Refrigerant Injection Pressure Control for Stable Compressor Cooling
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Solution Overview
Problem
Existing air-conditioning systems face limitations in operation modes, particularly in controlling refrigerant pressure during heating and cooling operations, leading to potential compressor damage and reduced stability.
Innovation Solution
The air-conditioning apparatus incorporates a second expansion device upstream of the first heat exchanger, an accumulator, a suction injection pipe, and sensors to detect refrigerant pressure and temperature, with a controller managing the expansion devices to regulate refrigerant flow and pressure, ensuring stable operation across various modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid refrigerant is injected into the compressor to lower discharge refrigerant temperature, then compressor damage is minimized, but the operation modes are limited and convenience is impaired
Solution Approach 1:
The patent implements dynamic control of the expansion device opening degree based on detected refrigerant pressure and temperature. The controller adjusts the opening degree in real-time according to operating conditions, enabling the system to adaptively perform injection across multiple operation modes (cooling, heating, mixed operation) while protecting the compressor. This dynamic adjustment resolves the contradiction by making the injection system flexible rather than fixed.
Solution Approach 2:
The patent changes the control parameter from fixed opening degree to variable opening degree based on pressure and temperature detection. By monitoring refrigerant pressure (via pressure detector) and temperature (via temperature detector), the system dynamically adjusts the expansion device opening to maintain optimal injection conditions across different operation modes, thereby achieving both compressor protection and operational versatility.
2Device complexity
If expansion device opening degree is not controlled, then intermediate pressure refrigerant injection is simple, but compressor damage is more likely and operational stability is reduced
Solution Approach 1:
The patent incorporates feedback control by using detectors to monitor refrigerant pressure and temperature, then feeding this information back to the controller. The controller adjusts the expansion device opening degree based on this feedback to maintain optimal injection conditions. This closed-loop feedback mechanism ensures reliable compressor protection while keeping the injection circuit relatively simple.
Solution Approach 2:
The patent replaces mechanical fixed-opening expansion devices with electronically controlled expansion devices that can be dynamically adjusted. This substitution of mechanical systems with electronic control enables precise regulation of refrigerant flow and pressure, improving compressor protection reliability while maintaining system simplicity through electronic rather than mechanical complexity.
3Ease of operation
If refrigerant pressure is not controlled according to operation mode, then the system is simple to operate, but discharge refrigerant temperature is not optimized and compressor stability is reduced
Solution Approach 1:
The patent implements self-service operation where the system automatically detects refrigerant pressure and temperature, then the controller autonomously adjusts the expansion device opening degree without user intervention. The system serves itself by making real-time adjustments based on detected parameters, achieving optimized discharge refrigerant temperature and compressor stability while maintaining ease of operation.
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 enhances the stability and reliability of the air-conditioning system by effectively lowering the compressor discharge refrigerant temperature, regardless of operation mode, thereby reducing the risk of compressor damage and improving overall system performance.
Implementation Method 1
a second expansion device provided on an upstream side of the first heat exchanger during the heating operation
Implementation Method 2
liquid refrigerant collected by the liquid receiver is supplied to a compressor via a liquid injection circuit to lower the temperature of discharge refrigerant from the compressor
Implementation Method 3
a third expansion device provided to the suction injection pipe
Implementation Method 4
a medium pressure detector that detects a refrigerant pressure or a refrigerant saturation temperature on an upstream side of the second expansion device during the heating operation
Implementation Method 5
a discharge refrigerant temperature detector that detects a discharge refrigerant temperature of the compressor
Implementation Method 6
a controller that controls an opening degree of the second expansion device and the third expansion device based on a detection result from the medium pressure detector and the discharge refrigerant temperature detector
Data Source
AI summary
A controller performs medium pressure control that controls the opening degree of a second expansion device based on a deviation between a target value of medium pressure, and a detection result of a medium pressure detector or a predicted value. The controller controls the opening degree of a third expansion device based on a target value of a discharge refrigerant temperature of a compressor or a target value related to the discharge refrigerant temperature, and a detection result of a discharge refrigerant temperature detector or a value related to the discharge refrigerant temperature computed using a detected detection result, and regulates a flow rate of refrigerant to supply to a suction side of the compressor via an injection pipe.