Multi-split system and liquid return prevention control method thereof
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Solution Overview
Problem
Multi-split air conditioning systems face challenges in defrosting efficiently under low temperature and high humidity conditions, leading to refrigerant liquid return issues that compromise system safety and reliability.
Innovation Solution
A control method that includes switching to a defrosting mode, real-time monitoring of compressor gas discharge pressure, gas return pressure, and gas discharge temperature, and adjusting the number of open electric control valves to minimize refrigerant return to the low-pressure gas-liquid separator, using a shunt device and electric control valves to manage refrigerant flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the system switches to defrosting mode using a four-way valve, then the outdoor heat exchanger is defrosted, but a large amount of liquid refrigerant returns to the low-pressure gas-liquid separator causing liquid return to the compressor
Solution Approach 1:
The patent segments the refrigerant flow path by introducing multiple electric control valves (first, second, and third electric control valves) at different locations in the system. These valves are controlled independently to manage refrigerant flow during defrosting, preventing liquid refrigerant from returning to the compressor while allowing defrosting to proceed. The segmentation of control functions across multiple valves resolves the contradiction between enabling defrosting and preventing liquid return.
Solution Approach 2:
The patent uses electric control valves as intermediary devices to manage the refrigerant flow during the defrosting process. Specifically, the first electric control valve is positioned to control refrigerant flow to the outdoor heat exchanger, while the second and third valves manage the return path. These intermediaries allow the system to switch to defrosting mode without directly connecting the high-pressure side to the low-pressure gas-liquid separator, thereby preventing liquid refrigerant from reaching the compressor.
2Productivity
If the outdoor heat exchanger operates in low temperature and high humidity conditions, then heat exchange capacity is reduced due to frosting, but defrosting measures cause liquid refrigerant to accumulate in the low-pressure gas-liquid separator
Solution Approach 1:
The patent applies preliminary action by controlling the first electric control valve to open before or during the defrosting process, and controlling the second and third electric control valves to remain closed during the defrosting period. This preliminary configuration of valve states ensures that when defrosting is initiated, liquid refrigerant generated during the process is directed away from the low-pressure gas-liquid separator and compressor, preventing accumulation before it becomes a problem.
Solution Approach 2:
The patent implements dynamic control of multiple electric control valves based on the operating conditions and defrosting status. The control system dynamically adjusts the state of each valve (open/closed) according to the refrigerant flow requirements during different phases of operation. This dynamic valve control allows the system to adapt to varying conditions, enabling effective defrosting while preventing liquid refrigerant accumulation in the low-pressure gas-liquid separator.
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 approach ensures proper system functioning and prevents liquid return to the compressor, enhancing safety and reliability by optimizing refrigerant management during defrosting.
Implementation Method 1
When the ambient temperature of the outdoor unit is below the freezing point, the water vapor in the outdoor air is condensed on the surface of the evaporator and becomes frost.
Implementation Method 2
the outdoor heat exchanger is defrosted due to a high-temperature gaseous refrigerant from the compressor
Implementation Method 3
the fluid is returned to the outdoor unit through a throttling device, and is evaporated after heat exchange with outdoor air
Data Source
AI summary
A multi-split air conditioning system and liquid return prevention control method thereof. When the multi-split air conditioning system is in heating operation, the multi-split air conditioning system is switched to a defrosting mode to operate for defrosting if an outdoor unit receives a defrosting instruction. After detecting gas exhaust pressure, gas return pressure and gas exhaust temperature of a compressor in real time, the multi-split air conditioning system sends a defrosting completion signal to a diverter, controls the compressor to reduce frequency and a plurality of electric-control valves to open, and controls any one of the electric-control valves to open and the rest of the electric-control valves to close during reversing of a four-way valve, so as to reduce the amount of a refrigerant returned to a low-pressure gas-liquid separator.