Compressor Injection Bypass Layout for Air Conditioner Mode Switching
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Solution Overview
Problem
Air-conditioning apparatuses face challenges in controlling compressor discharge temperature and maintaining appropriate subcooling during both cooling and heating operations, especially under low outside air temperatures, leading to inefficiencies and potential compressor damage.
Innovation Solution
The air-conditioning apparatus incorporates a refrigeration cycle with a compressor, subcooling heat exchangers, and bypass pipes to control refrigerant flow and injection, allowing for precise management of discharge temperature and subcooling, even with long extension pipes, using expansion devices and bypass pipes to inject refrigerant into the compressor in a two-phase state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid injection is performed from the high-pressure liquid pipe to the middle of the compressor, then the discharge temperature of the compressor is lowered, but the air-conditioning apparatus cannot handle cases where the circulation path is reversed (cooling and heating switching)
Solution Approach 1:
The liquid pipe is segmented into multiple injection paths: a first injection path for cooling operation and a second injection path for heating operation. This segmentation allows the system to selectively activate the appropriate injection path based on the current operation mode, thereby lowering discharge temperature in both cooling and heating modes while maintaining operation mode adaptability.
Solution Approach 2:
The system dynamically switches between different liquid injection paths based on the operation mode (cooling or heating). The control device activates the first injection path during cooling operation and the second injection path during heating operation, enabling the liquid injection system to adapt to varying operational requirements and maintain optimal discharge temperature control in both modes.
2Temperature
If the expansion device controls refrigerant flow through the subcooling heat exchanger to control discharge temperature, then the discharge temperature is controlled, but both discharge temperature and degree of subcooling cannot be controlled to target values individually
Solution Approach 1:
The control system is segmented into independent control mechanisms: the expansion device controls refrigerant flow through the subcooling heat exchanger to manage the degree of subcooling, while the liquid injection paths control discharge temperature. This segmentation of control functions allows both discharge temperature and degree of subcooling to be controlled to their respective target values independently without system conflict.
Solution Approach 2:
The subcooling heat exchanger acts as an intermediary component between the condenser and the liquid separator. It provides a dedicated pathway for subcooling control that is independent of the discharge temperature control mechanism. By introducing this intermediary subcooling control path, the system can simultaneously achieve target values for both degree of subcooling and discharge temperature without requiring a single complex control mechanism.
3Adaptability or versatility
If check valves are installed in parallel to expansion devices on both indoor and outdoor sides for liquid refrigerant suction and injection in both cooling and heating, then liquid refrigerant can be injected in both operations, but a special indoor unit is required and general indoor units cannot be used
Solution Approach 1:
The liquid injection functionality is extracted from the indoor unit and relocated to the outdoor unit. The outdoor unit is equipped with the liquid separator, liquid injection paths, and control device necessary for liquid refrigerant injection. This extraction allows the indoor units to remain simple and compatible with existing general configurations, while the outdoor unit assumes the complex liquid injection functions for both cooling and heating operations.
Solution Approach 2:
The outdoor unit is designed with universal liquid injection capability that serves both cooling and heating operations. By concentrating the liquid injection system in the outdoor unit with multi-functional injection paths, the system achieves operation mode versatility without requiring special configurations in indoor units. The outdoor unit's liquid injection system universally handles both operational modes, eliminating the need for mode-specific indoor unit variations.
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 effectively prevents excessive compressor discharge temperature, extends compressor lifespan, and ensures stable operation with enhanced heating capacity under low outside air temperatures.
Implementation Method 1
a first passage of a subcooling heat exchanger for exchanging heat between high-temperature refrigerant and low-temperature refrigerant to subcool the high-temperature refrigerant
Implementation Method 2
exchanging heat between high-temperature refrigerant and low-temperature refrigerant to subcool the high-temperature refrigerant
Implementation Method 3
an expansion device arranged together with the subcooling heat exchanger controls the flow rate of the refrigerant to be controlled to flow through the subcooling heat exchanger
Implementation Method 4
a second bypass pipe branched from the first bypass pipe between the subcooling heat exchanger and the first opening and closing device and connected to the injection port of the compressor through a second expansion device
Data Source
Figure 1
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AI summary
An air-conditioning apparatus (100) includes: a first bypass pipe (4a) connected to an inlet-side passage of an accumulator (15) through a second expansion device (14a), a second passage of a subcooling heat exchanger (13) for exchanging heat between refrigerant flowing through the second passage of the subcooling heat exchanger (13) and refrigerant flowing through a first passage of the subcooling heat exchanger (13), and a first opening and closing device (19a); a second bypass pipe (4b) branched from the first bypass pipe (4a) between the subcooling heat exchanger (13) and the first opening and closing device (19a) and connected to an injection port of a compressor (10) through a second opening and closing device (19b); and a third bypass pipe (4c) branched from a refrigerant pipe between a heat source-side heat exchanger (12) and a use-side heat exchanger (17) and connected to the second bypass pipe (4b) between the second opening and closing device (19b) and the injection port of the compressor (10) through a third expansion device (14b).