Thermometric Well Liquid Level Measurement in Pressure Vessels
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Solution Overview
Problem
Measuring liquid levels in pressure vessels under severe conditions, such as high pressure and temperature, or in corrosive environments, is challenging due to limitations in existing methods like membrane-based transmitters, radiation techniques, and radar-based measurements, which face issues with corrosion, safety hazards, and precision affected by fluid states near critical or supercritical conditions.
Innovation Solution
A method utilizing a thermometric well with a heated inner surface to detect temperature differences between reference and actual temperatures, estimating the liquid level based on varying heat transfer coefficients between liquid and gas phases, allowing indirect measurement without direct fluid contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If radar-based measurement is used, then liquid level can be measured remotely, but precision is affected by fluid state near critical point or supercritical condition
Solution Approach 1:
The patent replaces radar-based electromagnetic measurement with a thermal field-based measurement system. A heating element heats the inner surface of the pressure vessel, and temperature sensors detect temperature differences that indicate liquid level. This substitution of measurement physics (from electromagnetic to thermal) enables accurate measurement in supercritical and critical conditions where radar fails, as the thermal method directly senses the phase boundary through heat transfer characteristics.
Solution Approach 2:
The patent exploits the significant change in heat transfer coefficient at the liquid-gas interface. By heating the vessel wall and measuring temperature gradients, the system detects the phase boundary based on the abrupt change in thermal conductivity between liquid and gas phases. This parameter-based detection (using heat transfer coefficient changes) provides reliable liquid level measurement in severe conditions including supercritical states, where the thermal properties of the fluid change dramatically at the phase boundary.
2Measurement precision
If membrane-based transmitter is used, then liquid level can be measured, but corrosion and hydrogen permeation occur
Solution Approach 1:
The patent introduces the pressure vessel wall itself as an intermediary structure. Instead of using a membrane transmitter that directly contacts the corrosive fluid, the heating element and temperature sensors are mounted on the exterior of the vessel wall. The vessel wall acts as a protective barrier that isolates the measurement system from the corrosive environment while still allowing thermal energy to pass through for level detection. This eliminates the membrane component that was susceptible to corrosion and hydrogen permeation.
Solution Approach 2:
The patent replaces the mechanical membrane-based transmitter with a thermal field-based measurement system. By using electrical heating elements and temperature sensors mounted on the exterior of the pressure vessel, the system eliminates the need for membranes that are vulnerable to corrosion and hydrogen permeation. The measurement is performed remotely through the vessel wall, substituting mechanical contact-based measurement with non-contact thermal sensing.
3Measurement precision
If radiation level measurement technique is used, then liquid level can be measured, but safety hazards arise
Solution Approach 1:
The patent replaces radiation-based measurement (gamma rays) with a thermal field-based measurement system. Electrical heating elements heat the pressure vessel wall, and temperature sensors detect the temperature distribution to determine liquid level. This substitution of physics (from nuclear radiation to electrical heating and thermal sensing) completely eliminates the safety hazards associated with radiation exposure while maintaining the ability to measure liquid level remotely in severe conditions.
Solution Approach 2:
The patent converts the potentially harmful thermal energy into a beneficial measurement tool. Instead of using harmful radiation to penetrate the vessel wall, the system uses controlled electrical heating to warm the vessel wall and detect temperature gradients. The thermal field, which could be considered a form of energy that might cause damage, is instead harnessed as a safe and controllable means of detecting liquid level through the vessel wall.
4Measurement precision
If hollow tube is installed in urea reactor, then radar measurement precision is improved, but installation cost increases and reactor operation is negatively affected
Solution Approach 1:
The patent replaces the hollow tube structure with a heating element system mounted directly on the exterior of the pressure vessel. Instead of installing a large hollow tube that penetrates the vessel wall and affects reactor operation, the system uses surface-mounted electrical heating elements and temperature sensors. This substitution eliminates the need for complex hollow tube installations while achieving accurate liquid level measurement through thermal field detection.
Solution Approach 2:
The patent extracts the measurement function from the reactor interior and places it on the exterior surface. By mounting heating elements and temperature sensors on the outer wall of the pressure vessel, the system eliminates the need for internal hollow tubes or penetrations that would complicate reactor operation. The measurement system is completely extracted from the reactive environment, requiring no modification of the reactor's internal structure or operation.
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 and safe liquid level measurement in aggressive environments, resistant to mist, foam, and supercritical conditions, with improved precision and cost-effectiveness compared to traditional methods.
Implementation Method 1
the heat transfer coefficient of the fluid surrounding the thermometric varies significantly at the liquid-gas interface. The gaseous phase has a heat transfer coefficient much lower than the liquid phase. If surrounded by the liquid phase, the inner surface of the well tends to approach the temperature of the liquid, due to a good heat transfer between the inside and outside of the well.
Data Source
Figure 1~2
AI summary
A method for measuring a liquid level (L) in a pressure vessel (2) the method comprising: providing a thermometric well (10) inside the pressure vessel, heating an inner surface of the thermometric well which is not in contact with the fluid, detecting the temperature of at least one detection point of said inner surface; estimating a position of the liquid level based on the difference between a reference temperature and the temperature so detected.