Flow Rate Meter Using Pulsed Thermal Energy
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Solution Overview
Problem
Existing flow rate meters, particularly thermal transfer meters, face challenges in accurately determining flow rates due to slow temperature changes and energy inefficiency, making them difficult to use for repeated measurements and requiring continuous energy application.
Innovation Solution
A flow rate measurement apparatus and method using a heating element and a single temperature sensor to apply a known quantity of heat for a defined period, allowing for real-time measurement of temperature changes without waiting for steady state, and utilizing a control system with calibration tables to determine flow rates, which can be applied to conduits like catheters for urine measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous energy is applied to the heating element to maintain constant temperature differential, then flow rate measurement is continuous, but energy consumption increases and measurement accuracy decreases due to slow temperature changes
Solution Approach 1:
The patent applies periodic pulsed heating instead of continuous heating. The heating element receives energy in discrete pulses at specific time intervals (t1, t2, t3...), allowing the system to measure temperature changes during the pulse and immediately after, rather than maintaining continuous heating. This periodic action reduces overall energy consumption while providing sufficient data points for accurate flow rate calculation.
Solution Approach 2:
The patent measures the initial temperature Ti immediately after the heating pulse begins (at time t1 or shortly after), rather than waiting for steady state temperature differential to develop. This preliminary measurement approach allows the system to capture temperature changes during the heating process itself, eliminating the need to wait for slow steady-state equilibrium and improving measurement speed and accuracy.
2Measurement precision
If steady state temperature differential is waited for before measurement, then temperature stability is improved, but measurement time increases and repeated measurements become difficult
Solution Approach 1:
The system performs the temperature measurement Ti immediately after or during the heating pulse (at time t1), rather than waiting for steady state conditions. This preliminary action captures the temperature response during the active heating phase, providing sufficient data for flow rate calculation without the time-consuming wait for steady state equilibrium.
Solution Approach 2:
The patent skips the traditional steady-state waiting period by measuring temperature changes during and immediately after the heating pulse. Instead of rushing through to steady state and waiting, the system rushes through the heating pulse itself and measures the transient response, thereby eliminating the time loss associated with waiting for equilibrium while still obtaining accurate flow rate data.
3Stability of the object's composition
If ambient temperature of liquid increases slowly over time, then thermal equilibrium is maintained, but initial temperature Ti becomes inaccurate for subsequent measurements
Solution Approach 1:
By applying periodic heating pulses at defined time intervals (t1, t2, t3...), the system creates discrete measurement opportunities where Ti is measured immediately before or during each pulse. This periodic resetting of the measurement reference point eliminates drift errors from slow ambient temperature changes, as each pulse establishes a fresh baseline for comparison.
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 provides a simple, accurate, and energy-efficient method for determining flow rates, enabling real-time assessment of kidney function and early detection of acute kidney injury, with reduced energy consumption and improved measurement precision.
Implementation Method 1
a heating element in thermal contact with the liquid in the conduit, the heating element adapted to deliver a known quantity of heat in a known period of time to the flowing liquid
Implementation Method 2
a temperature sensor adapted to measure the instantaneous temperature of the heating element
Data Source
Figure 1~2
Figure 3A
Figure 3B
AI summary
The invention is an apparatus and method for measuring the flow rate of a liquid through a conduit. The apparatus is based on a flow rate meter which is adapted to accurately measure the volumetric flow rate of a liquid using a simple, cost and energy effective, and accurate method using only one temperature sensor. The method is based on applying a pulse of thermal energy to the flowing liquid and measuring the temperature increase as a function of time and energy input. By comparing these measurements to a calibration table made by performing similar measurements for known flow rates, the rate of flow can be determined. One application, which will be described to illustrate the features of the method and apparatus of the invention, is measurement of the flow rate of urine excreted by a catheterized patient.