Method for operating an energy meter device and energy meter device

Abstract

The present disclosure relates to a method for operating an energy meter device and an energy meter device. A method for operating an energy meter device (11) for determining an energy consumption (10) in a temperature control circuit (17) in which a mixture (18) of at least two fluids, in particular a water / glycol mixture, is circulated, wherein the energy meter device (11) comprises an ultrasonic measuring device (13) for determining a mixture flow rate (5) by means of a transit time measurement, a temperature measuring device (16) for determining a temperature difference between a supply (20) and a return flow (21) of the mixture (18), and a processing device (22) for determining the energy consumption (10) taking into account the flow rate (5) of the mixture (18), the temperature difference and a k-factor (9), which ultrasonic measuring device (13) also determines a sound speed (6) of the mixture (18), wherein the processing device (22) determines the k-factor (9) directly from the sound speed (6) and a mixture temperature (4) measured by the temperature measuring device at the location of the ultrasonic measuring device (13) on the basis of an empirically obtained determination rule (8).

Description

Technical Field

[0001] This invention relates to a method for operating an energy meter device for determining energy consumption in a temperature control loop in which a mixture of at least two fluids, particularly a water / ethylene glycol mixture, circulates. The energy meter device comprises: an ultrasonic measuring device for determining the flow rate of the mixture by means of transit-time measurement; a temperature measuring device for determining the temperature difference between the supply and return of the mixture; and a processing device for determining the energy consumption by taking into account the flow rate, temperature difference, and k-factor of the mixture. The invention also relates to the energy meter device itself. Background Technology

[0002] Energy metering devices (such as heat meters or cooling meters) are based on volumetric flow rate measurements combined with the temperature drop (T) of the fluid between supply and return. in -T out To measure energy consumption (W).

[0003] This energy consumption is calculated based on the following fundamental equation:

[0004]

[0005] Where ρ represents the density of the carrier fluid, c p This represents the specific heat capacity of the carrier liquid under constant pressure, where the product ρ·c p It is usually referred to as the k-factor, and The volumetric flow rate of the carrier fluid is described. It is customary in the art to use mixtures of different fluids (especially different liquids) as carrier fluids. A typical example is a water / glycol mixture, i.e., a mixture of ethylene glycol and water as an additional liquid. These mixtures most typically have two components. Water / glycol mixtures are commercially available either as ready-to-use mixtures or as ethylene glycol concentrates, and they require dilution with water to achieve the desired mixing ratio.

[0006] A problem encountered in practice is that the mixing ratio in the carrier fluid can change over time. This is due to the aging of the mixture, the loss of carrier fluid (usually water) to compensate for pressure through evaporation, or the subsequent replenishment of lost carrier fluid with water and / or ethylene glycol. This alters the thermal properties of the carrier fluid, which in turn directly affects the measured energy consumption. Other effects on the thermal properties of the carrier fluid can also be conceived in the different processes that the energy meter equipment undergoes.

[0007] To obtain certain certifications for energy meter devices, it is fundamentally necessary to be able to correct for such variations in the carrier fluid, or at least to account for them. One approach might be to check the ethylene glycol concentration annually and adjust it accordingly if the measured concentration differs from the specified concentration by more than one percent. Alternatively, it could be specified that, in the event of a pressure drop in the temperature control loop, a specified mixture is added to the carrier fluid at a specified mixing ratio.

[0008] Density ρ and specific heat capacity c p Each of these also exhibits temperature dependence, and therefore the k-factor is also temperature dependent, which must be taken into account. However, the temperature of the carrier fluid is known, since the temperature difference needs to be measured anyway, typically by measuring the temperature during supply and return.

[0009] To determine the actual k-factor of the carrier liquid, measurements, such as calorimetric measurements, have been proposed in the prior art. Using the relationship k = W / (VΔT), the value of k can be directly determined from the temperature rise ΔT of a known volume V of test liquid after heating with a known amount of energy W. For example, this process is possible in DE 10 2007 015 609A1, where the measuring device is designed to consider at least one measurement parameter given by a sensor component assigned to the measuring device and arranged in a temperature control loop, to determine the k-factor of the mixture and to consider this k-factor in order to determine the energy consumption.

