Method and apparatus for determining flow of fluid

Abstract

A method and apparatus are disclosed for determining the flow rate of a fluid in a channel, in particular wherein the fluid is a mixture of at least two different fluids, the method comprising: in a processing unit (21) of a flow meter (1), receiving measurement data of the fluid, the measurement data is measured by a sensor system (3) and comprises a measured flow rate of the fluid, a measured temperature of the fluid and a measured sound velocity in the fluid; determining, in the processing unit (21), the viscosity of the fluid using the measurement data and a defined relationship between the sound velocity, viscosity and temperature in the fluid; and calculating, in the processing unit (21), a corrected flow rate of the fluid using the measured flow rate and the determined viscosity.

Description

Technical Field

[0001] The present disclosure relates to methods and devices for determining the flow rate of a fluid in a channel. Background Art

[0002] To improve the efficiency of heating, ventilation, and air conditioning (HVAC) systems, it is necessary to accurately monitor and regulate the flow rate of a fluid. Of particular importance for HVAC systems is the monitoring of mixtures of water and antifreeze (e.g., ethylene glycol).

[0003] Other application areas where accurately monitoring and regulating the flow rate of a fluid is important are, for example, in data centers, where fluids are used to cool servers and other electronic hardware. Immersion cooling is a way in which electronic hardware is cooled by direct contact with a fluid. These fluids must be non-conductive and typically pure (i.e., non-mixed fluids comprising a single type of fluid).

[0004] Although various physical measurement principles can be used to measure the flow velocity of a fluid, ultrasonic flow meters have become popular because they do not have moving parts, especially inside the fluid channel, and provide robust and repeatable measurement results. These ultrasonic flow meters use two ultrasonic transducers to measure the transit time of ultrasonic waves along one or more measurement paths in the downstream and upstream directions. The measurement path can cross the fluid channel diagonally, or be U-shaped, V-shaped, or W-shaped, or be a spiral path, using acoustic reflectors arranged in the fluid channel, or by reflection from the channel walls. The flow velocity v of the fluid f is related to the transit time by the following equation: where t1 is the transit time in the downstream direction and t2 is the transit time in the upstream direction. The precise average flow velocity v in the channel f further depends on the length L of the measurement path, the geometry of the measurement path relative to the flow direction, and further flow-related effects (e.g., flow profile, side effects). The volume flow rate can then be calculated as the product of the flow velocity v f and the cross-sectional area A of the flow space or pipe.

[0005] In addition to the flow velocity v of the fluid f the ultrasonic flow meter can further measure the speed of sound v s . The speed of sound v s is related to the transit time by the following equation: where the speed of sound v sThe exact value also depends on the length L of the measurement path, the geometry of the measurement path relative to the flow direction, and further flow-related effects (e.g., flow profile, side effects).

[0006] Furthermore, ultrasonic flow meters additionally having a temperature sensor configured to measure the temperature T of the fluid are known. These ultrasonic flow meters are able to determine the concentration of ethylene glycol in the fluid by using the measured speed of sound v s , the measured temperature T, and a defined relationship between the speed of sound, temperature, and ethylene glycol concentration (e.g., implemented by a reference table).

[0007] Furthermore, ultrasonic flow meters that measure the heat flow dissipated from the heat transfer fluid when passing through a consumer (e.g., radiator) are known. These flow meters (also referred to as energy meters) require additional temperature sensors arranged on the opposite side of the consumer relative to the flow meter so that the temperature difference or differential temperature, which is the result of the heat flow, can be determined. According to basic physical principles, the following equation can be used to determine the heat flow: where ρ is the density of the fluid, c ρ is the specific heat capacity, is the volume flow rate of the fluid, and ΔT is the temperature difference across the consumer device.

[0008] It should be noted that the density ρ and heat capacity c of the fluid (especially a mixture of water and an antifreeze fluid such as ethylene glycol) ρ depend not only on the absolute temperature but also on the mixing ratio.

[0009] The accuracy of determining the concentration of ethylene glycol in the fluid depends not only on the accuracy of the speed of sound measurement and the temperature measurement but also on the accuracy of the reference table. Typically, the reference table is established in the laboratory by preparing mixtures of water and ethylene glycol with known mixing ratios and measuring the speed of sound at varying temperatures. However, creating mixtures with precisely known concentrations is very complex because hydrophilic substances and contaminants or transport during the production process of the antifreeze cannot be avoided. Regardless of the method of concentration measurement used (i.e., using a titration method that relies on a reference fluid or using indirect measurement results via measuring the refractive index), the resulting concentration has an uncertainty of approximately 2%. Summary of the Invention

[0010] An object of the present invention and the embodiments disclosed herein is to provide a method and a device for determining the flow rate of a fluid in a channel.

[0011] In particular, an object of the present invention and the embodiments disclosed herein is to provide a method and a device for determining the flow rate of a fluid in a channel, which do not have at least some of the disadvantages of the prior art.

[0012] The present disclosure relates to a method for determining the flow rate of a fluid in a channel. In particular, the fluid is a mixture of at least two different fluids (for example, water and antifreeze). The method includes: in a processing unit, receiving measurement data of the fluid, the measurement data including the measured flow velocity of the fluid, the measured temperature of the fluid, and the measured speed of sound in the fluid. The method includes: in the processing unit, using the measurement data and a defined relationship between the speed of sound, viscosity, and temperature in the fluid to determine the viscosity of the fluid. The method includes: in the processing unit, using the measured flow velocity and the determined viscosity to calculate a corrected flow velocity of the fluid.

[0013] In an embodiment, the method includes: further using a defined correction relationship to calculate a corrected flow velocity, where the defined correction relationship depends on the determined viscosity.

[0014] In an embodiment, the method includes: using the viscosity to calculate a Reynolds number of the fluid, and the defined correction relationship further depends on the Reynolds number of the fluid.

[0015] In an embodiment, the method includes: further using a flow rate measurement correction factor depending on a characteristic of how the flow velocity of the fluid is measured to calculate a corrected flow velocity of the fluid.

[0016] In an embodiment, the method further includes: in the processing unit, using the corrected flow velocity of the fluid and the cross-sectional area of the channel to calculate a volume flow rate of the fluid.

[0017] In an embodiment, the method further includes: in the processing unit, using the measurement data and a defined relationship between the speed of sound, density, and temperature in the fluid to determine the density of the fluid. The method includes: in the processing unit, using the volume flow rate of the fluid and the determined density of the fluid to calculate a mass flow rate of the fluid.

[0018] In an embodiment, the measurement data further includes the acoustic impedance in the fluid, and the method further includes: in the processing unit, using the measurement data and a defined relationship between the speed of sound, density, and acoustic impedance in the fluid to determine the density of the fluid. The method further includes: in the processing unit, using the volume flow rate of the fluid and the determined density of the fluid to calculate a mass flow rate of the fluid.

[0019] In an embodiment, the method further includes: in the processing unit, using the measurement data and a defined relationship among the speed of sound, specific heat capacity, and temperature in the fluid to determine the specific heat capacity of the fluid. The method further includes: in the processing unit, using the mass flow rate and the determined specific heat capacity to calculate the energy flow rate of the fluid.

[0020] In an embodiment, the fluid is a mixture of at least two different fluids including an antifreeze, and the method further includes: in the processing unit, using the measurement data, the determined viscosity, and a defined relationship among the viscosity, temperature, and antifreeze concentration in the fluid to determine the antifreeze concentration in the fluid. Additionally or alternatively, the method further includes: in the processing unit, using the measurement data, the determined density, and a defined relationship among the density, temperature, and antifreeze concentration in the fluid to determine the antifreeze concentration in the fluid. Additionally or alternatively, the method further includes: in the processing unit, using the measurement data, the determined specific heat capacity, and a defined relationship among the specific heat capacity, temperature, and antifreeze concentration in the fluid to determine the antifreeze concentration in the fluid.

[0021] In an embodiment, the method includes: in the processing unit, calculating one or more differences in the determined antifreeze concentration using at least the viscosity, density, and / or specific heat capacity as described herein. The method further includes: in the processing unit, if one of the one or more differences in the determined antifreeze concentration exceeds a defined difference threshold, detecting a change in the fluid properties, in particular, a change in the type of antifreeze in the fluid.

[0022] In an embodiment, the method further includes: in the processing unit, using the antifreeze concentration and a defined relationship between the antifreeze concentration and the freezing point to determine the freezing point of the fluid.

[0023] In an embodiment, the method further includes: in the processing unit, using the measurement data and a defined relationship among the speed of sound, freezing point, and temperature in the fluid to determine the freezing point of the fluid.

[0024] In an embodiment, the measurement data includes a second measured temperature of the fluid measured at a location different from the first measured temperature, and the method further includes: in the processing unit, using the density, the specific heat capacity, the volume flow rate, and the temperature difference between the first temperature measurement result and the second temperature measurement result to determine the heat flow rate dissipated from the fluid.

[0025] In an embodiment, the method further includes: in the processing unit, using the first measured temperature and the second measured temperature to determine an average measured temperature. The method includes: in the processing unit, using the measured sound speed, the average measured temperature, and a defined relationship among the sound speed, specific heat capacity, and temperature in the fluid to determine an average specific heat capacity. The method includes: in the processing unit, using the density, the average specific heat capacity, the volume flow rate, and the temperature difference between the first temperature measurement result and the second temperature measurement result to determine the heat flow rate.

[0026] In addition to the method for determining the flow rate of a fluid in a channel, the present disclosure also relates to a method for determining the energy flow rate of a fluid in a channel. In particular, the fluid is a mixture of at least two different fluids. The method includes: in a processing unit, receiving measurement data of the fluid, the measurement data including the measured flow velocity of the fluid, the first measured temperature of the fluid, and the measured sound speed in the fluid. The method includes: in the processing unit, using the measurement data and a defined relationship among the sound speed, density, and temperature in the fluid to determine the density of the fluid. The method includes: in the processing unit, using the measurement data and a defined relationship among the sound speed, specific heat capacity, and temperature in the fluid to determine the specific heat capacity of the fluid. The method includes: in the processing unit, using the flow velocity of the fluid, the cross-sectional area of the channel, and the determined density of the fluid to calculate the mass flow rate of the fluid. The method includes: in the processing unit, using the mass flow rate and the determined specific heat capacity to calculate the energy flow rate of the fluid.

