Internal Heat Exchanger Layout for Reversible Air Conditioning

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Solution Overview

Problem

Existing air-conditioning apparatuses that perform both cooling and heating operations require two internal heat exchangers or two expansion devices to increase refrigerant subcooling, leading to increased costs and size, and those using a single internal heat exchanger with a bridge circuit suffer from noise due to two-phase gas-liquid refrigerant flow.

Innovation Solution

An air-conditioning apparatus with a single internal heat exchanger and a single expansion device, utilizing a flow switching device to switch refrigerant flow passages between cooling and heating operations, and an internal heat exchanger with multiple flow passages to exchange heat between refrigerant streams, reducing cost and space while minimizing noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If two internal heat exchangers or two expansion devices are used to increase refrigerant subcooling in both cooling and heating operations, then the refrigeration cycle performance is improved, but the cost and size of the air-conditioning apparatus are increased

Engineering Contradiction:

Improverefrigeration cycle performanceVSAvoidnumber of heat exchangers and expansion devices

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The single internal heat exchanger is designed to perform subcooling functions in both cooling and heating operations by switching its connection configuration. In cooling operation, it subcools refrigerant between the outdoor heat exchanger (condenser) and expansion device. In heating operation, it subcools refrigerant between the indoor heat exchanger (condenser) and expansion device. This multi-functional design eliminates the need for separate heat exchangers for each operation mode.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system dynamically reconfigures the refrigerant flow paths using a four-way valve to switch between cooling and heating modes. The internal heat exchanger's role and connection points change dynamically based on the operational mode, allowing a single component to serve multiple subcooling functions that would otherwise require separate static components.

Inventive Principle:

Principle #15Dynamics

2Productivity

If a bridge circuit including four check valves is used with a single internal heat exchanger to increase subcooling, then the refrigeration cycle performance is improved, but the cost, size, and noise are increased

Engineering Contradiction:

Improverefrigeration cycle performanceVSAvoidnoise from two-phase gas-liquid refrigerant flow

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The invention extracts and eliminates the check valves from the system by using a four-way valve to directly control refrigerant flow direction. This removes the source of noise (two-phase gas-liquid flow through check valves) while maintaining the ability to achieve subcooling in both cooling and heating operations through controlled flow path configuration.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The mechanical check valve system is replaced with a four-way valve-controlled flow switching system. The four-way valve provides positive control over refrigerant direction without the reciprocating motion and two-phase flow issues that cause noise in check valves, achieving the same flow control function through a different mechanical mechanism.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 allows for increased refrigerant subcooling in both cooling and heating operations, improving refrigeration cycle performance without the need for additional heat exchangers or expansion devices, reducing costs and space requirements, and eliminating noise from two-phase refrigerant flow.

Implementation Method 1

an internal heat exchanger that exchanges heat between refrigerant flowing from a condenser to an expansion device and the refrigerant flowing from an evaporator

Methodology Applied

Scientific EffectHeat exchange: Heat Exchanger

Implementation Method 2

increasing the degree of subcooling of the refrigerant flowing from the condenser

Methodology Applied

Scientific EffectSubcooling: Supercooling

Data Source

PatentEP3217115B1Air conditioning apparatus

Publication Date: 2019.12.25 MITSUBISHI ELECTRIC CORP

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AI summary

An air-conditioning apparatus 100 includes a refrigeration cycle 1 and an internal heat exchanger 20. With the refrigeration cycle 1, both a cooling operation and a heating operation can be performed. The internal heat exchanger 20 includes a first flow passage 21 guiding refrigerant flowing between an evaporator and a compressor 2, a second flow passage 22 guiding the refrigerant flowing between an outdoor heat exchanger 4 and an expansion device 5, a third flow passage 23 guiding the refrigerant flowing between the expansion device 5 and an indoor heat exchanger 6. The internal heat exchanger 20 is configured to exchange heat between the refrigerant flowing through the first flow passage 21 and the refrigerant flowing through the second flow passage 22 in the cooling operation, and exchange heat between the refrigerant flowing through the first flow passage 21 and the refrigerant flowing through the third flow passage 23 in the heating operation.