Compressor Injection Control for Reversible Air-Conditioning Modes
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Solution Overview
Problem
Existing air-conditioning systems face limitations in operation modes, particularly in refrigerant injection during reversed flow directions, leading to potential compressor damage and reduced stability and reliability, especially when performing cooling, heating, or mixed operations.
Innovation Solution
An air-conditioning apparatus with a refrigerant circuit and heat medium circuit that allows for flexible operation modes, including cooling, heating, and mixed operations, using intermediate heat exchangers and expansion devices to control refrigerant pressure and temperature, ensuring stable compressor operation across various modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid refrigerant is injected into the compressor during cooling operation, then the discharge temperature of the compressor is lowered, but the system cannot perform injection when the flow direction of refrigerant is reversed (heating mode)
Solution Approach 1:
The injection circuit is designed to supply liquid refrigerant to the compressor in multiple operation modes (cooling, heating, and mixed operation) by using operation mode detection means to control the expansion device appropriately for each mode, making the injection system universal across different operating conditions
Solution Approach 2:
The system dynamically adjusts the expansion device opening degree based on the detected operation mode to control the pressure of intermediate pressure refrigerant, enabling adaptive injection control that responds to changing operational requirements
2Adaptability or versatility
If the opening degree of the expansion device on the injection circuit is not controlled, then the system can operate in various modes, but the pressure of the intermediate pressure refrigerant is not varied according to the situation, leading to potential compressor damage
Solution Approach 1:
The system uses operation mode detection means to detect the current operation mode and provides feedback control to adjust the expansion device opening degree accordingly, ensuring that the intermediate pressure refrigerant pressure is appropriately varied for each operation mode to maintain compressor reliability
Solution Approach 2:
The system changes the pressure parameter of the intermediate pressure refrigerant by dynamically adjusting the expansion device opening degree based on the detected operation mode, ensuring optimal pressure conditions for compressor operation in each mode
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 enhances operating stability and reliability by effectively lowering compressor discharge temperatures, regardless of operation mode, thereby reducing the risk of compressor damage and improving overall system performance.
Implementation Method 1
an expansion device provided on an injection circuit to inject refrigerant at an intermediate pressure
Implementation Method 2
a first heat exchanger; a second heat exchanger
Implementation Method 3
a compressor, having a low-pressure shell structure, into which a refrigerant that flows through injection piping flows
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A controller, at least during the heating operation, controls the opening degree of a second expansion device and/or a third expansion device based on a discharge refrigerant temperature detected by a discharge refrigerant temperature detector, or a value computed using the discharge refrigerant temperature, and causes refrigerant having a quality equal to or greater than 0.9 and less than or equal to 0.99 to be suctioned into a compressor.