7) of the ambient air around the water heater (1).

2. The method of claim 1, wherein the air temperature ambient (Ter) is measured by means of an ambient air probe (6).

3. Method according to one of claims 1 or 2, wherein the volume of water contained in the internal cavity is modeled as a stack of several horizontal layers, and in which for each layer of a first subset of layers (21) of the stack, a tem- The temperature of the layer is measured by means of a respective sensor (5) placed in contact with the external surface of the skin (11), opposite the horizontal layer.

4. A method according to claim 3, wherein for each layer of a second subset of layers (22) distinct from the first subset set of layers (21), the temperature of the water in the internal cavity is estimated by interpolation or extrapolation from temperatures measured for the layers of the first set of layers (21).

5. Method according to one of claims 1 to 4, in which the temperature (Tp;) water in the internal cavity of the water heater (1) or in a horizontal layer of the first set of layers (21) is determined according to the equation: Tp,= k(Tp,- Tair) +Tp, where k is a coefficient determined for each sensor (5), Zp, is the tem- temperature measured on the external surface of the skin and 7, is the tempera- ambient air temperature.

6. Method according to claim 5, comprising a calibration phase during which the coefficient k for each sensor (5) is determined according to the following successive steps: - detection of a charged state of the water heater (1); - detection of water withdrawal when a hot water temperature sanitary water leaving the tank (Tzcs), measured by an outgoing water probe (7) positioned along a water outlet (2) of the water heater (1), increases abruptly to a predefined threshold temperature (All) 3 - obtaining the temperature of domestic hot water leaving the tank (7 Ecs): - initiation of a recording of temperatures (7p,) measured by the sensors (5), and the ambient air temperature (7,;) around the water heater (1); - calculation of the coefficient k for each sensor (5) using the equation: Trcs-Fp, k svt EE thanked AND pair

7. A method according to claim 6, wherein the water heater (1) is considered to be in the loaded state when a load of the hot water heater was carried out for a period of time greater than a minimum time required to load the heater water (1).

8. Method for estimating the volume of hot water (V,) contained in a water heater (1) containing a total volume of water, the volume of water hot being defined as the volume of water having a tem- temperature greater than or equal to a value of 7,.« Including the steps of : - estimate a water temperature value in each layer of a plurality of horizontal layers of the total volume of water, by means of the method according to one of claims 3 to 7, - estimate the volume of hot water in the water heater (1) based on:

1. of a volume of each horizontal layer comprising water hot with a temperature greater than or equal to the Truit value it. of the estimated temperature of each horizontal layer including hot water having a temperature greater than or equal to the value you iii. a temperature of cold water entering the water heater.

9. A method according to claim 8, wherein the volume of hot water (V 7) contained in the water heater is obtained using the equation: V,= EL" v, 1e Where j and n represent, respectively, each T 1=t Train EF horizontal layer and the total number of horizontal layers comprising hot water having a temperature greater than or equal to the value T, or, Vi is the volume of water in the layer:, Ti is the layer temperature: and 7; is a cold water temperature entering the water heater.

10. Method for analyzing the scaling of a water heater (1) at a given instant given, including the following steps: - estimation of a first time interval necessary for heating a volume of water in a water heater when the water heater is not scaled; - estimation of a second time interval required for heating the same volume of water in the water heater at the given time; - comparison of the first time interval and the second interval of time, an increase in the time required to heat the volume of water being indicative of scaling of the water heater; each of the first and second time intervals corresponding to a time interval required for a volume temperature of hot water in the water heater (1) estimated using the method according to one of claims | to 7 is greater than a value All predefined.

11. Water heater kit, comprising: - a housing (4), - a sensor (5), the sensor being able to measure a temperature (7p,) of the surface external of a skin (11) of the water heater (1), the housing being capable of receive measurements made by the sensor (5), the housing (4) being in also capable of implementing the temperature estimation process hot water according to one of claims 1 to 7.

12. Kit according to claim 11, the housing (4) comprising an interface of communication capable of emitting a signal containing data repre- samples of temperature values ​​measured by the sensor (5) at a remote server (8) for data to be analyzed and / or transmitted to a portable terminal (9).

13. Kit according to the preceding claim, the housing (4) being further capable of send a notification to the portable terminal (9) when the water volume domestic hot water available in the water heater (1) passes below of a predefined volume, and / or the box being capable of receiving a remote control for starting the water heater from the portable terminal (9).

14. Set comprising - a water heater (1) comprising: 1j. a tank (13), the tank comprising a wall delimiting a cavity internal suitable for containing a volume of water to be heated, it. an envelope (12) made of insulating material surrounding the tank (13) and iii. a skin (11) surrounding the envelope (12) made of insulating material; - a sensor (5) placed in contact with an external surface of the skin {11)and - a housing (4) capable of receiving measurements taken by the sensor (5) and to implement the water temperature estimation process hot according to one of claims 1 to 7.

Images