CN118623483A - Method for determining inlet temperature, heat generator and control device - Google Patents

Abstract

A method for determining the inlet temperature of a fluid to be heated in a heat generator, a method for controlling a heat generator, a method for starting a heat generator, a heat generator and a control device. The heat generator has a burner device. The method includes operating the heat generator to heat the fluid flowing through the heat generator; collecting the outlet temperature of the fluid flowing out of the outlet of the heat generator; collecting the operating value of the modulation parameter of the burner device, the modulation parameter adjusting the heating power of the burner device; providing a heating power function of the heat generator, the heating power function describing the heating power of the burner device for heating the fluid based on the modulation parameter of the burner device; providing the volume flow rate of the fluid flowing through the heat generator, and determining the inlet temperature of the fluid flowing into the inlet of the heat generator, wherein the inlet temperature is determined based on the provided heating power function, the provided volume flow rate, the collected outlet temperature and the collected operating value of the modulation parameter.

Description

Method for determining inlet temperature, heat generator and control device

Technical Field

The invention relates to a method for determining the inlet temperature of a fluid to be heated in a heat generator, a method for controlling a heat generator, a method for starting a heat generator, a heat generator and a control device for use in a heat generator.

Background Art

Heat generators known in the prior art are used to heat a fluid flowing through the heat generator with the aid of a burner device, wherein the inflowing fluid needs to be heated starting from its inlet temperature until it reaches a desired target temperature.

The heat generator is often used in the water supply process of buildings, for example, in order to heat the drinking water provided from an external supply source to the required temperature for subsequent use. Afterwards, the heated water can be used as hot water for supplying showers and similar sanitary facilities.

Upon receipt of a request for hot water, for example by operating a sanitary tap, the water flowing through the heat generator is heated with the help of a burner device using a burner flame and then provided directly or after mixing with cold water.

For energy and related costs and comfort considerations, it is preferred to control the outlet temperature of the heat generator as accurately as possible, and it is necessary, including but not limited to, to reach and maintain the desired temperature as quickly as possible. Considering that the operating parameters of the heat generator will fluctuate greatly during operation, especially the inlet temperature parameters determined by the external supply source, these factors need to be considered accordingly to achieve optimal control of the heat generator.

For example, a heat generator for heating water using a gas-based burner arrangement is known from US 5 322 216 A1, in which the inlet and outlet temperatures of the water flowing into or out of the heat generator are detected via respective temperature sensors in order to keep the outlet temperature as close as possible to an ideal, usually preset value taking into account inlet temperature fluctuations.

In order to achieve the above-mentioned operation of the heat generator that is considered comfortable by the user, the operation of the heat generator becomes increasingly complex, including but not limited to extensive sensors and evaluation units for collecting and processing various operating parameters. This not only increases the manufacturing costs, but also increases the geometric size of the heat generator and the maintenance costs.

Summary of the invention

The object of the present invention is therefore to provide a more efficient possibility for heating a fluid by means of a heat generator compared to the prior art.

In order to achieve this object, a method according to the invention for determining the inlet temperature of a fluid to be heated in a heat generator, a method according to the invention for controlling a heat generator, a method according to the invention for starting a heat generator, a heat generator according to the invention and a control device according to the invention are provided.

Preferred embodiments Each of them may be provided alone or in combination.

According to a first aspect of the present invention, a method for determining the inlet temperature of a fluid to be heated in a heat generator having a burner device is provided. The method comprises operating the heat generator to heat the fluid flowing through the heat generator; collecting the outlet temperature of the fluid flowing out of the outlet of the heat generator; collecting the operating value of the modulation parameter of the burner device, the modulation parameter adjusting the heating power of the burner device; providing a heating power function of the heat generator, the heating power function describing the heating power of the burner device for heating the fluid based on the modulation parameter of the burner device; providing the volume flow rate of the fluid flowing through the heat generator, and determining the inlet temperature of the fluid flowing into the inlet of the heat generator, wherein the inlet temperature is determined based on the provided heating power function, the provided volume flow rate, the collected outlet temperature and the collected operating value of the modulation parameter.

A modulation parameter of a burner arrangement is understood here to mean any operating parameter of the burner arrangement by means of which the heating power of the burner arrangement can be adjusted and which usually also plays the role of an actuator in the control of the heat generator.

The heating power function is understood here to be any description of the relationship between the modulation parameter and the heating power of the burner device provided or available for heating the fluid. For example, this can be given in the form of a mathematical function, a table of values or a characteristic curve, but is not limited to it. For an example of a heating power function, refer to Figures 4A and 4B.

A burner device is a device that burns fuel, especially combustible gas, or air-fuel mixture in a flame-like manner to form a burner flame, and the heat energy released in the process is used to heat the fluid.

For example, the burner arrangement may include a premix burner in which air and fuel are premixed before entering the combustion chamber. As a non-limiting example, the modulation parameter in this case is a burner arrangement operating parameter that adjusts the amount of fuel in the premixed air-fuel mixture, such as the degree of opening of a fuel valve or the valve position of an air-fuel mixing valve. Another possible modulation parameter is the power of the blower unit that delivers the air-fuel mixture.

The burner arrangement may also include, for example, a diffusion burner in which air and fuel are first mixed in the combustion chamber. As a non-limiting example, the modulation parameter in this case is a burner arrangement operating parameter that adjusts the amount of fuel entering the combustion chamber, such as the degree of opening of a fuel valve.

The volume flow rate provided refers to the volume flow rate of the fluid during operation of the heat generator, and can be specified in liters per minute, for example. For example, in the case of a compressible fluid, the volume flow rate can be different at different locations along the flow path; but the volume flow rate can also be constant, for example in the case of an incompressible fluid. The volume flow rate provided here can be the volume flow rate at any point along the flow path from the inlet to the outlet. Preferably, it is the volume flow rate at the inlet or outlet, or the average volume flow rate thereof.

The inlet temperature of the fluid is usually subject to relatively large fluctuations and is essentially determined by the external supply source, for example, the drinking water supply may provide different temperatures at the inlet of the heat generator due to different external temperatures, different seasons, etc.

By knowing the inlet temperature, the aforementioned fluctuations can be taken into account during the control of the heat generator, so that the heat generator can still operate robustly and stably in the case of changes in the inlet temperature. Thus, it is possible to avoid overheating of the liquid exceeding the set target temperature or to reduce the time until the target temperature is reached, which not only increases the comfort when using the heat generator, but also optimizes the operation of the heat generator, according to which, for example, the energy costs generated during operation can be minimized or the service life of the heat generator can be increased (for example, by avoiding unfavorable operating conditions of overheating).

By means of the provided method for determining the inlet temperature, the inlet temperature of the fluid at the inlet of the heat generator can be advantageously determined based on other system variables available on the heat generator, without the need to use an additional temperature measuring device or temperature sensor arranged at the inlet. This means that, without having to abandon the advantageous possibility of using the inlet temperature to control the heat generating element, manufacturing costs and installation space are saved, and the maintenance costs of the heat generator are also reduced, because at least one less component needs to be maintained.

In this way, a particularly efficient method for heating a fluid by means of a heat generator is provided, which method does not require a temperature sensor to be arranged on the inlet side.