[0027] In an embodiment, the measurement data includes a second measured temperature of the fluid measured at a location different from the first measured temperature, and the method further includes: in the processing unit, using the density, the specific heat capacity, the volume flow rate, and the temperature difference between the first temperature measurement result and the second temperature measurement result to determine the heat flow rate dissipated from the fluid.

[0028] In an embodiment, the method further includes: in the processing unit, using the first measured temperature and the second measured temperature to determine an average measured temperature. The method further includes: in the processing unit, using the measured sound speed, the average measured temperature, and a defined relationship among the sound speed, specific heat capacity, and temperature in the fluid to determine an average specific heat capacity. The method further includes: in the processing unit, using the density, the average specific heat capacity, the volume flow rate, and the temperature difference between the first temperature measurement result and the second temperature measurement result to determine the heat flow rate.

[0029] In an embodiment, the method further comprises: retrieving, by the processing unit, past measurement data and / or past values of specific fluid properties. The fluid property values are related to a corrected flow rate, the volume flow rate, the mass flow rate, and / or the energy flow rate. The method comprises: calculating, by the processing unit, a current value of the specific fluid property using the past measurement data and / or the past values of the specific fluid property in addition to using the measurement data.

[0030] In an embodiment, the method further comprises: receiving, in the processing unit, a defined set point. The defined set point is related to a flow rate set point, a volume flow rate set point, a mass flow rate set point, and / or an energy flow rate set point. The method comprises: generating, in the processing unit, a control signal using the defined set point and a fluid property value. The fluid property value is related to a corrected flow rate, the volume flow rate, the mass flow rate, and / or the energy flow rate. The one or more fluid property values correspond to the one or more set points, i.e., the flow rate set point is related to the corrected flow rate, the volume flow rate set point is related to the volume flow rate, the mass flow rate set point is related to the mass flow rate, and the energy flow rate set point is related to the energy flow rate. The method comprises: controlling, in the processing unit, an actuator connected to a valve using the control signal.

[0031] In addition to the method for determining the flow rate of a fluid and the method for determining the energy flow rate of a fluid, the present disclosure also relates to a device for determining the flow rate of a fluid in a channel, comprising: a processing unit configured to perform at least one of the methods described herein.

[0032] In an embodiment, the method further comprises: determining, in the processing unit, whether the fluid (more specifically, defining the fluid or defining the value of the fluid property) satisfies one or more defined thresholds using the measurement data (i.e., temperature and speed of sound) or the value of the property of the fluid. The one or more defined thresholds are respectively related to the measurement data or the value of the property of the fluid. For example, the temperature may have one or more defined thresholds (e.g., an upper temperature threshold and / or a lower temperature threshold), where similar considerations are applied to the speed of sound and other (calculated) values of the fluid property, and the fluid property includes density, specific heat capacity, viscosity, and antifreeze concentration. The method comprises: generating, in the processing unit, a notification message if the fluid does not satisfy the one or more defined thresholds.

[0033] In an embodiment, the device further comprises: a sensor system connected to the processing unit. The sensor system is configured to: measure the flow rate of the fluid, the speed of sound in the fluid, and the temperature of the fluid. The sensor system is configured to: transmit measurement data to the processing unit, the measurement data including the flow rate of the fluid, the speed of sound in the fluid, and the temperature of the fluid.

[0034] In an embodiment, the device further comprises: a sensor system including an ultrasonic measurement component.

[0035] In an embodiment, the ultrasonic measurement component includes two ultrasonic transducers coupled to the channel. The ultrasonic measurement component is configured to: measure the transit time of one or more ultrasonic pulses transmitted from a first ultrasonic transducer and received by a second ultrasonic transducer; and measure the transit time of one or more ultrasonic pulses transmitted from the second ultrasonic transducer and received by the first ultrasonic transducer. Additionally or alternatively, the ultrasonic measurement component is configured to: measure the transit time of surface acoustic waves between the ultrasonic transducers. The ultrasonic measurement component is configured to use the transit time to determine the following properties of the fluid: flow rate, speed of sound, temperature, and / or acoustic impedance. The ultrasonic measurement component is configured to: transmit measurement data to the processing unit, the measurement data including one or more determined properties of the fluid. Alternatively, the ultrasonic measurement component is configured to: transmit the transit time to the processing unit, the processing unit being configured to use the transit time to determine the properties of the fluid.

[0036] In an embodiment, the sensor system includes a first temperature sensor disposed at a first location.

[0037] In an embodiment, the sensor system includes a second temperature sensor disposed at a second location, where the second location is different from the first location, in particular, where the second location is on the opposite side of the consumer device relative to the first location in the flow direction.

[0038] In addition to the method and device, the present disclosure also relates to a computer program product comprising computer program code configured to control a processing unit of a device such that the device performs the steps of one of the methods disclosed herein.

[0039] In particular, the present disclosure relates to a computer-readable medium comprising a non-transitory memory having stored thereon computer program code configured to control a processing unit of a device such that the device performs the steps of one of the methods disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The above and other aspects, features, and advantages of certain embodiments of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: Figure 1 A block diagram schematically illustrating a flowmeter having an integrated controller is shown; Figure 2 A block diagram schematically illustrating a flowmeter and a separate controller is shown; Figure 3 A diagram schematically illustrating a sensor system for measuring the flow velocity, sound velocity, and temperature of a fluid in a channel, wherein the sensor system includes two ultrasonic transducers arranged diagonally facing each other on opposite sides of the channel; Figure 4 A diagram schematically illustrating a sensor system for measuring the flow velocity, sound velocity, and temperature of a fluid in a channel, wherein the sensor system includes two ultrasonic transducers arranged adjacent to each other on the same side of the channel, and ultrasonic pulses are reflected off one or more channel walls; Figure 5 A diagram schematically illustrating a sensor system for measuring the flow velocity, sound velocity, and temperature of a fluid in a channel, wherein the sensor system includes two ultrasonic transducers arranged adjacent to each other on the same side of the channel, and ultrasonic pulses are reflected off a sound deflector arranged in the channel; Figure 6 A diagram schematically illustrating a sensor system for measuring the flow velocity, sound velocity, and temperature of a fluid in a channel, wherein the sensor system includes two ultrasonic transducers that are arranged adjacent to each other on the same side of the channel and are configured to measure the transit time of surface acoustic waves traveling along and through the channel; Figure 7 A 3D curve graph illustrating the relationship between viscosity, sound velocity, and temperature is shown; Figure 8 A 3D curve graph illustrating the relationship between specific heat capacity, sound velocity, and temperature is shown; Figure 9 A 3D curve graph illustrating the relationship between density, sound velocity, and temperature is shown; Figure 10 A curve graph illustrating the relationship between the Reynolds number and the correction factor for an exemplary ultrasonic measurement path is shown; Figure 11 A flowchart illustrating an exemplary sequence of steps for calculating a corrected flow velocity is shown; Figure 12 A flowchart illustrating an exemplary sequence of steps for calculating the volumetric flow rate of a fluid is shown; Figure 13 A flowchart illustrating an exemplary sequence of steps for calculating the mass flow rate of a fluid is shown; Figure 14 A flowchart showing an alternative exemplary sequence of steps for calculating the mass flow rate of a fluid; Figure 15 A flowchart showing an exemplary sequence of steps for calculating the energy flow rate of a fluid; and Figure 16 A flowchart showing an exemplary sequence of steps for determining the concentration of antifreeze in a fluid; Figure 17 A flowchart showing an exemplary sequence of steps for determining the heat flow rate dissipated from a fluid; Figure 18 A flowchart showing an exemplary sequence of steps for determining the heat flow rate using the average heat capacity; Figure 19 A flowchart showing an exemplary sequence of steps for determining the energy flow rate of a fluid; and Figure 20 A flowchart showing an exemplary sequence of steps for selecting and / or correcting the calculated values of the properties of a fluid. DETAILED DESCRIPTION

[0041] Reference will now be made in detail to certain embodiments, examples of which are illustrated in the accompanying drawings, in which some but not all features are shown. Indeed, the embodiments disclosed herein may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, like reference numerals will be used to refer to like parts or portions.

[0042] In Figure 1 , reference numeral 1 refers to flowmeter 1, for example, as adapted to measure the flow rate of a fluid in a heating, ventilation, and air conditioning (HVAC) system. Flowmeter 1 includes a controller 2 and a sensor system 3. Depending on the embodiment, the fluid is a binary fluid, more specifically, a water / antifreeze mixture, or even more specifically, a water / ethylene glycol mixture. In other embodiments, the fluid is unmixed, i.e., includes a single fluid type. For example, the fluid is a non-conductive fluid for immersion cooling of electronic devices.

[0043] The optional valve 4 controls the flow rate of fluid through the HVAC system (specifically, through the passage 6 for which the flow rate is measured by the flow meter 1). The passage is, for example, a pipe or duct of the HVAC system. The valve 4 is controlled by an optional actuator 5. The actuator 5 is an electromechanical device including an electric motor which, depending on the control signal, changes the opening or closing of the valve 4 to respectively allow more or less fluid to pass through the valve 4. The fluid is driven through the HVAC system by a pump. The fluid flows through a heater and / or a cooler which heats or cools the fluid. The fluid also flows through consumer devices such as heat exchangers. The heat exchanger deposits or absorbs thermal energy from the fluid into the environment surrounding the heat exchanger.

[0044] In some embodiments, one or more components of the flow meter 1 described above are integrated together. In another embodiment, for example, as described below with reference to Figure 2 the controller 2 and the sensor system 3 are implemented as separate devices communicatively coupled together.

[0045] In an embodiment, the valve 4 and the actuator 5 are arranged in a single device, as indicated by the dashed box 13.

[0046] In an embodiment, the sensor system 3, the valve 4 and the actuator 5 are arranged in a single device, as indicated by the dashed box 12.

