Liquid Level Detector Using Heat Flow and Seebeck Effect

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Solution Overview

Problem

Conventional liquid level detectors are unable to detect levels in closed vessels and cannot measure levels of liquids outside the vessel, as they rely on heat flux differences which are not present in closed systems and require embedding sensors in the vessel sidewall, making them impractical for repair and limited in application.

Innovation Solution

A liquid level detector system using a detecting element with a heating means and interlayer connection members that generates an electromotive force based on heat flow, allowing detection in both open and closed vessels, and capable of measuring external liquid levels by differing heat flow through the sensor unit.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If thermocouples are embedded in the sidewall of the vessel to detect liquid level, then the liquid level inside the vessel can be detected, but the liquid level cannot be detected in closed vessels and external liquids

Engineering Contradiction:

Improveliquid level detection capabilityVSAvoidapplicability to closed vessels and external liquids

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent inverts the conventional approach by placing the detecting element outside the vessel with its first surface facing the vessel exterior, rather than embedding it in the sidewall. The heating means generates heat flow that passes through the vessel wall and detecting element, exploiting thermal conductivity differences between liquid and gas to detect liquid level both in closed vessels and external liquids.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The detecting element design enables universal application across multiple scenarios: open vessels, closed vessels, and external liquid level detection. The same sensor configuration and detection principle work for all three cases, eliminating the need for different detection methods for different vessel types.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If thermocouples are embedded in the sidewall of the vessel, then the detection structure is fixed, but the device becomes difficult to repair and replace

Engineering Contradiction:

Improvedetection stabilityVSAvoidsensor replacement difficulty

Core Design Contradiction:

ReliabilityVSEase of repair

Solution Approach 1:

The detecting element is designed as a separate, modular component that can be independently attached to or removed from the vessel exterior. This segmentation allows the sensor to be replaced without damaging the vessel structure, improving ease of repair while maintaining reliable detection through consistent mounting on the vessel outer surface.

Inventive Principle:

Principle #1Segmentation

3Measurement precision

If the detecting element uses heat flux difference based on temperature difference between liquid and gas, then open vessel liquid level can be detected, but closed vessel liquid level cannot be detected due to no temperature difference

Engineering Contradiction:

Improveheat flux difference detectionVSAvoiddetection in closed vessels

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The heating means is activated to generate heat flow before detection occurs. This preliminary heating action creates the necessary thermal conditions for detection in closed vessels, where natural temperature differences do not exist. The heat flow passes through the vessel wall and detecting element, enabling liquid level detection through thermal conductivity differences rather than relying on ambient temperature differences.

Inventive Principle:

Principle #10Preliminary action

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 liquid levels in closed vessels and external liquids by exploiting thermal conductivity differences, providing a flexible and repairable solution for various applications.

Implementation Method 1

the heating means forms a heat flow passing through the detecting element from the second surface to the first surface, toward the liquid or a gas

Methodology Applied

Scientific EffectHeat conduction: Conduction (thermal)

Implementation Method 2

generates, in the first and second interlayer connection members alternately connected in series, an electromotive force corresponding to the heat flow passing through the detecting element

Methodology Applied

Scientific EffectSeebeck effect: Seebeck Effect

Data Source

PatentUS10113898B2Liquid level detector for open vessel and closed vessel

Publication Date: 2018.10.30 DENSO CORP

AI summary

A liquid level detector includes: a detecting element having one surface and the other surface opposite to the one surface, the one surface being opposed to a liquid, while being parallel to a height direction of liquid level; a Peltier element provided on the other surface side of the detecting element; and a control unit performing a detection processing for a liquid level of the liquid. The Peltier element forms a heat flow passing through the detecting element from the other surface to the one surface, toward the liquid or a gas. The control unit calculates a liquid level on the basis of an output value of an electrical signal outputted according to the heat flow passing through the detecting element, and a relationship between an output value of the detecting element and a liquid level.