In the following, the determination of the inlet temperature based on the relationship in the field of thermodynamics on the basis of the provided heating power function is described, taking into account simplifying assumptions. For simplicity, it is assumed that the changes in kinetic and potential energy and the pressure of the considered fluid flow can be ignored. However, the method provided by the present invention should not be understood as being limited to fluid flows with these simplifying assumptions. Modeling can also include changes in the above variables, thereby providing a more accurate description of the thermodynamic processes of the heat generator.

Taking into account the above assumptions, the first law of thermodynamics, taking into account the continuity equation (conservation of mass), simplifies for a steady fluid flow to the relationship according to Eq. 1, including the heat flow rate that can be transferred (provided by the burner device) to the fluid flow Mass flow rate of fluid And the specific enthalpy values h _F at the inlet Z and the outlet A. The dotted symbols correspond to the time difference quotient.

The differences in the above specific enthalpy values h _F,A , h _F,z can be given by the specific heat capacity _cp of the fluid according to equation 2 under the assumption of constant pressure.

(h _F,A -h _F,Z )=c _p ( _TA -T _Z )=c _p ΔT [Equation 2]

Based on equations 1 and 2, for the temperature change ΔT between the outlet and the inlet, the following relationship is obtained according to equation 3, where the mass flow rate Based on the density ρ _F of the fluid and the volume flow rate Q _F (corresponding to the volume flow rate through the heat generator) , Equation 3 should be taken as a starting point for interpreting the heating power function.

For example, the heating power function may be expressed as a function of the modulation parameter MP of the burner device (heating power function f(MP)) in the form of a convertible temperature change of a reference fluid flow rate between the outlet and the inlet according to Equation 4, wherein the reference fluid flow rate is the fluid flow rate of a reference fluid (preferably the same as the fluid to be heated during operation) having a reference mass flow rate Or a reference volume flow rate Q _ref and a reference density ρ _ref and a fluid-specific reference heat capacity _cp,ref .

f(MP)＝ΔT _ref bei Q _F ＝Q _ref ,ρ _F ＝ρ _ref ,c _p ＝c _p,ref [Equation 4]

In order to provide such a heating power function, it is preferred to initially calibrate the heat generator through which a reference fluid flows, during which the temperature differences corresponding to different modulation parameter MP values are collected.

The energetic consideration of the reference fluid flow in the sense of equation 3 in turn provides a relationship according to equation 5, which itself can be related to equation 3 to obtain a relationship according to equation 6, i.e., a convertible temperature change ΔT under conditions of deviation from the reference fluid flow rate, expressed as a function of the heating power function f(MP) of the reference fluid flow rate (given according to equation 4).

Based on the relationship in Equation 6, it should be noted that the heating power function can also be additionally defined on the basis of one or more other state variables related to the reference fluid flow, for example expressed as f ^* ( _MP )= _ΔTrefQref or expressed as f ^** (MP) _{= ΔTrefQrefρref} , whereby the state variables _will no longer be explicitly included in Equation 6.

Using the acquired outlet temperature _TA , the inlet temperature _TX can be given according to the following Equation 7.

Preferably, the fluid to be heated in the heat generator is a reference fluid, and the reference fluid is preferably an incompressible fluid or is simulated as an incompressible fluid, in particular water or an aqueous solution. This allows the assumption of constant density and the same specific heat capacity during the implementation of the method, resulting in a simplified relationship according to equation 8.

In the simplest case, the heat generator can be designed to always provide a constant volume flow rate of the fluid to be heated that does not change during operation, so that the volume flow rate and the reference volume flow rate always match. This gives a highly simplified relationship according to equation 9, especially in the incompressible case.

T _Z = _TA -f(MP) [Equation 9]

Alternatively, the heating power function can also be specified independently of the reference fluid flow rate, thus providing a more general description of the heating power. In this case, the heating power function g(MP) can directly describe the heat flow rate provided by the burner arrangement As a function of the modulation parameter MP (see equation 10). According to equation 3, the relationship of the inlet temperature T _Z according to equation 11 is obtained.

Based on the heating power function and the variables provided and collected during the determination of the inlet temperature, the inlet temperature of the fluid flowing into the heat generator can be determined without having to rely on a temperature sensor located on the inlet side.

With respect to the exemplary relationship of Equations 1 to 3, in a preferred embodiment, the method according to the present invention further comprises providing a thermodynamic heat equation which describes the temperature change of the fluid based on a heat flow rate supplied to the fluid, wherein the inlet temperature is determined additionally on the basis of the provided thermodynamic heat equation.

The thermodynamic heat equation is understood to include, but is not limited to, the relationship given in the manner of Eq. 2.

In this way, a heating power function can be provided which is independent of the fluid properties (compared to the case of a reference fluid flow), for example in the sense of equation 10, wherein the heating power function is supplemented by additional information from the thermodynamic heat equation to determine the inlet temperature. In this way, the heating power function can be used universally for various fluids, since only the thermodynamic heat equation needs to be adjusted during changes in the fluid to be heated, and not the heating power function itself which is specific to the heat generator.

In a preferred embodiment, determining the inlet temperature includes determining the heating power of the burner device of the heat generator based on the provided heating power function and the collected operating values of the modulation parameters; determining the heat flow rate provided by the heat generator to the fluid based on the determined heating power; determining the temperature change of the fluid caused by the heat generator based on the determined heat flow rate, the provided thermodynamic heat equation and the provided volume flow rate; and determining the inlet temperature based on the collected outlet temperature and the determined temperature change.

According to the above process, a step-by-step evaluation of the various energy variables can be achieved to determine the inlet temperature, for example according to a method based on equations 10 and 11, plus corresponding intermediate steps, which can also be recorded during the monitoring of the heat generator.

In contrast to the simple case of providing a continuous and constant volume flow rate, the heat generator also has the possibility of providing a variable volume flow rate. For example, the variable volume flow rate is set based on the volume flow rate requirement provided on the control device of the heat generator. In this case, the method provided by the present invention can be expanded to include a step of collecting the volume flow rate of the fluid to be heated.

Therefore, in a preferred embodiment of the method according to the present invention, the step of providing the volume flow rate of the fluid flowing through the heat generator includes collecting the volume flow rate of the fluid flowing through the heat generator, thereby extending the method to be used on a heat generator with a variable or adjustable volume flow rate.

The volume flow rate here can be measured at the outlet, at the inlet or at an intermediate collection point of the heat generator using a volume flow rate measuring device, for example in the form of a dynamic pressure sensor.

If the fluid to be heated is a compressible fluid (for example in the form of a gas), the method according to the invention preferably includes a step of providing density, in particular collecting the density, which is preferably carried out at the same collection point as the collection of the volume flow rate, so that the mass flow rate of the fluid flowing through the heat generator can be inferred from the combination of density and volume flow rate at the same collection point.

In a preferred embodiment, collecting the outlet temperature of the fluid flowing out of the outlet of the heat generator includes collecting the time trajectory of the outlet temperature of the fluid flowing out of the outlet of the heat generator; detecting the stable operating state of the heat generator based on the collected time trajectory of the outlet temperature; under the collected stable operating state, selecting an outlet temperature from the collected time trajectory of the outlet temperature; and outputting the selected outlet temperature as the collected outlet temperature for determining the inlet temperature.

In this way, the outlet temperature for determining the inlet temperature is acquired in a stable operating state of the heat generator without being influenced by possible transient processes, which increases the accuracy of the determined inlet temperature. An operating state is to be understood as stable if it is characterized by operating variables that remain essentially constant over a longer period of time (e.g., a constant outlet temperature).

