Hybrid Thermal Mass Flow Sensor for Protected IV Measurement
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Solution Overview
Problem
There is a need for a thermal mass flow probe tailored for use in measuring liquid delivered through an intravenous line (IV) to a patient, as existing flow probes are not designed for this application and may damage sensitive measurement electronics or require complex protective measures.
Innovation Solution
A hybrid thermal mass flow probe that combines calorimetric and anemometric elements, using a thin-film heater and thermally-conductive material in thermal contact with the liquid, with temperature sensors measuring the material rather than the liquid, and an online controller to dynamically adjust heater power to maintain a targeted temperature differential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing flow probes are used to measure liquid delivered through an intravenous line, then flow measurement can be achieved, but sensitive measurement electronics may be damaged or complex protective measures are required
Solution Approach 1:
A thin-film thermally-conductive material is introduced as an intermediary between the liquid and the temperature sensors/heating element. This mediator allows thermal contact with the liquid while physically protecting the sensitive electronics from direct exposure to the liquid environment, eliminating the need for complex protective measures.
Solution Approach 2:
The patent employs a thin-film thermally-conductive material that serves as both a protective barrier and a functional thermal coupling element. This thin film structure protects the underlying electronics while maintaining thermal contact with the liquid for accurate flow measurement.
2Measurement precision
If temperature sensors are placed in direct contact with the liquid, then temperature measurement accuracy is improved, but the risk of damage to sensors and contamination increases
Solution Approach 1:
The thin-film thermally-conductive material acts as an intermediary layer between the temperature sensors and the liquid. This mediator transmits thermal information from the liquid to the sensors with sufficient accuracy while preventing direct contact, thereby eliminating damage and contamination risks.
3Speed
If a heating element directly heats the liquid, then flow measurement response is faster, but power consumption increases and potential liquid damage occurs
Solution Approach 1:
The thin-film thermally-conductive material serves as an intermediary between the heating element and the liquid. This allows the heating element to heat the film rapidly for fast flow measurement response while the film acts as a thermal buffer, reducing the total energy required and preventing direct liquid damage from excessive heating.
Solution Approach 2:
The thin-film structure has low thermal mass, enabling rapid heating and cooling cycles for fast flow measurement response. This thin film geometry reduces the total energy consumption compared to bulk heating methods while maintaining fast response characteristics.
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
Provides accurate, high-frequency flow rate measurements with low electronic noise and power consumption, while withstanding radiation sterilization and ensuring biocompatibility, without directly heating the liquid.
Implementation Method 1
The controller is configured to control the heating element to apply heat to the thermally-conductive material
Implementation Method 2
a thermally-conductive material secured to a portion of the walls so that the thermally-conductive material is in thermal contact with a liquid flowing through the conduit
Implementation Method 3
a thermal mass fluid flow sensor for measuring fluid flow via thermal mass transport
Data Source
AI summary
Described herein are thermal mass flow sensors that combine calorimetric and anemometric (e.g., hot-wire) elements to provide a hybrid approach to determining flow rate of a liquid. The flow probes or flow sensors are configured to use a heater to apply heat to a thermally-conducting material in contact with the flowing liquid, to measure a temperature of the thermally-conducting material upstream of the heater and downstream or at the heater, to adjust power to the heater to achieve a targeted temperature difference, and to determine a flow rate based at least in part on the power supplied to the heater and the measured temperatures. This approach provides flow rate due at least in part to the fluid cooling the thermally-conductive material proportionate to flow rate with non-linear effects. This hybrid approach can provide accurate readings of flow rates of liquids delivered through an IV line to a patient.