Breathing machine and control method for temperature of output gas of breathing machine

Abstract

The invention relates to a breathing machine and a control method for the temperature of output gas of the breathing machine. The breathing machine comprises an air supply system, a breather pipe, a heating and humidifying mechanism and a breathing mask, one end of the breather pipe is connected with the air supply system, the other end of the breather pipe is connected with the breathing mask, the heating and humidifying mechanism comprises a water tank, a heating assembly and an atomizing assembly, one end of the atomizing assembly is communicated with the water tank, and the other end of the atomizing assembly is communicated with the breathing mask. One end of the heating assembly is communicated with the water tank, the other end of the heating assembly is communicated with the ventilation pipe, the atomization assembly is used for changing water in the water tank into water vapor so as to be introduced into the ventilation pipe, and the heating assembly is used for heating the water in the water tank so as to change the temperature of the water vapor generated by the atomization assembly. The ventilation pipe does not need to be heated, the temperature in the ventilation pipe is evenly distributed, and when the temperature in the ventilation pipe is detected through the temperature probe, the problem that the measurement temperature is too high due to heating of the ventilation pipe cannot be caused.

Description

Technical Field

[0001] The present application relates to the technical field of ventilators, and in particular to a ventilator and a method for controlling the output gas temperature of the ventilator. Background Art

[0002] A ventilator uses a mechanical device to create a pressure differential, delivering air or oxygen into the lungs. This pressure change then causes the lungs to expel gas, simulating the human respiratory process and assisting or replacing the patient's spontaneous breathing. A ventilator consists of an air supply system, a heating circuit, and a breathing mask. The heating circuit is located on the side of the air supply system near the breathing mask. The air supply system is used to supply air or oxygen to the patient, and the heating circuit heats the air or oxygen provided by the air supply system to provide the patient with air or oxygen at a specific temperature.

[0003] In the related art, a temperature probe is generally provided in the heating pipeline to detect the temperature of the air or oxygen in the gas supply pipeline, so as to control the power of the heating pipeline according to the detected temperature.

[0004] However, since a heating element is wound around the outer wall of the heating pipeline, the heating element is used to heat the gas passing through the heating pipeline, and the temperature probe is arranged in the heating pipeline, the temperature probe is affected by the heating element, and the measured temperature is likely to be too high. Summary of the Invention

[0005] Based on this, it is necessary to provide a ventilator and a method for controlling the output gas temperature of the ventilator to address the problems of high measured temperature and low detection accuracy when using a temperature probe to detect temperature.

[0006] A ventilator comprises an air supply system, a ventilation tube, a heating and humidifying mechanism, and a breathing mask. One end of the ventilation tube is connected to the air supply system, and the other end is connected to the breathing mask. The heating and humidifying mechanism comprises a water tank, a heating component, and an atomizing component. One end of the atomizing component is connected to the water tank, and the other end is connected to the ventilation tube. The atomizing component is used to convert water in the water tank into water vapor to be passed into the ventilation tube. The heating component is used to heat the water in the water tank to change the temperature of the water vapor generated by the atomizing component.

[0007] In one embodiment, the heating assembly includes a bottom heating element and a side wall heating element, wherein the bottom heating element is located at the bottom of the water tank, and the side wall heating element is arranged around the circumference of the water tank.

[0008] In one embodiment, a temperature sensor is provided in the water tank, and the temperature sensor is used to detect the water temperature in the water tank.

[0009] In one embodiment, a flow sensor is provided in the ventilation pipe or the gas supply system, and the flow sensor is used to detect the gas flow in the ventilation pipe.

[0010] In one embodiment, a pressure sensor is provided in the ventilation pipe or the gas supply system, and the pressure sensor is used to detect the gas pressure in the ventilation pipe.

[0011] A method for controlling the output gas temperature of a ventilator, the control method comprising:

[0012] S1, detect the water temperature T in the water tank through the temperature sensor in , detecting the gas flow V in the ventilation pipe by a flow sensor, and detecting the gas pressure Q in the ventilation pipe by a pressure sensor;

[0013] S2. Set the desired temperature ;

[0014] S3, through formula 1 Calculate the water temperature T in the water tank in Heat to desired temperature , the required heating power P of the heating component 总 ; where k, j, and ε are proportionality coefficients; ρ is the gas density in the vent tube; A is the cross-sectional area of ​​the vent tube; is the specific heat capacity of the gas in the vent pipe.

[0015] In one embodiment, the control method includes:

[0016] S4. Calculate the change ΔT of the water temperature per unit time;

[0017] S5, through formula 2 Calculate the temperature at the vent pipe outlet , where θ is the heat loss coefficient, ∆t is the unit time; ρ 水 is the density of water; C 水 is the specific heat capacity of water; m 水 is the quality of the water in the current tank.