[0010] However, calorimetry is difficult to implement in energy meter devices because, although the influence of the surrounding environment and the effect of heat dissipation on the surrounding environment are not negligible, these two effects are difficult to define. Furthermore, as proposed in EP 1 975 582 B1, integrating calorimetric measurements into the energy meter device would incur additional costs. Besides calorimetry, the k-factor can be indirectly determined by measuring λ and a using the relationship between the k-factor, thermal conductivity λ, and thermal diffusivity a, k = λ / a. However, this also requires additional sensor elements and complex measurement methods within the energy meter device.

[0011] EP 2 746 742 A1 relates to an apparatus for metering thermal energy, in which the concentration of antifreeze (particularly ethylene glycol) in a carrier fluid is measured in order to determine other properties of the carrier fluid.

[0012] WO 2012 / 065 276 A1 relates to a method for determining the heat flux of a heat transfer fluid, which is a mixture of at least two different fluids, wherein the density and specific heat of the heat transfer fluid are determined by measuring the speed of sound in the fluid. The density and specific heat are then used to determine the heat flux. Specifically, the method uses a temperature difference and a measurement of the speed of sound to determine the concentration of an antifreeze (particularly ethylene glycol).

[0013] Energy meter devices for determining volumetric flow rates using ultrasonic measurement equipment have also been proposed in the prior art. These can be designed using, for example, a measurement arrangement comprising two ultrasonic transducers, one pointing upstream and the other downstream, and the transducers facing each other at a known distance apart. The volume of the carrier fluid that has flowed can be determined based on the transit time difference of the ultrasonic signals along the path in both directions, specifically using a set of characteristic curves, thereby determining the flow rate of the mixture.

[0014] Generally speaking, for metering devices, and therefore energy meter devices, the goal is to make the electronics and thus energy consumption as simple and straightforward as possible. Therefore, the processes known in the prior art for determining the actual k-factor are disadvantageous because they require additional sensors or at least many additional processing steps. Summary of the Invention

[0015] Therefore, the object of the present invention is to define a facility for accurately determining heat consumption in a simple manner in an energy meter device using an ultrasonic measurement principle.

[0016] To achieve this objective, the present invention proposes a method of the type mentioned in the introduction, wherein the ultrasonic measuring device also determines the sound velocity of the mixture, wherein the processing device determines the k-factor directly from the sound velocity and the temperature of the mixture measured by the temperature measuring device at the location of the ultrasonic measuring device, based on empirically obtained determination rules.

[0017] According to the present invention, studies of a series of measurements and measurement results with the greatest variation have determined that there exists a direct correlation between sound velocity, temperature, and the k-factor that is suitable for determining the k-factor with sufficient accuracy. For example, if the temperature dependence of the k-factor and the temperature dependence of the sound velocity are measured, then it can be assumed that these datasets are linked to each other, and as a result, this can also be explained in terms of the k-factor when the sound velocity is measured.

[0018] In other words, a method for determining the k-factor based on measurements of the velocity of sound in the carrier fluid is proposed. In any energy meter device, the temperatures of the carrier fluid and its main components (at least two fluids, such as water and a predefined type of ethylene glycol (or other antifreeze)) are known, since the temperature difference between supply and return must be determined. The velocity of sound can now be determined using ultrasonic measuring equipment. Empirically derived rules (particularly those derived through analysis of measurement and / or simulation results) directly correlate the temperature and velocity of sound at the ultrasonic measurement location with the k-factor, thus allowing the k-factor to be readily and directly determined.

