EP4206554A1 - System for determining the remaining service life of the heat exchanger of water heaters - Google Patents

Abstract

System (200) for detecting a blockage in the second volume (152) of a heat exchanger (150) of a water heater (100), comprising a first line (110) which is hydraulically connected to a central heating circuit (310) and a second line (120 ) hydraulically connected to a domestic water line (320); a heater cell (130) connected to the first conduit (110) for heating liquid in the first conduit (110); and a heat exchanger (150) for heat transfer between the first line (110) and the second line (120) comprising a first volume (151) hydraulically connected to the first line (110), a second volume (152), hydraulically connected to the second conduit (120), a heat transfer element (153) provided between the first volume (151) and the second volume (152). Accordingly, the system is characterized in that the heat exchanger (150) comprises a control unit (210) comprising the following method steps: determining a heat transfer coefficient depending on a logarithmic mean temperature difference and a heat transfer rate depending on the heat transfer area of the heat exchanger; determining lifetime using an aging model according to the stored heat transfer coefficients when the heat transfer coefficient exceeds a first threshold and the heat transfer coefficient exceeds a second threshold.

Description

TECHNICAL AREA

The invention relates to a system for determining the remaining service life of water heaters. In particular, the invention relates to a system for detecting blockages and the remaining service life of the heat exchanger of combination water heaters.

STATE OF THE ART

Water heaters, in particular combination water heaters, are connected to a central heating circuit and to a domestic water pipe. They heat the liquid in the central heating circuit and the water in the domestic water pipe. The water in the central heating circuit is fed into the water heater, heated by a heating cell and fed back into the central heating circuit. Heating components such as radiators in the central heating circuit ensure that the rooms are heated.

The water in the domestic water pipe is heated in that a heat transfer is carried out between the water from the central heating circuit after it has been heated and the water from the domestic water pipe using a heat exchanger. The heat exchanger comprises a first volume through which the water from the central heating circuit flows and a second volume through which the water from the domestic water line flows. The first volume and the second volume exchange heat via a heat transfer element. In this case, heat is transferred from the water heated by a heating cell in the first volume of the central heating circuit to the water in the second volume of the domestic water pipe.

If there is a blockage in the heat exchanger, the water in the domestic water pipe is not heated sufficiently or the water pressure drops. This negatively affects user comfort. A blockage can damage the heat exchanger in subsequent steps and cause fluid leakage between the two volumes of the heat exchanger. The clogging of the heat exchanger leads to the fact that the water is not heated to the desired temperature, which reduces the comfort of use and increases energy consumption.

In the German patent application DE102009042994 discloses a system that allows temperature measurements to be taken at various points in the plate heat exchanger and to generate a warning signal to prevent possible heat-related damage to the heat exchanger when the temperature measurements exceed a certain threshold.

All of the above problems have required innovation in the related technical field.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to a system for determining the remaining life of a water heater in order to eliminate the above disadvantages and to provide new advantages in the relevant technical field.

An object of the invention is to provide a system for determining the remaining life of heat exchangers of water heaters.

Another object of the invention is to provide a system for detecting blockages in heat exchangers.

• Überwachung der Wärmeübertragungskoeffizienten,
• Bestimmen der Lebensdauer mittels eines Alterungsmodells gemäß den gespeicherten Wärmeübertragungskoeffizienten, wenn der Wärmeübertragungskoeffizient einen ersten Schwellenwert überschreitet und der Wärmeübertragungskoeffizient einen zweiten Schwellenwert überschreitet.