[0018] S6. Determine the temperature of the vent outlet calculated by formula 1 Is it equal to the expected temperature? , if equal, then the required heating power P calculated by formula 1 总 Heat the water tank; if not equal, repeat steps S1 to S6.

[0019] In one embodiment, the specific step of S5 includes: when the water temperature is stable, calculating the ventilation pipe outlet temperature using Formula 2.

[0020] In one embodiment, when the temperature change of water per unit time ΔT≤2° C., the water temperature in the water tank is considered stable, and the unit time includes but is not limited to 1 breathing cycle.

[0021] In one embodiment, the control method further includes:

[0022] S7, determine whether the gas flow or the gas pressure has changed, if not, continue to use formula 1 to calculate the required heating power P 总 Heat the water tank; if so, re-execute steps S1 to S6.

[0023] In the above-mentioned ventilator and the method for controlling the output gas temperature of the ventilator, the heating component heats the water in the water tank, which increases the temperature of the water entering the atomizing component, and also increases the temperature of the water vapor atomized by the atomizing component. When the heated water vapor enters the ventilation pipe, the water vapor is mixed with the gas in the ventilation pipe, which can increase the temperature of the mixed gas at the outlet of the entire ventilation pipe, that is, heat the temperature of the gas inhaled by the patient. That is, the present application does not need to heat the ventilation pipe, and the temperature in the ventilation pipe is evenly distributed. When the temperature in the ventilation pipe is detected by the temperature probe, the problem of high measured temperature caused by heating the ventilation pipe will not be caused. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 1 is a system diagram of a ventilator in one embodiment.

[0025] Figure 2 FIG. 1 is a step diagram of a method for controlling the output gas temperature of a ventilator in one embodiment.

[0026] Figure numerals: 10, air supply system; 20, ventilation tube; 30, breathing mask; 40, water tank; 41, heating component; 42, atomization component; 43, temperature sensor; 50, flow sensor; 60, pressure sensor. DETAILED DESCRIPTION

[0027] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0028] In the description of this application, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or position relationship indicated by these terms is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0029] In addition, if the terms "first" or "second" appear, these terms are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of this application, if the term "plurality" appears, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0030] In this application, unless otherwise specified or limited, the terms "mounted," "connected," "connected," "fixed," etc., should be interpreted broadly. For example, these terms may refer to fixed connections, removable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediary; and internal communication between two components or interaction between two components, unless otherwise specified. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0031] In this application, unless otherwise expressly specified or limited, if a first feature is described as being "above" or "below" a second feature, or similar descriptions, this may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is described as being "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is described as being "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0032] It should be noted that if an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element. If an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. If any, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are for illustrative purposes only and do not represent the only embodiment.

[0033] See Figure 1 An embodiment of the present application discloses a ventilator, which includes an air supply system 10, a ventilation tube 20, a heating and humidifying mechanism, and a breathing mask 30. One end of the ventilation tube 20 is connected to the air supply system 10, and the other end is connected to the breathing mask 30. The heating and humidifying mechanism includes a water tank 40, a heating component 41, and an atomizing component 42. One end of the atomizing component 42 is connected to the water tank 40, and the other end is connected to the ventilation tube 20. The atomizing component 42 is used to convert the water in the water tank 40 into water vapor to be passed into the ventilation tube 20. The heating component 41 is used to heat the water in the water tank 40 to change the temperature of the water vapor generated by the atomizing component 42.

[0034] In this embodiment, the heating component 41 heats the water in the water tank 40, which increases the temperature of the water entering the atomizing component 42, and also increases the temperature of the water vapor atomized by the atomizing component 42. When the heated water vapor enters the ventilation tube 20, the water vapor is mixed with the gas in the ventilation tube 20, which can increase the temperature of the mixed gas at the outlet of the entire ventilation tube 20, that is, heat the temperature of the gas inhaled by the patient. That is, the present application does not need to heat the ventilation tube 20, and the temperature distribution in the ventilation tube 20 is uniform. When the temperature in the ventilation tube 20 is detected by the temperature probe, the problem of the measured temperature being too high due to the heating of the ventilation tube 20 will not be caused.

[0035] Specifically, the heating component 41 may be a heating wire, which is arranged on the bottom wall of the water tank 40 and / or the side wall of the water tank 40 . When the heating wire is energized, it can heat the water in the water tank 40 .