[0019] Therefore, no additional sensor is required in this invention for determining the k-factor. When two ultrasonic transducers are opposite each other in the flow direction, the sound velocity can be determined from the average or sum of transit time values ​​measured downstream and upstream, and / or from a single measurement in the case of a stationary mixture. In particular, in this context, the measurement arrangement described above is suitable, where the two ultrasonic transducers are arranged in a container carrying the liquid and facing each other at a known distance apart in the flow direction, thus enabling both downstream and upstream measurements. Since the distance between the transmitting and receiving ultrasonic transducers is known, the sound velocity can be determined by a single measurement of the transit time of a stationary mixture; otherwise, if flow is present, the sound velocity can be determined from the sum or average of the transit times measured upstream and downstream, or from the sum of the reciprocal transit times measured upstream and downstream. This eliminates the influence of flow. For example, if L is the distance between the transmitting and receiving ultrasonic transducers, c f It is the speed of sound, and t1 and t2 are the absolute transit times measured from upstream and downstream, respectively, and also if u represents the flow velocity of the fluid. Let the angle between the direction of ultrasonic propagation and the direction of fluid flow be represented. Then the following holds true:

[0020]

[0021] as well as

[0022]

[0023] eliminate We get c f The exact correlation between the measured transit times t1 and t2:

[0024]

[0025] Using approximation u< <c fThe series expansion of 1 / (1+x)≈1-x (for small x) yields:

[0026]

[0027] Microcontrollers for determining both the absolute transit time and the transit time difference for a metering application are known in the prior art, for example, under serial number "TI MPS430FR6047" from Texas Instruments.

[0028] Moreover, advantageously, the mixing ratio in the carrier liquid need not be determined in this invention, and the density and specific heat capacity of the carrier liquid can also remain unknown. This greatly simplifies the determination of heat flux. In summary, an empirical correlation between the k-factor and the velocity of sound in the carrier liquid is used, where the velocity of sound can be readily determined as a byproduct of ultrasound-based flow rate measurements. It should be mentioned here that this invention can be applied to various types of variations in thermal properties and is not limited to the mixture properties mainly discussed below.

[0029] In the research that forms part of this invention, it has been discovered that particularly accurate rules for determining the k-factor characteristic value can be obtained when considering a particular mixture, i.e., the individual fluids forming the carrier fluid are known. Therefore, in the context of this invention, it is particularly advantageous to provide, when determining the k-factor, fluid information of at least one fluid identifying the mixture (particularly identifying ethylene glycol as an additional fluid in water) is considered, particularly using rules specific to the fluid or fluid combination. Thus, in particular, the fluid information specifies the composition of the mixture, i.e., the main components of the mixture. Therefore, even though there may not be a clear correlation between sound velocity and the k-factor for all conceivable fluids, or even for all conceivable ethylene glycols in a water / ethylene glycol mixture, it has still been found that for each set of data points belonging to the same mixture composition (i.e., belonging to the same main components, particularly water and ethylene glycol), a clear correlation between sound velocity and the k-factor can be inferred, and thus a clear determination rule can be inferred, allowing for extremely accurate determination of the k-factor. In this respect, it has been found that increasing the proportion of ethylene glycol in the water / ethylene glycol mixture itself manifests as an increase in the speed of sound and a decrease in the k-factor.

[0030] Therefore, in this invention, if the main components of the carrier liquid, i.e., the main components of the mixture, particularly the type of ethylene glycol used with water, are known, then the k-factor of the mixture can be determined with high accuracy based on the measured velocity of sound and temperature using the corresponding determination rules, without needing to know the mixing ratio precisely. Nor is it necessary to know the density or specific heat capacity to determine the appropriate k-factor, which greatly simplifies the derivation.

[0031] An improvement to this invention can be provided by hard-coding fluid information and / or fluid-specific determination rules in the storage component of the processing device before or during the commissioning of the energy meter device. In other words, for example, information about the ethylene glycol used can be hard-coded into the firmware of the energy meter device, i.e., stored there in a way that cannot be altered. This provides particularly high protection against tampering, for example, by heat consumers. On the other hand, the energy meter device is then applied only to that specific carrier liquid or specific fluid mixture, particularly to the hard-coded ethylene glycol or mixture composition having a comparable k-factor.