The stable operating state is detected if the outlet temperature is within a predetermined limit range around the target temperature for a predetermined time. For example, but not limited to, the stable operating state is detected after the outlet temperature is within a limit range of ±0.5°C around the target temperature for 10 seconds.

Alternatively, a stable operating state may be detected based on the time rate of change of the acquired time trajectory of the outlet temperature. In this case, a stable state is acquired if the rate of change over time is within a predetermined limit range around zero for a predetermined time range. For example, but not limited to, a stable state is detected when the rate of change over time is within a limit range of ±0.5°C/s around a value of 0°C/s for 10 seconds.

According to a second aspect of the present invention, there is provided a method for controlling a heat generator having a burner arrangement for heating a fluid, the method comprising determining an inlet temperature of the fluid heated by the heat generator according to the method of the first aspect of the present invention, and controlling the heat generator at least based on the determined inlet temperature.

By knowing the inlet temperature, fluctuations in this inlet temperature can be taken into account when controlling the heat generator so that the heat generator can still operate robustly and stably under varying inlet temperatures.

Preferably, the heat generator is additionally controlled based on the heating power function provided during the determination of the inlet temperature. In this way, the information provided by the heating power function can be advantageously used when setting the modulation parameters during the control of the heat generator.

In a preferred embodiment, the method according to the invention further comprises providing a target temperature for the fluid flowing out of the heat generator, wherein the control of the heat generator is additionally carried out based on the provided target temperature, and to this end the method comprises at least adjusting the operating value of the modulation parameter of the burner device based on the provided target temperature and the determined inlet temperature, in particular based on the provided heating power function.

Based on the known inlet temperature, information about the temperature change of the fluid that will be brought about by the heat generator can be obtained to achieve the required target temperature, on this basis, efficient control of the heat generator can be achieved.

For example, the heating power adjusted by the modulation parameter can be limited to avoid overheating of the liquid and exceeding the set target temperature. Similarly, the heating power can be set so that the time to reach the target temperature is as short as possible.

This not only increases the comfort when using the heat generator, but also makes it possible to optimize the operation of the heat generator so that, for example, the energy costs incurred during operation can be minimized or the service life of the heat generator can be extended (for example by avoiding unfavorable operating conditions such as overheating).

Preferably, the method according to the present invention further comprises collecting the outlet temperature of the fluid flowing out of the outlet of the heat generator, wherein the control of the heat generator is additionally performed based on the collected outlet temperature, in particular adjusting the operating value of the modulation parameter of the burner device based on the provided target temperature, the determined inlet temperature and the collected outlet temperature.

Regarding the outlet temperature of the fluid, control based on the deviation between the actual temperature and a provided target temperature can be implemented.

In a preferred embodiment, the method according to the invention further comprises acquiring a volume flow rate of a fluid flowing through the heat generator, wherein adjustment of an operating value of a modulation parameter of a burner arrangement when controlling the heat generator is additionally performed based on the acquired volume flow rate.

This provides another input variable that can be used in the process of controlling the heat generator.

In a preferred embodiment, the method according to the present invention includes providing a PI controller, which is configured to adjust the operating value of a modulation parameter of a burner device for controlling a heat generator; the method also includes setting at least one control parameter of the PI controller, which is based at least on the acquired inlet temperature and optionally additionally on the acquired volume flow rate and/or the provided target temperature.

The PI controller is preferably configured to control the outlet temperature based on the difference between the provided target temperature and the collected outlet temperature (actual temperature) so as to achieve the desired target temperature as quickly as possible while maintaining stability during the control of the heat generator. In addition, excessive overshoot or undershoot is prevented during the process of reaching the set target temperature.

The advantages of a PI controller are well known and in the method provided by the invention it can be optimally adapted to the respective environmental conditions (inlet temperature, volume flow rate, etc.) in order to achieve a stable and robust control of, for example, the outlet temperature.

According to a third aspect of the present invention, a method for starting a heat generator is provided, the heat generator having a burner device for heating a fluid, the method comprising at least determining an inlet temperature of the fluid to be heated by the heat generator according to the method of the first aspect of the present invention, and storing the determined inlet temperature, thereby igniting a combustion flame of the burner device during a startup phase of a second operating phase of the heat generator, the second operating phase being subsequent to the first operating phase.

By storing the inlet temperature, this stored inlet temperature can advantageously be used to control subsequent operating phases of the heat generator, in particular a startup phase of the second operating phase of the heat generator, during which, due to the generally extremely dynamic processes, the inlet temperature cannot be determined according to the method according to the first aspect, since determining the inlet temperature requires that the burner has already been ignited and has reached a steady state. Therefore, the startup phase of the second operating phase can advantageously be carried out using the inlet temperature determined in the previous startup phase.

Preferably, in each further operating phase after the first operating phase, the stored inlet temperature is updated so that during the control process, in particular during the start-up phase of each phase, up-to-date information on the inlet temperature is always available.

In a preferred embodiment, the method according to the present invention further includes providing a target temperature for the fluid flowing out of the heat generator for the second operating stage; providing a volume flow rate of the fluid flowing through the heat generator for the second operating stage; setting initial operating values of the modulation parameters of the burner device for the startup phase of the second operating stage, at least based on the stored inlet temperature and the provided target temperature, and optionally additionally based on the volume flow rate provided for the second operating stage; and igniting the burner flame of the burner device with the set initial operating values of the modulation parameters.

In this way, an ignition load is set for the start-up phase, which determines the amount of fuel provided for igniting the burner flame. The ignition load is selected to ensure, on the one hand, that the burner flame can be reliably ignited, e.g. without flame breakage, and, on the other hand, to avoid excessive amounts of fuel (overburning) during the ignition process, which would prevent, for example, the formation of undesirable soot. Ideally, the ignition load should be selected so that it can start quickly and reach the required stable operating state of the heat generator in the shortest possible time, so that the required outlet temperature of the fluid can be provided within a short time.

In a preferred embodiment, the method according to the present invention further comprises providing a plurality of predetermined initial operating values for a modulation parameter of the burner device, wherein setting the initial operating value for the modulation parameter of the burner device comprises selecting an initial operating value for a startup phase from the plurality of provided predetermined initial operating values, based on a stored inlet temperature and a provided target temperature, and optionally additionally based on a provided volume flow rate for a second operating phase.

In this way, a large number of predefined ignition loads are provided, from which the ignition load most suitable for the upcoming start-up phase is selected. Preselecting the ignition load is particularly advantageous, since it can avoid unfavorable operating conditions in certain situations. For example, if there are some operating ranges where more adverse effects such as vibrations, soot deposits, flame extinguishing, etc. are present, it is preferred that no selectable ignition load is placed in these operating ranges. If an optimal ignition load is placed in such an operating range, the next preselected ignition load will be used during the start-up phase in order to avoid the above-mentioned adverse effects.

