Process Fluid Flow Measurement With Polynomial Energy Calculation
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Solution Overview
Problem
Existing field devices in industrial processes face challenges in accurately computing energy flow rates for natural gas and steam or water applications, particularly due to the complexity of enthalpy calculations which can strain low-power devices, and require efficient methods to simplify these computations.
Innovation Solution
The implementation of a generalized energy per unit mass relationship combined with mass flow, using a two-dimensional Chebychev polynomial approximation to approximate enthalpy, allows for efficient computation of energy flow rates in field devices, enabling accurate energy flow indication for various fluids by multiplying mass flow rate by a constant heating value or variable enthalpy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If exact enthalpy calculations are performed for steam or water flow, then measurement precision of energy flow rate is improved, but device complexity and computational load increase
Solution Approach 1:
The patent transforms the complex enthalpy calculation problem into a simpler polynomial approximation problem by changing the mathematical parameters from exact thermodynamic equations to a two-dimensional polynomial form h = a0 + a1*P + a2*T + a3*P^2 + a4*P*T + a5*T^2, where P is pressure and T is temperature. This parameter transformation maintains sufficient measurement precision while dramatically reducing computational complexity for low-power field devices.
2Measurement precision
If complex enthalpy calculations are implemented, then energy flow rate accuracy is improved, but power consumption increases
Solution Approach 1:
The patent reduces power consumption by transforming the computational parameters from complex iterative enthalpy solutions to direct polynomial evaluations. The polynomial approximation h = a0 + a1*P + a2*T + a3*P^2 + a4*P*T + a5*T^2 requires only basic arithmetic operations, enabling accurate energy flow rate calculation in low-power field devices without excessive power consumption.
3Device complexity
If simplified enthalpy approximation is used, then device complexity is reduced, but measurement precision of energy flow rate deteriorates
Solution Approach 1:
The patent optimizes the polynomial parameters (a0 through a5) to accurately represent the enthalpy-pressure-temperature relationship across the operating range. This parameter optimization ensures that the simplified polynomial form h = a0 + a1*P + a2*T + a3*P^2 + a4*P*T + a5*T^2 maintains measurement precision comparable to exact enthalpy calculations while providing computational simplicity suitable for field devices.
Data Source
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AI summary
A process fluid flow device (12) includes a power supply module (24), a process communication module (20), a processor (26) and measurement circuitry (28). The process communication circuitry (20) is coupled to the power supply module (24) and to the processor (26). The measurement circuitry (28) is operably coupleable to plurality of process variable sensors to obtain an indication of differential pressure, static pressure and process fluid temperature. The processor (26) is configured to compute process fluid mass flow, and to use the static pressure and process fluid temperature to obtain an energy per unit mass value relative to the process fluid and to provide an energy flow indication.