In order to achieve all the objects mentioned above and which will become apparent from the detailed description below, the present invention relates to a system for detecting a blockage in the second volume of the heat exchanger of a water heater, comprising a first line hydraulically connected to a central heating circuit and a second pipe hydraulically connected to a domestic water pipe; a heating cell connected to the first line for heating the liquid in the first line; and a heat exchanger for heat transfer between the first line and the second line, comprising a first volume hydraulically connected to the first line, a second volume hydraulically connected to the second line, and a heat transfer element connected between the first Volume and the second volume is provided. Accordingly, the system is characterized in that it comprises a first temperature sensor for measuring the temperature of the liquid entering the first volume; a second temperature sensor for measuring the temperature of the liquid exiting the first volume; a third temperature sensor for measuring the temperature of the liquid entering the second volume; a fourth temperature sensor for measuring the temperature of the fluid exiting the second volume Liquid; a flow measuring device for measuring the mass flow of the liquid in the second line or in the domestic water line; a control unit arranged to receive temperature and flow measurements from the first temperature sensor, the second temperature sensor, the third temperature sensor, the fourth temperature sensor and the flow meter, the control unit being configured to use the received temperature and stores flow measurements in a storage unit by associating the received temperature and flow measurements with their times of receipt; determining a heat transfer rate of the second volume according to measurements received from the third temperature sensor, the fourth temperature sensor, and the flow meter and according to a specific heat value; determine a logarithmic mean temperature difference for the heat exchanger according to measurements received from the first temperature sensor, the second temperature sensor, the third temperature sensor, and the fourth temperature sensor; depending on the heat transfer area of the heat exchanger, determines a heat transfer coefficient according to the logarithmic mean temperature difference and the heat transfer rate; periodically calculates the heat transfer coefficient and stores it in the storage unit, wherein the control unit is configured to carry out the following method steps:

• monitoring of heat transfer coefficients,
• determining lifetime using an aging model according to the stored heat transfer coefficients when the heat transfer coefficient exceeds a first threshold and the heat transfer coefficient exceeds a second threshold.

In this way, the blockage on the central heating circuit side of the heat exchanger can be detected. According to the detected clogging, the service life of the heat exchanger is determined. Users can use this remaining life information to take precautions before clogging occurs. The user is less exposed to the negative effects of constipation.

The feature of a possible embodiment of the invention is that the aging model is a stochastic machine learning model trained with stored heat transfer coefficients. In this way, a blockage in the heat exchanger can be detected with higher accuracy.

The feature of another possible embodiment of the invention is that the control unit is configured to calculate the heat transfer coefficient by multiplying the flow measurement, the specific heat value and the difference of the Temperature measurements of the third temperature sensor and the fourth temperature sensor are determined.

The feature of another possible embodiment of the invention is that it comprises a user interface controlled by means of a control unit, which control unit is configured to monitor the lifetime on the user interface. This allows the user to track the lifespan of the heat exchanger on the user interface.

The feature of another possible embodiment of the invention is that the control unit is configured to generate a warning signal when the lifetime exceeds a first lifetime threshold. This alerts the user that the heat exchanger needs to be replaced.

The feature of another possible embodiment of the invention is that the control unit is configured to display the warning signal on the user interface. In this way, the user is informed when the lifespan of the heat exchanger reaches a certain value.

The invention also relates to a water heater comprising a system as described above.

The feature of another possible embodiment of the invention is that the heater is a combination water heater. So the user can keep track of the remaining life of the combi water heater with this system.

The invention is further a method of detecting clogging in the second volume of a heat exchanger of a water heater comprising a first line hydraulically connected to a central heating circuit and a second line hydraulically connected to a domestic water line; a heating cell connected to the first line for heating the liquid in the first line; and a heat exchanger for heat transfer between the first conduit and the second conduit comprising a first volume hydraulically connected to the first conduit, a second volume hydraulically connected to the second conduit, and a heat transfer element interposed between the first volume and the second volume is provided.

• Bestimmen der Temperatur der in der zweiten Leitung befindlichen und in das zweite Volumen eintretenden Flüssigkeit, der Temperatur der in der zweiten Leitung befindlichen und aus dem zweiten Volumen austretenden Flüssigkeit, des Massenstroms der Flüssigkeit in der Hauswasserleitung und einer Wärmeübertragungsrate des zweiten Volumens gemäß einem spezifischen Wärmewert
• Bestimmen einer logarithmischen mittleren Temperaturdifferenz für den Wärmetauscher gemäß den Temperaturen der in den Wärmetauscher eintretenden und aus ihm austretenden Flüssigkeiten
• Bestimmen eines Wärmeübertragungskoeffizienten in Abhängigkeit von der Wärmeübertragungsfläche des Wärmetauschers gemäß der logarithmischen mittleren Temperaturdifferenz und der Wärmeübertragungsrate; zeitabhängiges Speichern des besagten Wärmeübertragungskoeffizienten in einer Speichereinheit;
• Überwachen des Wärmeübertragungskoeffizienten
• Bestimmen der Lebensdauer mittels eines Alterungsmodells gemäß den gespeicherten Wärmeübertragungskoeffizienten, wenn der Wärmeübertragungskoeffizient einen ersten Schwellenwert überschreitet und der Wärmeübertragungskoeffizient einen zweiten Schwellenwert überschreitet. So kann die Restlebensdauer des Wärmetauschers bestimmt werden.