According to a fourth aspect of the present invention, a heat generator for heating a fluid is provided, comprising at least one burner device for heating a fluid flowing through the heat generator, a temperature measuring device arranged at the outlet of the heat generator for collecting the outlet temperature of the fluid flowing through the heat generator, and a control device configured to control the heat generator and at least connected to the temperature measuring device and the burner device. The control device of the heat generator is configured to determine the inlet temperature of the fluid flowing into the inlet of the heat generator, the determination of the inlet temperature is based on a heating power function of the heat generator provided to the control device, the function describes the heating power of the burner device for heating the fluid based on a modulation parameter for adjusting the heating power of the burner device, and the determination of the inlet temperature is also based on the volume flow rate flowing through the heat generator provided to the control device, the outlet temperature collected by the temperature measuring device, and the current operating value of the modulation parameter of the burner device.

The heat generator is therefore arranged for carrying out the method for determining the inlet temperature according to the invention, thereby providing the advantages already described during the description of the first aspect of the invention, in particular with regard to the optimized operation of the heat generator, without the need to use a separate temperature sensor.

The heating power function is preferably provided in a storage unit of the control device.The determination of the inlet temperature is preferably performed in an evaluation unit of the control device.

Preferably, a thermodynamic heat equation is also provided to the control device, in particular in the storage unit, which equation describes the temperature change of the fluid based on the heat flow rate provided to the fluid, wherein the control device is arranged to determine the inlet temperature additionally based on the provided thermodynamic heat equation.

Preferably, in the process of determining the inlet temperature, the control device is configured to determine the heating power of the burner device of the heat generator based on the provided heating power function and the acquired operating value of the modulation parameter; determine the heat flow rate provided by the heat generator to the fluid based on the determined heating power; and calculate the temperature change of the fluid caused by the heat generator based on the determined heat flow rate, the provided thermodynamic heat equation and the provided volume flow rate, and determine the resulting inlet temperature while taking into account the acquired outlet temperature.

Preferably, the heat generator comprises a volume flow rate sensor arranged along the fluid path between the inlet and the outlet and associated with the control device to transmit the collected volume flow rate of the fluid flowing through the heat generator to the control device.

In a preferred embodiment, the control device is further arranged for controlling the heat generator based on the inlet temperature determined by the control device.

Therefore, the heat generator is also arranged to carry out the method of controlling and starting a heat generator according to the invention, thereby providing the advantages described in the course of describing the second and third aspects of the invention.

Preferably, the control device is configured here to adjust the operating value of the modulation parameter of the burner device, the adjustment being based on a target temperature of the fluid flowing out of the heat generator, which target temperature is provided to the control device via a target temperature transmitter; the control device is further configured here to adjust the determined inlet temperature.

Preferably, the control device comprises a control unit with a PI controller, which is configured to adjust an operating value of a modulation parameter of the burner arrangement, wherein the control device is configured to adjust at least one control parameter of the PI controller based on the determined inlet temperature.

Preferably, the control device is configured to store the inlet temperature determined in the first operating phase of the heat generator in a storage unit of the control device. In this way, the determined inlet temperature can be used in the start-up phase of the heat generator in order to ignite the burner flame of the burner device in a second operating phase after the first operating phase.

Preferably, the control device is configured here to set initial operating values of the modulation parameters of the burner device for a start-up phase of the second operating phase, the setting being based at least on an inlet temperature stored in a storage unit and a target temperature provided to the control device, and optionally additionally on a provided or acquired volume flow rate of the second operating phase; the control device is also configured to send an ignition signal to the burner device so as to ignite the burner flame based on the set initial operating values of the modulation parameters.

According to a fifth aspect of the present invention, there is provided a control device for use with a heat generator according to the fourth aspect of the present invention.

In this way, a retrofitting option is provided by which existing heat generators can be retrofitted with a control device in a simple and cost-effective manner in order to expand the advantageous functionality of the heat generator according to the fourth aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

More specific embodiments of the above-mentioned aspects and features of the present invention and further advantages thereof are described below with the aid of the accompanying drawings.

1A to 1C show flow charts of an embodiment of a method according to the invention for determining an inlet temperature, controlling a heat generator and starting the heat generator.

2A shows exemplary, qualitative time curves of various operating variables of a heat generator during an embodiment of a method according to the invention for determining an inlet temperature and an embodiment of a method according to the invention for starting up a heat generator.

FIG. 2B shows exemplary, qualitative time curves of various operating variables of a heat generator during one embodiment of a method according to the invention for controlling a heat generator.

FIG. 3A shows a schematic diagram of a first embodiment of a heat generator according to the present invention.

FIG. 3B shows a schematic diagram of a second embodiment of a heat generator according to the present invention.

4A and 4B illustrate exemplary qualitative graphs of a heating power function used in a method for determining an inlet temperature according to the present invention.

It should be emphasized that the present invention is by no means limited to the embodiments and their implementation features described below. The present invention further includes modifications to the embodiments, in particular modifications and/or combinations of single or multiple features of the embodiments within the scope of protection of the independent claims.

DETAILED DESCRIPTION

FIG. 1A shows a flow chart of an exemplary embodiment of a method according to the invention for determining the inlet temperature of a fluid to be heated in a heat generator with a burner arrangement.

In step S1 , a heat generator is operated to heat a fluid flowing through the heat generator.

In step S2 , a heating power function of the heat generator is provided, which function describes the heating power of the burner device for heating the fluid based on a modulation parameter of the burner device, wherein the modulation parameter regulates the heating power of the burner device.

In step S3, the outlet temperature of the fluid flowing out of the outlet of the heat generator is collected.

In step S4 , operating values of modulation parameters of the burner arrangement are recorded.

In step S5 , the volume flow rate of the fluid flowing through the heat generator is provided, wherein step S5 preferably comprises a sub-step for acquiring the volume flow rate of the fluid flowing through the heat generator, in particular by means of a volume flow rate measuring device.

In step S6, the inlet temperature of the fluid flowing into the inlet of the heat generator is determined, wherein the inlet temperature is determined based on the provided heating power function, the provided volume flow rate, the acquired outlet temperature and the acquired operating value of the modulation parameter.

Based on the above-mentioned embodiment of the method for determining the inlet temperature according to the present invention, the inlet temperature of the fluid to be heated in the heat generator can be determined without using an additional temperature measuring device arranged at the inlet, thereby, including but not limited to, saving costs and installation space, and reducing the maintenance cost of the heat generator.

FIG. 1B shows a flow chart of an embodiment of a method according to the invention for controlling a heat generator, which method is based on the method according to the invention for determining the inlet temperature.

Steps S1 to S6 in the flow chart shown in FIG1B correspond to the steps in FIG1A , and therefore, they will not be described in detail.

In step S6 the inlet temperature of the fluid flowing into the heat generator is determined, and starting from step S6 , in step S7 a target temperature of the fluid flowing out of the outlet of the heat generator is provided.

Based on the inlet temperature determined in step S6 and the target temperature provided in step S7, in particular based on the difference between these two values, the heat generator is controlled in step S8. Preferably, step S7 comprises a sub-step of setting the modulation parameters of the burner device, based on the determined inlet temperature and the provided target temperature or based on the difference between them.

FIG. 1C shows a flow chart of one embodiment of a method according to the present invention for starting a heat generator.

Steps S1 to S6 in the flow chart shown in FIG1C correspond to the steps in FIG1A , and therefore, they will not be described in detail.

In step S6, the inlet temperature of the fluid flowing into the heat generator is determined during the first operating phase of the heat generator. Starting from step S6, the inlet temperature determined in step S7* is stored for use in the startup phase of the heat generator so as to ignite the burner flame of the combustion device in the second operating phase after the first operating phase.