[0047] In a preferred embodiment, the controller 2 and the sensor system 3 are part of a single device.

[0048] In an embodiment, the controller 2, the sensor system 3, the valve 4 and the actuator 5 are integrated into a single device, as indicated by the dashed box 11.

[0049] In an embodiment, the sensor system 3 further includes a processing unit (e.g., a microprocessor) and a memory (e.g., a flash memory), and one or more functions and / or steps described in the present disclosure are performed by processing in the sensor system 3. Further, depending on the embodiment, certain data described in the present disclosure is stored in the memory of the sensor system 3.

[0050] The sensor system 3 includes one or more functional and / or structural modules, parts or components configured to determine measurement data of a fluid, and more particularly, to measure physical properties of the fluid. In particular, the measurement data includes the measured temperature of the fluid, the measured speed of sound in the fluid, and / or the measured flow rate of the fluid. To this end, the sensor system 3 includes one or more of the following modules: a temperature module 31, a speed-of-sound module 32, and / or a flow module 33. The above-mentioned modules 31, 32, 33 are configured to measure temperature, speed of sound, and / or flow rate, respectively. Depending on the embodiment, the module is implemented as a structural module (i.e., using one or more dedicated circuits, particularly integrated circuits) or as a functional module (particularly, implemented as a software module in the processing unit of the sensor system 3). One or more sensors, actuators, and / or transducers based on one or more types of measurement principles can be used to measure the measurement data. Depending on the specific measurement principle used, a specific measurement principle can be used to determine one or more of the physical properties included in the measurement data, as explained in more detail below and illustrated as an example of what is described.

[0051] For example, the sensor system 3 includes a temperature sensing element 35 (not shown), such as a thermistor or a resistive temperature detector (RTD), configured such that the temperature of the fluid can be measured in the temperature module 31. The temperature sensing element 35 is in direct or indirect contact with the fluid.

[0052] In another example, the sensor system 3 includes a flow sensing assembly, such as a magnetic flow assembly in which a voltage proportional to the flow rate of the fluid is measured, a mechanical flow assembly having a rotating device (such as a paddle wheel or a propeller) that rotates proportionally to the flow rate, and an ultrasonic flow assembly in which ultrasonic signals are used to measure the flow rate, as explained in more detail below.

[0053] In an example, the sensor system 3 includes a speed-of-sound sensing assembly configured to measure the speed of sound using a pressure transducer.

[0054] In an embodiment, the sensor system 3 includes a first ultrasonic transducer 34A and a second ultrasonic transducer 34B (not shown) that enable the measurement of multiple physical properties of the fluid. Using the transit time of ultrasonic signals transmitted from the first ultrasonic transducer 34A and received by the second ultrasonic transducer 34B and vice versa, the speed of sound and the flow rate can be measured by the sensor system 3, particularly in the speed-of-sound module 32 and in the flow module 33.

[0055] Alternatively or additionally, the ultrasonic transducers 34A, 34B and the sensor system 3 are configured to measure the transit time of surface acoustic waves (SAWs) between the ultrasonic transducers 34A, 34B. The surface acoustic waves (SAWs) travel not only through the fluid in the channel, but also along the channel walls and / or through other structural components located between the first ultrasonic transducer 34A and the second ultrasonic transducer 34B. By measuring the transit time of the surface acoustic waves (SAWs), the sensor system 3 (specifically, the temperature module 31) can further measure the temperature of the fluid without requiring a separate temperature sensor 35.

[0056] Depending on the embodiment, the sensor system 3 is configured to directly transmit the measurement data received from the one or more sensors to the controller 2 in one or more forms. For example, the measurement data includes "raw" sensor signals directly received from the sensors (e.g., time-varying analog or digital signals received from the ultrasonic transducers 34A, 34B and / or the temperature sensor 35). These "raw" sensor signals are then processed by the controller 2 (specifically, by the processing unit 21 of the controller) to determine the physical properties of the fluid (i.e., temperature, sound velocity, and / or flow velocity).

[0057] Additionally or alternatively, the sensor system 3 is configured to: process the sensor signals received from the sensors; and transmit measurement data that directly indicates the value of the physical property to the controller 2.

[0058] Additionally or alternatively, the sensor system 3 is configured to: process the sensor signals received from the sensors; and transmit intermediate values (specifically, the transmission time of the ultrasonic signal) to the controller 2, which enables the controller 2 to determine the physical property using the known relationships between the transit time and the sound velocity, the flow velocity in the fluid, and / or the temperature.

[0059] In an embodiment, the sensor system 3 is part of a calorimeter and includes an additional temperature sensor installed at a second location different from the first location, which allows the sensor system 3 to measure the temperature difference and allows the sensor system 3 and / or the controller 2 to determine the heat transferred to and / or from the environment by the consumer device. Thus, the second location is on the opposite side of the consumer device from the first location. Specifically, if the consumer device is downstream from the first location, then the second location is further downstream compared to the consumer device. Similarly, if the consumer device is upstream from the first location, then the second location is further upstream compared to the consumer device. The calculation of the heat transfer is performed by a controller in the sensor system 3 itself or in the controller 2.

[0060] The sensor system 3 is connected to the controller 2. The sensor system 3 is configured to send the measurement data to the controller 2, and the controller 2 receives the measurement data.

[0061] The sensor system 3 is configured to receive a measurement command from the controller 2. When the measurement command is received, the sensor system 3 performs a measurement and transmits the measurement data to the controller 2.

[0062] In an embodiment, the sensor system 3 continuously performs measurements at a predetermined interval. For example, the controller 2 queries the sensor system 3, and the sensor system 3 periodically transmits the measurement data to the controller 2 when the query is received.

[0063] The controller 2 includes an electronic circuit, which includes a processing unit 21 and various modules. The modules include a memory 22 and a communication interface 23, such as a BACnet and / or Modbus interface. Depending on the embodiment, the module further includes a display, a battery, and / or a user interface. The battery can also be part of the sensor system 3. The user interface can be integrated into the display in the form of a touch-sensitive display. The user interface includes buttons in the example. The modules of the controller 2 are connected to each other via a data connection mechanism such that they can transmit and / or receive data. The communication interface 23 is configured for wired and / or wireless communication with the sensor system 3. The controller 2 is also connected to one or more of the following: an actuator 5, a pump or a heater and / or a cooler, and is configured to transmit a control signal to these for controlling the operation of the flow meter 1. Depending on the embodiment, the communication interface 23 is configured to communicate with a remote server via a communication network 10.

[0064] As depicted below in Figure 2 The communication network 10 includes the Internet and other intermediate networks. Wireless communication occurs using a mobile data network and / or a short-range wireless communication interface. The mobile data network is such as GSM, CDMA, and LTE networks, and the short-range wireless communication interface uses Wi-Fi networks, Bluetooth, NFC, and / or other wireless network types and standards. In the example, the processing unit 21 provides an internal network server that hosts a web page, and the web page provides a user interface.

[0065] In an embodiment, the controller 2 communicates with a remote server via a local gateway, which forwards messages from the controller 2 to the remote server and vice versa (i.e., the local gateway also forwards messages from the remote server to the controller 2).

[0066] The term "data connection mechanism" is related to a mechanism that facilitates data communication between two modules, devices, systems, or other entities. The data connection mechanism is a wired connection across a cable or a system bus or a wireless connection using direct or indirect wireless transmission.

[0067] Depending on the embodiment, the electronic circuit or processing unit 21 includes, respectively, a system-on-chip (SoC), a central processing unit (CPU), and / or other more specific processing units, such as a graphics processing unit (GPU), an application-specific integrated circuit (ASIC), a reprogrammable processing unit (such as a field-programmable gate array (FPGA)), and a processing unit specifically configured to accelerate certain applications (such as an artificial intelligence (AI) accelerator for accelerating neural networks and / or machine learning processes).

[0068] The memory 22 includes one or more volatile (transient) and / or non-volatile (non-transient) storage components. The storage components can be removable and / or non-removable and can also be integrated with the controller 2 in whole or in part. Examples of storage components include RAM (random access memory), flash memory, hard disks, data memories, and / or other data storages. Computer program code is stored on the memory 22 and is configured to control the processing unit 21 of the controller 2 such that the controller 2 performs one or more steps and / or functions as described herein. The memory 22 additionally stores data related to the fluid, in particular, the relationships, functions, tables, etc. described herein.

[0069] The memory 22 may further include: a data log, in particular, a data log that records measurement data and / or one or more values of the properties of the fluid determined using the methods described herein. The data log may include: periodic entries, in particular, periodic entries of measurement data and / or values of the properties. Periodic entries can be recorded whenever a measurement and / or calculation is performed. Periodic entries can be recorded at a defined time interval. The data log may further include event entries indicating and / or in response to a specific event. For example, if one or more of the measurement data and / or the properties of the fluid do not meet a specific defined threshold (e.g., a threshold related to a maximum and / or minimum permitted value) or the rate of change of the measurement data and / or the properties exceeds a defined rate of change, the memory may store an event entry.

[0070] Depending on the embodiment, the computer program code is compiled or uncompiled program logic and / or machine code. Thus, the controller 2 is configured to perform one or more steps and / or functions. The computer program code defines a discrete software application and / or is part of a discrete software application. Those skilled in the art will understand that the computer program code may also be distributed across multiple software applications. The software application is installed in the controller 2. Alternatively, the computer program code may also be retrieved and executed by the controller 2 on demand. In an embodiment, the computer program code further provides an interface, such as an API (Application Programming Interface), such that the functions and / or data of the controller 2 can be remotely accessed, such as via a client application or via a web browser. In an embodiment, the computer program code is configured such that one or more steps and / or functions are not executed in the controller 2, but in a remote server at a location different from the controller 2 (e.g., in a cloud-based computer system).

[0071] Figure 2 A diagram is shown schematically illustrating an embodiment of the present invention, in which the controller 2 is separated from the flowmeter 1 and connected to the flowmeter 1 using a data connection mechanism. In particular, the communication interface 23 of the controller 2 is connected to the sensor system 3 of the flowmeter 1 using a data connection mechanism. Further, in an embodiment, the sensor system 3 also has a communication interface configured for wired and / or wireless transmission.

