Bubble Sensor Using Thermal Conductivity Thresholds
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Solution Overview
Problem
Existing technologies cannot accurately detect bubbles in the gas phase within a liquid flowing through a flow path, especially when liquid flow velocity changes, as they cannot distinguish between temperature changes caused by velocity alterations and the presence of bubbles.
Innovation Solution
A sensor system with a heating element, transducer arrangement, and comparator, which generates a measurement signal compared to a predetermined threshold based on the heating element's power and minimum liquid velocity, allowing for robust bubble detection by exploiting differences in thermal conductivity between the liquid and gas bubbles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature monitoring is used to detect bubbles, then bubble detection capability is improved, but the system cannot distinguish between temperature changes caused by velocity alterations and the presence of bubbles
Solution Approach 1:
The monitoring function is divided into two independent measurement channels: one dedicated to temperature monitoring (for bubble detection) and another to velocity monitoring (for flow rate measurement). This segmentation allows each sensor to specialize in detecting its specific parameter without interference from the other, enabling the system to distinguish between temperature changes caused by bubbles versus those caused by velocity changes.
Solution Approach 2:
The control unit acts as an intermediary that receives and processes signals from both the temperature sensor and velocity sensor. It compares the temperature change signal with the velocity change signal to determine whether a temperature anomaly is caused by bubble presence or velocity variation, thereby resolving the information loss problem.
2Device complexity
If a single temperature sensor is used, then device complexity is reduced, but measurement precision for bubble detection deteriorates due to inability to account for velocity changes
Solution Approach 1:
Instead of using a single multi-functional sensor, the system employs two separate single-functional sensors: a temperature sensor for bubble detection and a velocity sensor for flow rate monitoring. This segmentation of measurement functions improves measurement precision while keeping each individual sensor simple.
Solution Approach 2:
The control unit is designed with multi-functionality, handling both temperature signal processing and velocity signal processing, as well as performing the comparative analysis to distinguish bubble-induced temperature changes from velocity-induced temperature changes.
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 detection of gas bubbles in liquids, preventing harmful air bubbles from reaching patients in medical applications by providing reliable output signals indicative of bubble presence and quantity, thus ensuring safe intravenous infusion and anesthesia flow control.
Implementation Method 1
a heating element (210) arranged for heating the liquid (208)
Implementation Method 2
a transducer arrangement (108) arranged for generating a measurement signal (114) representing a measurement value indicative for a temperature (T heat ) of the heating element (210)
Implementation Method 3
By selecting the predetermined threshold such that it corresponds to said reference temperature, and by employing the characteristic that the fluid has a thermal conductivity that exceeds a bubbles' thermal conductivity, a conceivable exceeding of the predetermined threshold level by the heating element's temperature is merely attributable to the presence of bubbles in gas phase
Data Source
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AI summary
The invention relates to a sensor (102, 202, 402, 502) for detecting bubbles in gas phase present in a liquid (208, 408, 527) flowing through a flow path (204, 406, 508). The sensor comprises a heating element (106, 210) for heating the liquid, which heating element is provided with a predetermined level of power at least during detecting, and a transducer arrangement (108, 112, 212) arranged for generating a measurement signal (114) indicative for the temperature of the heating element. The sensor furthermore comprises a comparator arrangement (116) for comparing a measurement value of the measurement signal with a predetermined threshold level, which predetermined threshold level corresponds to a reference temperature attainable by the heating element in response to said predetermined level of power and a minimum velocity attainable by the liquid in the flow path. Based on the latter comparison, the comparator arrangement generates an output signal (118) indicative for a possible presence of bubbles in gas phase.