Refrigerant Bypass Injection for Air Conditioner Discharge Temperature Control
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Solution Overview
Problem
Existing air-conditioning apparatuses face challenges in maintaining appropriate subcooling and controlling compressor discharge temperature 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, ensuring the refrigerant enters the indoor unit in a liquid state even with long extension pipes, thereby stabilizing control and preventing excessive compressor discharge temperatures.
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 to a set temperature, but the air-conditioning apparatus cannot handle cases where the circulation path of the refrigeration cycle is reversed (cooling and heating switching)
Solution Approach 1:
The patent divides the liquid refrigerant supply path into multiple separate injection circuits: one circuit injects liquid refrigerant into the suction side of the compressor, while another circuit injects liquid refrigerant into the middle of the compression chamber. This segmentation allows independent control of injection timing and location for different operation modes (cooling and heating), resolving the contradiction between temperature control and operational versatility
Solution Approach 2:
The patent employs dynamic control mechanisms including opening/closing valves and expansion devices that can adjust their state based on the current operation mode. The system dynamically switches between different injection circuits and adjusts refrigerant flow rates to maintain appropriate discharge temperatures in both cooling and heating operations, enabling adaptability across different operational states
2Adaptability or versatility
If check valves are installed in parallel to expansion devices on both indoor and outdoor sides to enable liquid refrigerant injection in both cooling and heating operations, then liquid refrigerant can be injected in both modes, but a special indoor unit is required and general indoor units cannot be used
Solution Approach 1:
The patent extracts the complex check valve mechanism from the indoor unit configuration and relocates the primary liquid injection control to the outdoor unit. By positioning the liquid injection circuit and control valves in the outdoor unit, the system achieves multi-mode operation capability without requiring special indoor unit configurations, thereby reducing overall system complexity while maintaining versatility
Solution Approach 2:
The patent designs the outdoor unit with universal multi-functionality to handle both cooling and heating operations. The outdoor unit incorporates the liquid injection circuits, expansion devices, and control valves that enable the entire system to operate in different modes, allowing standard indoor units to be used while achieving operation mode adaptability through the outdoor unit's multi-functional design
3Temperature
If an expansion device controls the flow rate of refrigerant through the subcooling heat exchanger to control discharge temperature, 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 refrigerant flow control into two independent control paths: one path controls the flow rate through the subcooling heat exchanger to manage the degree of subcooling, while another path controls liquid refrigerant injection into the compressor to manage discharge temperature. This segmentation enables independent precision control of both parameters without mutual interference
Solution Approach 2:
The patent introduces an intermediary liquid injection circuit that mediates between the subcooling heat exchanger and the compressor. This intermediary injection path allows fine-tuning of the discharge temperature independently from the subcooling degree by controlling the amount of liquid refrigerant injected into the compression chamber, thereby achieving precise control of both parameters simultaneously
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 increases, extends compressor lifespan, and ensures the required heating capacity is exerted during 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
Implementation Method 3
a first expansion device
Data Source
Figure 1
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Figure 3
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 a refrigerant pipe between an inlet side of the compressor (10) and an outlet side of the accumulator (15) through a third expansion device (14b).