A vapour compression system with a suction line liquid separator
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Solution Overview
Problem
In vapour compression systems, the risk of liquid refrigerant reaching the compressor unit poses a threat to damage, necessitating methods to prevent liquid refrigerant from entering the compressor while maintaining efficient operation, particularly in systems where liquid refrigerant presence is desirable for efficient heat transfer.
Innovation Solution
A method involving a liquid separating device in the suction line with a liquid level sensor, which monitors and adjusts control parameters such as pressure and temperature to increase the flow rate of refrigerant to the ejector or decrease the flow rate of liquid refrigerant from the evaporator, ensuring liquid refrigerant is not sent to the compressor unit, thereby maintaining energy efficiency and preventing compressor damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If liquid refrigerant is allowed to pass through the evaporator for efficient heat transfer, then heat transfer efficiency is improved, but the risk of compressor damage increases
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 protecting the compressor while enabling flooded evaporator operation
Solution Approach 2:
A liquid level sensor monitors the liquid level in the liquid separating device and provides feedback to a controller. When the liquid level exceeds a threshold, the controller activates an ejector to remove excess liquid, maintaining the liquid level within safe operating limits and preventing compressor damage
2Reliability
If a liquid separating device is installed in the suction line to prevent liquid refrigerant from reaching the compressor, then compressor safety is improved, but system complexity increases
Solution Approach 1:
The liquid separating device serves as a simple intermediary component that passively separates liquid and vapor phases based on density differences, adding minimal complexity while effectively protecting the compressor
Solution Approach 2:
The liquid separating device operates passively using gravity and density differences to separate liquid from vapor, requiring no active control or additional energy input for the separation function itself, thereby minimizing added system complexity
3Use of energy by moving object
If the liquid level in the liquid separating device is maintained at a high level for efficient heat transfer, then heat transfer efficiency is improved, but the risk of liquid refrigerant reaching the compressor increases
Solution Approach 1:
The liquid level sensor continuously monitors the liquid level in the liquid separating device and provides feedback to the controller. When the liquid level approaches a threshold that would allow liquid to reach the compressor, the controller activates the ejector to remove excess liquid, maintaining the liquid level within a safe range that prevents compressor damage while maximizing heat transfer efficiency
Solution Approach 2:
The liquid separating device acts as an intermediary buffer between the evaporator and compressor, containing and managing liquid refrigerant at controlled levels. The ejector serves as an active intermediary mechanism that removes excess liquid when needed, preventing liquid from reaching the compressor while allowing the evaporator to operate with liquid for efficient heat transfer
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 effectively prevents liquid refrigerant from reaching the compressor unit while allowing liquid refrigerant to be present in the evaporator for efficient heat transfer, ensuring the vapour compression system operates in an energy-efficient manner without risking compressor damage.
Implementation Method 1
a liquid separating device arranged in a suction line of the vapour compression system... 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 2
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 3
a liquid level sensor arranged in the liquid separating device, the method comprising the steps of: monitoring a liquid level in the liquid separating device by means of the liquid level sensor
Implementation Method 4
When refrigerant passes through an evaporator arranged in a vapour compression system, the refrigerant is at least partly evaporated while heat exchange takes place with the ambient or with a secondary fluid flow across the evaporator, in such a manner that heat is absorbed by the refrigerant
Implementation Method 5
heat exchange between the fluid medium and the ambient takes place in one or more heat rejecting heat exchangers, e.g. in the form of condensers or gas coolers, and in one or more heat absorbing heat exchangers, e.g. in the form of evaporators
Data Source
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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).