Oil Separator Injection Control for Low-Speed AC Compression

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Solution Overview

Problem

Conventional air conditioners experience decreased compression efficiency when operated in cooling mode, particularly at low speeds, due to inefficiencies in refrigerant flow and compression.

Innovation Solution

The air conditioner employs a dual-compressor system with parallel operation, a subcooling heat exchanger, and controlled refrigerant flow channels, including injection and bypass valves, to manage refrigerant pressure and flow, ensuring efficient compression even at low speeds by selectively injecting refrigerant into compressors and guiding it through subcooling and gas-liquid separation processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the compressor is operated at a low speed in cooling mode, then energy consumption is reduced, but compression efficiency is decreased

Engineering Contradiction:

Improveenergy consumptionVSAvoidcompression efficiency

Core Design Contradiction:

Use of energy by moving objectVSProductivity

Solution Approach 1:

The system dynamically switches between single-compressor and dual-compressor operations based on cooling load requirements. The controller activates the second compressor when the cooling load exceeds the capacity of the first compressor alone, enabling the system to maintain high compression efficiency even when overall system capacity is reduced through partial operation of compressors

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The compression function is segmented into two independent compressors that can operate independently or in parallel. This segmentation allows the system to operate one compressor at a time during low-load conditions, maintaining optimal efficiency points for each compressor while reducing total energy consumption compared to running a single oversized compressor at low speed

Inventive Principle:

Principle #1Segmentation

2Productivity

If refrigerant is injected into the compressor during cooling mode, then compression efficiency is improved, but oil return to the compressor is hindered

Engineering Contradiction:

Improvecompression efficiencyVSAvoidoil return

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system implements periodic oil injection into the compressor during cooling mode to compensate for oil loss caused by refrigerant injection. The controller timing is synchronized to inject oil at intervals that ensure adequate lubrication while maintaining the refrigerant injection benefit for compression efficiency

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The oil injection system acts as an intermediary mechanism that resolves the conflict between refrigerant injection and oil return. By introducing additional oil into the compressor, the system compensates for the oil that would otherwise be carried away by the injected refrigerant, maintaining proper lubrication levels

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If a single compressor is used in cooling mode, then device complexity is reduced, but compression efficiency is insufficient

Engineering Contradiction:

Improvecompressor system complexityVSAvoidcompression efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The compression system is divided into two separate compressors with independent control, allowing each compressor to operate within its optimal efficiency range. The controller intelligently manages which compressor(s) to activate based on cooling load, maintaining high compression efficiency without requiring a single oversized compressor to operate inefficiently at part load

Inventive Principle:

Principle #1Segmentation

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 configuration maintains high compression efficiency and prevents refrigerant leakage, enhancing overall system performance and compressor longevity by optimizing refrigerant flow and pressure management.

Implementation Method 1

a subcooling heat exchanger that evaporates a refrigerant

Methodology Applied

Scientific EffectSubcooling: Supercooling

Implementation Method 2

an oil separator that separates oil from refrigerant discharged from the compressor

Methodology Applied

Scientific EffectCentrifugal separation: Centrifugal Separation

Implementation Method 3

guiding it through subcooling and gas-liquid separation processes

Methodology Applied

Scientific EffectGas-liquid separation: Density Gradient

Data Source

PatentUS10145593B2Air conditioner with oil separator and injection control thereof

Publication Date: 2018.12.04 LG ELECTRONICS INC

AI summary

An air conditioner is provided. The air conditioner may include a subcooling heat exchanger that evaporates a refrigerant, a compressor that compresses the refrigerant, an injection flow channel through which the evaporated refrigerant flows into the compressor, an injection valve that opens and closes the injection flow channel, an oil separator that separates oil from refrigerant discharged from the compressor, and an oil injection line, which communicates at a first end thereof with the oil separator and at a second end thereof with the injection flow channel so as to guide the oil separated by the oil separator toward the injection flow channel. The oil separated by the oil separator may selectively flow into the compressor through the oil injection line and the injection flow channel in accordance with a mode of operation of the air conditioner.