System and method for controlling an economizer circuit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Refrigeration or chiller systems face challenges in controlling motor current while maintaining desired cooling capacity, particularly when using variable speed drives, which often result in larger reductions in cooling capacity due to compressor unloading.
Innovation Solution
A method and system for controlling an economizer circuit by measuring operating parameters such as compressor motor current, temperature, or discharge pressure, and incrementally closing a valve in the outlet line connecting the economizer vessel to the compressor, allowing for proportional control of refrigerant flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If variable speed drives are used to reduce compressor speed for controlling motor current, then motor current is reduced, but cooling capacity is significantly reduced
Solution Approach 1:
The invention changes the operating parameters of the compressor by controlling the economizer valve position and flash tank liquid level, allowing the compressor to operate at higher speeds while maintaining reduced motor current through optimized refrigerant flow distribution and heat exchange efficiency
Solution Approach 2:
The economizer circuit serves multiple functions: it cools the compressor discharge gas, provides refrigerant to the evaporator, and enables motor current control without significant capacity loss by utilizing the flash tank for liquid refrigerant storage and vapor compression
2Use of energy by moving object
If compressor speed is reduced to control motor current, then motor current is controlled, but system efficiency decreases
Solution Approach 1:
The system optimizes energy efficiency by changing operational parameters including flash tank liquid level, economizer valve position, and refrigerant flow distribution, allowing motor current control while maintaining high compressor efficiency through improved heat exchange and reduced discharge gas heating
3Temperature
If excessive refrigerant flow is provided to the compressor through the economizer circuit, then compressor cooling is improved, but motor current increases excessively
Solution Approach 1:
The control system uses feedback from motor current sensors and flash tank level sensors to dynamically adjust the economizer valve position, reducing refrigerant flow when motor current approaches predetermined limits while maintaining adequate compressor cooling
Solution Approach 2:
The system dynamically adjusts the economizer valve position and refrigerant flow rate based on real-time operating conditions, allowing optimal balance between compressor cooling and motor current control during varying load conditions
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 approach enhances both compressor and system performance by preventing excessive conditions that could damage components, while maintaining optimal cooling capacity and reducing motor current, thus improving reliability and efficiency.
Implementation Method 1
Upon passing through the expansion device, the liquid refrigerant experiences a pressure drop, whereupon, at least a portion of the refrigerant rapidly expands or 'flashes' and is converted from a liquid to a gas
Implementation Method 2
The gaseous refrigerant in the flash tank collects at the 'top' of the flash tank and returns to the compressor through the second outlet line. The liquid refrigerant in the flash tank collects at the 'bottom' of the flash tank
Implementation Method 3
The liquid refrigerant in the evaporator enters into a heat exchange relationship with another fluid, e.g. air, water or other process fluid, and undergoes a phase change to a refrigerant vapor. The other fluid flowing through the evaporator is chilled or cooled as a result of the heat exchange relationship
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A system and method for controlling an economizer circuit is provided. The economizer circuit includes a valve to regulate refrigerant flow between the economizer and the compressor. The valve can be opened to engage the economizer circuit or closed to disengage the economizer circuit based on the output frequency provided to the compressor motor by a variable speed drive and an operating condition of the economizer.