[0072] In an embodiment, the controller 2 is directly connected to the flowmeter 1 using a data connection mechanism. In this embodiment, the controller 2 is located at or near the location of the flowmeter 1, such as in the same building as the flowmeter 1 or on the same premises as the flowmeter 1. In an example, the controller 2 is implemented as a mobile communication device, such as a mobile phone. The mobile phone (e.g., a smart phone running the Android operating system or the iOS operating system) is configured to download and install computer program code from a server (e.g., from an App store). Further examples of the controller 2 are a tablet computer, a smart watch, etc. Another example of the controller 2 implemented as a mobile communication device is a portable computer, such as a laptop computer.

[0073] In an embodiment, in addition to being connected to the flowmeter 1, the controller 2 is also connected to a remote server via the Internet 10 using the communication interface 23. The connection to the remote server enables the controller 2 to exchange data with the remote server while exchanging data with the flowmeter 1.

[0074] In an embodiment, the controller 2 is located remotely from the flow meter 1 and is connected to the flow meter 1 via the Internet 10. In particular, the controller 2 is implemented on a remote server and exchanges data with the sensor unit 3 of the flow meter 1. Optionally, a local gateway acts as an intermediary between the controller 2 and the sensor system 3.

[0075] Figures 3 to 5 Illustrated are various ultrasonic measurement components that are part of the sensor system 3. The ultrasonic measurement components are mounted on the channel 6 through which fluid flows in the flow direction f. The channel has a diameter D and is part of a flow circuit. Depending on the embodiment, the flow circuit includes one or more pumps, valves, heaters and / or coolers, and / or heat exchangers.

[0076] As illustrated by the different lengths of the arrows indicating flow, the flow velocity through the channel is not the same at each point in the channel 6. In particular, due to the interaction with the side walls of the channel 6, the flow velocity closer to the channel walls is less than the flow velocity along the center line of the channel 6. The exact flow velocity profile through the channel 6 depends on the geometry of the cross-section of the channel, the geometric particularities of the channel, whether the flow is laminar or turbulent (which can be expressed by the Reynolds number), etc. In particular, the arrows illustrate a laminar flow. However, different scenarios are possible, in particular, a turbulent flow.

[0077] Each ultrasonic measurement component includes: a first ultrasonic transducer 34A and a second ultrasonic transducer 34B, configured to emit ultrasonic pulses through the fluid (and optionally along the channel wall). The ultrasonic measurement component is connected to the sensor system 3 (or can be considered part of the sensor system 3).

[0078] A temperature sensor 35 is also mounted on the side wall of the channel 6.

[0079] In Figure 3 it, the first ultrasonic transducer 34A is arranged in a recess in the channel side wall and is oriented such that the emitted ultrasonic signal travels diagonally across the channel towards the second ultrasonic transducer 34B, and the second ultrasonic transducer 34B is arranged in a recess on the opposite side of the channel 6 and downstream from the first ultrasonic transducer 34A. The sensor system 3 is configured to: measure the transit time t1 of a first ultrasonic pulse traveling from the first ultrasonic transducer 34A to the second ultrasonic transducer 34B; and measure the transit time t2 of a second ultrasonic pulse traveling from the second ultrasonic transducer 34B to the first ultrasonic transducer 34A. By using the known distance d between the ultrasonic transducers 34A, 34B and the diameter D of the channel or the angle formed by the line between the ultrasonic transducers 34A, 34B and the center line of the channel 6, the speed of sound and the flow velocity of the fluid in the channel 6 are measured.

[0080] Figure 4The sensor system 3 is shown, in which the first and second ultrasonic transducers 34A, 34B are arranged on the same side of the channel 6, preferably in a common housing. The first and second ultrasonic transducers 34A, 34B are configured to exchange ultrasonic pulses and measure the transit time of ultrasonic pulses that can be reflected at least once by the inner channel wall.

[0081] In particular, the first ultrasonic transducer 34A is configured to: emit a first ultrasonic pulse into the channel 6, which can travel along a path R1, in which it is reflected once at a reflection point P1 on the opposite channel sidewall and received by the second ultrasonic transducer 34B. The sensor system 3 is configured to measure a first transit time t1a of the first ultrasonic pulse.

[0082] Depending on the specific geometry of the channel 6, the first ultrasonic pulse can also travel along a further path in which it is reflected two or more times by the channel wall. For example, when the channel 6 is a cylinder, the first ultrasonic pulse also travels along a path R2, in which the first ultrasonic pulse is reflected twice by the channel sidewall before it is received in the second ultrasonic transducer 34B - once at a reflection point P22 and once at a reflection point P23. The path R2 thus has a triangular shape centered on the centerline of the cylinder. Depending in particular on the geometry of the channel 6, other geometries and paths are possible. The sensor system 3 is configured to measure a second transit time t1b of the first ultrasonic pulse.

[0083] Similarly, the second ultrasonic transducer 34B emits a second ultrasonic pulse, which is reflected one or more times in the channel 6 before being received by the first ultrasonic transducer 34A. The sensor system 3 is configured to measure a first transit time t2a of the second ultrasonic pulse and a second transit time t2b of the second ultrasonic pulse.

[0084] The sensor system 3 is configured to determine the flow velocity of the fluid and the speed of sound of the fluid using at least the transit times t1a and t2a of the ultrasonic pulses, the distance d between the first and second ultrasonic transducers, and the geometric characteristics of the channel 6, in particular using the diameter D of the channel and the cross - sectional shape of the channel 6. Preferably, the sensor system 3 is further configured to: further use the transit times t1b and t2b of the ultrasonic pulses to determine the flow velocity of the fluid and the speed of sound of the fluid.

[0085] The sensor system 3 further includes: a temperature sensor 35, attached to the channel 6 at a first location. Depending on the implementation, the temperature sensor 35 can be separate from the housing including the ultrasonic transducers 34A, 34B or integrated into the same housing.

[0086] Figure 5 The sensor system 3 is shown, in which in relation to the reference Figure 4The first and second ultrasonic transducers 34A, 34B are arranged in a manner similar to the described manner. However, the channel 6 includes: two acoustic deflectors 61, 62, which are arranged on the opposite sides of the channel 6 from the ultrasonic transducers 34A, 34B and are configured such that an ultrasonic pulse emitted by the first ultrasonic transducer 34A is reflected off the first acoustic deflector 61 at the deflection point P1. Thereafter, it travels parallel to the flow direction f until it is deflected off the second acoustic deflector 62 at the deflection point P2 and deflected towards the second ultrasonic transducer 34B. Thus, at least part of the path R1 of the ultrasonic pulse is parallel to the flow direction, which simplifies the calculations for determining the speed of sound and the flow velocity.

[0087] Figure 6 The sensor system 3 is shown, for example, as Figure 4 implemented in 4 or 5, where in addition to or instead of determining the "classical" transit time of ultrasonic pulses in the channel as described herein, the sensor system is configured to determine the transit time of one or more surface acoustic waves (SAWs) traveling between the first ultrasonic transducer 34A and the second ultrasonic transducer 34B. The sensor system 3 is configured to measure the SAWs traveling between the ultrasonic transducers 34A, 34B in both directions, however for clarity, Figure 6 only the SAW traveling from the first ultrasonic transducer 34A to the second ultrasonic transducer 34B is shown.

[0088] The SAWs travel from the first ultrasonic transducer 34A to the second ultrasonic transducer 34B along multiple paths R1, R2, R3... The first path R1 is along the channel sidewall. The sensor system 3 is configured to: determine the transit time t1 of the SAW from the first ultrasonic transducer 34A to the second ultrasonic transducer 34B; and using the distance d between the ultrasonic transducers 34A, 34B and the known material properties of the channel sidewall, determine the temperature T of the channel sidewall and thus also determine the temperature T of the fluid. Thus, a separate temperature sensor 35 for measuring temperature is not necessary.

[0089] A second path R2 appears when the SAW couples out of the channel sidewall at the Raleigh angle into the fluid. The SAW that has coupled into the fluid reflects off the opposite channel sidewall and is reflected. The SAW can then couple back into the channel sidewall and travel along the channel sidewall along path R2 to the second ultrasonic transducer 34B, or be further reflected off the channel sidewall along path R3. Path R3 thus branches off path R2 and has a further reflection off the opposite sidewall of channel 6 before coupling back into the channel sidewall of ultrasonic transducers 34A, 34B. Depending on the specific configuration of the ultrasonic transducers 34A, 34B (specifically, depending on the distance d between them), the channel diameter D, and the cross-sectional geometry of channel 6, further paths are possible.

[0090] By determining the transit times of the SAW along the various paths R1, R2, R3, it is possible to calculate the flow velocity of the fluid and the speed of sound in the fluid using the transit times of the ultrasonic pulses along the various paths R1, R2, R3 in addition to the temperature T mentioned above.

[0091] In addition, the sensor system 3 is configured to: use the amplitude of the ultrasonic pulses received in the receiving ultrasonic transducers 34A, 34B to calculate the acoustic impedance in the fluid. It is further configured to determine the fluid density by using the defined relationships between the acoustic impedance, the speed of sound, and the speed of sound, acoustic impedance, and density in the fluid.

[0092] Figure 7 、 8 Figures 9 respectively show the defined relationships of the kinematic viscosity v (mm 2 / s), specific heat capacity c ρ (kj / kg / K), and density ρ (kg / m 3 ) of the fluid and how these relate to the measured speed of sound (m / s) and the measured temperature (°C). The relationships specify a set of points in 3D space corresponding to the possible physical states of the fluid, where the physical state of the fluid is defined by: the temperature, speed of sound, and kinematic viscosity of the fluid (the relationship shown in Figure 7 ); the temperature, speed of sound, and specific heat capacity of the fluid (the relationship shown in Figure 8 ); and the temperature, speed of sound, and density of the fluid (the relationship shown in Figure 9 ).

[0093] The relationships and thus the set of points can be plotted as a geometry in the form of a two-dimensional surface illustrated in Figures 7 - 9 .

