Bypass Expansion Control for Dual-Temperature Air Conditioning
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Solution Overview
Problem
The dual evaporation temperature control in air-conditioning systems leads to changes in refrigerant flow rate, causing pressure loss and degradation in heat exchange efficiency, and can result in a liquid return phenomenon, which affects the operation efficiency and energy savings in the system.
Innovation Solution
The controller adjusts the opening degree of the bypass expansion unit based on the bypass flow rate, inflow flow rate, and inlet quality to optimize the operation efficiency and prevent liquid return, thereby maintaining the separation ratio and heat exchange efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the opening degree of the expansion device is controlled to maintain evaporation temperature within a predetermined range, then the evaporation temperature is stabilized, but the refrigerant flow rate changes causing pressure loss and degraded heat exchange efficiency
Solution Approach 1:
The controller continuously monitors the evaporation temperature and adjusts the expansion device opening degree based on feedback from temperature sensors. This closed-loop control stabilizes evaporation temperature while minimizing unnecessary flow rate changes that would cause pressure loss. The system only adjusts the expansion device when temperature deviations are detected, rather than continuously adjusting, thereby reducing energy loss.
Solution Approach 2:
The system changes the control parameter from continuous flow rate adjustment to discrete temperature-based adjustment. By monitoring evaporation temperature and only adjusting the expansion device when temperature exceeds predetermined ranges, the system maintains temperature stability while minimizing flow rate fluctuations that cause pressure loss and energy waste.
2Temperature
If the opening degree of the expansion device is adjusted to control evaporation temperature, then the temperature stability is improved, but the separation ratio of the gas-liquid separator changes causing gas refrigerant to flow through the heat source-side heat exchanger
Solution Approach 1:
The controller uses feedback from temperature sensors to adjust the expansion device opening degree, maintaining evaporation temperature within predetermined ranges. This controlled adjustment prevents excessive changes in refrigerant flow rate that would disrupt the gas-liquid separator's separation ratio, ensuring reliable phase separation and preventing gas refrigerant from reaching the heat source-side heat exchanger.
Solution Approach 2:
The system establishes predetermined temperature ranges before operation begins. By keeping evaporation temperature within these pre-set ranges, the system proactively prevents conditions that would cause improper separation ratio changes, thereby maintaining reliable refrigerant separation throughout operation.
3Object-affected harmful factors
If the on-off valve on the bypass pipe is closed to prevent liquid return, then liquid refrigerant is prevented from flowing into the bypass pipe, but the gas-liquid separator can no longer perform its expected function and energy saving effect is lost
Solution Approach 1:
The controller continuously monitors evaporation temperature and adjusts the expansion device opening degree to maintain temperature within predetermined ranges. This feedback control prevents liquid return by stabilizing the refrigeration cycle operation, eliminating the need to close the bypass valve while preserving the gas-liquid separator's function and energy saving benefits.
Solution Approach 2:
The system changes the approach from mechanical prevention (closing the bypass valve) to parameter-based prevention (controlling evaporation temperature within optimal ranges). By maintaining evaporation temperature within predetermined ranges, the system prevents liquid return while keeping the bypass valve open, allowing the gas-liquid separator to function properly and maintain energy efficiency.
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 adjustment improves the overall operation efficiency of the air-conditioning system by minimizing pressure loss and ensuring optimal separation of refrigerants, allowing for better energy savings and performance during dual evaporation temperature control.
Implementation Method 1
a gas-liquid separator configured to separate the refrigerant
Implementation Method 2
a bypass expansion unit provided to the bypass pipe and configured to adjust a flow rate of the refrigerant
Implementation Method 3
a heat source-side heat exchanger acting as an evaporator or a condenser
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An air-conditioning apparatus including a compressor, a load-side heat exchanger, an expansion unit, and a heat source-side heat exchanger connected to one another via a pipe to allow refrigerant to circulate also includes a gas-liquid separator configured to separate the refrigerant, a bypass pipe connecting between the gas-liquid separator and a suction side of the compressor, a bypass expansion unit provided to the bypass pipe and configured to adjust a flow rate of the refrigerant, a heat source-side expansion unit configured to adjust a flow rate of the refrigerant flowing into the heat source-side heat exchanger, and a controller configured to adjust an opening degree of the bypass expansion unit on the basis of a bypass flow rate of the refrigerant flowing through the bypass pipe calculated from an opening degree of the heat source-side expansion unit, an inflow flow rate of the refrigerant flowing into the gas-liquid separator, and inlet quality of the gas-liquid separator.