Multi-Compressor Air-Conditioning System for Low-Load Efficiency

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Solution Overview

Problem

Existing air-conditioning systems face challenges with high costs due to complex refrigerant circuits and inefficient operation at low loads, particularly when using multiple compressors, which leads to frequent on/off cycles and reduced compressor lifespan.

Innovation Solution

An air-conditioning system that utilizes a heat pump cycle as a heat source, incorporating multiple outdoor units with variable-frequency compressors and a control system to manage compressor operation and frequency based on load demand, reducing on/off cycles and optimizing efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple compressors are provided in the refrigerant circuit to reduce on/off cycle operation, then operation efficiency is improved, but device complexity and cost increase

Engineering Contradiction:
Improveoperation efficiencyVSAvoidrefrigerant circuit complexity
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

The system divides the refrigerant circuit into multiple independent heat pump cycles, each with its own compressor. This segmentation allows independent control of each compressor based on load requirements, improving operational efficiency while managing complexity through modular design

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The control system dynamically adjusts the operating frequency of compressors based on real-time load conditions. By continuously monitoring and adjusting compressor speeds, the system optimizes efficiency without requiring excessive compressors, thus balancing performance with complexity

Inventive Principle:
Principle #15Dynamics

2Loss of energy

If compressor operating frequency is reduced to match low air-conditioning load, then energy saving is improved, but on/off cycle operation increases and reliability decreases

Engineering Contradiction:
Improveenergy consumptionVSAvoidcompressor lifespan
Core Design Contradiction:
Loss of energyVSReliability

Solution Approach 1:

The control system dynamically adjusts compressor operating frequencies to match load conditions continuously, preventing the compressor from stopping and starting repeatedly. This dynamic speed adjustment maintains reliability by avoiding on/off cycles while optimizing energy consumption during low-load periods

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The system maintains continuous compressor operation at adjusted frequencies rather than allowing on/off cycles. By keeping the compressor running continuously at lower speeds during low-load conditions, the system preserves reliability while achieving energy savings

Inventive Principle:
Principle #20Continuity of useful action

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 system achieves a low-cost, high-efficiency air-conditioning solution by minimizing compressor on/off cycles at low loads, extending component lifespan and improving overall operational efficiency.

Implementation Method 1

an air-conditioning system including a plurality of outdoor units (4) and having heat pump cycles (100)

Methodology Applied
Scientific EffectHeat pump cycle: Heat Exchanger

Implementation Method 2

a plurality of compressors (41) provided in the heat pump cycles (100)

Methodology Applied
Scientific EffectCompression: Compression

Data Source

PatentEP3034966B1Air-conditioning system
Publication Date: 2021.06.09 MITSUBISHI ELECTRIC CORP
  • EP3034966B1 patent drawingFigure 1
  • EP3034966B1 patent drawingFigure 2
  • EP3034966B1 patent drawingFigure 3

AI summary

A low-cost and highly-efficient air-conditioning system including an AHU using refrigerant of a heat pump cycle as a heat source, and capable of reducing an on/off cycle operation of compressors at a time of a low load, the system including: a plurality of outdoor units (4); an air handling unit (2); a plurality of independent heat pump cycles formed by connecting the plurality of outdoor units (4) and the air handling unit (2) by refrigerant pipes (6), each of the plurality of independent heat pump cycles including a compressor (41), an indoor heat exchanger (27), an expansion valve (44), and an outdoor heat exchanger (43); and a number control unit (5b) controlling, to satisfy a capacity demand corresponding to an air-conditioning load, based on a particular frequency range associated with the compressor (41), in which a certain compressor efficiency or more is obtained, a number of the compressors (41) in operation and operating frequencies of the respective compressors (41) in operation.