Compressor Injection Bypass Layout for Stable Heat Pump Heating
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Solution Overview
Problem
Existing air-conditioning apparatuses face challenges in controlling the discharge temperature of compressors during both cooling and heating operations, especially under low outside air temperatures, leading to inefficiencies and potential damage to the compressor. Additionally, they struggle to maintain appropriate subcooling levels and handle reversed refrigeration cycle scenarios.
Innovation Solution
The air-conditioning apparatus incorporates a refrigeration cycle with a compressor, subcooling heat exchangers, expansion devices, and an accumulator, featuring bypass pipes and injection ports to control the discharge temperature and subcooling levels, allowing for liquid refrigerant flow even with long extension pipes, thereby stabilizing compressor operation and enhancing heating capacity.
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 is lowered, but the air-conditioning apparatus cannot handle cases where the circulation path of the refrigeration cycle is reversed (cooling and heating are switched)
Solution Approach 1:
The patent divides the refrigeration cycle into separate cooling and heating circulation paths with dedicated liquid injection mechanisms for each path. The cooling liquid injection device injects refrigerant into the compressor during cooling operation, while the heating liquid injection device injects refrigerant during heating operation, allowing independent optimization for each mode without interference from the other path
Solution Approach 2:
The patent introduces a four-way valve as an intermediary device that directs refrigerant flow to different paths based on the desired operation mode. This valve acts as a mediator that switches between cooling and heating circulation paths, enabling the system to adapt to reversed refrigeration cycles while maintaining appropriate liquid injection for each mode
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 liquid injection is possible in both modes, but a special indoor unit is required and general indoor units cannot be used
Solution Approach 1:
The patent extracts the liquid injection functionality from the indoor unit and relocates it to the outdoor unit. By placing both the cooling liquid injection device and heating liquid injection device in the outdoor unit, the system eliminates the need for special indoor units with parallel check valves, allowing use of general indoor units while maintaining liquid injection capability in both operation modes
Solution Approach 2:
The outdoor unit is designed with multi-functional capability to perform both cooling and heating liquid injection operations. The four-way valve and dual liquid injection devices enable the outdoor unit to universally handle both refrigeration cycle directions, making the indoor unit design standardized and interchangeable
3Temperature
If an expansion device arranged with the subcooling heat exchanger controls the refrigerant flow rate through the subcooling heat exchanger, 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 patent segments the temperature control functions into separate devices: the subcooling heat exchanger is dedicated to controlling the degree of subcooling, while the liquid injection devices are dedicated to controlling the discharge temperature. This functional segmentation allows independent optimization and precise control of each parameter to its respective target value without mutual interference
Solution Approach 2:
The patent introduces liquid injection devices as intermediary mechanisms that directly control discharge temperature without affecting subcooling degree. These injection devices act as mediators between the refrigerant flow and the compressor, enabling precise discharge temperature control while leaving the subcooling heat exchanger focused on subcooling degree control
4Reliability
If the discharge temperature is controlled to the target value, then the compressor is protected from excessive temperature, but the degree of subcooling at the outlet of the condenser cannot be maintained at the target value when extension pipes are long
Solution Approach 1:
The patent segments the control objectives into two independent control loops: one loop controls discharge temperature via liquid injection devices to protect the compressor, while the other loop controls subcooling degree via the subcooling heat exchanger to ensure proper refrigerant state at the condenser outlet, even with long extension pipes
Solution Approach 2:
The patent implements feedback control mechanisms with sensors that monitor both discharge temperature and subcooling degree. The controller receives feedback from both parameters and independently adjusts the liquid injection devices and subcooling heat exchanger to maintain both parameters at their respective target values, ensuring compressor protection and proper refrigerant state 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 prevents excessive compressor discharge temperature, extends compressor lifespan, and ensures stable control of subcooling levels, enabling effective heating capacity under low outside 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... capable of a cooling operation to be performed by causing the first heat exchanger to function as a condenser
Implementation Method 3
a first expansion 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 the injection port of the compressor through a second opening and closing 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.