[0094] Depending on the embodiment, the relationship can be stored, for example, in the memory 22 of the controller 2, in the form of data points (e.g., in a look-up table), or using one or more coefficients of one or more functions (e.g., polynomial functions), or other methods for directly or indirectly storing the relationship (e.g., when necessary, by storing parameters of specific points that can be used by the processing unit 21 to generate the relationship and / or curve).

[0095] In an embodiment, the defined relationships described herein can be implemented as a function and / or a look-up table that includes the speed of sound and temperature as variable inputs and has one or more values of a specific property of the fluid to be determined (e.g., kinematic viscosity, specific heat capacity, or density) as outputs. In an embodiment, the defined relationships have the speed of sound and temperature as their only variable inputs and have one or more values of a specific property of the fluid to be determined as outputs. The reason the defined relationships can output two values is due to the fact that for a specific combination of temperature and speed of sound, two values of the specific property to be determined (i.e., kinematic viscosity, specific heat capacity, or density) can be physically possible. This ambiguity can be resolved as described herein by considering past values of the specific property.

[0096] In an example, each defined relationship is implemented as a look-up table in which each combination of temperature and speed of sound is associated with the property to be determined.

[0097] In an example, each relationship is implemented using the defined polynomial and a plurality of associated polynomial coefficients.

[0098] For example, a 3rd or 4th order polynomial can be used to define a specific relationship. One or more exponential functions can also be used alone or in combination with the polynomial. Nested exponential functions can also be used. Additionally or alternatively, logarithmic functions can also be used.

[0099] For example, the defined relationships described herein between the speed of sound, temperature, and further properties of the fluid (specifically, density, specific heat capacity, and viscosity) can be represented at least approximately as a quadric surface in three dimensions. Thus, the defined relationships can be expressed using quadratic equations. Therefore, one or more of the defined relationships can be stored in the form of quadratic equations defined in a specific functional form, along with the specific coefficients associated therewith. These Figures 7 - 9 show exemplary relationships for a specific fluid component (e.g., for a specific mixture of a binary fluid). Specifically, the figures show exemplary relationships for a water / ethylene glycol mixture at a specific ethylene glycol concentration.

[0100] The defined relationship between the speed of sound, viscosity, and temperature in a fluid defines one or two values of kinematic viscosity for each pair of temperature and speed-of-sound values (i.e., for each combination of temperature and speed of sound). The value(s) of kinematic viscosity are defined for multiple values of temperature between 0 °C and 100 °C (e.g., one value per degree Celsius). The value(s) of kinematic viscosity are defined for multiple values of speed of sound between 1400 m / s and 1800 m / s (e.g., one value per 10 m / s). The value(s) of kinematic viscosity are in the range of 0 to 30 mm 2 / s. For some pairings (combinations) of temperature and speed of sound, particularly for fluids that are binary mixtures of water and ethylene glycol, two values of kinematic viscosity can be mathematically possible due to the curvature of the relationship (in 3D representation).

[0101] The defined relationship between the speed of sound, specific heat capacity, and temperature in a fluid defines one or two values of specific heat capacity for each pair of temperature and speed-of-sound values (e.g., for each combination of temperature and speed of sound). The value(s) of specific heat capacity are defined for multiple values of temperature between 0 °C and 100 °C (e.g., one value per degree Celsius). The value(s) of specific heat capacity are defined for multiple values of speed of sound between 1400 m / s and 1800 m / s (e.g., one value per 10 m / s). The value(s) of specific heat capacity are in the range of 3 to 4.5 kJ / kg / K. For some pairings (combinations) of temperature and speed of sound, particularly for fluids that are binary mixtures of water and ethylene glycol, two values of specific heat capacity can be mathematically possible due to the curvature of the relationship (in 3D representation).

[0102] The defined relationship between the speed of sound, density, and temperature in a fluid defines one or two values of density for each pair of temperature and speed-of-sound values (i.e., for each combination of temperature and speed of sound). The value(s) of density are defined for multiple values of temperature between 0 °C and 100 °C (e.g., one value per degree Celsius). The value(s) of density are defined for multiple values of speed of sound between 1400 m / s and 1800 m / s (e.g., one value per 10 m / s). The value(s) of density are in the range of 950 to 1050 kg / m 3 ³. For some pairings (combinations) of temperature and speed of sound, particularly for fluids that are binary mixtures of water and ethylene glycol, two values of density can be mathematically possible due to the curvature of the relationship (in 3D representation).

[0103] Similar considerations apply to the further defined relationships described herein, in particular, the defined relationships that relate viscosity and temperature to the concentration of antifreeze in a fluid, density and temperature to the concentration of antifreeze in a fluid, and specific heat capacity and temperature to the concentration of antifreeze.

[0104] Typically, the defined relationships described herein are determined in a laboratory setting where, in a tightly controlled environment, various fluid mixtures are prepared, brought to a specific set of temperatures, and their properties (in particular, the speed of sound, kinematic viscosity, specific heat capacity, and density) are measured using precise laboratory instruments. Subsequently, during, for example, commissioning of the manufacture, the determined relationships are stored in the memory 22 of the controller 2 of the flowmeter 1 such that the flowmeter 1 can use a relatively simple measurement setup as described herein (in particular, with reference to Figures 3 to 6 ) to determine the kinematic viscosity, specific heat, and / or density of the fluid with high accuracy.

[0105] Depending on the embodiment, the relationships can additionally or alternatively be retrieved on demand by the controller 2, for example, from a local gateway, from a remote server, or from another data storage system.

[0106] Since each relationship is associated with a specific fluid type and concentration (e.g., a specific mixture of water and a specific type of antifreeze), multiple relationships as described herein can be stored for a specific set of fluids, such as for each of kinematic viscosity, specific heat, and / or density.

[0107] It can also be seen that the curvature of the surface of the relationship as shown in Figures 7 - 9 is such that for certain values of temperature, there is no unambiguous mapping between the speed of sound and a further fluid property to be determined (i.e., kinematic viscosity, specific heat capacity, and / or density). Thus, the measured temperature of the fluid and the measured speed of sound in the fluid are not necessarily sufficient to unambiguously determine the further fluid properties.

[0108] Therefore, depending on the embodiment, in cases where more than one value will satisfy the relationship, the recorded measurement values of the speed of sound and temperature can be used, and optionally also past determined values of kinematic viscosity, specific heat capacity, and / or density (in particular, values determined after installation and commissioning of the flowmeter 1), to disambiguate the determined further properties.

[0109] In an embodiment, further functions, properties, and / or quantities are associated with one or more of the relationships, and these can be stored or generated on demand. These include partial derivatives of the relationship at specific points with respect to specific parameters and / or quantities including maxima, minima, inflection points, etc.

[0110] In an embodiment, new or updated relationships are received by the controller 2 from a remote server for a particular fluid (e.g., a fluid having a particular antifreeze type), and the controller 2 stores the updated relationships for the particular fluid.

[0111] Figure 10 A defined correction relationship between the Reynolds number of the fluid and the correction factor k is shown. The Reynolds number can be determined using the viscosity of the fluid. The correction factor is used to determine a corrected flow velocity of the flow in the fluid using the measured flow velocity. The correction relationship (or correction factor k) depends on the characteristics of how the flow velocity of the fluid is measured. For example, if the transit time of an ultrasonic pulse (as explained herein) is used to measure the flow velocity, the correction relationship depends on the measurement path, i.e., the path of the ultrasonic pulse between the first and second ultrasonic transducers 34A, 34B. Specifically, the correction relationship is different when the measurement path is diagonal across the channel 6 than when the measurement path is V-shaped or U-shaped (as shown in Figure 3 , 4 , 5 respectively).

[0112] As described below with reference to Figures 11 to 19 , the one or more defined relationships can be used to calculate fluid properties other than those directly measured by the sensor system 3 (i.e., other than temperature, speed of sound, and flow velocity). The one or more defined relationships can also be used to correct particular measurement results of fluid properties, in particular, the measured flow velocity.

[0113] In an embodiment, values of the properties of the fluid calculated according to the methods described herein are stored by the processing unit 21 in the memory 22. Each property of the fluid can be associated with one or more thresholds. The processing unit 21 can be configured to determine whether the value of a particular property of the fluid (in particular, the current value) meets the one or more associated thresholds. The processing unit 21 can be configured to generate a message, in particular, a notification message (alternatively, the notification message can be an alarm message) if the property of the fluid does not meet the one or more associated thresholds. The notification message can be stored in the memory 22 and / or transmitted by the communication interface 23 to, for example, a remote server.

[0114] The steps described below with reference to Figures 11 to 19 are described as being performed by the processing unit 21 of the controller 2. However, depending on the embodiment, some or all of the steps described in whole or in part can also be performed by appropriate circuits and / or functional modules of the sensor system 3, the gateway, and / or the remote server.

[0115] In a preparation step S0 (not shown), the sensor system 3 measures measurement data of the fluid by measuring values directly and / or indirectly related to temperature, sound velocity, and flow velocity. The sensor system 3 is configured to transmit the measurement data to the controller 2, in particular, the processing unit 21.

[0116] In Figure 11 step S1, the processing unit 21 is configured to receive the measurement data of the fluid. The measurement data is received from the sensor system 3 and is related to the measured physical properties of the fluid, which particularly include the measured temperature, the measured sound velocity, and the measured flow velocity.

[0117] The measurement data is optionally stored in the memory 22 and / or transmitted to a remote server via the communication interface 23.

[0118] As explained above, the measurement data can be received in various forms, which include sensor signals from one or more sensors of the sensor system 3, intermediate values calculated using the sensor signals (in particular, the transit time of ultrasonic pulses), or measured values of physical properties.

[0119] In an embodiment, the controller 2 detects whether the measurement data of the fluid has changed. If the measurement data has changed by more than a predetermined amount, the change in the measurement data is detected by the processing unit 21. For example, if the measured sound velocity changes by more than 20 m / s within a one-week period, the change is detected by the controller 2 and the change is stored in the memory 22. In an embodiment, the detection of the change is transmitted by the controller 2 via the communication interface 23 to the remote server. Since the sound velocity depends on the temperature of the fluid, and the temperature of the fluid can vary in the HVAC system, particularly over time in the duct 6, the measurement unit 21 uses a relationship to account for the change in the sound velocity due to the change in temperature when the change is detected. Only when the change is detected does the processing unit 21 of the controller 2 continue beyond step S1.