Accordingly, the method is characterized in that the control unit is configured to carry out the following method steps;

• determining the temperature of the liquid in the second line and entering the second volume, the temperature of the liquid in the second line and exiting the second volume, the mass flow rate of the liquid in the domestic water line, and a heat transfer rate of the second volume according to a specific heat value
• determining a logarithmic mean temperature difference for the heat exchanger according to the temperatures of the fluids entering and exiting the heat exchanger
• determining a heat transfer coefficient depending on the heat transfer area of the heat exchanger according to the logarithmic mean temperature difference and the heat transfer rate; storing said heat transfer coefficient over time in a storage unit;
• Monitoring the heat transfer coefficient
• determining lifetime using an aging model according to the stored heat transfer coefficients when the heat transfer coefficient exceeds a first threshold and the heat transfer coefficient exceeds a second threshold. In this way, the remaining service life of the heat exchanger can be determined.

The feature of another possible embodiment of the invention is that the aging model is a stochastic machine learning model trained with stored heat transfer coefficients. In this way, the remaining service life of the heat exchanger can be determined with greater accuracy.

The feature of another possible embodiment of the invention is that it is configured to issue a warning signal when the lifetime exceeds a first lifetime threshold. In this way, the user is informed when the lifespan of the heat exchanger reaches a certain value.

BRIEF DESCRIPTION OF THE FIGURE

• figure 1 shows a representative view of the water heater.
• figure 2 shows a representative view of the system.

DETAILED DESCRIPTION OF THE INVENTION

In this detailed description, a system (200) for determining the remaining life of water heaters (100), which is the subject of the invention, is described only by way of non-limiting examples for a better understanding of the subject.

The invention relates to a system (200) for detecting a blockage in a heat exchanger (150) of a water heater (100) and thus the remaining service life of the heat exchanger (150). As in figure 1 shown, the water heater (100) comprises a first line (110) hydraulically connected to a central heating circuit (310) and a second line (120) hydraulically connected to a domestic water line. The circulating fluid from the central heating circuit (310) enters the first line (110) where it is heated, then exits and re-enters the central heating circuit (310). The tap water coming from a pipe such as the municipal water supply is introduced into the second pipe (120) and after being heated it is introduced into the domestic water pipe (320) to be used by the consumers via components such as faucets etc. The liquid in the first line (110) can be water or another liquid used for heating purposes. The first line (110) may also include a pump for moving the liquid.

The water heater (100) includes a heating cell (130) for heating the liquid in the first line (110). The heater cell (130) supplies heat by consuming energy elements such as electricity, gas and the like. The heater cell (130) can be controlled by thermostat-like devices or a control unit (210). In other words, the cycles in which the heater cell (130) is turned on and off can be controlled by these components.

The water heater (100) includes a heat exchanger (150) to ensure heat transfer between the heated liquid in the first line (110) and the water in the second line (120) without mixing with each other. The heat exchanger (150) comprises a first volume (151) receiving the liquid in the first line (110), a second volume (152) receiving the liquid in the second line (120), and a heat transfer medium (153) for heat transfer between the first volume (151) and the second volume (152). The heat transfer element (153) is made of a thermally conductive material. The heat exchanger (150) may be of a type known in the art as a plate type. The innovation in the system (200) according to the invention consists in determining a lifetime of the heat exchanger (150) as a function of the state of clogging in the second volume (152) of the heat exchanger (150).

The system (200) includes a first temperature sensor (221) for measuring the temperature of the liquid entering the first volume (151) of the heat exchanger (150). The first temperature sensor (221) measures the temperature of the liquid in the first line (110) before entering the first volume (151). In a preferred embodiment of the invention, the first temperature sensor (221) is provided at the inlet of the first volume (151). The system (200) also includes a second temperature sensor (222) for measuring the temperature of the liquid exiting the first volume (151). The second temperature sensor (222) measures the temperature at which the liquid exits the first volume (151) in the first line (110). In a preferred embodiment of the invention, the second temperature sensor (222) is provided at the outlet of the first volume (151).

