Vibratory Sensor for PCM Thermal Storage Charge Measurement
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Solution Overview
Problem
Current methods for measuring the state of charge in thermal storage systems (TSS) using solid/liquid phase change materials (PCMs) are complex, costly, and inefficient due to issues with sensor placement, data interpretation, and the need for airtight seals, especially when dealing with systems that have a flooded heat exchanger or significant metal components.
Innovation Solution
A vibratory member is introduced into the TSS reservoir, excited to induce vibrations that depend on the position of the liquid-solid phase separation front, allowing for the measurement of a vibration parameter that represents the charge rate, which is simple, robust, and does not require sealing the tank or relying on volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature sensors are used to measure the state of charge, then the measurement can be performed continuously, but the sensors are not suitable because the phase change occurs without temperature change
Solution Approach 1:
The patent replaces temperature-based sensing with a mechanical vibration-based sensing system. A vibratory element is introduced whose natural frequency changes in response to the liquid-solid phase distribution, allowing measurement of state of charge through mechanical vibration characteristics rather than thermal properties.
Solution Approach 2:
The invention exploits the phase transition properties of the PCM by using a vibratory element whose oscillation characteristics change as the PCM transitions between liquid and solid phases. The natural frequency of the vibratory element serves as an indicator of the phase distribution and state of charge.
2Measurement precision
If optical sensors are used to evaluate the state of PCM, then the state can be determined at a point, but a large number of sensors are required which generates maintenance difficulties and data interpretation complexity
Solution Approach 1:
The single vibratory element performs multiple functions: it serves as both the sensing element and the measurement transducer. Its natural frequency directly indicates the state of charge, eliminating the need for multiple distributed sensors and complex data interpretation systems.
Solution Approach 2:
The vibratory element's natural frequency acts as a simplified copy or representation of the complex phase distribution state. Instead of measuring multiple spatial points and interpreting complex data, the system uses a single frequency parameter that encapsulates the overall state of charge information.
3Measurement precision
If radar waves are used to determine the liquid phase fraction, then the measurement can be performed, but the technique is only suitable for simple panels without flooded exchangers due to metal reverberations and wave absorptions
Solution Approach 1:
The patent replaces electromagnetic radar wave measurement with a mechanical vibration-based measurement system. The vibratory element's natural frequency is affected by the phase distribution but is not interfered with by metal heat exchanger components, making the system versatile for different architectures including flooded exchangers.
4Measurement precision
If pressure variation measurement is used to determine charge rate, then the measurement can be performed, but the reservoir must be perfectly sealed which is difficult and costly to achieve
Solution Approach 1:
The invention replaces pressure-based measurement with vibration-based measurement. The vibratory element's natural frequency responds to phase distribution changes without requiring sealed containment, thereby eliminating the manufacturing complexity and cost associated with perfect sealing.
5Measurement precision
If volume expansion during phase change is used for measurement, then the charge rate can be determined, but the technique is only applicable to PCMs presenting sufficient volume variation
Solution Approach 1:
The invention uses the vibratory element's natural frequency response to detect phase transitions. This approach does not depend on volume expansion characteristics of the PCM, making it universally applicable to different PCM types regardless of their volume change properties during phase change.
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 method provides accurate and durable measurement of the charge rate without degrading over time, is applicable to systems with flooded heat exchangers, and does not impose constraints on compactness or require significant data interpretation, offering a cost-effective solution.
Implementation Method 1
a vibratory member (300), a device for exciting said at least one vibratory member, and a sensor of a vibration parameter
Implementation Method 2
The MCP changes phase by melting/solidification and is configured so that part of a separation front between its liquid phase and its solid phase has, in the reservoir, a position representative of a charge rate of the SST
Data Source
Figure 1~2
Figure 3~4
Figure 5a~6
AI summary
The invention relates to a thermal storage system (TSS) using a phase change material (PCM). More particularly, the invention relates to the integration of a device for measuring the charge level within a TSS 100. TSSs exhibiting at least partial separation 203 along a principal axis of the liquid and solid phases of the PCM 200 are suitable for incorporating the invention. The invention finds application in urban, rural, or industrial heating and/or cooling networks, as well as in solar energy storage. The invention also finds applications in housing and off-grid thermal transport (trucks, boats, etc.). The measuring device comprises a vibrating element 300 arranged within the reservoir 101 containing the PCM such that its natural vibration frequencies indicate a certain height of the liquid-phase PCM 201 in the reservoir and thus the charge level of the TSS.