[0032] Therefore, as part of this invention, it is also possible to alternatively provide receiving fluid information via an input component or communication interface of the energy meter device. For example, it is conceivable to select the type of ethylene glycol or other components of the mixture during the assembly or installation of the energy meter device and / or during service. For this purpose, a suitable communication interface and / or input component on the energy meter device can be used. However, it is advantageous in this case to employ at least one security measure to prevent end-users from attempting to tamper with the fluid information, such as encoding, encryption, and / or the use of suitable passwords and / or other authentication means. This prevents end-users from deliberately selecting a mixture composition with a smaller k-factor, such as ethylene glycol, as this would result in a determined lower energy consumption.

[0033] However, in an alternative embodiment of the invention, as part of the method, it is also possible to obtain determination rules for at least two different components of the mixture (particularly multiple different ethylene glycols in an ethylene glycol / water mixture) from empirical results (particularly from data points). If a common temperature-related correlation between the speed of sound and the k-factor is assumed, then an energy meter device with a universal k-factor determination form (i.e., independent of the mixture) can be achieved. For example, this correlation and thus the determination rules can be found by fitting all relevant data points using the least squares method. Thus, an "average" curve is effectively assumed. However, it should be noted that the groups containing different components of the mixture used herein do not necessarily include all conceivable components of the mixture, but rather, for example, water / ethylene glycol mixtures exhibiting extremely similar behavior can be grouped together, and therefore, the energy meter device can be used for these groups of different components of the mixture. The determining factor for forming these groups can be a specification of a certain accuracy in determining the k-factor. Thus, a group can be selected such that the data points or characteristic curves of the group lie together within a sufficiently narrow range to still allow for sufficiently accurate determination of the k-factor for specified purposes (e.g., in relation to the certification of the energy meter device). For example, at least one group of different compositions of a mixture can be formed based on a specified accuracy (e.g., 1% accuracy) used to determine the k-factor. The above-described process related to fluid information can be applied to group information specifying at least two different compositions; furthermore, the fluid information can be used to verify the membership of the group.

[0034] Data points obtained from measurements and / or simulations can be used to derive deterministic rules, with measurement results being preferred. Specifically, lookup tables and / or mathematical associations can be obtained as deterministic rules. Deterministic rules can be obtained by fitting (particularly using the least squares method) to the measured and / or simulated points (collectively referred to as data points). In this case, lookup tables are particularly suitable because they can be easily implemented electronically in the energy meter device.

[0035] In an advantageous improvement to the method according to the invention, it can be configured that, in addition to energy consumption, at least one currently determined k-factor is transmitted via a communication link during the readout processing and / or energy consumption transmission processing. The energy supplier thereby receives information about the state of the energy meter device, particularly any changes that have occurred in the thermal properties of the mixture (i.e., the carrier fluid). Specifically, it can be configured that the energy supplier (particularly automatically) assesses the changes in the k-factor over time. For example, it can check for changes exceeding a threshold relative to the original value and / or the most recently transmitted value, or perform similar checks.

[0036] In addition to this method, the present invention also relates to an energy meter device for determining energy consumption in a temperature control loop in which a mixture of at least two fluids, particularly a water / ethylene glycol mixture, circulates. The energy meter device comprises: an ultrasonic measuring device for determining the flow rate of the mixture by means of transit time measurement; a temperature measuring device for determining the temperature difference between the supply and return of the mixture; and a processing device for determining energy consumption taking into account the flow rate, temperature difference, and k-factor of the mixture. The device is characterized in that it is designed to perform the method according to the invention. All statements relating to the method according to the invention can be similarly applied to the energy meter device according to the invention, and therefore, the aforementioned advantages can also be achieved by said device. Attached Figure Description

[0037] Further advantages and details of the invention are set forth in the exemplary embodiments described below and with reference to the accompanying drawings, wherein:

[0038] Figure 1 This is a graph showing the relationship between the velocity of sound and the k-factor for different water / glycol mixtures and temperatures;

[0039] Figure 2 This is a flowchart illustrating an exemplary embodiment of the method according to the present invention; and

[0040] Figure 3 An energy meter device according to the present invention is shown. Detailed Implementation

[0041] Exemplary embodiments of the invention are discussed below with respect to a two-component mixture, specifically a carrier fluid consisting of water and defined ethylene glycol. However, this does not substantially limit the applicability of the invention to other liquids (particularly antifreeze agents) or generally fluids and combinations thereof.

