Multi-Indoor AC Expansion Valve Balancing for Uniform Rise Time
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Solution Overview
Problem
In air conditioning systems with multiple indoor units connected to a single outdoor unit, differences in refrigerant flow rates due to varying installation conditions and heat exchanger configurations lead to unequal rise times across indoor units, causing discomfort as some units take longer to reach set temperatures.
Innovation Solution
An air conditioner with a controller that adjusts the opening degrees of expansion valves in each indoor unit to equalize refrigerant superheating or subcooling degrees, ensuring consistent operation across all units by calculating and averaging maximum and minimum values of these parameters during cooling and heating operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If each indoor unit operates independently with its own expansion valve control to achieve individual temperature setpoints, then each unit can reach its target temperature, but differences in refrigerant flow rates due to varying installation conditions and heat exchanger configurations cause unequal rise times across indoor units
Solution Approach 1:
The controller continuously monitors refrigerant superheating or subcooling degrees from multiple indoor units and uses this feedback to dynamically adjust expansion valve opening degrees. This closed-loop control ensures that units with longer rise times receive increased refrigerant flow while maintaining overall system balance, thereby reducing rise time differences without sacrificing temperature control accuracy.
Solution Approach 2:
The system changes the operating parameters (expansion valve opening degrees) of individual indoor units based on their specific performance characteristics. By adjusting these parameters dynamically rather than uniformly, the system compensates for differences in installation conditions and heat exchanger configurations, enabling all units to reach target temperatures simultaneously.
2Loss of time
If expansion valve opening degrees are adjusted to equalize refrigerant flow rates across indoor units, then rise times become more uniform, but the system must continuously monitor and calculate refrigerant superheating or subcooling degrees which increases control complexity
Solution Approach 1:
The controller performs multiple functions using the same sensor data: it monitors refrigerant superheating or subcooling degrees for both control purposes (adjusting expansion valves) and diagnostic purposes (detecting abnormal conditions). This multi-functionality reduces the need for separate monitoring systems while maintaining comprehensive control and safety.
Solution Approach 2:
The system uses its own operational data (refrigerant superheating or subcooling degrees already being measured for control purposes) to automatically detect abnormal conditions and adjust operations. No additional external monitoring equipment is needed, as the control system serves its own diagnostic needs, simplifying the overall system architecture.
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 solution reduces the difference in rise times among indoor units, enhancing comfort by ensuring all units reach set temperatures at a similar rate, thereby improving overall system performance and user experience.
Implementation Method 1
expansion valves respectively provided to a plurality of indoor units, the expansion valves adjusting flow rates of a refrigerant in the indoor heat exchangers
Implementation Method 2
a plurality of indoor units respectively including indoor heat exchangers
Implementation Method 3
a controller for executing a refrigerant amount balance control for adjusting opening degrees of the expansion valves so that operation state amounts, with which the indoor heat exchangers exert heat exchange amounts, of the plurality of indoor units become equal to each other
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
An air conditioner includes: an outdoor unit; a plurality of indoor units respectively including indoor heat exchangers; expansion valves respectively provided to the plurality of indoor units, the expansion valves being configured to adjust flow rates of a refrigerant in the indoor heat exchangers; and a controller for executing a refrigerant amount balance control for adjusting opening degrees of the expansion valves so that operation state amounts, with which the indoor heat exchangers exert heat exchange amounts, of the plurality of indoor units become equal to each other.