The system (200) includes a third temperature sensor (231) for measuring the temperature of the liquid entering the second volume (152) of the heat exchanger (150). The third temperature sensor (231) measures the temperature of the liquid in the second line (120) before it enters the second volume (152). In a preferred embodiment of the invention, the third temperature sensor (231) is provided at the inlet of the second volume (152). The system (200) further includes a fourth temperature sensor (232) for measuring the temperature of the liquid exiting the second volume (152). The fourth temperature sensor (232) measures the temperature at which the liquid exits the second volume (152) in the second line (120). In a preferred embodiment of the invention, the fourth temperature sensor (232) is provided at the outlet of the second volume (152).

The system (200) includes a flow meter (240) which is provided in the second line (120) or in the house water line (320). The flow measuring device (240) measures the mass flow or volume flow of the liquid in the second line (120) or in the house water line (320). In a preferred embodiment of the invention, the flow measuring device (240) measures the mass flow of the liquid in the second line (120) or in the domestic water line (320). In a possible embodiment of the invention the flow measuring device (240) measures the volume flow of the liquid in the second line (120) or in the domestic water line (320). The flow meter (240) may be an electromagnetic, ultrasonic, vortex, spiral or other flow meter known in the art.

The system (200) includes a control unit (210) that receives the temperature and flow measurements. The control unit (210) comprises a processor unit (211) for receiving temperature and flow measurements from a first temperature sensor (221), a second temperature sensor (222), a third temperature sensor (231), a fourth temperature sensor (232) and a flow measuring device ( 240). The control unit (210) comprises a memory unit (212) which is assigned to the processor unit (211) in such a way that the processor unit (211) can read data and record data. Said processor unit (211) may be a microprocessor on which software codes are executed. The control unit (210) stores the received temperature and flow measurements in the memory unit (212) by associating them with their times of reception. The control unit (210) determines a heat transfer rate of the second volume (152) according to the measurements received from the third temperature sensor (231), the fourth temperature sensor (232) and the flow meter (240) and according to a specific calorific value. The specific calorific value referred to here refers to the amount of thermal energy required for a temperature increase of a unit mass of the liquid circulating in the domestic water line (320) or in the second line (120). The control unit (210) determines a logarithmic mean temperature difference for the heat exchanger (150) according to the measurements received from the first temperature sensor (221), the second temperature sensor (222), the third temperature sensor (231) and the fourth temperature sensor (232). Said logarithmic mean temperature difference is an average of the temperature changes in the first volume (151) and in the second volume (152) of the heat exchanger (150) according to the measurements received from the temperature sensors. The control unit (210) determines a heat transfer coefficient according to the logarithmic mean temperature difference and the heat transfer rate calculated depending on the heat transfer area of the heat exchanger (150). The heat transfer area refers to the surface area of the heat transfer element (153) provided between the first volume (151) and the second volume (152). The control unit (210) periodically calculates the heat transfer coefficient and stores it in the storage unit (212).

The system (200) includes a user interface (260) through which a user can track the measurements or calculated values received from the control unit (210). The controller (210) monitors the heat transfer coefficient on the user interface (260). The user interface (260) can be located on the water heater (100). In one possible embodiment, the user interface (260) can be located in a room remote from the water heater (100) and enable wired or wireless communication with the control unit (210).

The controller (210) determines a lifetime when the heat transfer coefficient exceeds a first threshold. This lifetime is calculated based on the stored heat transfer coefficients using an aging model. Life refers to the remaining life of the heat exchanger (150) after the heat transfer coefficient has exceeded a second threshold. The service life mentioned here refers to the estimated remaining service life of the heat exchanger (150) without falling below a certain level of efficiency. If the heat exchanger (150) falls below the stated efficiency, sufficient heat transfer between the first volume (151) and the second volume (152) cannot be guaranteed and more energy than necessary is consumed. The aging model mentioned is a software algorithm. The aging model is a stochastic machine learning model trained with stored heat transfer coefficients. Accordingly, the controller (210) determines the aging model of the heat exchanger (150) based on the previous heat transfer coefficients. As a non-limiting example, the detection of a decrease in the heat transfer coefficient may indicate a clogging in the heat exchanger (150). Here, the aging model trained with the stored heat transfer coefficients shows a decreasing trend in the heat transfer coefficient. Accordingly, if the heat transfer coefficient exceeds a first threshold, the remaining life of the heat exchanger (150) may be calculated as a result of exceeding a second threshold.