[0120] In step S2, the processing unit 21 is configured to: use the measurement data (in particular, the measured sound velocity and the measured temperature) to determine the viscosity of the fluid. The viscosity is determined using a defined relationship between the sound velocity, temperature, and viscosity in the fluid. The defined relationship is described in more detail herein (in particular, with reference to Figure 7 ).

[0121] In step S3, the processing unit 21 is configured to: use the measured flow velocity and the determined viscosity to determine the corrected flow velocity of the fluid.

[0122] In an embodiment, a corrected flow rate is determined in the processing unit 21 using a defined correction relationship between the measured flow rate in the fluid and the determined viscosity. The defined correction relationship can be based on an analytical relationship (e.g., a first-principles physical analysis based on fluid flow) or on an experimentally established relationship (e.g., based on measurements of the fluid performed in a laboratory). The defined correction relationship is stored, for example, in the memory 22 of the controller 2. Depending on the embodiment, multiple correction relationships can be stored for multiple types of fluids and / or fluid mixtures.

[0123] The corrected flow rate is determined from the measured flow rate u according to the following relationship where k is a correction factor according to the defined correction relationship.

[0124] The corrected flow rate is designed to reflect the average flow rate of the fluid in the channel 6. Thus, the corrected flow rate accounts for different flow profiles occurring at different measured flow rates.

[0125] In an embodiment, the defined correction relationship between the measured flow rate and the determined viscosity is further designed to account for the diameter D of the channel 6 and the cross-sectional shape of the channel 6.

[0126] In an embodiment, the processing unit 21 is configured to: calculate the Reynolds number Re of the fluid using the determined viscosity, as described herein (specifically, with reference to Figure 10 ). The Reynolds number Re is related to the (kinematic) viscosity v according to the following relationship: where u is the measured flow rate in the fluid (m / s) and L is the characteristic linear dimension (m).

[0127] Depending on the embodiment, the corrected flow rate is used directly For example, it is transmitted by the controller 2 to a remote server for monitoring and / or logging. The corrected flow rate can also be displayed on the display of the controller 2, or transmitted via a wired or wireless interface to a tool device communicatively connected to the controller 2.

[0128] The corrected flow rate can further be used to more accurately calculate other properties of the fluid or the HVAC system through which the fluid flows, as described in more detail below with reference to Figures 12 to 18 as described in more detail below.

[0129] In an embodiment, the controller 2 (specifically, the processing unit 21 of the controller) is configured to: receive the corrected flow rate and according to the corrected flow rate and the defined flow setpoint to generate a control signal and transmit the control signal to the actuator 5 of the valve 4 for controlling the flow rate of the fluid. The defined flow setpoint can be retrieved from the memory 22 or received via the communication interface 23.

[0130] In addition to the steps S1... S3 described above Figure 10 described, Figure 12 step S4 is also shown, in which the processing unit 21 is configured to calculate the volumetric flow rate of the fluid passing through the channel 6. The volumetric flow rate of the fluid is calculated using the cross-sectional area A of the channel 6. The cross-sectional area can be determined using the diameter D and a factor depending on the cross-sectional shape.

[0131] As explained above regarding the corrected flow velocity the volumetric flow rate can be directly displayed by the controller 2 or provided to the user, or transmitted to a remote server for monitoring and / or logging, etc.

[0132] As explained above regarding the corrected flow velocity the volumetric flow rate can also be used by the controller 2 to control the actuator 5 of the valve 4 based on the volumetric flow rate and the defined volumetric flow setpoint. In particular, the processing unit 21 of the controller is configured to: receive the volumetric flow rate; and generate a control signal based on the volumetric flow rate and the defined volumetric flow setpoint and transmit the control signal to the actuator 5 of the valve 4 for controlling the volumetric flow rate of the fluid. The defined volumetric flow setpoint can be retrieved from the memory 22 or received via the communication interface 23.

[0133] In addition to the steps S1... S4 described above Figure 13 step S5 is also shown, in which the processing unit 21 is configured to determine the density ρ of the fluid using the measurement data (in particular, the measured speed of sound and the measured temperature) and the defined relationship between the speed of sound, density, and temperature in the fluid. The defined relationship is explained in more detail above Figure 9 referred to.

[0134] In step S6, the determined density ρ and the previously calculated volumetric flow rate are used in the processing unit 21 to calculate the mass flow rate of the fluid in the processing unit 21. The mass flow rate is particularly calculated as the product of the density ρ and the volumetric flow rate.

[0135] As described above, the mass flow rate can be provided to the user by the controller 2 (via the display of the flow meter 1), transmitted to a tool device, or transmitted to a remote server.

[0136] As explained above, the mass flow rate can also be used by the controller 2 to actuate the actuator 5 of the control valve 4. In particular, the processing unit 21 of the controller is configured to: receive the mass flow rate; and generate a control signal based on the mass flow rate and a defined mass flow rate set point and transmit the control signal to the actuator 5 of the valve 4 for controlling the mass flow rate of the fluid. The defined mass flow rate set point can be retrieved from the memory 22 or received via the communication interface 23.

[0137] Figure 14 A sequence of alternative steps for determining the mass flow rate is shown. The steps S1... S4 shown above were referred to Figure 11 and 12 described. In step S7, the processing unit 21 is configured to use the measurement data to determine the density of the fluid, the measurement data further including the acoustic impedance in the fluid. The acoustic impedance is determined, for example, by measuring the amplitude of the SAW between the ultrasonic transducers 34A, 34B as described in more detail above with reference to Figure 6 . The processing unit 21 is configured to: use the measured acoustic impedance and the measured speed of sound and a defined relationship between the density, speed of sound and acoustic impedance in the fluid to determine the density, as mentioned.

[0138] In step S6, the processing unit 21 is configured to: use the volume flow rate and the determined density to determine the mass flow rate of the fluid, as described above with reference to Figure 13 .

[0139] Figure 15 A series of steps for determining the energy flow rate of the fluid is shown. Steps S1... S6 are performed as described above with reference to Figures 11 - 14 . In step S8, the processing unit 21 is configured to: use the measurement data (in particular, the measured speed of sound and the measured temperature) and a defined relationship between the speed of sound, specific heat capacity and temperature in the fluid to determine the specific heat capacity of the fluid. The defined relationship was described in more detail above with reference to Figure 8 .

[0140] In step S9, the processing unit 21 is configured to: use the mass flow rate and the determined specific heat capacity to calculate the energy flow rate of the fluid. In particular, the energy flow rate is calculated as the product of the mass flow rate and the determined specific heat capacity.

[0141] By calculating the energy flow rate as described herein, it is possible to obtain an accurate measure of the energy flow rate. Prior art methods for determining the energy flow rate require knowledge of the antifreeze concentration of the fluid, as described above, which is subject to an error of 2%, resulting in an error of at least 2% in the resulting energy flow rate, which is too high for some applications.

[0142] Refer to Figures 11 - 15The above-described steps apply to all ways of fluids, including mixtures. However, the fluid does not have to be a mixture.

[0143] The energy flow can be provided to the user by the controller 2 (e.g., via the display of the flow meter 1), emitted to the tool device, and / or emitted to the remote server.

[0144] As explained above, the energy flow can also be used by the controller 2 for the actuator 5 of the control valve 4. In particular, the processing unit 21 of the controller is configured to: receive the energy flow; and generate a control signal based on the energy flow and the defined energy flow set point and transmit the control signal to the actuator 5 of the valve 4 to control the energy flow of the fluid. The defined energy flow set point can be retrieved from the memory 22 or received via the communication interface 23.

[0145] Figure 16 Step S10 is shown, which applies to fluids containing antifreeze, such as water / ethylene glycol mixtures.

[0146] In step S10, the processing unit 21 is configured to: determine the antifreeze concentration in the fluid using the determined density, the determined viscosity, and / or the determined specific heat capacity. Use the defined relationships as described herein to determine the density, viscosity, and / or heat capacity as described in the reference Figures 7 to 9 as described to determine the density, viscosity, and / or heat capacity.

[0147] Each of the physical properties of density, viscosity, and / or heat capacity further depends on the antifreeze concentration and temperature.

[0148] The processing unit 21 is configured to: determine the antifreeze concentration in the fluid using one or more of the determined density, the determined viscosity, and / or the determined specific heat capacity of the fluid.

[0149] For example, the processing unit 21 is configured to: determine a first antifreeze concentration value using measurement data (in particular, the measured temperature), the determined viscosity, and the defined relationship between viscosity, temperature, and antifreeze concentration.

[0150] For example, the processing unit 21 is configured to: determine a second antifreeze concentration value using measurement data (in particular, the measured temperature), the determined density, and the defined relationship between density, temperature, and antifreeze concentration.

[0151] For example, the processing unit 21 is configured to: determine a third antifreeze concentration value using measurement data (in particular, the measured temperature), the determined specific heat capacity, and the defined relationship between specific heat capacity, temperature, and antifreeze concentration.

[0152] The antifreeze concentration of the fluid is determined in the processing unit 21, for example, by using the average of the first, second, and / or third values determined as described above. Other statistical metrics can also be used. In particular, the variance or range of the values can also be calculated in the processing unit 21 as a measure of uncertainty.

[0153] In an embodiment, the antifreeze concentration of the fluid is determined by using the measured speed of sound, the measured temperature, and a predefined relationship between the speed of sound, the antifreeze concentration, and the temperature in the fluid.