[0036] In other embodiments, when the ambient temperature is high and the temperature of the gas inhaled by the patient needs to be lowered, a cooling component can also be provided on the water tank 40 so as to cool the water in the water tank 40 through the cooling component.

[0037] In the related art, since the air in the ventilation pipe 20 is in a flowing state, the temperature distribution in the ventilation pipe 20 is affected by many factors, such as air flow, heat radiation, heat conduction of surrounding objects, etc., resulting in a nonlinear relationship between the resistance of the temperature probe and the air temperature, so the detection accuracy of the temperature probe is low.

[0038] Furthermore, a temperature sensor 43 is provided in the water tank 40 , and the temperature sensor 43 is used to detect the water temperature in the water tank 40 .

[0039] Temperature sensor 43 is used to detect the water temperature in water tank 40. Because the water in water tank 40 is relatively uniform relative to the air flowing through vent pipe 20, temperature sensor 43 is in direct contact with the water. These two advantages greatly improve the detection accuracy of temperature sensor 43, allowing precise control of the heating power of heating assembly 41 and, consequently, the temperature at the outlet of vent pipe 20.

[0040] Furthermore, a flow sensor 50 is provided in the ventilation pipe 20 or the gas supply system 10 , and the flow sensor 50 is used to detect the gas flow in the ventilation pipe 20 .

[0041] In this embodiment, a blower and a flow sensor 50 are provided within the air supply system 10. The blower is used to draw outside air into the air supply system 10, and the flow sensor 50 is used to detect the gas flow within the air supply system 10, thereby calculating the gas flow rate based on the gas flow rate and feeding the gas flow rate back to the control system to adjust the blower speed. This also facilitates the ventilator controller to obtain the gas flow rate, thereby calculating the heating power of the heating assembly 41 at the current gas flow rate and accurately controlling the outlet temperature of the ventilation tube 20.

[0042] Furthermore, a pressure sensor 60 is provided in the ventilation pipe 20 or the gas supply system 10 , and the pressure sensor 60 is used to detect the gas pressure in the ventilation pipe 20 .

[0043] In this embodiment, a pressure sensor 60 is provided in the gas supply system 10. The pressure sensor 60 is used to detect the gas pressure in the gas supply system 10, so that the controller of the ventilator can obtain the gas pressure, so as to calculate the heating power of the heating component 41 under the current gas pressure, and facilitate precise control of the outlet temperature of the ventilation tube 20.

[0044] In some embodiments, the heating assembly 41 includes a bottom heating element and a sidewall heating element. The bottom heating element is located at the bottom of the water tank 40, and the sidewall heating elements are arranged around the periphery of the water tank 40. In other words, by simultaneously heating the water tank 40 with the bottom heating element and the sidewall heating element, the temperature in the water tank 40 can be quickly brought to a preset temperature. At the same time, the uniformity of the water temperature in the water tank 40 can also be ensured.

[0045] Furthermore, the temperature sensor 43 is located in the middle of the water tank 40 and does not contact the side walls or the bottom of the water tank 40, thereby preventing the heating assembly 41 from affecting the detected temperature of the temperature sensor 43. For example, the temperature sensor 43 is mounted on a float, which is connected to a weight block via a rope. The weight block is located at the center of the bottom of the water tank 40.

[0046] Combine Figure 2 An embodiment of the present application discloses a method for controlling the output gas temperature of a ventilator, the control method comprising:

[0047] S1, detect the water temperature T in the water tank through the temperature sensor in , detecting the gas flow V in the ventilation pipe by a flow sensor, and detecting the gas pressure Q in the ventilation pipe by a pressure sensor;

[0048] S2. Set the desired temperature ;

[0049] S3, through formula 1 Calculate the water temperature T in the water tank in Heat to desired temperature , the heating power P required for the heating component 总 ; where k, j, and ε are proportionality coefficients; ρ is the gas density in the vent tube; A is the cross-sectional area of ​​the vent tube; is the specific heat capacity of the gas in the vent pipe.

[0050] In this embodiment, the water temperature in the water tank is directly obtained, and the required heating power of the heating component is calculated by formula 1. When the heating component is heated by the calculated required heating power, the temperature of the vent outlet can reach the preset temperature. Therefore, there is no need to control the heating power by detecting the temperature of the vent outlet, that is, there is no need to detect the temperature of the vent outlet, and there will be no problem of affecting the patient's inhalation effect due to the poor accuracy of the temperature probe when detecting the gas temperature. In addition, the present application directly heats the water in the water tank through the heating component, and the temperature sensor is used to obtain the water temperature in the water tank. On the one hand, the water temperature in the water tank is relatively uniform relative to the gas flowing in the vent; on the other hand, the temperature sensor can directly contact the water, so the detection accuracy of the temperature sensor can be greatly improved.

