Refrigerant Leak Control in Multi-Unit Air-Conditioning Pipes

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Solution Overview

Problem

In air-conditioning systems using combustible refrigerants, refrigerant leakage detection leads to increased refrigerant concentration in indoor spaces due to insufficient retention in outdoor units, especially when additional refrigerant is required for multiple indoor units and long pipes, causing safety concerns.

Innovation Solution

An air-conditioning apparatus with a refrigerant leakage sensor in the indoor unit and a control unit in the outdoor unit that stops the compressor and fully closes the flow control valve upon leakage detection, then gradually opens the valve at a slower speed to reduce refrigerant flow, thereby minimizing refrigerant leakage and concentration in indoor spaces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the valve of the refrigerant pipe is rapidly opened to restore refrigerant flow after leakage detection, then the refrigeration cycle can quickly resume normal operation, but the concentration of leaked refrigerant in the indoor space is drastically increased

Engineering Contradiction:

Improverefrigeration cycle recovery speedVSAvoidrefrigerant concentration in indoor space

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies dynamics by changing the valve opening speed from rapid to gradual. The flow control valve opens at a controlled, reduced speed after leakage detection, dynamically adjusting the refrigerant flow rate to prevent sudden concentration increases while allowing the system to recover. This dynamic control resolves the contradiction between quick recovery and safety.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of valve opening speed from high to low. By reducing the opening speed parameter of the flow control valve, the system controls the refrigerant flow rate to avoid drastic concentration increases in the indoor space while still restoring the refrigeration cycle function.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If additional refrigerant is added to accommodate multiple indoor units and long pipes, then the system can operate with more indoor units, but the amount of refrigerant sealed exceeds the outdoor unit retention capacity

Engineering Contradiction:

Improvenumber of indoor units connectedVSAvoidrefrigerant retention capacity

Core Design Contradiction:

Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The patent introduces a refrigerant leakage detection sensor as an intermediary device that monitors refrigerant concentration in real-time. This sensor enables the system to detect and respond to leakage conditions, allowing safe operation with expanded refrigerant quantities across multiple indoor units without exceeding retention capacity limits.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution effectively reduces refrigerant leakage and concentration in indoor spaces, ensuring safer conditions while managing refrigerant distribution within the system.

Implementation Method 1

a first refrigerant leakage sensor configured to detect leakage of refrigerant flowing through the first refrigerant pipe and a concentration of leaked refrigerant

Methodology Applied

Scientific EffectGas detection:

Implementation Method 2

a compressor configured to compress the refrigerant flowing through the first refrigerant pipe

Methodology Applied

Scientific EffectCompression: Compression

Implementation Method 3

a first flow control valve configured to adjust a flow rate of the refrigerant flowing through the first refrigerant pipe

Methodology Applied

Scientific EffectFluid flow control:

Data Source

PatentUS11781795B2Air-conditioning apparatus

Publication Date: 2023.10.10 MITSUBISHI ELECTRIC CORP

AI summary

An air-conditioning apparatus includes a first indoor unit and an outdoor unit in a single refrigeration cycle and connected via a first refrigerant pipe. The first indoor unit is provided with a first refrigerant leakage sensor configured to detect leakage of refrigerant and a concentration of leaked refrigerant, and the outdoor unit includes a compressor, a first flow control valve configured to adjust a flow rate of the refrigerant flowing through the first refrigerant pipe, and a control unit configured to stop the compressor and fully close the first flow control valve when leakage of the refrigerant flowing through the first refrigerant pipe is detected by the first refrigerant leakage sensor, and configured to change an opening speed of the first flow control valve to a speed less than an opening speed of the first flow control valve adopted before the leakage of the refrigerant is detected.