In step S8*, a target temperature and a volume flow rate of the fluid flowing out of the heat generator are provided for the second operating phase.

In step S9*, initial operating values of the modulation parameters of the burner device for the startup phase of the second operating phase are set, and the initial operating values are selected from a set of two (optionally, more) predetermined initial operating values, and the selection is based on the stored inlet temperature provided by step S7* and the target temperature and volume flow rate provided by step S8* for the second operating phase.

In step S10 *, the burner flame of the burner arrangement is ignited with the initial operating values of the modulation parameters set in step S9 *.

In this way, an energy-optimized start-up of the heat generator can be carried out, in which the initial operating values are selected in such a way that, for example, the time until the target temperature is reached is as short as possible.

2A shows exemplary, qualitative time curves of various operating variables of a heat generator during an embodiment of a method according to the invention for determining an inlet temperature and an embodiment of a method according to the invention for starting up a heat generator.

The role of the modulation parameter here is played by the degree of opening α of the fuel valve of the burner unit, whose course is shown in the form of dashed lines and dots. The outlet temperature _TA of the fluid at the burner outlet is shown in the form of a solid line. The determined inlet temperature TZ _,E at the inlet of the heat generator, which serves as a basis for controlling the heat generator, is shown in the form of a dashed line. On the other hand, the actual inlet temperature is marked as TZ _,Ist and is constant at TZ _,Ist = 25°C.

2A shows two operating phases by way of example, each of which has a start-up phase and a subsequent steady-state operating state of the heat generator. The start-up phase of the first operating phase is based on an underestimated inlet temperature compared to the actual inlet temperature T _Z,Ist , while the start-up phase of the second operating phase is based on an "updated" inlet temperature, which is determined during the first operating phase according to the method for determining the inlet temperature.

The first stage of operation of the heat generator is arrive The time period is carried out, wherein the fluid needs to be heated from the actual inlet temperature T _Z,Ist = 25°C to the target temperature T _A,soll = 50°C. Assuming that there is no more accurate information about the actual inlet temperature T _Z,Ist = 25°C, the inlet temperature is set to a default value for controlling the heat generator, here, the "default value" T _Z,E = 10°C.

In from arrive During the startup phase, the burner flame is ignited at α=60% (firing load), based on the difference between the target temperature _TA,Soll and the default value of the inlet temperature.

Due to the overestimation of the temperature difference of 50°C (the actual temperature difference is only 25°C), the outlet temperature T _A is adjusted to a stable operating state by reducing α. Previously, the fluid was relatively strongly superheated above the target temperature TA _,Soll .

When a stable operating state is reached, the inlet temperature is determined according to the method for determining the inlet temperature of the present invention, during which the determined inlet temperature is corrected to T _Z,E =25° C.

The effect of this correction on the behavior of the heat generator is subsequently The second operating phase begins, in which the inlet temperature determined and "updated" in the first operating phase is set to T _Z,E = 25°C and used to arrive during the startup phase, which basically corresponds to the actual inlet temperature T _Z,Ist .

Depending on the difference between the target temperature _TA,Soll and the determined inlet temperature _ＴZ,E corrected relative to the first stage, which difference now corresponds to (or at least substantially corresponds to) an actual difference of 25°C, a lower ignition load of α=40% can be selected for igniting the burner flame of the burner arrangement.

Therefore, the outlet temperature _TA does not rise too high and the heat generator is cooled to a low temperature compared with the first operation stage (Δt ⁽¹⁾ > Δt ⁽²⁾ ). Steady-state operation is achieved in a substantially shorter time, which significantly reduces energy costs.

2B shows an exemplary, qualitative time curve of various operating variables of a heat generator during an implementation of the method according to the invention for controlling a heat generator, the figure showing a comparison of two operating states after a startup phase (not shown here).

The figure compares the optimal operation of a heat generator (left) and a suboptimal operation (right), the difference between the two being the different assumed inlet temperatures T _Z,E when controlling the heat generator.

For both figures, the ordinates in the left figure which represent the outlet temperature _TA and the determined inlet temperature TZ _,E, and the ordinate in the right figure which represents the opening degree α of the fuel valve apply.

The temperature T _Z,E in this figure corresponds to the determined inlet temperature used in the control process. In the left figure, it is basically consistent with the actual inlet temperature T _Z,Ist = 25°C, while in the right figure it is underestimated by 10°C compared to the actual value. This is to illustrate the impact of incorrectly determining or generally inaccurately providing the inlet temperature when used to control the heat generator.

The left figure shows a roughly constant performance over the entire period from t ₀ to t ₁ , during which the outlet temperature _TA is maintained at the target temperature TA _,soll .

Compared to the optimal operating state in the left figure, the right figure shows an unfavorable operating state of the heat generator, which is caused by the wrong estimation of the inlet temperature, which leads to an assumed temperature difference of 50°C between the target temperature _TA,Soll and the inlet temperature in the control process, which is twice the actual temperature difference of 25°C.

This results in an increase in the value of α from 20% at _t0 to 40% in order to provide a heating power corresponding to the higher temperature difference of 50° C. However, since the temperature difference was greatly overestimated, the liquid at the outlet is overheated, causing the burner device to be shut down (α drops to 0%).

After the outlet temperature _TA drops, the burner flame is ignited again, resulting in an overestimated temperature difference, followed by overheating and the shutdown of the burner device in a short period of time. This process is repeated, resulting in an unfavorable fluctuation process of the outlet temperature _TA and an unfavorable operating state of the heat generator that changes with the opening and closing of the burner device, which is also called "cycling" (see the right figure of Figure 2B).

The comparison of the operating conditions in FIG. 2B illustrates the advantages of providing an inlet temperature which ideally corresponds to the actual inlet temperature in controlling the heat generator in terms of the operating conditions after the start-up phase.

FIG. 3A shows a schematic diagram of a first embodiment of a heat generator 100 according to the present invention.

The heat generator 100 is used to provide hot water by heating a fluid, here water, flowing into an inlet 10 of the heat generator 100 with a volume flow rate Q _Z and an inlet temperature T _Z and supplying it as a hot water flow with a volume flow rate Q _A and an outlet temperature T _A at an outlet 40 of the heat generator 100, for further use, e.g. in a sanitary facility.

In the case of liquid fluids, such as water used here, the incompressibility assumption (constant density) is particularly suitable for describing the volume flow rate. Under this assumption, the inflow volume flow rate Q _Z always corresponds to the outflow volume flow rate Q _A. The volume flow rate Q _F of the fluid flowing through the heat generator, including but not limited to, can be used to determine the inlet temperature during the method according to the invention and satisfies the following relationship Q _F =Q _Z =Q _A.

To this end, the heat generator 100 includes a burner device 20 for heating water flowing through the heat generator 100 or water flowing through the heat exchanger 30, a control device 50 for controlling the heat generator 100, and a temperature sensor 51 arranged at the outlet 40 and a volume flow rate sensor 52 arranged at the inlet 10.

The burner device 20 comprises a premixing device 21 for an air-fuel mixture, a supply line 22 for said mixture and a flame body 23, which is supplied with said mixture through the supply line 22 and on the surface of which the air-fuel mixture burns to form a burner flame 23a, the heat energy released in the process being the heat flux (eg, specified in watts or kilowatts) for heating water flowing through heat generator 100 .

