QCM Sensor Thermal Ballast for Rapid Condensate Sublimation
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Solution Overview
Problem
Current devices for determining vapor concentration using QCMs require lengthy cleaning cycles due to high thermal mass heating and cooling, limiting sensor element service life and efficiency.
Innovation Solution
A sensor element with a thermal transfer element and insulation, allowing for rapid heating and cooling to sublimate condensate, combined with a gas flow opposite the vapor transport direction to manage mass accumulation, reducing cleaning times to 2-3 minutes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sensor element is heated to sublimate condensate for cleaning, then the cleaning effectiveness is improved, but the cleaning cycle time increases due to high thermal mass heating and cooling
Solution Approach 1:
The sensor element is segmented into a sensor element proper and a separate thermal ballast element. The thermal ballast has high thermal mass and is thermally coupled to the sensor element through a thermal transfer element. During cleaning, the thermal ballast supplies stored heat to rapidly sublime condensate from the sensor surface without requiring prolonged heating of the entire assembly, thereby reducing cleaning cycle time while maintaining cleaning effectiveness.
Solution Approach 2:
The thermal ballast element is pre-heated during normal operation to store thermal energy before the cleaning phase begins. This preliminary heating action ensures that when cleaning is initiated, the stored heat is immediately available to rapidly sublimate condensate, avoiding the need to heat a large thermal mass from a low temperature during the cleaning cycle itself.
2Measurement precision
If the sensor element is cooled to condense vapor for measurement, then the measurement function is improved, but the service life is limited by maximum mass accumulation
Solution Approach 1:
The sensor element operates in periodic cycles between measurement phases and cleaning phases. During measurement, the sensor is cooled to condense vapor and measure concentration. When maximum mass accumulation is approached, the system transitions to a cleaning phase where the thermal ballast rapidly heats the sensor to sublime condensate. This periodic alternation extends the effective service life by enabling frequent, rapid cleaning without requiring replacement of the sensor element.
3Stability of the object's composition
If a high thermal mass is used for heating during cleaning, then the heating stability is improved, but the cooling time after cleaning increases
Solution Approach 1:
The thermal ballast element is extracted as a separate component with high thermal mass, while the sensor element itself is designed with low thermal mass. The thermal transfer element provides controlled thermal coupling between them. During cleaning, the ballast supplies heat for stable heating. After cleaning, the ballast can be thermally isolated or actively cooled while the low-mass sensor element cools rapidly back to measurement temperature, minimizing cooling time while maintaining heating stability during the cleaning phase.
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
The solution significantly shortens cleaning cycles while maintaining sensor element sensitivity and service life, allowing for more efficient vapor concentration measurement.
Implementation Method 1
the vapor is transported in a transport direction to a sensor surface of a sensor element, which is temperature-controlled to a temperature below the condensation temperature of the vapor, so that the vapor condenses as a mass accumulation that influences an oscillation frequency of the sensor element on the sensor surface
Implementation Method 2
The resonance frequency of the sensor element drifts away from an initial value as the mass accumulation increases, wherein the change in frequency per unit of time is a measure for the vapor concentration in the volume
Implementation Method 3
the sensor element must be heated for cleaning purposes. To this end, the sensor element is heated to a temperature lying above the condensation temperature of the vapor, so that the condensate is sublimated from the sensor surface
Implementation Method 4
the rear side of the sensor element lying opposite the sensor surface rests upon a thermal transfer surface of a heat conductor, which transports the heat from the sensor element to a cooling element
Implementation Method 5
an insulation element can be arranged between the heating element and cooling element, which has a lower thermal conductivity than the thermal transfer element formed by the heating element
Data Source
AI summary
A device for determining the partial pressure or concentration of a vapor in a volume includes a sensor element that can be caused to oscillate and temperature-controlled to a temperature below the condensation temperature of the vapor. The sensor element has an oscillation frequency that is influenced by a mass accumulation formed by condensed vapor on the sensor surface thereof. The rear side of the sensor element pointing away from the sensor surface contacts a thermal transfer surface of a thermal transfer element. The thermal transfer element is formed from an electrically heatable heating element that is connected to a cooling element in a thermally conductive manner by a thermal dissipation surface, which is different from the thermal transfer surface. The thermal transfer surface extends substantially parallel to the thermal dissipation surface.