Flow Density Measurement with Spatial Thermodynamic Correction
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Solution Overview
Problem
Industrial measuring systems face significant measurement errors in determining flow parameters like volume flow, temperature, and density due to spatial variances in the Reynolds number and thermodynamic state of compressible and two-phase media, especially when using flow conditioning devices like nozzles and diffusers, leading to inaccuracies in mass flow calculations.
Innovation Solution
The measuring system incorporates a density correction mechanism that accounts for momentary positional variability of thermodynamic state variables and Reynolds number along the flow axis, using both provisional and correction density values to generate accurate density measurements, and communicates with flow sensors to adjust for local flow parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard density measurement methods are used based on pressure and temperature sensors, then the measurement system is simple and cost-effective, but measurement accuracy deteriorates due to spatial variances in thermodynamic state and Reynolds number
Solution Approach 1:
The patent divides the flow path into multiple measurement sections with separate pressure and temperature sensors positioned at different locations. This segmentation allows the system to capture spatial variations in thermodynamic state, enabling more accurate density calculations by accounting for local conditions rather than assuming uniformity throughout the flow path.
Solution Approach 2:
The patent transitions from point measurements to distributed measurements by positioning sensors at multiple locations along the flow axis. This adds a spatial dimension to the measurement approach, capturing the gradient and variation of thermodynamic parameters that exist in compressible and two-phase flows, thereby improving accuracy without requiring a complete redesign of the measurement system.
2Ease of operation
If flow conditioning devices like nozzles and diffusers are used, then flow measurement is facilitated, but measurement accuracy deteriorates due to induced spatial variances in Reynolds number and thermodynamic state
Solution Approach 1:
The patent implements a feedback mechanism where pressure and temperature measurements from multiple locations are continuously monitored and used to calculate density and mass flow rates. The system compensates for the effects of flow conditioning devices by using the actual measured thermodynamic states at each location, rather than relying on theoretical assumptions, thereby maintaining accuracy despite the presence of nozzles and diffusers.
Solution Approach 2:
The patent accounts for parameter changes induced by flow conditioning devices by measuring pressure and temperature at multiple points where the thermodynamic state varies. By capturing these parameter changes spatially, the system can accurately calculate density and mass flow even when nozzles and diffusers create significant gradients in the flow field.
Data Source
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AI summary
The invention relates to a measuring system for measuring a density of a medium flowing in a process line, said medium being variable regarding its thermodynamic state, especially at least being proportionally compressible, along an imaginary axis of flow of the measuring system. The measuring system comprises at least one temperature sensor that is located in a temperature measuring point and that primarily reacts to a local temperature, 9, of a medium flowing past, said temperature sensor supplying at least one temperature measurement signal that is influenced by the local temperature of the medium to be measured, at least one pressure sensor that is located in a pressure measuring point and that primarily reacts to a local, especially static, pressure, p, of a medium flowing past, said pressure sensor supplying at least one pressure measurement signal that is influenced by the local pressure, p, in the medium to be measured, and at least one electronic measuring unit that at least temporarily communicates with at least the temperature sensor and the pressure sensor. The electronic measuring unit generates a provisional density value, using the temperature measurement signal and at least the pressure measurement signal, said density value representing a density which the flowing medium only apparently has in a virtual density measuring point that is especially interspaced from the pressure measuring point and/or the temperature measuring point along the axis of flow at a defined distance. The electronic measuring unit further generates at least temporarily at least one especially digital density value, which is different from the provisional density value, using the provisional density value and at least one correctional density value that depends on a flow speed of the medium and on the local temperature prevailing in the temperature measuring point, said correctional value being determined during operation time. The digital density value momentarily represents a local density, ?, which the flowing medium actually has in the virtual density measuring point, more correctly than the provisional density value.