Refrigeration Cycle Pressure Control with Non-Azeotropic Mixture

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Solution Overview

Problem

Refrigeration cycle apparatuses using tetrafluoropropene-based non-azeotropic refrigerant mixtures face issues with negative pressure in low-pressure circuits, leading to air and moisture ingress, decomposition of the refrigerant, and subsequent clogging or damage, requiring costly and time-consuming maintenance, and lack detection mechanisms for varying refrigerant compositions affecting safety and reliability.

Innovation Solution

A refrigeration cycle apparatus with a non-azeotropic refrigerant mixture comprising a high-boiling refrigerant and low-boiling refrigerants, controlled by a controller adjusting decompressor openings to maintain a saturated vapor line pressure below -45°C, and an intermediate-pressure injection circuit to adjust composition ratios, preventing negative pressure and ensuring reliable operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If tetrafluoropropene-based non-azeotropic refrigerant mixture is used, then global warming potential is reduced, but negative pressure occurs in low-pressure circuit

Engineering Contradiction:

Improveglobal warming potentialVSAvoidnegative pressure in low-pressure circuit

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent adjusts the composition ratio of the refrigerant mixture (specifically the ratio of high-boiling to low-boiling refrigerants) to change the saturation vapor pressure characteristics, ensuring that at -45°C the pressure remains at or above atmospheric pressure, thus preventing negative pressure while maintaining low GWP

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses a composite refrigerant mixture comprising multiple components (high-boiling refrigerant and low-boiling refrigerant) in specific proportions, combining the low GWP advantage of tetrafluoropropene with the pressure-stabilizing properties of other refrigerants to prevent negative pressure

Inventive Principle:

Principle #40Composite materials

2Reliability

If negative pressure occurs in low-pressure circuit, then air and moisture are sucked into the circuit, but refrigerant decomposition and clogging occur

Engineering Contradiction:

Improveprevention of air and moisture ingressVSAvoidrefrigerant decomposition and clogging

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent prevents negative pressure from occurring in the first place by carefully selecting the refrigerant composition ratio, thereby preemptively preventing air and moisture ingress and the subsequent decomposition and clogging problems that would result

Inventive Principle:

Principle #9Preliminary anti-action

3Productivity

If refrigerant composition varies, then operation efficiency changes, but detection mechanism is lacking

Engineering Contradiction:

Improveoperation efficiencyVSAvoidrefrigerant composition variation

Core Design Contradiction:

ProductivityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent introduces a detection mechanism that monitors refrigerant composition variations and provides feedback to the control system, enabling the system to detect and respond to composition changes that would affect operation efficiency

Inventive Principle:

Principle #23Feedback

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

The solution prevents negative pressure in low-pressure circuits, maintaining reliable operation, reducing maintenance needs, and enabling detection of refrigerant composition variations to ensure safety and efficiency.

Implementation Method 1

a non-azeotropic refrigerant mixture which circulates in a refrigeration cycle... a non-azeotropic refrigerant mixture consisting of a high-boiling refrigerant and a or some low-boiling refrigerant(s) mixed at a predetermined mixing ratio

Methodology Applied

Scientific EffectPhase change: Phase Change

Implementation Method 2

a first decompressor, a vapor/liquid separator, a second decompressor... a controller for adjusting the pressure in the vapor/liquid separator by controlling opening of the first decompressor and the second decompressor

Methodology Applied

Scientific EffectPressure reduction: Depressurisation

Implementation Method 3

a condenser... an evaporator which are connected sequentially... a refrigeration cycle apparatus using the refrigeration cycle

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Data Source

PatentEP2306121B1Refrigeration cycle apparatus with non azeotropic refrigerant mixture

Publication Date: 2020.04.15 MITSUBISHI ELECTRIC CORP

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AI summary

Disclosed is a non-azeotropic refrigerant mixture containing tetrafluoropropane as a high-boiling refrigerant and a refrigeration cycle apparatus in which a non-azeotropic refrigerant mixture containing tetrafluoropropane as a high-boiling refrigerant circulates through a refrigeration cycle so as to avoid occurrence of negative pressure in a low-pressure circuit. The non-azeotropic refrigerant mixture is characterized in that a mixing ratio of a high-boiling refrigerant and a low-boiling refrigerant is determined so that a saturated vapor line where pressure is 0.00 MPa is not higher than - 45°C in a low-pressure circuit formed between the decompressor to the compressor.