Parallel Heat Exchanger Defrosting Without Interrupting Indoor Heating

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Solution Overview

Problem

Existing air-conditioning systems using heat pump technology face challenges in efficiently defrosting outdoor heat exchangers during heating operations, particularly due to the need for high or medium-pressure refrigerant control, which requires time to accumulate refrigerant and can disrupt indoor heating.

Innovation Solution

An air-conditioning apparatus with a main circuit including a compressor, indoor heat exchanger, parallel heat exchangers, and an accumulator, allowing for a high-pressure or medium-pressure defrosting operation by branching off refrigerant to a selected parallel heat exchanger, enabling efficient defrosting without stopping indoor heating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If low-pressure defrosting is used to defrost the outdoor heat exchanger, then the defrosting operation can be performed, but indoor heating is suspended during defrosting leading to discomfort

Engineering Contradiction:

Improvedefrosting operationVSAvoidindoor heating continuity

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The outdoor heat exchanger is divided into multiple independent heat exchanger units, allowing one unit to be defrosted while other units continue to provide heating, thus maintaining indoor heating continuity during defrosting operation

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Multiple heat exchanger units are combined in parallel configuration, where at least one unit serves as a backup evaporator to compensate for the unit being defrosted, ensuring continuous heating supply to indoor spaces

Inventive Principle:

Principle #5Merging (Combining)

2Productivity

If high-pressure defrosting is used to defrost the outdoor heat exchanger, then defrosting efficiency is improved, but time is required to accumulate refrigerant before defrosting can begin

Engineering Contradiction:

Improvedefrosting efficiencyVSAvoidrefrigerant accumulation time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The system maintains liquid refrigerant in the accumulator during normal heating operation, preparing the refrigerant in advance for immediate use during defrosting operation, eliminating the need for refrigerant accumulation time before defrosting begins

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The accumulator serves as an intermediary storage device that holds liquid refrigerant ready for rapid discharge to the heat exchanger unit during defrosting, enabling immediate high-pressure defrosting without system reconfiguration delays

Inventive Principle:

Principle #24Intermediary (Mediator)

3Duration of action of stationary object

If medium-pressure defrosting is used to defrost the outdoor heat exchanger, then heating can be continuously performed, but the defrosting speed is reduced compared to high-pressure defrosting

Engineering Contradiction:

Improveheating operation continuityVSAvoiddefrosting speed

Core Design Contradiction:

Duration of action of stationary objectVSSpeed

Solution Approach 1:

The system dynamically adjusts the pressure level of refrigerant supplied to the heat exchanger unit during defrosting, allowing switching between high-pressure and medium-pressure modes depending on the defrosting stage and requirements, optimizing both speed and continuity

Inventive Principle:

Principle #15Dynamics

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

Enables quick and efficient defrosting of outdoor heat exchangers at high or medium pressure without interrupting indoor heating, improving defrosting speed and efficiency by directly supplying liquid refrigerant to the heat exchanger.

Implementation Method 1

a liquid refrigerant transporting unit for transferring liquid refrigerant from the accumulator to the heat exchanger to be defrosted

Methodology Applied

Scientific EffectFluid transport:

Implementation Method 2

supplies, to the heat exchanger to be defrosted, the liquid refrigerant transferred by the liquid refrigerant transporting unit

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 3

defrosting operation where a specific one of the plurality of parallel heat exchangers is a heat exchanger to be defrosted

Methodology Applied

Scientific EffectPhase change: Melting

Data Source

PatentUS10775060B2Air-conditioning apparatus

Publication Date: 2020.09.15 MITSUBISHI ELECTRIC CORP

AI summary

An air-conditioning apparatus is capable of performing a heating-defrosting operation where a specific one of a plurality of parallel heat exchangers is a heat exchanger to be defrosted and serves as a condenser while at least one parallel heat exchanger other than the heat exchanger to be defrosted serves as an evaporator. The air-conditioning apparatus includes a liquid refrigerant transporting unit for transferring liquid refrigerant from an accumulator to the heat exchanger to be defrosted. To perform the heating-defrosting operation, the air-conditioning apparatus supplies, to the heat exchanger to be defrosted, the liquid refrigerant transferred by the liquid refrigerant transporting unit.