[0051] In this embodiment, Formula 1 The required heating power is recorded as a label and the other parameters are analyzed as features (analysis methods include but are not limited to logic analysis, neural network analysis, etc.).

[0052] Formula 1 is the addition of polynomials, where the first term It is based on the principle of conservation of thermodynamic energy, which means that the gas is Heat to desired temperature The theoretical power required, where k is the efficiency coefficient. This term reflects the compensation for heating power due to gas pressure Q and gas flow rate V (e.g., the effect of gas compression heat). Experimental results show that when high pressure and low flow rate occur in a pipeline, gas is compressed and generates heat, requiring a reduction in heating power. However, when low pressure and high flow rate occur, gas expands and absorbs heat, requiring an increase in heating power. This inference suggests a linear relationship with heating power, which was further verified through experiments. The heating power compensation in the second term is related to and , with the coefficient j derived through data fitting. The third term, ε, is an empirical correction term. Through calibration, ε accounts for unmodeled heat losses or other nonlinear factors.

[0053] Specifically, the calibration method of k, j and ε proportional coefficient includes:

[0054] Step 1: Data collection, including but not limited to ambient temperature, water tank heating power, water temperature, gas flow rate, gas pressure, vent pipe outlet temperature, etc. Data under different conditions are collected based on the principle of single variable. For example: fix other parameters, only change the gas flow rate V, and record the temperature when the desired temperature is reached. Required P 总 Then, in the same way, change the gas pressure Q, water temperature wait.

[0055] Step 2: Linear regression fitting, put the collected data into Formula 1 and calculate k, j and ε by the least squares method.

[0056] Step 3: Verify and adjust, check the prediction error. If the prediction error is less than the target error, complete the coefficient calibration. If the prediction error is greater than the target error, recalibrate.

[0057] In some embodiments, the control method further includes:

[0058] S4. Calculate the change ΔT of the water temperature per unit time;

[0059] S5, through formula 2 Calculate the temperature at the vent pipe outlet , where θ is the heat loss coefficient, ∆t is the unit time; ρ 水 is the density of water; C 水 is the specific heat capacity of water; m 水 is the mass of water in the current water tank; where m 水The water level sensor is installed in the water tank. When the water level drops, water can be automatically added to keep the water level in the water tank constant.

[0060] S6. Determine the temperature of the vent outlet calculated by formula 1 Is it equal to the expected temperature? , if equal, then the heating power P calculated by formula 1 总 Heat the water tank; if not equal, repeat steps S1 to S6.

[0061] Furthermore, in order to increase the outlet temperature of the vent pipe of the present application, after the water in the water tank is heated by the current processing power, the outlet temperature of the vent pipe is further calculated by the required heating power to compare the outlet temperature of the vent pipe with the expected temperature to further verify whether the calculation result in step S3 is accurate. If the outlet temperature of the vent pipe is equal to the expected temperature, it means that the current temperature calculated in S3 is accurate, and the outlet temperature of the vent pipe can be guaranteed by directly heating the water tank by the current power; if the outlet temperature of the vent pipe is lower than the expected temperature, or the outlet temperature of the vent pipe is lower than the expected temperature, the water temperature in the water tank is obtained again, and the required heating power of the heating component is calculated by formula 1; then the outlet temperature of the vent pipe is calculated by the required heating power; until the outlet temperature of the vent pipe is equal to the expected temperature.

[0062] Furthermore, in step S5, the outlet temperature of the ventilation tube is calculated according to the required heating power, which can also facilitate medical staff to directly obtain the outlet temperature of the ventilation tube.

[0063] In addition, the control method also includes obtaining multiple consecutive ventilation tube outlet temperatures. If the multiple consecutive ventilation tube outlet temperatures are all greater than the expected temperature, it means that at least one of the temperature sensor, pressure sensor or flow sensor has failed. At this time, the ventilator's control system can trigger an alarm to alert medical staff of the sensor failure.

[0064] Among them, formula 2 can be deduced based on the principles of thermodynamics and energy conservation that the temperature at the outlet of the ventilation pipe is The heat output of the heating element and the heat absorbed by water On this basis, and through the heat loss coefficient θ and the density of water ρ 水 The correction is made, and Formula 2 is obtained by fitting the actual output heating temperature at different powers.

[0065] In some embodiments, the specific step of S5 includes: when the water temperature is stable, calculating the ventilation pipe outlet temperature using Formula 2.