[0154] The antifreeze concentration of the fluid determined as above is more accurate than previous methods for determining the antifreeze concentration of the fluid using the measured speed of sound and the measured temperature. This is because: as explained herein, the reference table (i.e., relationship) between the antifreeze concentration, the speed of sound, and the temperature has a relatively large uncertainty due to the difficulty of preparing water / ethylene glycol mixtures of known ratios or measuring the proportion of ethylene glycol in fluids of unknown mixing ratios. This is further because the above-described steps of determining the antifreeze concentration by first determining one or more of density, viscosity, and / or specific heat capacity via separately defined relationships are accurate, and also because the subsequent step(s) of determining the antifreeze concentration via the defined relationship between the following are also very accurate: density, temperature, and antifreeze concentration; viscosity, temperature, and antifreeze concentration; and / or specific heat capacity, temperature, and antifreeze concentration.

[0155] In an example, one or more differences between the first, second, and / or third values are calculated. The processing unit 21 is configured to: if one of the one or more differences in the determined antifreeze concentration exceeds a defined difference threshold, detect a change in the fluid properties. If it is a single type of fluid, the fluid properties are related to a change in the type of the fluid, or if the fluid is a binary mixture, the fluid properties are related to a change in one or both of the components of the fluid. In particular, the fluid properties can include the type of antifreeze in the fluid.

[0156] The specific defined relationships referred to above Figure 16 are stored in the memory 22 as described for other defined relationships described herein and are also established in a laboratory setting.

[0157] In an embodiment, the processing unit 21 is further configured to determine the freezing point of the fluid. The freezing point of the fluid is determined using a defined relationship between the antifreeze concentration and the freezing point.

[0158] Additionally or alternatively, the processing unit 21 is configured to: use the measurement data (in particular, the measured speed of sound and the measured temperature) and a defined relationship between the speed of sound, the temperature, and the freezing point in the fluid to determine the freezing point of the fluid.

[0159] In an embodiment, the processing unit 21 is further configured to: generate a warning message if the measured temperature is within a predefined safety threshold relative to the freezing point of the fluid. For example, if the measured temperature is 5 °C higher or lower than the antifreeze temperature, then a warning message is generated.

[0160] Figure 17 Relates to the following embodiment: wherein the sensor system 3 includes a temperature sensor at a second location such that a temperature difference is determined by the sensor system 3, in particular, a temperature difference across a consumer device (such as, a heat exchanger). In step S11, the processing unit 21 determines the heat flow rate dissipated from the fluid. The heat flow rate is calculated using the determined density, the determined specific heat capacity, the volume flow rate, and the temperature difference between the first and second temperature measurements.

[0161] Figure 18 Relates to the following embodiment: wherein the heat flow rate is to be determined with higher accuracy. The calculated heat flow rate (e.g., calculated as described above with reference to Figure 17 is dependent on the specific heat capacity. However, the specific heat capacity depends on the temperature of the fluid. Therefore, accurate calculation of the heat flow rate must take into account that the specific heat capacity of the fluid changes as the temperature changes.

[0162] In step S11, the first measured temperature and the second measured temperature are used in the processing unit 21 to determine the average measured temperature. For example, the average value is the mean of the two measured temperatures.

[0163] In step S12, the processing unit 21 is configured to: determine the average heat capacity by calculating the heat capacity as described above with reference to Figure 15 described.

[0164] Additionally or alternatively, the average heat capacity can also be calculated by determining a first value of the heat capacity using the first measured temperature and a second value of the heat capacity using the second measured temperature and then averaging the first and second values.

[0165] In step S13, the density, the average specific heat capacity, the volume flow rate, and the temperature difference between the first temperature measurement and the second temperature measurement are used to determine the heat flow rate, in particular, as the product of the items mentioned above.

[0166] Figure 19 Relates to the following embodiment: wherein the energy flow rate of the fluid in the channel 6 is determined.

[0167] In a preparation step S0 (not shown), the sensor system 3 measures measurement data of the fluid by measuring values directly and / or indirectly related to temperature, sound speed, and flow rate.

[0168] In step S21, the processing unit 21 receives the measurement data of the fluid.

[0169] In step S22, the processing unit 21 uses the measurement data (in particular, the measured temperature and the measured speed of sound) and the defined relationships between the speed of sound, density, and temperature in the fluid described above with reference to Figure 9 to determine the density of the fluid.

[0170] In step S23, the processing unit 21 uses the measurement data (in particular, the measured temperature and the measured speed of sound) and the defined relationships between the speed of sound, specific heat, and temperature in the fluid described above with reference to Figure 8 to determine the specific heat capacity of the fluid.

[0171] In step S24, the processing unit 21 calculates the mass flow rate of the fluid using the measured flow rate of the fluid, the cross-sectional area of the channel 6, and the determined density of the fluid.

[0172] In step S26, the processing unit 21 calculates the energy flow rate of the fluid using the determined mass flow rate and the determined specific heat capacity.

[0173] In an embodiment, the processing unit 21 is further configured to determine the heat flow rate dissipated from the fluid as described in step S10 above with reference to Figure 17 .

[0174] In an embodiment, the processing unit 21 is further configured to determine the heat flow rate using the average specific heat capacity as described in step S12 above with reference to Figure 18 .

[0175] In an embodiment, the processing unit 21 is further configured to determine the heat flow rate using, in particular, one of the methods and / or steps described herein over a defined duration. For example, considering the duration between each time point, the heat flow rates at multiple time points can be summed and / or integrated to calculate the total amount of heat transferred. The total amount of heat transferred or, in other words, the total heat energy consumption can be expressed, for example, in joules or British thermal units (BTUs). The total amount of heat transferred can be provided to the user, stored in a memory, and / or transmitted to a further device using the communication interface 23 using the techniques described herein.

[0176] In an example where heat is transferred from the fluid to the environment, the heat flow rate can be positive. In an example where heat is transferred from the environment to the fluid (e.g., in a cooling application), the heat flow rate can also be negative.

[0177] In one example, the processing unit 21 is configured to maintain the total amount of heat flow in the memory 22. The total amount of heat flow may include one or more values indicating the total amount of heat flow within one or more defined time periods, on the current day, in the current month, in the current year, and / or during the current billing cycle. The processing unit 21 may be configured to update the total amount of heat flow using the current heat flow, for example, periodically or in real time.

[0178] Figure 20 A method for disambiguating fluid property values is shown, particularly for a specific combination or pairing of a measured temperature and a measured speed of sound, for which the relationships described herein between these measured values and the values of further properties of the fluid (specifically, viscosity, specific heat capacity, and density) permit two possible values for a particular further property. The method includes steps S31 - S35. At least some of steps S31 - S35 may be performed as part of other methods described herein. Steps S34 and S35 are optional steps, where one and / or both of them may be performed. The method may be performed by the processing unit 21 of the controller 2.

[0179] In step S31, measurement data of the fluid is received, for example, as described in step S1 as shown above in Figure 11 The measurement data of the fluid is preferably received substantially in real time, particularly immediately or shortly after being measured by one or more sensors. Thus, the measurement data is related to the current state or substantially the current state of the fluid.

[0180] In step S32, the measurement data of the fluid (particularly, the current measurement data of the fluid) is used to calculate the value of a specific property of the fluid (such as viscosity, density, and / or specific heat capacity) using a specific defined relationship between the measurement data and the specific property (as described with reference to Figures 7 to 9 )

[0181] Optionally, the measurement data and / or the calculated value of the specific property is recorded, for example, in the memory 22 of the controller 2. The measurement data and / or the calculated value may be recorded at defined intervals and / or at defined time points (such as every second, every minute, or on time).

[0182] Optionally, a statistical analysis of the measurement data and / or the calculated value of the specific property is performed. For example, an average value is calculated and / or recorded in the memory 22, such as a moving average over a predefined previous time interval (such as a moving average over the past hour).

[0183] In step S33, past measurement data and / or past values of the specific property are retrieved, for example, from the memory 22. Additionally and / or alternatively, one or more values associated with the past measurement data and / or past values of the specific property are retrieved.

[0184] In particular, past measurement data and / or past values of a particular property respectively refer to measured and / or calculated values for a particular fluid of the HVAC system. In other words, the past measurement data and / or past values of a particular property go back in time at least to the time point of installation and / or commissioning of the controller 2. In an example, the past measurement data and / or past values of a particular property go back in time at least to the time point of pre-filling and / or exchange of the fluid of the HVAC system of which the flowmeter 1 is a part.

[0185] The past measurement data is related to one or more temperature measurements and / or one or more sound speed measurements of the fluid at one or more past time points. For example, the time points may comprise or define a measurement log of a sequence of measurement data, e.g., recorded at regular intervals. Values associated with the past measurement data may include data derived from or calculated using the past measurement data, such as a moving average, a rate of change, or a function thereof.

[0186] The past values of a particular property are related to one or more calculated values of a particular property of the fluid (e.g., viscosity, specific heat capacity, and / or density) at one or more past time points. For example, the time points may comprise or define a measurement log of a sequence of values of the particular property, e.g., recorded at regular intervals. Further values associated with the particular property may include data derived from or calculated using the values of the particular property, such as a moving average, a rate of change (in particular, a partial derivative), or a function thereof.

[0187] If there are two mathematically possible values specifically for the current measurement data (in particular, the currently measured temperature and the currently measured sound speed), the past measurement data and / or past values of a particular property can be used to disambiguate the current value of the property.

[0188] The past measurement data can of course be used to (re)calculate past values of a particular property using (one or more) specific defined relationships.

[0189] The past measurement data and / or past values of a particular property are used by the processing unit to calculate a value of a particular property.

[0190] In step S34, which is an optional step, a value of a particular property is calculated by selecting the most likely value of the particular property using the past measurement data and / or past values of a particular property. Specifically, in a case where the measurement data provides ambiguous values of a particular property (i.e., two values of the particular property satisfy a particular defined relationship), the past measurement data and / or past values of a particular property are used to select the most likely value that represents the actual, physical value of the particular property. The assumption made is that the actual, physical value of the particular property changes slowly over time.

[0191] For example, if at a current time point and using current measurement values, two values of a specific property satisfy a specific defined relationship, then one or more past values of the specific property (or values derived therefrom, such as a moving average) (e.g., the most recent past value of the specific property) are compared with the two values that satisfy the specific defined relationship. The value closest to the one or more past values (or values derived therefrom, such as a moving average) is selected as the value of the specific property.

