EXV Superheat Control to Prevent Liquid Refrigerant Entry
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Solution Overview
Problem
Air conditioning systems face challenges in ensuring all refrigerant entering the compressor is in a gaseous state, leading to potential compressor damage and shortened lifespan due to the entry of liquid-state refrigerant during startup and transient states, which prior art electronic expansion valves (EXVs) fail to quickly address.
Innovation Solution
An EXV controller measures the refrigerant's state upstream of the compressor and adjusts the EXV to maintain a desired superheat level, preventing liquid entry and minimizing valve opening and closing, thereby extending compressor life and improving system efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If prior art EXV implementations maintain appropriate flow of superheated gaseous refrigerant during steady state operation, then refrigerant superheat is controlled, but the EXV does not react quickly to transient states such as startup or fan speed change
Solution Approach 1:
The patent implements a feedback control system where the EXV controller continuously monitors superheat levels and adjusts the EXV opening degree in real-time based on actual refrigerant state measurements, enabling quick response to transient conditions while maintaining precise superheat control during steady state operation
Solution Approach 2:
The patent dynamically adjusts the EXV opening degree based on operating conditions - using larger opening degrees during transient states (startup, fan speed changes) to prevent liquid entry, and transitioning to precise feedback control during steady state to maintain optimal superheat levels
2Ease of operation
If the EXV is controlled to respond to startup condition or fan speed change by applying preprogrammed adjustment, then some response is achieved, but liquid-state refrigerant may still enter the compressor due to predictions not accounting for all circumstances
Solution Approach 1:
The system uses real-time superheat measurement feedback to validate and adjust preprogrammed adjustments, ensuring that predicted refrigerant behavior matches actual conditions and preventing liquid entry even when circumstances deviate from predictions
Solution Approach 2:
The patent combines preprogrammed adjustments for anticipated transient states with real-time feedback control, applying preliminary valve positioning based on predicted conditions while continuously monitoring to ensure actual refrigerant state matches predictions
3Reliability
If the EXV is completely opened or closed to handle dramatic changes in refrigerant superheat level during startup and transient states, then superheat changes are managed, but valve life is shortened
Solution Approach 1:
The patent implements dynamic control that adapts the degree of EXV adjustment based on the severity and type of transient state - using moderate adjustments for minor disturbances and larger adjustments only when necessary, thereby managing superheat changes while minimizing wear on the valve
Solution Approach 2:
The system applies partial actions (moderate valve adjustments) for minor transient disturbances and reserves excessive actions (large valve openings/closings) for severe transient states, optimizing the balance between superheat control and valve life extension
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
The solution ensures all refrigerant entering the compressor is in a gaseous state, lengthening compressor life and enhancing air conditioning system performance and efficiency by quickly responding to changes in superheat levels.
Implementation Method 1
the EXV controller receives a temperature measurement and a pressure measurement of the refrigerant downstream of the evaporator outlet and upstream of the compressor
Implementation Method 2
The liquid refrigerant then flows though the throttling device with a significant pressure drop. In particular, the throttling device controls the refrigerant's mass flow by regulating the degree to which the valve is opened
Implementation Method 3
The saturated refrigerant passes through the evaporator. A blower typically forces indoor air past the evaporator to cool the indoor air. As the indoor air heats up the refrigerant, the refrigerant evaporates into a vapor state
Implementation Method 4
The condenser rejects heat to the ambient air typically though the use of an electric fan
Data Source
AI summary
A control procedure operates an expansion valve of an air conditioning system. The control procedure utilizes a first control procedure to bring a calculated superheat value within a range of a target superheat value, and a second control procedure to cause the calculated superheat value to match the target superheat value. Both the first and second control procedures preferably use Proportional, Integral, Derivative control algorithms.