The controller (210) is configured to generate a warning signal when the lifetime exceeds a first lifetime threshold. The first lifetime threshold is related to a specific period of time. The first lifetime threshold can be set during production or by the user. For example, if the first lifespan threshold is set to 90 days, the controller (210) generates the warning signal when the lifespan falls below 90 days.

In one possible embodiment, the warning signal is monitored by the control unit (210) on the user interface (260). In a possible embodiment of the invention, a second lifetime threshold can be determined. If the second lifetime threshold is exceeded, the controller (210) may stop operation of the water heater (100).

The control unit (210) receives the temperature and flow measurements in real time. The processor unit (211) continuously processes the received measured values. The heat transfer rate is calculated from the following formula (1). $$\left({\dot{Q}}_{\mathit{CH}}={\dot{m}}_{\mathit{CH}\times \mathit{CP},\mathit{CH}}\times {\mathit{\Delta T}}_{\mathit{CH}}\right)$$

Where " Q _CH " is the heat transfer rate in the domestic water line (320); " m _CH" is the mass flow in the domestic water line (320); " Cp , CH " is the specific heat of the liquid in the second conduit (120); "Δ T _CH " is the liquid temperature difference at the inlet and outlet of the second volume (152).

The logarithmic mean temperature difference is calculated by the following formula (2). $$\mathit{LMTD}=\frac{\left(T_{\mathit{CH},\mathit{inlet}}-T_{\mathit{DHW},\mathit{outlet}}\right)-\left(T_{\mathit{CH},\mathit{outlet}}-T_{\mathit{DHW},\mathit{inlet}}\right)}{\ln \left(\frac{T_{\mathit{CH},\mathit{inlet}}-T_{\mathit{DHW},\mathit{outlet}}}{T_{\mathit{CH},\mathit{outlet}}-T_{\mathit{DHW},\mathit{inlet}}}\right)}$$

"LMTD" stands for the logarithmic mean temperature difference; "T" stands for temperature; "CH" stands for the central heating circuit (310); "DHW" stands for the domestic water line (320); "inlet" stands for the inlet; "outlet" stands for the outlet.

The heat transfer coefficient is calculated by the following formula (3). $$u=\frac{{\dot{Q}}_{\mathit{CH}}}{A.\mathit{LMTD}}$$

where "U" is the heat transfer coefficient; " Q _CH " the heat transfer rate in the domestic water line (320); "A" the heat transfer area of the heat transfer element (153); "LMTD" the logarithmic mean temperature difference.

In an exemplary embodiment, a lifetime calculation is performed when the heat transfer coefficient exceeds a first threshold. The main purpose of using the first threshold is to give the processing unit (211) time to get enough data. The lifetime refers to the estimated remaining lifetime of the heat exchanger (150) after the heat transfer coefficient has exceeded a second threshold.

The scope of the invention is indicated in the appended claims and should not be limited to what is explained in this detailed description for the purpose of giving examples. It is obvious that the person skilled in the technical field can create similar embodiments in the light of the above explanations.

THE REFERENCE NUMBERS INDICATED IN THE FIGURES

• 100 water heaters
• 110 First line
• 120 second line
• 130 heater cell
• 150 heat exchangers
• 151 First volume
• 152 Second Volume
• 153 heat transfer element
• 200 systems
• 210 control unit
• 211 processor unit
• 212 storage unit
• 221 First temperature sensor
• 222 Second temperature sensor
• 231 Third temperature sensor
• 232 Fourth temperature sensor
• 240 flow meter
• 260 user interface
• 310 central heating circuit
• 320 domestic water pipe

Claims (11)