[0042] As part of this invention, measurements showing the greatest variation in the form of data points have been combined to verify the speed of sound in the mixture (hereinafter referred to as c). f The question asks whether there exists a sufficiently unique correlation between the k-factor and the sound velocity and the actual temperature of the mixture to determine the actual k-factor in measurements of heat energy consumption directly from the sound velocity and the actual temperature of the mixture. For example, the above description by Sebastian Baack includes an example of such a potential measurement.

[0043] Figure 1 Examples are given for various stationary temperatures of 20°C, 30°C, and 40°C, showing the speed of sound c. fThe correlation between the data point and the k-factor k is shown. Data point 1, visible in the upper left corner, is correlated with pure water, while data point group 2 is correlated with a first water / ethylene glycol mixture containing "Antifrogen N" as ethylene glycol, and the second data point group 3 is correlated with a second water / ethylene glycol mixture containing "Tyfocor L" as ethylene glycol. The data points shown are measurements obtained for different mixing ratios, but these mixing ratios do not play a further role in the empirical determination rules that can be derived from data points 1, 2, and 3.

[0044] from Figure 1 What is clear is that for each group of data points 2 and 3 associated with the same type of ethylene glycol, a well-defined rule between the velocity of sound and the k-factor can be derived for different temperatures. Increasing the proportion of ethylene glycol in the mixture leads to an increase in the velocity of sound and a decrease in the k-factor, and therefore... Figure 1 In the diagram, for each data point, the ethylene glycol concentration increases from left to right. Therefore, if the main component of the mixture (in this case, the type of ethylene glycol used with water) is known, the k-factor can be inferred from temperature and sound velocity using a deterministic rule (particularly derived through fitting), and this rule can exist as a lookup table and / or mathematical association. The k-factor can be directly derived, meaning that the mixing ratio, density, or specific heat capacity does not need to be known.

[0045] like Figure 1 As shown, similar general curves may exist for different temperatures. Depending on the ethylene glycol used and the mixing ratio, changes in the velocity of sound in the mixture will cause shifts in all data points, but the overall trend remains.

[0046] Here, deterministic rules can be obtained for specific water / ethylene glycol mixtures (i.e., particularly for specific types of ethylene glycol) to determine the k-factor with high accuracy. However, it is also conceivable to form groups of different compositions of mixtures, in which case it is conceivable to form different water / ethylene glycol mixtures whose data points are close enough together to keep the error in determining the k-factor within a certain range, for example, less than 1%. Therefore, in this case, common deterministic rules can be defined for such groups.

[0047] During the manufacture or installation of the energy meter device, fluid information indicating the ethylene glycol used can be stored in the device in a manner that cannot be altered (i.e., it can be hard-coded). In this case, in particular, determination rules associated with the fluid information or with a set of water / ethylene glycol mixtures forming the basis of determination rules can be hard-coded in the storage component. In other exemplary embodiments, determination rules for different compositions of mixtures and / or different groups (one or more) of mixture composition can also be provided in the storage component of the energy meter device. In this case, the fluid information (or group information) can be received via the input component and / or communication interface of the energy meter device, but preferably, security measures are provided to prevent prohibited alterations (e.g., by end users intending to measure their heat consumption).

