Air-conditioning apparatus
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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 and reliability.
Innovation Solution
The air-conditioning apparatus incorporates a second expansion device upstream of the first heat exchanger during heating, an accumulator, a suction injection pipe, and a controller to manage the opening degrees of expansion devices based on discharge refrigerant temperature, ensuring refrigerant quality and pressure control across various operation 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 system dynamically adjusts the injection circuit configuration based on operation mode. During heating operation, the suction injection pipe connects to the upstream side of the second expansion device, enabling injection with intermediate pressure refrigerant. During cooling operation, the injection connects to the downstream side of the condenser, enabling injection with high pressure liquid refrigerant. This dynamic reconfiguration allows the system to maintain compressor protection across multiple operation modes.
Solution Approach 2:
The injection circuit is designed with multiple connection points and configurable pathways that enable it to serve multiple functions across different operation modes. The same injection circuit can inject liquid refrigerant during cooling modes and intermediate pressure refrigerant during heating modes, making the system universal rather than mode-specific.
2Adaptability or versatility
If intermediate pressure refrigerant is injected during heating operation, then operation versatility is improved, but the pressure control is not specified and compressor damage risk increases
Solution Approach 1:
The system incorporates a discharge refrigerant temperature detector that continuously monitors the compressor discharge temperature. The controller uses this feedback information to adjust the opening degree of the second expansion device and/or third expansion device, thereby controlling the pressure and temperature of the intermediate pressure refrigerant being injected. This closed-loop control ensures the injected refrigerant parameters remain within safe ranges that protect the compressor.
Solution Approach 2:
The controller dynamically adjusts the opening degree of expansion devices to change the pressure and temperature parameters of the intermediate pressure refrigerant. By varying the expansion device opening based on detected discharge temperature, the system optimizes the injection parameters to balance between achieving sufficient cooling effect and maintaining safe operating conditions for the compressor.
3Device complexity
If expansion device opening degree is not controlled during injection, then device complexity is reduced, but discharge refrigerant temperature is not lowered effectively and compressor damage occurs
Solution Approach 1:
The discharge refrigerant temperature detector provides real-time feedback on the actual temperature outcome of the injection process. The controller uses this information to adjust the expansion device opening degree, creating a closed-loop control system that automatically optimizes the injection parameters to achieve the desired temperature reduction while protecting the compressor.
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 compressor discharge refrigerant temperature across all operation modes, 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
an accumulator for accumulating excess refrigerant provided on an upstream side of the compressor
Implementation Method 4
a first heat exchanger, a first expansion device, and a second heat exchanger connected via refrigerant pipes
Data Source
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.