Refrigerant Injection Bypass Layout for Compressor Temperature Control
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Solution Overview
Problem
Existing 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, expansion devices, and bypass pipes to control refrigerant flow and temperature, allowing for injection of refrigerant into the compressor and accumulator, thereby regulating discharge temperature and subcooling levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid injection is performed to the middle of the compressor from the high-pressure liquid pipe, then the discharge temperature of the compressor can be controlled, but the system cannot handle cases where the circulation path is reversed (cooling and heating switching)
Solution Approach 1:
The patent divides the liquid injection function into two separate systems: one for cooling operation (injection to middle of compressor) and one for heating operation (injection to suction side). This segmentation allows each injection path to be optimized for its specific operation mode while maintaining overall system versatility through selective activation based on circulation direction.
Solution Approach 2:
The system dynamically switches between different injection configurations based on operation mode. During cooling, the high-pressure liquid pipe connects to the middle of the compressor; during heating, the liquid refrigerant is injected to the suction side. This dynamic reconfiguration enables the system to adapt to circulation path reversal while maintaining effective discharge temperature control.
2Adaptability or versatility
If check valves are installed in parallel to expansion devices on both indoor and outdoor sides to enable liquid refrigerant suction and injection in both cooling and heating, then injection can occur in both operations, but a special indoor unit is required and general indoor units cannot be used
Solution Approach 1:
The patent extracts the complex check valve parallel configuration from the indoor unit and relocates the injection control functionality to the outdoor unit. By placing the liquid injection mechanism and control valves in the outdoor unit, the system achieves dual-operation injection capability without requiring special indoor unit configurations, thereby reducing overall system complexity while maintaining versatility.
Solution Approach 2:
The outdoor unit is designed with multi-functional capability to perform both the condensing function and the liquid injection control function. The outdoor unit's expansion device and valve system can handle refrigerant distribution for both cooling and heating operations, eliminating the need for special indoor unit configurations and enabling general indoor units to be used universally.
3Temperature
If an expansion device controls the flow rate of refrigerant through the subcooling heat exchanger, then discharge temperature can be controlled, but both discharge temperature and degree of subcooling cannot be controlled to target values individually
Solution Approach 1:
The patent segments the temperature control function into two independent control points: one for discharge temperature (via liquid injection to compressor) and one for subcooling degree (via subcooling heat exchanger flow control). This segmentation allows each parameter to be controlled independently through dedicated control mechanisms, enabling simultaneous optimization of both discharge temperature and subcooling level.
Solution Approach 2:
The patent introduces an intermediary control system that coordinates between the subcooling heat exchanger and the liquid injection mechanism. The controller acts as an intermediary, adjusting the flow rate through the subcooling heat exchanger and the injection amount separately to achieve target values for both subcooling degree and discharge temperature, thereby enabling individual control of both parameters.
4Device complexity
If the expansion device is arranged in the indoor unit, then the system configuration is simplified, but two-phase refrigerant generated on the inlet side of the expansion device causes noise and unstable control
Solution Approach 1:
The patent applies preliminary subcooling action before the refrigerant reaches the indoor unit expansion device. By controlling the flow rate through the subcooling heat exchanger in the outdoor unit, the refrigerant is pre-subcooled to ensure it remains in liquid state throughout the extension pipe and into the indoor unit. This preliminary subcooling prevents two-phase refrigerant formation at the indoor expansion device inlet, eliminating noise and control instability while maintaining simplified system configuration.
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
a compressor, a first heat exchanger... the compressor including an injection port for introducing the refrigerant from outside into a compression chamber of the compressor
Implementation Method 3
a first expansion device... connected to an inlet-side passage of the accumulator through a second expansion device
Data Source
AI summary
An air-conditioning apparatus includes: a first bypass pipe connected to an inlet-side passage of an accumulator through a second expansion device, a second passage of a subcooling heat exchanger for exchanging heat between refrigerant flowing through the second passage of the subcooling heat exchanger and refrigerant flowing through a first passage of the subcooling heat exchanger, and a first opening and closing device; 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 an injection port of a compressor through a second opening and closing device; and a third bypass pipe branched from a refrigerant pipe between a heat source-side heat exchanger and a use-side heat exchanger and connected to a refrigerant pipe between an inlet side of the compressor and an outlet side of the accumulator through a third expansion device.