Oil return control method of multi-functional multi-split system with double four-way valves
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Solution Overview
Problem
Multi-split air conditioner systems face challenges in oil return, leading to compressor failure due to oil accumulation and risk of water freezing in hydraulic modules, especially when switching between refrigeration and water heating modes, resulting in inefficient operation and user complaints.
Innovation Solution
A multi-functional multi-split system with double four-way valves and electronic expansion valves, which adjusts operation modes to ensure oil return while preventing freezing, by powering down valves and adjusting fan states and expansion valve openings based on previous operation modes, incorporating an oil separator and gas-liquid separator for efficient oil recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydraulic modules are converted into water refrigeration state for oil return, then refrigerant can flow back to compressor, but water temperature becomes very low causing freezing risk and pipeline bursting
Solution Approach 1:
The system performs preliminary heating of water in hydraulic modules before converting to water refrigeration mode. The control unit detects the water temperature and only allows mode conversion when temperature exceeds the preset threshold, preventing freezing before it can occur
Solution Approach 2:
The patent introduces temperature threshold as an intermediary condition between the desire for oil return and the risk of freezing. By setting a minimum temperature threshold, the system mediates between these conflicting requirements, allowing oil return only when temperature conditions are safe
2Reliability
If hydraulic modules in water heating mode are converted into water refrigeration state for oil return, then refrigerant flow is enabled, but hot water temperature is reduced causing user complaints
Solution Approach 1:
The system performs preliminary temperature assessment before mode conversion. By detecting current water temperature and comparing with thresholds, the system determines whether conversion to water refrigeration mode will adversely affect user comfort, and prevents conversion when temperature is too low
3Adaptability or versatility
If hydraulic modules in off state are converted into water refrigeration state for oil return, then mode flexibility is improved, but refrigerant flow still cannot occur causing oil accumulation and compressor burnout
Solution Approach 1:
The system applies preliminary anti-action by preventing mode conversion to water refrigeration when hydraulic modules are in off state. The control unit detects the off state and blocks the conversion command, thereby preventing the harmful outcome of oil accumulation and compressor damage before it can occur
Solution Approach 2:
The system uses feedback from the operational state detection of hydraulic modules to control mode conversion. The control unit continuously monitors whether modules are in heating, refrigeration, or off state, and uses this feedback to determine whether water refrigeration mode conversion is appropriate for oil return
4Reliability
If all indoor units are converted to refrigeration state for oil return, then oil recovery is enabled, but system functionality is reduced and energy consumption increases
Solution Approach 1:
The system applies local quality by enabling water refrigeration mode only in specific hydraulic modules that meet temperature criteria, rather than converting all indoor units to refrigeration state. This localized approach maintains refrigeration functionality in other areas while enabling oil return where safe
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
The system effectively recovers hot water, reduces energy consumption, ensures reliable operation, and prevents freezing, achieving a rich set of functionalities with improved oil return efficiency and system reliability.
Implementation Method 1
A first electronic expansion valve is arranged between the liquid pipe and each hydraulic heat exchanger and each indoor heat exchanger
Implementation Method 2
One end of the liquid pipe is connected to the outdoor heat exchanger, and the other end of the liquid pipe is respectively connected to the other end of a hydraulic heat exchanger of each set of hydraulic modules and the other end of an indoor heat exchanger of each set of indoor modules
Implementation Method 3
The outdoor unit includes a compressor, a first four-way valve, a second four-way valve
Implementation Method 4
An output end of the compressor is respectively connected to port D of the first four-way valve and port D of the second four-way valve
Data Source
AI summary
An oil return control method of a multi-functional multi-split system with double four-way valves. The multi-functional multi-split system includes an outdoor unit, at least one set of hydraulic modules and at least one set of indoor modules. When the multi-split system is switched from a normal operation mode to an oil return mode, a first four-way valve and a second four-way valve are powered down, and operation modes of each set of indoor modules and each set of hydraulic modules, the on/off state of fans of an indoor heat exchanger and a hydraulic heat exchanger, opening degrees of a first electronic expansion valve of the indoor heat exchanger and a first electronic expansion valve of the hydraulic heat exchanger, and the on/off state of a first electromagnetic valve and a second electromagnetic valve are correspondingly adjusted based on the previous operation modes.