A vapour compression system with a suction line liquid separator
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Solution Overview
Problem
Vapour compression systems face the challenge of operating efficiently while preventing liquid refrigerant from reaching the compressor unit, which could cause damage, and existing methods either restrict liquid refrigerant in the evaporator or require a liquid separating device to remove it from the suction line.
Innovation Solution
A method involving a liquid separating device in the suction line with a liquid level sensor to monitor and adjust control parameters, such as flow rates and pressures, to ensure liquid refrigerant is redirected to an ejector rather than the compressor, maintaining efficient operation and preventing liquid refrigerant from reaching the compressor unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If liquid refrigerant is allowed to pass through the evaporator to improve heat transfer efficiency, then energy efficiency is improved, but liquid refrigerant may reach the compressor causing damage
Solution Approach 1:
A liquid separating device is introduced as an intermediary component in the suction line between the evaporator and compressor. This device separates liquid refrigerant from gaseous refrigerant, allowing liquid to be removed while permitting vapor to pass to the compressor, thus resolving the contradiction between maintaining liquid refrigerant for heat transfer and preventing liquid from reaching the compressor
Solution Approach 2:
A liquid level sensor is implemented in the liquid separating device to monitor the liquid level and provide feedback to a control system. When the liquid level exceeds a threshold, the control system adjusts system parameters to increase liquid removal rate or decrease liquid generation rate, ensuring the liquid separator functions effectively without compromising compressor safety or energy efficiency
2Reliability
If a liquid separating device is installed in the suction line to remove liquid refrigerant, then compressor safety is improved, but system complexity increases
Solution Approach 1:
The liquid separating device is designed to perform multiple functions: it separates liquid from vapor, stores excess liquid refrigerant, and works with the control system to regulate refrigerant flow. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in system complexity while maintaining compressor protection
3Quantity of substance
If the liquid level in the liquid separating device is increased to improve liquid removal, then liquid refrigerant is better removed, but liquid may reach the compressor
Solution Approach 1:
The liquid level sensor continuously monitors the liquid level in the separating device and provides feedback to the control system. When the liquid level approaches a critical threshold that could allow liquid to reach the compressor, the control system automatically adjusts parameters to reduce liquid level, thus preventing compressor damage while maintaining effective liquid removal
Solution Approach 2:
The system dynamically adjusts operating parameters based on real-time liquid level conditions. The control system modulates refrigerant flow rates and system pressure to maintain the liquid level within a safe operating range, allowing maximum liquid removal without compromising compressor safety
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 method allows vapour compression systems to operate efficiently by ensuring liquid refrigerant is not present at the compressor unit, thereby preventing damage while maintaining optimal refrigerant flow through the evaporator, ensuring energy-efficient operation.
Implementation Method 1
a liquid separating device arranged in a suction line of the vapour compression system
Implementation Method 2
a liquid separating device arranged in a suction line... comprising a gaseous outlet connected to the inlet of the compressor unit and a liquid outlet connected to a secondary inlet of the ejector
Implementation Method 3
adjusting a control parameter of the vapour compression system in order to increase a flow rate of refrigerant from the liquid separating device to the secondary inlet of the ejector
Implementation Method 4
a liquid level sensor arranged in the liquid separating device
Implementation Method 5
monitoring a liquid level in the liquid separating device by means of the liquid level sensor
Data Source
AI summary
A method for controlling a vapour compression system (1) is disclosed. The vapour compression system (1) comprises an ejector (6) and a liquid separating device (10) arranged in a suction line. A liquid level sensor (18) is arranged in the liquid separating device (10). A liquid level in the liquid separating device (10) is monitored by means of the liquid level sensor (18). In the case that the liquid level in the liquid separating device (10) is above a predefined threshold level, a control parameter of the vapour compression system (1) is adjusted in order to increase a flow rate of refrigerant from the liquid separating device (10) to the secondary inlet (15) of the ejector (6) and/or decrease a flow rate of liquid refrigerant from the evaporator(s) (9) to the liquid separating device (10).