[0066] In this embodiment, after the heating power is calculated using Formula 1, since it takes a certain amount of time for the water temperature to rise, the vent pipe outlet temperature can only be obtained more accurately by calculating the vent pipe outlet temperature using the required heating power after the water temperature stabilizes.

[0067] In some embodiments, when the temperature change of water per unit time ΔT≤2° C., the water temperature in the water tank is considered stable, and the unit time includes but is not limited to 1 breathing cycle.

[0068] Specifically, since the heating component typically requires a certain heating time to significantly change the water temperature in the tank, if the unit time is much longer than the breathing cycle, water temperature fluctuations may not be detected in a timely manner, affecting temperature control accuracy. If the unit time is too short, the heating power will fluctuate frequently. Using the breathing cycle as the unit ensures that the gas temperature within each breathing cycle is adjusted based on the latest water temperature status.

[0069] Combine Figure 2 In some embodiments, the control method further includes:

[0070] S7. Determine whether the gas flow rate or the gas pressure has changed. If not, maintain the desired heating power. If so, re-execute steps S1 to S6. Since the gas flow rate and / or the gas pressure affect the heating power, when the gas flow rate and / or the gas pressure changes, recalculate the heating power using Formula 1 and verify it using Formula 2 to ensure that the ventilation pipe outlet temperature returns to the desired temperature.

[0071] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0072] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A ventilator comprising an air supply system, a ventilation tube, a heating and humidifying mechanism, and a breathing mask, wherein one end of the ventilation tube is connected to the air supply system, and the other end is connected to the breathing mask, characterized in that: The heating and humidifying mechanism includes a water tank, a heating component and an atomizing component. One end of the atomizing component is connected to the water tank, and the other end is connected to the ventilation pipe. The atomizing component is used to convert the water in the water tank into water vapor to pass into the ventilation pipe. The heating component is used to heat the water in the water tank to change the temperature of the water vapor generated by the atomizing component.

2. The ventilator according to claim 1, wherein: The heating assembly includes a bottom heating element and a side wall heating element. The bottom heating element is located at the bottom of the water tank, and the side wall heating element is arranged around the circumference of the water tank.

3. The ventilator according to claim 1, characterized in that A temperature sensor is provided in the water tank, and the temperature sensor is used to detect the water temperature in the water tank.

4. The ventilator according to claim 1, wherein A flow sensor is provided in the ventilation pipe or the gas supply system, and the flow sensor is used to detect the gas flow in the ventilation pipe.

5. The ventilator according to claim 1, characterized in that A pressure sensor is provided in the ventilation pipe or the gas supply system, and the pressure sensor is used to detect the gas pressure in the ventilation pipe.

6. A method for controlling the output gas temperature of a ventilator according to any one of claims 1 to 5, characterized in that: The control method includes: S1, detect the water temperature T in the water tank through the temperature sensor in , detecting the gas flow V in the ventilation pipe by a flow sensor, and detecting the gas pressure Q in the ventilation pipe by a pressure sensor; S2. Set the desired temperature ; S3, through formula 1 Calculate the water temperature T in the water tank in Heat to desired temperature , the required heating power P of the heating component 总 ; where k, j, and ε are proportionality coefficients; ρ is the gas density in the vent tube; A is the cross-sectional area of ​​the vent tube; is the specific heat capacity of the gas in the vent pipe.

7. The method for controlling the output gas temperature of a ventilator according to claim 6, wherein: The control method includes: S4. Calculate the change ΔT of the water temperature per unit time; S5, through formula 2 Calculate the temperature at the vent pipe outlet , where θ is the heat loss coefficient, ∆t is the unit time; ρ 水 is the density of water; C 水 is the specific heat capacity of water; m 水 is the quality of the water in the current tank; S6. Determine the temperature of the vent outlet calculated by formula 1 Is it equal to the expected temperature? , if equal, then the required heating power P calculated by formula 1 总 Heat the water tank; if not equal, repeat steps S1 to S6.

8. The method for controlling the output gas temperature of a ventilator according to claim 7, wherein: The specific step of S5 includes: when the water temperature is stable, calculating the ventilation pipe outlet temperature using Formula 2.

9. The method for controlling the output gas temperature of a ventilator according to claim 8, characterized in that: When the temperature change of water per unit time ΔT≤2° C., the water temperature in the water tank is considered stable, and the unit time includes but is not limited to 1 breathing cycle.

10. The method for controlling the output gas temperature of a ventilator according to claim 6, wherein: The control method further includes: S7, determine whether the gas flow or the gas pressure has changed, if not, continue to use formula 1 to calculate the required heating power P 总 Heat the water tank; if so, re-execute steps S1 to S6.

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