Air Conditioner Sensor Layout for Accurate Refrigerant Leak Detection

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Solution Overview

Problem

Existing air-conditioning apparatuses with refrigerant leakage sensors are prone to erroneous detection due to gases other than refrigerant entering the system, which can lead to false alarms.

Innovation Solution

The air-conditioning apparatus is designed with a housing, air inlet, heat exchanger, air outlet, and a sensor configuration where the heat exchanger is above the fan and the sensor is below, using refrigerant denser than air, with the sensor positioned outside the main air passage and facing the bottom side to reduce false detection and ensure accurate refrigerant leakage detection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a gas sensor is provided in the indoor unit to detect refrigerant leakage, then refrigerant leakage detection capability is improved, but erroneous detection by other gases (such as insecticide gas) increases

Engineering Contradiction:

Improverefrigerant leakage detection accuracyVSAvoidfalse alarm rate

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The sensor is positioned at a specific location (below the fan) where refrigerant gas accumulates due to its higher density, while other gases do not reach this area. This creates a localized detection zone that is selective to refrigerant gas, resolving the contradiction between detection capability and false alarm reduction.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The solution adds a spatial dimension to the detection system by positioning the sensor vertically below the fan rather than in the general air passage. This dimensional change exploits the density difference between refrigerant and other gases, allowing the sensor to detect refrigerant accumulation at the bottom while ignoring other gases that remain in upper areas.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Measurement precision

If the sensor is positioned in the air passage to detect refrigerant, then detection sensitivity is improved, but the sensor is exposed to more interfering gases from the air inlet

Engineering Contradiction:

Improverefrigerant detection sensitivityVSAvoidinterference from other gases

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The sensor is positioned in a specific local area (below the fan) rather than in the general air passage. This localized positioning creates a detection zone that is naturally filtered from interfering gases, as only dense refrigerant gas that sinks to the bottom reaches this area.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The solution converts the harmful effect of gas density differences into a beneficial feature. The higher density of refrigerant gas, which causes it to sink and potentially cause problems, is actually exploited to direct refrigerant specifically to the sensor location below the fan, while lighter interfering gases remain above and do not reach the sensor.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Measurement precision

If multiple air holes are provided in the sensor housing to allow gas detection, then gas detection capability is improved, but the sensor becomes more susceptible to erroneous detection by sprayed gases

Engineering Contradiction:

Improvegas detection capabilityVSAvoidresistance to false detection

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The sensor is extracted from the general air passage and placed in a separate location (below the fan) that is not directly connected to the air inlet through which sprayed gases enter. This extraction isolates the sensor from the harmful influence of sprayed gases while maintaining its ability to detect refrigerant that accumulates in the bottom area.

Inventive Principle:

Principle #2Taking out (Extraction)

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 minimizes the likelihood of erroneous gas detection as refrigerant leakage and allows reliable detection of refrigerant accumulation at the bottom of the housing, preventing false alarms and ensuring timely detection of refrigerant leaks before reaching the lower flammability limit.

Implementation Method 1

a heat exchanger that transfers heat between the refrigerant and the air that flows into the housing through the air inlet

Methodology Applied

Scientific EffectHeat transfer: Heat Exchanger

Implementation Method 2

a sensor configured to detect leakage of the refrigerant

Methodology Applied

Scientific EffectGas detection:

Implementation Method 3

a fan provided in an air passage extending from the air inlet to the air outlet

Methodology Applied

Scientific EffectForced convection: Forced Convection

Data Source

PatentUS11339987B2Air-conditioning apparatus

Publication Date: 2022.05.24 MITSUBISHI ELECTRIC CORP

AI summary

An air-conditioning apparatus that uses refrigerant having a higher density than that of air, and includes a housing, an air inlet provided in a front surface of the housing to allow air in a room to flow into the housing, a heat exchanger that transfers heat between the refrigerant and the air that flows into the housing through the air inlet, an air outlet that allows the air subjected to heat exchange at the heat exchanger to be blown from the housing, a fan provided in an air passage extending from the air inlet to the air outlet, and a sensor that detects leakage of the refrigerant. The heat exchanger is provided above the fan, and the sensor is provided below the fan.