Refrigerant Carryover Control Using Capped Compressor Operation
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Solution Overview
Problem
Refrigerant systems face inefficiencies and potential compressor damage due to liquid refrigerant carryover, especially at high cooling loads, as existing separators add cost and create flow restrictions.
Innovation Solution
A method and system that monitor and control thermodynamic variables to selectively operate in normal and capped modes, limiting capacity and dynamic pressure to prevent liquid carryover, using a microprocessor-based controller to adjust compressor and expansion valve operations based on feedback signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid/gas separators are added to address carryover, then compressor protection is improved, but system cost and flow restriction increase
Solution Approach 1:
The invention extracts the liquid refrigerant carryover problem from the system by implementing control methods that prevent liquid carryover at the source (evaporator outlet), eliminating the need for additional liquid/gas separator components while still protecting the compressor from liquid damage
Solution Approach 2:
The invention replaces the mechanical solution (physical liquid/gas separators) with a control-based solution that uses monitoring of thermodynamic variables and selective operation modes to prevent liquid carryover, substituting mechanical separation with intelligent control
2Productivity
If refrigerant system operates at higher cooling loads, then cooling capacity is improved, but liquid carryover risk increases
Solution Approach 1:
The invention implements dynamic operation modes (normal and capped modes) that adapt the system's thermodynamic variable limits based on cooling load conditions, allowing the system to operate at higher capacities when safe and restrict capacity when liquid carryover risk increases
Solution Approach 2:
The invention changes the operating parameters by establishing different limits for thermodynamic variables (such as suction pressure, temperature, or superheat) depending on the operating mode, allowing optimization of both cooling capacity and carryover prevention through parameter adjustment
Data Source
AI summary
A refrigerant system comprising a compressor, a condenser, an electronic expansion valve, and an evaporator is controlled in a normal operating mode to meet moderate cooling loads; however, when the load approaches that which is sufficient to induce liquid refrigerant carryover from the evaporator to the compressor, the system is controlled in a capped operating mode to limit a certain thermodynamic variable rather than controlled to meet the high load. In the normal mode, the compressor and/or the expansion valve might be controlled in response to the amount of superheat of the refrigerant leaving the evaporator or the level of liquid refrigerant in the evaporator. In the capped operating mode, the compressor and/or the expansion valve might be controlled to limit a variable such as the compressor's capacity, the saturated pressure or dynamic pressure of the refrigerant entering the compressor, or the refrigerant's mass flow rate.