[0192] In step S35, which is an optional step, the value of a specific property is calculated by adjusting and / or correcting the value of the specific property using past measurement data and / or past values of the specific property. Specifically, the calculated value of the specific property calculated using current measurement data can be adjusted and / or corrected based on past values of the specific property. For example, a moving average of one or more past values of the specific property can be used to determine a smoothed value of the specific property. In this way, outliers caused by incorrect measurement results can be corrected.

[0193] The above-described embodiments of the present disclosure are exemplary, and those skilled in the art know that at least some of the components and / or steps described in the above embodiments can be rearranged, omitted, or introduced into other embodiments without departing from the scope of the present disclosure.

Claims

1. A method for determining the flow rate of a fluid in a channel (6), in particular, where the fluid is a mixture of at least two different fluids, the method comprises: In a processing unit (21), receiving (S1) measurement data of the fluid, the measurement data including the measured flow velocity of the fluid, the measured temperature of the fluid, and the measured speed of sound in the fluid; In the processing unit (21), using the measurement data and a defined relationship between the speed of sound, viscosity, and temperature in the fluid to determine (S2) the viscosity of the fluid; and In the processing unit (21), using the measured flow velocity and the determined viscosity to calculate (S3) the corrected flow velocity of the fluid.

2. The method according to claim 1, wherein the method comprises: Further using a defined correction relationship to calculate the corrected flow velocity, where the defined correction relationship depends on the determined viscosity.

3. The method according to claim 2, wherein the method comprises: Using the viscosity to calculate the Reynolds number of the fluid, and the defined correction relationship depends on the Reynolds number of the fluid.

4. The method according to any one of claims 1 to 3, wherein the method comprises: Further using a flow rate measurement correction factor depending on characteristics of how the flow velocity of the fluid is measured and / or characteristics of the flow velocity distribution to calculate the corrected flow velocity of the fluid.

5. The method according to any one of claims 1 to 4, further comprises: In the processing unit (21), using the corrected flow velocity of the fluid and the cross-sectional area of the channel (6) to calculate (S4) the volume flow rate of the fluid.

6. The method according to claim 5, further comprises: In the processing unit (21), using the measurement data and a defined relationship between the speed of sound, density, and temperature in the fluid to determine (S5) the density of the fluid; and In the processing unit (21), using the volume flow rate of the fluid and the determined density of the fluid to calculate (S6) the mass flow rate of the fluid.

7. The method according to claim 5, wherein the measurement data further includes the acoustic impedance in the fluid, the method further comprises: In the processing unit (21), using the measurement data and a defined relationship between the speed of sound, density, and acoustic impedance in the fluid to determine (S7) the density of the fluid; and In the processing unit (21), using the volume flow rate of the fluid and the determined density of the fluid to calculate (S6) the mass flow rate of the fluid.

8. The method according to any one of claims 6 or 7, further comprises: In the processing unit (21), using the measurement data and a defined relationship between the speed of sound, specific heat capacity, and temperature in the fluid to determine (S8) the specific heat capacity of the fluid; and In the processing unit (21), using the mass flow rate and the determined specific heat capacity to calculate (S9) the energy flow rate of the fluid.

9. The method according to any one of claims 1 to 8, wherein the fluid is among at least two different fluids, one of the fluids being an antifreeze, and the method further comprises: in the processing unit (21), determining (S10) the concentration of antifreeze in the fluid using one or more of the following: the measurement data, the determined viscosity, and the defined relationship between the viscosity, temperature, and antifreeze concentration in the fluid, the measurement data, the determined density, and the defined relationship between the density, temperature, and antifreeze concentration in the fluid, or the measurement data, the determined specific heat capacity, and the defined relationship between the specific heat capacity, temperature, and antifreeze concentration in the fluid.

10. The method according to claim 9, further comprises: in the processing unit (21), calculating one or more differences in the determined antifreeze concentration using the antifreeze concentration determined using at least two of the following: the viscosity, the density, or the specific heat capacity; and in the processing unit (21), if one of the one or more differences in the determined antifreeze concentration exceeds a defined difference threshold, detecting a change in the fluid properties, in particular, a change in the type of antifreeze in the fluid.

11. The method according to any one of claims 9 or 10, further comprises: in the processing unit (21), determining the freezing point of the fluid using the antifreeze concentration and the defined relationship between the antifreeze concentration and the freezing point.

12. The method according to any one of claims 1 to 11, further comprises: in the processing unit (21), determining the freezing point of the fluid using the measurement data and the defined relationship between the speed of sound, the freezing point, and the temperature in the fluid.

13. The method according to any one of claims 5 to 12, wherein the measurement data includes a second measured temperature of the fluid measured at a location different from the first measured temperature, and the method further comprises: in the processing unit (21), determining (S11) the heat flow rate dissipated from the fluid using the density, the specific heat capacity, the volume flow rate, and the temperature difference between the first temperature measurement result and the second temperature measurement result.

14. The method according to claim 13, wherein the method further comprises: in the processing unit (21), determining (S11) the average measured temperature using the first measured temperature and the second measured temperature; in the processing unit (21), determining (S12) the average specific heat capacity using the measured speed of sound, the average measured temperature, and the defined relationship between the speed of sound, specific heat capacity, and temperature in the fluid; and and in the processing unit (21), determining (S13) the heat flow rate using the density, the average specific heat capacity, the volume flow rate, and the temperature difference between the first temperature measurement result and the second temperature measurement result.

15. A method for determining the energy flow rate of a fluid in a channel (6), in particular, where the fluid is a mixture of at least two different fluids, and where the method comprises: in a processing unit (21), receiving (S21) measurement data of the fluid, the measurement data including the measured flow rate of the fluid, a first measured temperature of the fluid, and the measured speed of sound in the fluid; in the processing unit (21), using the measurement data and a defined relationship between the speed of sound, density, and temperature in the fluid to determine (S22) the density of the fluid; in the processing unit (21), using the measurement data and a defined relationship between the speed of sound, specific heat capacity, and temperature in the fluid to determine (S23) the specific heat capacity of the fluid; in the processing unit (21), using the flow rate of the fluid, the cross-sectional area of the channel (6), and the determined density of the fluid to calculate (S24) the mass flow rate of the fluid; and in the processing unit (21), using the mass flow rate and the determined specific heat capacity to calculate (S25) the energy flow rate of the fluid.

16. The method according to claim 15, wherein the measurement data includes a second measured temperature of the fluid measured at a location different from the first measured temperature, and the method further comprises: in the processing unit (21), using the density, the specific heat capacity, the volume flow rate, and the temperature difference between the first temperature measurement result and the second temperature measurement result to determine the heat flow rate dissipated from the fluid.

17. The method according to claim 16, further comprises: in the processing unit (21), using the first measured temperature and the second measured temperature to determine an average measured temperature; in the processing unit (21), using the measured speed of sound, the average measured temperature, and a defined relationship between the speed of sound, specific heat capacity, and temperature in the fluid to determine an average specific heat capacity; and in the processing unit (21), using the density, the average specific heat capacity, the volume flow rate, and the temperature difference between the first temperature measurement result and the second temperature measurement result to determine the heat flow rate.

18. The method according to any one of claims 1 to 17, further comprises: retrieving, by the processing unit (21), one or more of the following: past measurement data or past values of specific fluid properties, and the fluid property values are related to one or more of the following: corrected flow rate, the volume flow rate, the mass flow rate, or the energy flow rate; and using, by the processing unit (21), one or more of the following in addition to the measurement data to calculate the current value of the specific fluid property: the past measurement data or the past values of the specific fluid properties.

19. The method according to any one of claims 1 to 18, further comprises: In the processing unit (21), a defined setpoint is received, where the defined setpoint is related to one or more of the following: a flow rate setpoint, a volumetric flow rate setpoint, a mass flow rate setpoint, or an energy flow rate setpoint; In the processing unit (21), a control signal is generated using the defined setpoint and fluid property values, where the fluid property values are related to one or more of the following: a corrected flow velocity, the volumetric flow rate, the mass flow rate, or the energy flow rate; and In the processing unit (21), the control signal is used to control an actuator (5) connected to a valve (4).

20. The method according to any one of claims 1 to 19, further comprising: In the processing unit (21), one or more of the following are used to determine whether the fluid meets one or more defined thresholds: the measurement data or values of properties of the fluid, and the one or more defined thresholds are respectively associated with one or more of the following: the measurement data or values of properties of the fluid; and In the processing unit (21), if the fluid does not meet the one or more defined thresholds, a notification message is generated.

21. An apparatus for determining the flow rate of a fluid in a channel (6), comprising: A processing unit (21) configured to perform the method according to any one of claims 1 to 20.

22. The apparatus according to claim 21, further comprising: A sensor system (3) connected to the processing unit (21) and configured to: Measure the flow velocity of the fluid, the speed of sound in the fluid, and the temperature of the fluid; and Transmit measurement data to the processing unit (21), the measurement data including the flow velocity of the fluid, the speed of sound in the fluid, and the temperature of the fluid.

23. The apparatus according to any one of claims 21 or 22, further comprising: A sensor system (3) including an ultrasonic measurement component.

24. The apparatus according to claim 23, wherein the ultrasonic measurement component includes two ultrasonic transducers (34A, 34B) coupled to the channel (6), and wherein the ultrasonic measurement component is configured to: Measure the transit time of surface acoustic waves between the ultrasonic transducers; Use the transit time to determine one or more of the following properties of the fluid: flow velocity, speed of sound, temperature, or acoustic impedance; and Transmit measurement data to the processing unit (21), the measurement data including one or more of the determined properties of the fluid.

25. The apparatus according to any one of claims 21 to 24, wherein the sensor system (3) includes a first temperature sensor (35) arranged at a first position.

26. The apparatus according to claim 25, wherein the sensor system (3) includes a second temperature sensor arranged at a second position, where the second position is on the opposite side of the consumer device relative to the first position in the flow direction.

27. A computer program product comprising computer program code configured to control a processing unit (21) of a device such that the device performs the steps of the method according to any one of claims 1 to 20.

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