[0048] Figure 2 A flowchart illustrating an exemplary embodiment of a method for operating an energy meter device according to the present invention is shown, specifically for determining consumption while taking into account potentially altered carrier fluid (mixture). The energy meter device uses ultrasound to measure the flow rate of the mixture in the reflux, which is why its measuring apparatus includes an ultrasonic measuring device for determining the flow rate of the mixture by means of transit time measurement. A temperature measuring device is also provided, which can determine the absolute temperature of the mixture in the supply and reflux of a temperature control loop, and thus determine the temperature difference between the supply and reflux. The processing device is designed to determine energy consumption based on equation (1) while taking into account the flow rate of the mixture, the temperature difference, and the k-factor.

[0049] In the method according to the invention, in step S1, not only is the temperature 4 (and therefore the temperature difference) and the flow rate 5 determined, but the actual sound velocity 6 is also now determined. The sound velocity 6 can be measured either by averaging the transit times of the upstream and downstream measurements, or by summing the reciprocals of the transit times, without the mixture moving during the measurement, as explained above with reference to formulas (2) and (3). Suitable microcontrollers for ultrasonic measuring devices are already known.

[0050] In step S2, optionally, the sound velocity 6 and temperature at the reflux point (where, in the current case, the sound velocity or flow rate is also measured) are used together with fluid information 7 (or group information) as input variables for empirically obtained determination rule 8 in order to directly determine the k-factor 9. Determination rule 8 can be obtained, for example, by fitting the associated data points 1, 2, 3 using least squares, as a mathematical correlation. Preferably, determination rule 8 exists in the energy meter device in the form of a lookup table.

[0051] In step S3, as is generally known, the energy consumption 10 is then determined using the k-factor 9, the temperature difference obtained from temperature 4, and the flow rate 5.

[0052] In the exemplary embodiments shown, it is also conceivable that, in addition to energy consumption, at least one currently determined k-factor 9 may be transmitted via a communication link during the readout processing and / or energy consumption transmission processing. Thus, for example, if a communication link to the readout device is established or an existing communication link is used to transmit energy consumption information, the latest k-factor 9 is also transmitted along with that information, for example, as an indicator of the state of the energy meter device. The energy supplier thus receives information about any potential changes in the thermal properties of the mixture (i.e., the carrier fluid). The supplier can then assess the k-factor 9 and / or its changes over time accordingly.

[0053] Figure 3 A schematic diagram of an energy meter device 11 according to the invention is shown, comprising a measuring device 12. The measuring device 12 includes an ultrasonic measuring device 13, which, in the illustrated example, uses two ultrasonic transducers (ultrasonic probes) 14 to determine the flow rate through the flow tube 15 of the measuring device 12. The measuring device 12 also includes a temperature measuring device 16 for detecting the temperature difference between the supply and return of a mixture 18 (particularly a water / ethylene glycol mixture) flowing in a temperature control loop 17 (indicated only here). The measuring device 12 is integrated into the temperature control loop 17. The temperature measuring device 16 includes two temperature sensors 19, one of which is arranged, for example, in the supply 20, and the other in the return 21 (in this case, within the flow tube 15 itself). In this case, the ultrasonic measuring device 13 is arranged in the return 21, but in other exemplary embodiments, it may also be located in the supply 20, in which case the supply temperature rather than the return temperature must be selected as the mixture temperature at the location of the ultrasonic measuring device 13. At least one heat or cooling energy consumer V (also indicated here only) is incorporated into the temperature control loop 17. A corresponding heat or cooling energy generator E is also indicated.

[0054] In the present case, the ultrasonic measuring device 13 is also designed to determine the speed of sound 6, for example, by summing or averaging the transit times or reciprocal transit times of the ultrasonic signals upstream and downstream between the ultrasonic transducers 14.

[0055] Measurement data from the ultrasonic measuring device 13 and the temperature measuring device 16 are processed in the processing device 22 of the measuring apparatus 12. This involves determining the k-factor 9 according to step S2 by means of determining rule 8, and determining the heat energy consumption 10 according to step S3.

[0056] Furthermore, as already mentioned, if the energy meter device 11 has not been hard-coded in the storage component (not shown in any detail) of the energy meter device 11 by selecting a specific determination rule 8 or in the form of fluid information 7, then the energy meter device 11 may also include an input component (not shown in any detail) and / or a communication interface 23 for receiving fluid information 7.