In addition, the burner device 20 also includes an ignition electrode (not shown here) for igniting the air-fuel mixture flowing out of the perforated surface of the flame body. Preferably, the burner device further includes an ionization electrode for collecting the ionization current in the burner flame 23a, on the basis of which burner flame detection can be performed.

The flame body 23 of the burner device is arranged in a heat exchanger, which is shown in the figure but not limited to a tubular coil heat exchanger, having a tubular coil 32 extending spirally in a housing 31 of the heat exchanger 30 and connecting the inlet 10 and the outlet 40. The heat energy released during the combustion process is thereby transferred to the water flowing in the tubular coil 32 to heat it.

The premixing device 21 mixes one of the provided air flow rates Q _L and the provided fuel flow rate Q _B (here, gas) according to a variable mixing ratio β between fuel and air predetermined for the premixing device 21, which can also be understood as a modulation parameter of the combustion device 20. Subsequently, the air-fuel mixture is supplied to the flame body 23 through the supply line 21 for combustion.

The mixture ratio β is preferably specified on the basis of the stoichiometric ratio of the combustion in order to be able to describe a lean or full combustion. For a constant mixture ratio β, a variable and adjustable air-fuel mixture volume flow rate Q _LB via the premixing device 21 can also be understood as a modulation parameter of the burner device 20.

A modulation parameter of a burner arrangement is understood to be any operating parameter of the burner arrangement by means of which the heating output of the burner arrangement can be adjusted and which usually acts as an actuator in the control of the heat generator.

However, the heat generator according to the invention should not be understood as being limited to the burner device 20 with premixing device 21 shown in FIG4. Likewise, for example, diffusion burners can also be used, in which air and fuel are first mixed in the combustion chamber. In this case, for example, operating parameters that can adjust the amount of fuel supplied to the combustion chamber can be understood as modulation parameters of the fuel device.

The control device 50 for controlling the heat generator is electronically coupled to the premixing device 21 of the burner device 20, the volume flow rate sensor 52 of the inlet 10 and the temperature sensor 51 of the outlet 40. In the embodiment shown, the control device 50 includes a control unit 50a, an evaluation unit 50b and a storage unit 50c, which are each coupled to each other.

The control unit 50a of the control device 50 is arranged to set the air-fuel mixture mixing ratio β and/or the volume flow rate _QLB at the premixing device 21 of the burner device 20 on the basis of a control request supplied to the control device 50a, for example on the basis of a PI controller supplied to the device.

The evaluation unit 50a of the control device 50 is arranged to determine the inlet temperature _TZ of the water flowing into the inlet 10, based on the heating power function of the heat generator 100 supplied to the control device 50 in the storage unit 50c, the volume flow rate _QZ supplied to the control device 50 and detected by the volume flow rate sensor 52, the outlet temperature _TA detected by the temperature sensor 51 and the operating value of the modulation parameter of the burner device 20. As mentioned above, this modulation parameter can be the mixing ratio β or the volume flow rate _QLB or the device parameters regulating the above variables, for example, valve position parameters for air and fuel.

The heating power function of the heat generator 100 describes the relationship between the heating power of the burner device 20 provided for heating the fluid, here water, and the modulation parameters of the burner device 20 .

This advantageous function of the control device 50 of the heat generator 100 enables the water inlet temperature _TZ to be determined without having to rely on a temperature sensor arranged on the inlet 10. Thus, installation space and manufacturing costs can be saved, and compared with prior art solutions, there is at least one less component to maintain (the temperature sensor at the inlet).

In the following, with regard to a method performed by the heat generator for determining the inlet temperature, a heating power function of the heat generator used for this purpose will be explained in more detail with reference to FIGS. 4A and 4B .

For example, according to Equation 10 above, the heating power function provided in the storage unit 50c can describe the heat flow rate of the fluid that can be transferred to the heat generator 100 Based on a function of the mixing ratio β which is used here as modulation parameter MP (see also FIG. 4A ).

According to the above equation 11, the inlet temperature T _Z can be determined by the evaluation unit 50a according to the following equation 12, where represents the mass flow rate of the fluid, Q _F represents the volume flow rate of the fluid, which are related to each other through the density of the fluid ρ _{F. cp} represents the specific heat capacity of the fluid, and g(β) represents the heating power function depending on the mixing ratio β. Preferably, the density ρ _F is already assigned, assuming a constant density of water of 1 g/cm ³ .

Alternatively, the heating power function can also be calculated using Equation 4 above, expressed as the temperature difference between the outlet temperature _TA and the (unclear) inlet temperature _TX at a reference fluid flow rate, based on the mixing ratio β used here as a modulation parameter (see also Figure 4B).

According to the above equation 8, the inlet temperature T _Z can be determined by the evaluation unit 50a according to the following equation 13, where the fluid water used here corresponds to the reference fluid and is assumed to be incompressible. Q _ref represents the reference volume flow rate, the heating power function f(β) based on the mixing ratio β.

Only two examples of heating power functions of the heat generator 100 are given above, and generally speaking the heating power function should not be understood to be limited to these examples. In addition, the parameter β is understood to be a general modulation parameter not limited to the mixing ratio.

The evaluation unit 50a uses the heating power function to determine the inlet temperature _TZ ; depending on the specific heating power function, for example by equation 12 or equation 13. For example, the evaluation unit is preferably configured to store the determined inlet temperature _TZ in the storage unit 50c and/or directly provide it to the control unit 50a.

Preferably, the control unit 50a of the control device 50 is arranged to use the inlet temperature _TZ determined by the evaluation unit 50b, which can be selectively stored in the memory unit 50c and called up by the control unit 50a during the control of the heat generator 100.

To this end, the control unit 50a is preferably configured to set the modulation parameters of the burner device 20, i.e. the mixing ratio β or the volume flow rate _QLB or the device parameters of the premixing device 21 regulating the above variables, at least based on the inlet temperature _TZ determined and supplied to the control unit 50a. In particular, the modulation parameters are set based on the difference between the determined inlet temperature _TZ and the ideal temperature of the water flowing out of the outlet 40 supplied to the control device 50 in the storage unit 50c.

In particular, during the startup phase of the heat generator 100, the burner flame 23a of the burner device is ignited, and the control unit 50a of the control device 50 is preferably arranged to set the initial value of the modulation parameter of the startup phase based on the difference between the determined inlet temperature T _Z and the provided target temperature, so as to reach the target temperature at the outlet 40 as quickly and stably as possible (without extreme overshoot) taking into account the energy consumption required for this purpose.

FIG. 3B shows a second embodiment of a heat generator 100 according to the present invention.

As in the case of the first embodiment, the function of the heat generator 100 is to provide hot water and, for this purpose, to heat a fluid, here water, flowing into the inlet 10 of the heat generator 100, with a volume flow rate Q _Z and an inlet temperature T _Z and to provide it as a hot water flow at the outlet 40 of the heat generator 100 with a volume flow rate Q _A and an outlet temperature T _A , for further use in a sanitary facility, for example. To this end, the heat generator 100 according to the second embodiment comprises, similar to the first embodiment of FIG. 3A , a burner device 20, a heat exchanger 30 coupled to the burner device 20, a control device 50 for controlling the heat generator 100, and a temperature sensor 51 arranged at the outlet 40 and a volume flow rate sensor 52 arranged at the inlet 10. In addition to the heat generator according to the first embodiment, the present heat generator 10 also comprises a plate heat exchanger 60.

