A method for controlling a vapour compression system during gas bypass valve malfunction
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Solution Overview
Problem
Vapour compression systems, such as refrigeration and air conditioning systems, face instability and shutdowns due to malfunctioning or saturated gas bypass valves, leading to inefficiencies and increased costs.
Innovation Solution
A method to control the vapour compression system by adjusting the gaseous refrigerant supply to maintain a target pressure within the receiver, allowing continued operation even when the gas bypass valve is malfunctioning or saturated, by measuring and comparing pressure values and adjusting the refrigerant flow through the heat rejecting heat exchanger and expansion devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the gas bypass valve is used to control mass flow of gaseous refrigerant, then the system can adapt to ambient conditions and provide required cooling or heating capacity, but the system becomes unstable or shuts down when the valve malfunctions or saturates
Solution Approach 1:
The system changes the control parameter from gas bypass valve opening degree to receiver pressure setpoint. By adjusting the receiver pressure setpoint dynamically based on ambient conditions and system state, the system maintains adaptability while providing a backup control mechanism that prevents shutdown during valve malfunction
Solution Approach 2:
The system implements a dual-control strategy where the receiver pressure control is prepared in advance as a backup mechanism. This allows the system to withstand valve malfunction or saturation without immediate shutdown, providing time for service intervention
2Ease of manufacture
If a small capacity gas bypass valve is selected for receiver compressor systems, then the valve size matches the typical refrigerant flow, but the valve saturates at fully open position when receiver compressors go into alarm
Solution Approach 1:
The system dynamically adjusts the receiver pressure setpoint based on system state, including when receiver compressors are alarmed. This parameter change allows the small capacity valve to operate effectively within its capacity range by modifying the pressure target rather than requiring increased valve capacity
3Reliability
If the system shuts down immediately upon gas bypass valve malfunction, then system safety is maintained, but operational disruptions and costs increase significantly
Solution Approach 1:
The system prepares a backup control strategy (receiver pressure control) in advance that can be activated when the primary control (gas bypass valve) fails. This cushioning mechanism allows continued operation with reduced capacity rather than immediate shutdown, maintaining safety while improving productivity
Solution Approach 2:
The system converts the limitation of a small capacity valve into a beneficial feature by using receiver pressure control to manage the reduced flow capacity. This approach transforms what would be a harmful constraint into a manageable operating condition that prevents shutdown
Data Source
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AI summary
A method for controlling a vapour compression system (1) is disclosed, the vapour compression system (1) comprising at least one compressor (2, 16), a heat rejecting heat exchanger (3), a high pressure expansion device (4, 15, 17), a receiver (5), an evaporator expansion device (6), an evaporator (7) and a gas bypass valve (8), arranged in a refrigerant path. It is registered that the gas bypass valve (8) is malfunctioning or saturated, and a pressure value for a pressure prevailing inside the receiver (5) is obtained. Finally, the vapour compression system (1) is controlled in order to control a gaseous refrigerant supply to the receiver (5) to adjust the pressure prevailing inside the receiver (5) to reach a target pressure level.