Flow Rate Meter Self-Calibration for Unknown Liquid Properties
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Solution Overview
Problem
Conventional thermal flow meters require prior knowledge of the liquid's properties, such as density and heat capacity, to accurately measure flow rates, which is not feasible in situations where these properties are unknown or variable, leading to inaccurate readings and the need for recalibration.
Innovation Solution
A flow rate measurement apparatus and method that isolates a known volume of liquid, applies a known quantity of heat, and measures temperature changes to determine the flow rate without needing pre-known liquid properties, using a control system with heating or cooling elements and temperature sensors to calculate the flow rate based on measured temperature differences and known volumes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional thermal flow meters are used to measure liquid flow rate, then flow rate can be measured continuously, but accurate measurement requires prior knowledge of liquid properties (density and heat capacity) which are often unknown or variable
Solution Approach 1:
The system performs self-calibration by automatically measuring the liquid's heat capacity and density through thermal response tests. The processor uses the measured thermal response data to calculate the liquid's physical properties and update the flow rate measurements accordingly, eliminating the need for manual calibration or prior knowledge of liquid properties.
Solution Approach 2:
The system changes the measurement approach by introducing thermal response parameters (temperature change over time) as new measurement dimensions. Instead of relying on fixed liquid property values, the system measures how the liquid responds to thermal input, using these dynamic thermal response parameters to determine both the liquid's physical properties and the flow rate simultaneously.
2Productivity
If thermal transfer principles are applied to measure flow rate, then continuous measurement is enabled, but the system becomes complex requiring multiple sensors and calibration procedures
Solution Approach 1:
The single heating element serves multiple functions: it acts as both the thermal transfer element for flow measurement and the calibration element for determining liquid properties. The same temperature sensor used for continuous flow monitoring also measures the thermal response needed for calibration. This multi-functionality reduces the number of separate components needed.
Solution Approach 2:
The system uses feedback from temperature sensors to continuously monitor both the flow rate and the liquid's thermal properties. The measured thermal response feedback is used to automatically adjust and recalibrate the flow rate measurements, allowing the system to adapt to changing liquid properties without manual intervention.
3Ease of manufacture
If manual urine output measurement is performed in medical settings, then no specialized equipment is needed, but the process is laborious and inaccurate
Solution Approach 1:
The system replaces manual mechanical measurement with automated thermal sensing and electronic calculation. Instead of visual estimation by personnel, the system uses temperature sensors, heating elements, and processor-based calculations to automatically determine urine flow rate, eliminating human error and labor while improving precision.
Solution Approach 2:
The system automatically performs calibration and measurement without requiring manual intervention. The processor uses the measured thermal response to self-determine the liquid's properties and calculate the flow rate, replacing the need for manual urine collection and visual estimation by hospital personnel.
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
Enables accurate and cost-effective measurement of liquid flow rates without prior knowledge of the liquid's properties, allowing for real-time monitoring and dynamic calibration, particularly useful in medical applications like urine output measurement.
Implementation Method 1
at least one heating or cooling element adapted to add or subtract a known quantity of heat to or from the isolated volume of liquid
Implementation Method 2
at least one temperature sensor adapted to measure the instantaneous temperature of the liquid
Implementation Method 3
a section of the conduit adapted to form at least one chamber in which a known volume of the liquid can be isolated
Data Source
AI summary
The present invention is flow rate meters which are able to accurately measure the volumetric rate of flow of a liquid through a conduit without requiring foreknowledge of the physicochemical characteristics of the liquid, e.g., for the purpose of calibration of the thermal mass flow rate. One application of the flow meters of the invention is to incorporate them in a system for measuring the flow rate of urine excreted by a catheterized patient. The invention also provides methods for using the flow rate meters.