The structure of the heat generator 100 according to the second embodiment is different from that of FIG. 3A in that, here, the fluid to be heated flowing into the inlet 10 is not directly heated by the burner device 20 .

The fluid to be heated flows in a domestic water system 70 which is spatially separated from the burner device 20. The burner device 20 heats an energy transfer medium, for example water, which flows in a closed burner device circuit 80 and flows through the outlet 62 of the burner device 20 into the plate heat exchanger 60 and there transfers the heat flow rate of the fluid to be heated flowing in through the plate heat exchanger 60 to the heat transfer medium. The energy transfer medium is transferred to the domestic water system 70 in order to be heated accordingly starting from the inlet 10 to the outlet 40. The energy transfer medium is thus cooled and then flows back to the burner device 20 via the inlet 61 in order to be heated again there. In order to ensure that the energy transfer medium flows through the burner device circuit 80, the burner device 20 comprises a pump device (not shown here).

The other components of the heat generator 100 according to the second embodiment basically correspond to the components of the heat generator in FIG. 3A , and thus the functions of these components are not described in detail herein.

One advantage of an embodiment with independent fluid systems (domestic water system 70 and burner device loop 80) is, including but not limited to, that in the burner device loop 80, another fluid or a fluid optimized for the operation of the burner device can be used as an energy transfer medium, such as decalcified water, in order to reduce the amount of scale deposits or contamination in the pipe coil 32, which in turn improves the heat exchange of the heat exchanger 30.

FIG. 4A shows a qualitative curve of an exemplary heating power function g(MP) for the method according to the invention, the inlet temperature being determined on the basis of Examples 1 and 2, which curve describes the heating power transferable to the fluid in the heat generator in the form of a heat flow rate based on the modulation parameter MP (see also the heat flow rate in FIG. 3A / 3B ). ).

The heating power function is specific to the heat generator, so different heat generators usually have different heating power functions. Example 1 and Example 2 refer to two different heat generators with different heating power functions. Accordingly, in the case of Example 1, there is a linear relationship between the modulation parameter MP and the heating power, and in the case of Example 2, there is a quadratic relationship.

In order to provide a heating power function, the method according to the invention can further comprise determining a heating power function of the heat generator, which preferably comprises determining heating power values of a burner device of the heat generator for a plurality of modulation parameter values set on the burner device. The heating power values are respectively represented as point distributions (circles or squares) in FIG. 4A . Preferably, the plurality of modulation parameter values are at least within a range of modulation parameter values used later in the operation of the heat generator, so as to obtain an estimated value of the heating power at least within a relevant value range, for example but not limited thereto, between 15% and 85%.

The determination of the heating power function can be carried out separately for each individual heat generator in order to be able to take into account deviations brought about during production between the individual heat generators, or it can be carried out once on a reference heat generator so that the heating power function determined in this way is subsequently available to heat generators of identical construction, for example in a storage unit of its control device.

According to the determined heating power values for each control parameter value, the definition of the heating power function g (MP) is preferably based on a regression method (Example 1: linear regression, Example 2: quadratic regression), wherein the heating power function with the modulation parameter MP as function parameter takes the following form, and the parameters m, d, a, b and c are determined in the regression process.

Example 1: g(MP)=m(MP)+d; Example 2: g(MP)=a(MP) ² +b(MP)+c.

The provision of the heating power function is not limited to the exemplary regression curve or regression function, but may also be given in the form of a table of values, on the basis of which extrapolation or interpolation is performed, or simply using a graphical characteristic curve.

Figure 4B shows a qualitative curve f(MP) of an exemplary heating power function, used for determining the inlet temperature according to the method of the present invention on the basis of Examples 3 and 4, which describes the temperature change (in Kelvin) between the outlet and the inlet of a specific fluid (here water), which is achieved by the heat generator based on the modulation parameter MP at a reference volume flow rate Q _ref and a reference density ρ _F of water.

The reference volume flow rate Q _ref may, for example, describe the volume flow rate at the inlet, at the outlet or an average thereof. Instead of a reference volume flow rate, it is also possible to specify a reference mass flow rate of the fluid flowing through the heat generator.

In order to provide the heating power function, the method according to the invention can in this case comprise determining the heating power function of the heat generator, which preferably comprises determining the temperature difference between the inlet and the outlet of a reference fluid flowing at a reference volume flow rate, for a plurality of modulation parameter values set on the burner device. Preferably, the plurality of values of the modulation parameter lies at least within a range of values of the modulation parameter subsequently used in the operation of the heat generator, so as to obtain an estimated value of the heating power at least within a relevant range of values, which is exemplarily, but not limited thereto, between 15% and 85%.

Although the heating power functions according to examples 1 and 2 in FIG4A are of a more general nature, being independent of a specific fluid and a reference volume flow rate, the advantages of the method according to examples 3 and 4 are, on the one hand, that no complex energy conversion of the measurement results obtained during the measurement of the heat generator is required, and, on the other hand, that the heating power function can be specified relatively simply and quickly by acquiring the temperature difference between the inlet and the outlet. However, examples 3 and 4 cannot be used for different fluids to be heated, but are limited to the fluid associated with the heating power function, which in FIG4B is water.

Similar to Examples 1 and 2 in FIG. 4A , f(MP) in Examples 3 and 4 is also provided by a definition based on a regression method (Example 3: linear regression, Example 4: quadratic regression).

Above, the embodiments of the present invention and their advantages have been described in detail with reference to the accompanying drawings.

Finally, it is emphasized again that the present invention is by no means limited to the above-described embodiments and their implementation features. The present invention further includes modifications to the above-described embodiments, in particular modifications resulting from modifications and/or combinations of single or multiple features of the embodiments within the scope of protection of the independent claims.

List of Reference Symbols

10 Heat generator inlet

20 Burner device

21 Premixing device

22 Air-fuel mixture supply line

23 Flame Body

23a Burner flame

30 Heat exchanger

31 Shell

32 Tubular Coil

40 Heat generator outlet

50 Control device

50a Control unit

50b Evaluation Unit

50c Storage Unit

51 Temperature sensor

52 Volume flow rate sensor

60 Plate heat exchanger

61 Burner device import

62 Burner unit outlet

70 Domestic water systems

80 Burner unit circuit

100 Heat Generator

α Fuel valve opening

β Fuel-air mixture ratio

MP Modulation Parameters (General)

Q _Z ,Q _A volume flow rate at the inlet (Z), volume flow rate at the outlet (A)

Q _F is the volume flow rate of the fluid flowing through the heat generator

Q _L ,Q _B ,Q _LB Volume flow rates of air (L), fuel (B) and air-fuel mixture (LB)

T _Z , _TA heat generator inlet temperature (Z), heat generator outlet temperature (A).