[0057] Reference Symbol List

[0058] 1 data point

[0059] 2 Data point groups

[0060] 3 Data point groups

[0061] 4. Temperature

[0062] 5. Flow rate

[0063] 6. Speed ​​of sound

[0064] 7. Fluid Information

[0065] 8. Define the rules

[0066] 9 k-factor

[0067] 10 Energy Consumption

[0068] 11. Energy meter equipment

[0069] 12 Measuring devices

[0070] 13 Ultrasonic measuring equipment

[0071] 14. Ultrasonic transducer

[0072] 15 Flow tubes

[0073] 16 Temperature measuring equipment

[0074] 17 Temperature control loop

[0075] 18. Mixture

[0076] 19 Temperature Sensor

[0077] 20 supplies

[0078] 21 Reflux

[0079] 22 Processing equipment

[0080] 23 Communication Interface

[0081] Steps S1-S3

Claims

1. A method for operating an energy meter device (11) for determining energy consumption (10) in a temperature control loop (17), wherein a mixture (18) of at least two fluids is circulated in the temperature control loop (17), wherein, The energy meter device (11) includes: an ultrasonic measuring device (13) for determining the flow rate (5) of the mixture by means of transit time measurement; a temperature measuring device (16) for determining the temperature difference between the supply (20) and return (21) of the mixture (18); and a processing device (22) for determining energy consumption (10) taking into account the flow rate (5), temperature difference and k-factor (9) of the mixture (18), characterized in that the ultrasonic measuring device (13) also determines the sound velocity (6) of the mixture (18), wherein the processing device (22) determines the k-factor (9) directly from the sound velocity (6) and the temperature (4) of the mixture measured by the temperature measuring device at the location of the ultrasonic measuring device (13) based on an empirically obtained determination rule (8), the determination rule (8) being obtained from empirical results for at least two different compositions of the mixture (18), and the determination rule (8) being a common determination rule for said at least two different compositions.

2. The method according to claim 1, characterized in that, The lookup table and / or mathematical association are obtained as the determining rule (8), and / or the determining rule is obtained by fitting the measured and / or simulated points (8).

3. The method according to claim 1 or 2, characterized in that, When two ultrasonic transducers (14) are opposite each other in the flow direction, the sound velocity (6) is determined based on the average or sum of the transit time values ​​measured downstream and the transit time values ​​measured upstream, or the sum of the reciprocal transit time values, and / or in the case of a stationary mixture (18), the sound velocity (6) is determined based on a single measurement.

4. The method according to claim 1 or 2, characterized in that, In addition to energy consumption (10), at least one currently determined k-factor (9) is transmitted via the communication link during readout processing and / or energy consumption transmission processing.

5. The method according to claim 4, characterized in that, The k-factor (9) was assessed over time by the energy supplier.

6. The method according to claim 1, characterized in that, The mixture (18) is a water / ethylene glycol mixture, and the determination rule (8) is derived from empirical results for a variety of different ethylene glycols in the ethylene glycol / water mixture.

7. The method according to claim 2, characterized in that, Deterministic rules are obtained by fitting the measured and / or simulated points using the least squares method (8).

8. An energy meter device (11) for determining energy consumption (10) in a temperature control loop (17), in which a mixture (18) of at least two fluids circulates, wherein the energy meter device (11) comprises: An ultrasonic measuring device (13) for determining the flow rate (5) of a mixture by means of transit time measurement; a temperature measuring device (16) for determining the temperature difference between the supply (20) and reflux (21) of the mixture (18); and a processing device (22) for determining energy consumption (10) taking into account the flow rate (5), temperature difference and k-factor (9) of the mixture (18), characterized in that an energy meter device (11) is designed to perform the method according to any one of the preceding claims 1 to 7.

9. The energy meter device according to claim 8, characterized in that, The mixture (18) is a water / ethylene glycol mixture.

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