Liquid Level Measurement Using Parallel Thermoelement Tubes
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Solution Overview
Problem
Existing level measurement devices in nuclear reactors face inaccuracies due to temperature gradients and limited redundancy, which can lead to misinterpretation of liquid level changes and are prone to failure if the heating wire is damaged.
Innovation Solution
The use of multiple parallel measuring tubes with heated and unheated thermocouples spaced apart to minimize mutual influence, allowing for precise level measurement by processing difference signals and providing redundancy, with unheated thermocouples acting as reference signals for multiple heated thermocouples, and each thermocouple pair being at the same height to account for vertical temperature gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If heated and unheated thermocouples are arranged at different levels to protect unheated thermocouples from heating influence, then thermal interference is reduced, but measurement accuracy deteriorates due to temperature gradients over liquid level
Solution Approach 1:
The patent transitions from vertical arrangement (different heights) to horizontal arrangement (different radial positions) of thermocouples. By placing heated and unheated thermocouples side-by-side at the same height but different radial distances from the heating element, the solution eliminates temperature gradient errors while still protecting against thermal interference through spatial separation in the radial dimension.
Solution Approach 2:
The patent creates different radial positions with distinct thermal characteristics: unheated thermocouples are positioned closer to the heating element to serve as reference, while heated thermocouples are positioned farther away for measurement. This local differentiation in radial position allows each thermocouple to experience its intended thermal environment while both remain at the same vertical level.
2Measurement precision
If multiple measuring positions are implemented to improve height resolution, then level measurement precision is improved, but device complexity increases due to geometric constraints of probe housing
Solution Approach 1:
The patent divides the single measuring tube into multiple segments or positions along its length, with each segment containing pairs of heated and unheated thermocouples at different radial positions. This segmentation allows multiple measurement heights to be achieved within a single tube, improving vertical resolution without requiring multiple separate tubes or complex housing geometries.
Solution Approach 2:
The single measuring tube serves multiple functions: it contains multiple radial positions for thermal measurement, multiple vertical positions for height resolution, and houses both heated and unheated thermocouples. This multi-functionality achieves high measurement precision while keeping the probe housing geometry simple and manageable.
3Device complexity
If a common heating wire with series-connected heating zones is used to heat all thermocouples, then device complexity is reduced, but reliability deteriorates because the entire device fails if the wire is damaged
Solution Approach 1:
The patent segments the heating system into independent heating zones, each with its own heating element. This allows individual heating zones to be controlled separately and prevents a single point of failure from disabling the entire system. Each heating zone can be independently activated based on the specific measurement requirements at different vertical positions.
Solution Approach 2:
The patent changes the electrical configuration from a single series-connected heating wire to multiple independent heating elements that can be controlled with different power levels. This parameter change in the heating system allows for both high reliability (independent operation) and flexibility (variable heating intensity) while maintaining manageable device complexity through modular control.
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 configuration enhances measurement precision and reliability, reduces interference, and allows for high sensor density with redundancy, ensuring accurate level monitoring even under adverse conditions.
Implementation Method 1
the heat generated by it is quickly dissipated, so that even in its immediate vicinity the temperature is only slightly above the ambient temperature
Implementation Method 2
heat transfers from a heating element to a liquid coolant surrounding the heating element
Implementation Method 3
thermocouples are generally used as temperature sensors, which deliver a thermoelectric voltage that is essentially proportional to the temperature
Data Source
Figure 1
Figure 2~3
AI summary
The invention (2) relates to a device (2) that is simply constructed and displays a high fail safeness for using heated thermoelements (HT) and unheated thermoelements (UHT) as transmitters for measuring a liquid in a liquid container, in particular in the reactor container (4) of a nuclear installation, makes an especially precise and reliable measurement of the level height (H) possible. In addition, the invention proposes a plurality of elongated measuring tubes (6), at a distance from one another, wherein each measuring tube (6) exhibits a number of thermoelements (HT, UHT) arranged such that they are distributed in a longitudinal direction, and wherein an unheated thermoelement (UHT), acting as a reference transmitter, is allocated to a thermoelement (HT), acting as a primary transmitter, arranged at a first measuring tube (6) and heated by a heating element (HE) and which is arranged at a measuring tube (6) that is different from the first measuring tube (6).