Liquid level detector and air conditioning apparatus including the liquid level detector

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Solution Overview

Problem

Existing air-conditioning apparatus with horizontally-mounted accumulators face accuracy issues in detecting the liquid surface of refrigerant due to rippling and require multiple temperature detectors, leading to increased costs.

Innovation Solution

A vertically-mounted accumulator with a heater, temperature detector, pressure detector, and controller that uses surface temperature and refrigerant pressure to accurately detect the liquid surface position, reducing the need for multiple temperature detectors and minimizing rippling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a horizontally-mounted accumulator is used, then the structure is simple and easy to manufacture, but the accuracy of detecting the liquid surface position deteriorates due to rippling

Engineering Contradiction:

Improveaccumulator structureVSAvoidliquid surface position detection accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent inverts the conventional horizontal mounting orientation of the accumulator to a vertical mounting orientation. This inversion fundamentally changes the fluid dynamics inside the accumulator, eliminating rippling on the liquid surface and enabling accurate liquid level detection by a single temperature detector without the interference of surface waves that plague horizontal accumulators.

Inventive Principle:

Principle #13The other way round (Inversion)

2Measurement precision

If multiple temperature detectors are installed to detect the liquid surface position, then the detection accuracy is improved, but the cost increases

Engineering Contradiction:

Improveliquid surface position detection accuracyVSAvoidnumber of temperature detectors

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent employs a single temperature detector that leverages the natural thermal characteristics of the accumulator system itself. By detecting temperature differences at different heights along the accumulator wall, the system uses the refrigerant's own thermal behavior to determine liquid level position, eliminating the need for multiple detectors or complex external sensing systems.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The patent introduces the accumulator wall temperature as an intermediary measurement parameter. Instead of directly measuring liquid surface position, the temperature detector measures the temperature of the accumulator wall at different heights, which indirectly indicates the liquid level based on thermal conduction from the refrigerant to the wall, simplifying the detection system.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If a vertically-mounted accumulator is used, then the accuracy of detecting the liquid surface position is improved by minimizing rippling, but the device complexity increases

Engineering Contradiction:

Improveliquid surface position detection accuracyVSAvoidaccumulator mounting configuration

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #13The other way round (Inversion)

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

Improves the accuracy of detecting the refrigerant's liquid surface position while reducing costs by eliminating the need for multiple temperature detectors and minimizing rippling in the vertically-mounted accumulator.

Implementation Method 1

a heater (32) configured to heat the accumulator (31)

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 2

a temperature detector (33) configured to detect a surface temperature of the accumulator (31)

Methodology Applied

Scientific EffectTemperature detection:

Implementation Method 3

a pressure detector (34) configured to detect a pressure of the refrigerant in the accumulator (31)

Methodology Applied

Scientific EffectPressure detection:

Data Source

PatentUS12000636B2Liquid level detector and air conditioning apparatus including the liquid level detector

Publication Date: 2024.06.04 MITSUBISHI ELECTRIC CORP

AI summary

A liquid level detector includes: a vertically-mounted accumulator that stores refrigerant; a heater that heats the accumulator; a temperature detector that detects a surface temperature of the accumulator; a pressure detector that detects a pressure of the refrigerant in the accumulator; and a controller. The controller detects a position of a liquid surface of the refrigerant in the accumulator based on a surface temperature of the accumulator detected by the temperature detector when the accumulator is heated by the heater, and a pressure of the refrigerant in the accumulator detected by the pressure detector.