System (200) for detecting a blockage in the second volume (152) of a heat exchanger (150) of a water heater (100), comprising a first line (110) which is hydraulically connected to a central heating circuit (310) and a second line (120 ) hydraulically connected to a domestic water line (320); a heater cell (130) connected to the first conduit (110) for heating liquid in the first conduit (110); and a heat exchanger (150) for heat transfer between the first line (110) and the second line (120), comprising a first volume (151) hydraulically connected to the first line (110), a second volume (152) , hydraulically connected to the second line (120), a heat transfer element (153) provided between the first volume (151) and the second volume (152), characterized in that it comprises a first temperature sensor (221) for measuring the temperature of the liquid entering the first volume (151); a second temperature sensor (222) for measuring the temperature of the liquid exiting the first volume (151); a third temperature sensor (231) for measuring the temperature of the liquid entering the second volume (152); a fourth temperature sensor (232) for measuring the temperature of the liquid exiting the second volume (152); a flow measuring device (240) for measuring the mass flow of the liquid in the second line (120) or in the domestic water line (320); a control unit (210) arranged to receive temperature and flow measurements from the first temperature sensor (221), the second temperature sensor (222), the third temperature sensor (231), the fourth temperature sensor (232) and the flow measuring device (240 ) receives, wherein the control unit (210) is configured to store the received temperature and flow measurements in a storage unit (212) by associating the received temperature and flow measurements with their times of receipt; determining a heat transfer rate of the second volume (152) according to measurements received from the third temperature sensor (231), the fourth temperature sensor (232), and the flow meter (240) and according to a specific heat value; a logarithmic determining average temperature difference for the heat exchanger (150) according to measurements received from the first temperature sensor (221), the second temperature sensor (222), the third temperature sensor (231), and the fourth temperature sensor (232); depending on the heat transfer area of the heat exchanger (150), determining a heat transfer coefficient according to the logarithmic mean temperature difference and the heat transfer rate; periodically calculates the heat transfer coefficient and stores it in the storage unit (212),
wherein the control unit is configured to perform the following method steps: - monitoring of heat transfer coefficients, - determining the lifetime using an aging model according to the stored heat transfer coefficients when the heat transfer coefficient exceeds a first threshold and the heat transfer coefficient exceeds a second threshold. The system (200) of claim 1, characterized in that the aging model is a stochastic machine learning model trained with stored heat transfer coefficients. The system (200) of claim 1, characterized in that the controller (210) is configured to calculate the heat transfer coefficient by multiplying the flow measurement, the specific heat value, and the difference in the temperature measurements of the third temperature sensor (231) and the fourth temperature sensor (232 ) certainly. System (200) according to claim 1, characterized in that it comprises a user interface (260) controlled by a control unit (210), the control unit (210) being configured to display the lifetime on the user interface (260) supervised. The system (200) of claim 1, characterized in that the controller (210) is configured to generate a warning signal when the lifetime exceeds a first lifetime threshold. The system (200) of claim 1, characterized in that the control unit (210) is configured to display the warning signal on the user interface (260). A heater comprising a system (200) according to any one of claims 1 to 6. System (200) according to claim 7, characterized in that the heater is a combination water heater. A method of detecting an obstruction in the second volume (152) of a heat exchanger (150) of a water heater (100), comprising a first line (110) hydraulically connected to a central heating circuit (310) and a second line (120) connected is hydraulically connected to a domestic water line (320); a heater cell (130) connected to the first conduit (110) for heating liquid in the first conduit (110); and a heat exchanger (150) for heat transfer between the first line (110) and the second line (120) comprising a first volume (151) hydraulically connected to the first line (110), a second volume (152), which is hydraulically connected to the second line (120), a heat transfer element (153) which is provided between the first volume (151) and the second volume (152), characterized in that the control unit (210) is configured such that it performs the following procedural steps; - determining the temperature of the liquid in the second line (120) and entering the second volume (152), the temperature of the liquid in the second line (120) and exiting the second volume (152), the mass flow of the liquid in the domestic water line (320) and a heat transfer rate of the second volume (152) according to a specific calorific value - determining a logarithmic mean temperature difference for the heat exchanger (150) according to the temperatures of the liquids entering and leaving the heat exchanger (150). - determining a heat transfer coefficient depending on the heat transfer area of the heat exchanger (150) according to the logarithmic mean temperature difference and the heat transfer rate; storing said heat transfer coefficient over time in a storage unit (212); - Monitoring the heat transfer coefficient - determining the lifetime using an aging model according to the stored heat transfer coefficients when the heat transfer coefficient exceeds a first threshold and the heat transfer coefficient exceeds a second threshold. Method according to claim 9, characterized in that the aging model is a stochastic machine learning model trained with the stored heat transfer coefficients. 10. The method of claim 9, characterized in that it is configured to issue a warning signal when the lifetime exceeds a first lifetime threshold.

Images