Method for operating an energy meter and energy meter
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Solution Overview
Problem
Energy metering devices face inaccuracies in measuring energy consumption due to changes in the mixing ratio of carrier fluids like water-glycol mixtures over time, affecting fluid dynamic properties and leading to errors in ultrasonic transit time measurements.
Innovation Solution
The method involves determining the current speed of sound of the mixture during transit time measurements to correct deviations from a reference mixture, using a characteristic map and empirically derived rules to modify the determination factor, without requiring additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ultrasonic transit time measurement is used to determine flow rate, then measurement non-invasiveness and lack of moving parts are achieved, but measurement precision deteriorates due to changes in fluid dynamic properties from mixing ratio variations
Solution Approach 1:
The invention changes the measurement parameter from direct transit time to speed of sound determination. By measuring the speed of sound in the mixture and using empirically derived relationships, the system compensates for mixing ratio variations without adding mechanical complexity. The computing device calculates fluid dynamic properties based on speed of sound measurements, maintaining measurement simplicity while improving precision.
2Measurement precision
If calorimetric measurements are performed to determine k-factor, then measurement precision is improved, but device complexity and cost increase due to additional sensor elements and complex measurement procedures
Solution Approach 1:
The invention replaces complex calorimetric measurement systems with ultrasonic speed of sound measurements. Instead of using additional temperature sensors and heat input systems for calorimetric measurements, the system uses ultrasonic transducers to measure speed of sound and computationally derives the k-factor through empirically determined relationships, significantly reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The invention introduces speed of sound measurement as an intermediary parameter. Rather than directly measuring k-factor through complex calorimetric procedures, the system measures speed of sound and uses this as an intermediate step to computationally determine k-factor and other fluid dynamic properties, simplifying the measurement process.
3Measurement precision
If mixing ratio is monitored and adjusted to maintain reference mixture composition, then measurement precision is maintained, but ease of operation deteriorates due to annual checks and manual adjustments required
Solution Approach 1:
The invention enables the measurement system to self-correct for mixing ratio variations. By continuously measuring speed of sound and computationally deriving fluid dynamic properties, the system automatically compensates for changes in mixture composition without requiring manual intervention, annual checks, or operator knowledge of the exact mixing ratio.
Solution Approach 2:
The system uses speed of sound measurements as feedback to continuously adjust and compensate for mixing ratio variations. The computing device uses the measured speed of sound to calculate current fluid dynamic properties and determination factors, creating a closed-loop system that automatically maintains measurement precision despite changes in mixture composition.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the accuracy of energy consumption measurements by compensating for fluid property changes, simplifying the process and reducing complexity and cost, while maintaining precision without needing to know the exact mixing ratio.
Implementation Method 1
an ultrasonic measuring device for determining the mixture flow rate by means of a transit time measurement
Implementation Method 2
the ultrasonic measuring device also determines a current speed of sound of the mixture
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Method for operating an energy metering device (11) for determining the energy consumption in a temperature control circuit (17) in which a mixture (18) of at least two fluids, in particular a water-glycol mixture, circulates, wherein the energy metering device (11) comprises an ultrasonic measuring device (13) for determining the mixture flow rate by means of a transit time measurement, a temperature measuring device (16) for determining a temperature difference between the supply (20) and the return (21) of the mixture (18), and a computing device (22) for determining the energy consumption taking into account the flow rate, the temperature difference, and a k-factor of the mixture (18), wherein, for determining the mixture flow rate, a transit time difference value is calculated using a characteristic curve (5) specified for a reference mixture, in particular as a function of the transit time difference value and the temperature of the mixture during the transit time measurement.The determination factor is multiplied, whereby the ultrasonic measuring device (13) also determines the current speed of sound of the mixture (18), the determination of the determination factor depending on the current speed of sound being used to correct a deviation of the mixture (18) from the reference mixture.