Segmented Heat Exchanger Defrost Control for Air-Conditioning

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Solution Overview

Problem

Air-cooled air-conditioning systems face challenges during defrosting operations, as frost on the heat source side heat exchanger melts into water, which can form bridges or freeze on other parts, reducing heating capacity and requiring additional heat exchangers, making the system expensive and inefficient.

Innovation Solution

An air-conditioning apparatus with a controller that dynamically controls the opening and closing of flow switching valves and expansion devices to direct refrigerant flow through a vertically divided heat source side heat exchanger, prioritizing defrosting based on capacity and arrangement to prevent water from reaching unfrosted areas, ensuring efficient frost removal and maintaining heating capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a heat exchanger for defrosting is added to perform defrosting operation while continuing heating operation, then heating capacity is maintained during defrosting, but device complexity and cost increase

Engineering Contradiction:

Improveheating capacityVSAvoiddevice complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The heat source side heat exchanger is divided into multiple sections (first, second, third sections) with independent flow path control. This segmentation allows selective defrosting of specific sections while maintaining heating operation in other sections, avoiding the need for additional heat exchangers while maintaining heating capacity during defrosting.

Inventive Principle:

Principle #1Segmentation

2Ease of operation

If fixed order defrosting is performed regardless of heat exchanger arrangement, then control is simple, but water from melted frost forms bridges or freezes on undefrosted heat exchangers, reducing heat exchanger capacity

Engineering Contradiction:

Improvecontrol simplicityVSAvoidheat exchanger capacity

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

The defrosting control system dynamically determines the defrosting order based on the actual vertical arrangement of heat exchanger sections. The controller adjusts the defrosting sequence adaptively, preventing water from flowing down to freeze on undefrosted sections, thereby maintaining heat exchanger capacity while keeping control relatively simple.

Inventive Principle:

Principle #15Dynamics

3Productivity

If additional heat exchangers are used to maintain heating capacity during defrosting, then heating operation continues, but system cost increases

Engineering Contradiction:

Improveheating capacityVSAvoidsystem cost

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The existing heat source side heat exchanger is made multi-functional by dividing it into multiple sections that can independently perform heating or defrosting operations. This eliminates the need for separate dedicated defrosting heat exchangers, reducing system cost while maintaining the ability to continue heating during defrosting operation.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 allows for reliable frost melting on the heat source side heat exchanger while maintaining heating capacity, avoiding the need for additional heat exchangers and reducing defrosting time, thus enhancing the system's efficiency and cost-effectiveness.

Implementation Method 1

a refrigerant discharged from a compressor is caused to flow through the heat source side heat exchanger

Methodology Applied

Scientific EffectHeat absorption: Absorption (physical)

Implementation Method 2

controls the opening and closing of the first flow switching valves, the second flow switching valves, and the third flow switching valves accordingly, and performs defrosting operation in which a refrigerant discharged from the compressor is caused to flow through the heat source side heat exchanger

Methodology Applied

Scientific EffectFluid flow control:

Data Source

PatentUS10024588B2Air-conditioning apparatus and control method therefor

Publication Date: 2018.07.17 MITSUBISHI ELECTRIC CORP

AI summary

An air-cooled air-conditioning apparatus including a heat source side heat exchanger comprising a plural number of heat source side heat exchanger parts that are connected together, and each of the heat source side heat exchanger parts is connected by a corresponding flow switching valve to a compressor. The air-cooled air-conditioning apparatus includes a controller configured to perform a defrosting operation in which a refrigerant discharged from the compressor is caused to flow separately through each of the heat source side heat exchanger parts by opening and closing the corresponding flow switching valves. The controller performs the defrosting operation on the basis of the heat exchanger capacity of each of the heat source side heat exchanger parts, the necessary heating capacity of each of the heat source side heat exchanger parts, and the arrangement of the heat source side heat exchanger parts.