Expansion valve control system and method for air conditioning apparatus
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Solution Overview
Problem
HVAC systems face inefficiencies and unpredictability during cyclical operations due to temperature sensing bulb inconsistencies and reliance on last known good expansion valve positions, leading to overshooting, undershooting, and vacillation of superheat values.
Innovation Solution
A method of controlling electronic expansion valves (EEVs) in HVAC systems by determining an optimal position based on ambient environment enthalpy and operating as a percentage of a determined steady-state position, ensuring predictable and efficient operation by integrating indoor and outdoor condition feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermo-mechanical thermal expansion valve (TXV) is used that operates in response to actual refrigerant line temperature, then the valve responds to real-time temperature conditions, but the system experiences vacillation between overshooting and undershooting desired superheat values during startup
Solution Approach 1:
The system determines an optimal expansion valve position based on ambient environment enthalpy before startup, and uses this predetermined position as the initial setting. This preliminary action prevents the vacillation and overshooting/undershooting problems that occur when relying solely on real-time temperature feedback during startup, as the valve starts from an optimized position rather than responding reactively to temperature changes.
2Ease of operation
If the expansion valve position is determined based on last known good value, then the system maintains continuity from previous operation, but environmental condition changes render the previous position suboptimal
Solution Approach 1:
The system changes the basis for determining expansion valve position from static 'last known good value' to dynamic 'ambient environment enthalpy'. By using environmental parameters (temperature, humidity) that reflect current conditions, the system adapts the valve position to match present environmental realities rather than relying on historical data that may no longer be applicable.
3Adaptability or versatility
If real-time temperature feedback control is used during startup, then the system responds to current conditions, but cyclic losses increase due to overshooting and undershooting superheat values
Solution Approach 1:
The system performs preliminary determination of the optimal expansion valve position based on ambient environment enthalpy before startup occurs. This pre-calculated position serves as a stable starting point that eliminates the need for aggressive real-time adjustments during startup, thereby reducing cyclic losses from overshooting and undershooting while still allowing the system to adapt to current environmental conditions.
Data Source
AI summary
Systems and methods of controlling an HVAC system electronic expansion valve (EEV) include determining an optimal EEV position for the HVAC system as a function of a variable related to an ambient environment enthalpy and operating the HVAC system as a function of the optimal EEV position.