Claims (16)

1. A method for determining an inlet temperature (T _Z) of a fluid to be heated in a heat generator (100), the heat generator (100) having a burner arrangement (20), the method comprising:

-operating the heat generator (100) to heat a fluid flowing through the heat generator (100);

-collecting an outlet temperature (T _A) of the fluid flowing out of the outlet (40) of the heat generator (100);

-acquiring an operating value of a modulation parameter (α; β; MP) of the burner device (20), which modulation parameter adjusts the heating power of the burner device (20);

Determining an inlet temperature (T _Z) of the fluid flowing into the inlet (10) of the heat generator (100),

It is characterized in that the method comprises the steps of,

The method further comprises the steps of:

-providing a heating power function of the heat generator (100) describing the heating power of the burner arrangement (20) for heating the fluid based on the modulation parameter (α; β; MP) of the burner arrangement (20); and

Providing a volumetric flow rate (Q _F) of fluid through the heat generator (100),

Wherein the inlet temperature (T _Z) is determined from the supplied heating power function, the supplied volumetric flow rate (Q _F), the collected outlet temperature (T _A) and the collected operating values of the modulation parameters (alpha; beta; MP).

2. A method according to claim 1, characterized in that,

The method further comprises the steps of:

-providing a thermodynamic heat equation describing the temperature change of the fluid based on the heat flow rate provided to the fluid, wherein the determination of the inlet temperature (T _Z) is additionally made on the basis of the thermodynamic heat equation provided.

3. A method according to claim 2, characterized in that,

Determining the inlet temperature (T _Z) includes:

-determining the heating power of the burner means (20) of the heat generator (100) from the provided heating power function and the acquired operational value of the modulation parameter (α; β; MP);

-determining a heat flow rate provided to the fluid by the heat generator (100) based on the determined heating power;

-determining a temperature change of the fluid caused by the heat generator (100) from the determined heat flow rate, the provided thermodynamic heat equation and the provided volumetric flow rate (Q _F); and

-Determining an inlet temperature (T _Z) from the acquired outlet temperature (T _A) and the determined temperature change.

4. A process according to any one of claim 1 to 3, wherein,

The providing a volumetric flow rate (Q _F) of fluid through the heat generator (100) includes:

-collecting the volumetric flow rate (Q _F) of the fluid flowing through the heat generator (100).

5. A process according to any one of claim 1 to 3, wherein,

The collecting of the outlet temperature (T _A) of the fluid flowing out of the outlet of the heat generator (100) comprises:

-acquiring a time trace of an outlet temperature (T _A) of the fluid flowing out of the outlet of the heat generator (100);

-detecting a steady operation state of the heat generator (100) according to the acquired time trajectory of the outlet temperature (T _A);

-in the acquired steady-state operation, selecting an outlet temperature (T _A) from the acquired time trace of outlet temperatures (T _A);

-outputting the selected outlet temperature (T _A) as the acquired outlet temperature (T _A) for determining the inlet temperature (T _Z).

6. The method according to claim 4, wherein,

The collecting of the outlet temperature (T _A) of the fluid flowing out of the outlet of the heat generator (100) comprises:

-acquiring a time trace of an outlet temperature (T _A) of the fluid flowing out of the outlet of the heat generator (100);

-detecting a steady operation state of the heat generator (100) according to the acquired time trajectory of the outlet temperature (T _A);

-in the acquired steady-state operation, selecting an outlet temperature (T _A) from the acquired time trace of outlet temperatures (T _A);

-outputting the selected outlet temperature (T _A) as the acquired outlet temperature (T _A) for determining the inlet temperature (T _Z).

7. A method for controlling a heat generator (100), the heat generator (100) having a burner arrangement (20) for heating a fluid, the method comprising:

-determining an inlet temperature (T _Z) of a fluid heated by the heat generator (100) according to the method of any one of the claims 1 to 6; and

-Controlling the heat generator (100) based at least on the determined inlet temperature (T _Z).

8. The method of claim 7, wherein,

The method further comprises the steps of:

Providing a target temperature for the fluid exiting the heat generator (100),

Wherein the control of the heat generator (100) is additionally based on the provided target temperature, and for this purpose the method comprises at least:

-adjusting an operating value of a modulation parameter (α; β; MP) of the burner arrangement (20) based on the provided target temperature and the determined inlet temperature (T _Z).

9. The method of claim 8, wherein,

The method further comprises the steps of:

-collecting the volumetric flow rate (Q _F) of the fluid flowing through the heat generator (100);

Wherein the adjustment of the operating value of the modulation parameter of the burner device (20) is performed additionally on the basis of the acquired volumetric flow rate (Q _F) when controlling the heat generator (100).

10. A method according to any one of claims 7 to 9, characterized in that,

The method further comprises the steps of:

-providing a PI-controller, the PI-controller, the PI controller is arranged for adjusting a modulation parameter (α;

Beta; MP) for controlling the heat generator (100); and

-Setting at least one control parameter of the PI controller based on the acquired inlet temperature (T _Z).

11. A method for starting a heat generator (100), the heat generator (100) having a burner arrangement (20) for heating a fluid, comprising:

-determining an inlet temperature (T _Z) of a fluid to be heated by the heat generator (100) according to the method of any one of claims 1 to 6 during a first operating phase of the heat generator (100); and

-Storing the determined inlet temperature (T _Z) so as to ignite the combustion flame (23) of the burner device (20) during a start-up phase of a second operating phase of the heat generator (100), which is subsequent to the first operating phase.

12. The method of claim 11, wherein,

The method further comprises the steps of:

-providing a target temperature of the fluid exiting the heat generator (100) for a second operating phase;

-providing a volumetric flow rate (Q _F) of fluid through the heat generator (100) for the second operating phase;

-setting an initial operating value of a modulation parameter (α; β; MP) of the burner device (20) for a start-up phase of the second operating phase, based at least on the stored inlet temperature (T _Z) and the provided target temperature, and optionally additionally on the volumetric flow rate (Q _F) provided for the second operating phase; and

-Igniting the burner flame (23 a) of the burner device (20) with the initial operating value of the set modulation parameter (α; β).

13. The method of claim 12, wherein,

The method further comprises the steps of:

providing a plurality of predetermined initial operating values of the modulation parameters (alpha; beta; MP) of the burner device (20),

Wherein setting the initial operating values of the modulation parameters (alpha; beta; MP) of the burner device (20) comprises:

-selecting an initial operating value for the start-up phase from a plurality of predetermined initial operating values provided, based on the stored inlet temperature (T _Z) and the provided target temperature, and optionally additionally based on the provided volumetric flow rate (Q _F) for the second operating phase.

14. A heat generator for heating a fluid, comprising at least:

a burner device (20) for heating a fluid flowing through the heat generator (100),

-A temperature measuring device (51) arranged at the outlet (10) of the heat generator (100) for detecting the outlet temperature (T _A) of the fluid flowing through the heat generator (100), and

-A control device (50) arranged for controlling the heat generator (100) and associated with at least said temperature measuring device (51) and said burner device (20);

It is characterized in that the method comprises the steps of,

The control device (50) of the heat generator (100) is configured to determine an inlet temperature (T _Z) of the fluid flowing into the inlet (10) of the heat generator (100), the determination of the inlet temperature being based on a heating power function of the heat generator (100) supplied to the control device (50), the function being based on a modulation parameter (alpha; beta; MP) regulating the heating power of the burner device (20) describing the heating power of the burner device for heating the fluid, the determination of the inlet temperature being further based on a volumetric flow rate (Q _F) through the heat generator supplied to the control device, an outlet temperature (T _A) acquired by the temperature measuring device (51) and a current operating value of the burner device.

15. The heat generator (100) of claim 14, wherein,

The control device (50) is further arranged for controlling the heat generator (100) based on the inlet temperature (T _Z) determined by the control device (50).

16. A control device (50) for a heat generator (100) according to claim 14 or 15.