Multi-Indoor AC Expansion Valve Balancing for Uneven Refrigerant Flow
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Solution Overview
Problem
In air conditioning systems with multiple indoor units connected to a single outdoor unit, uneven refrigerant flow due to installation height differences and pipe length variations can lead to insufficient refrigerant supply, resulting in reduced cooling capacity, especially when the total capacity of indoor units exceeds the outdoor unit's capacity or when indoor units are installed at higher elevations.
Innovation Solution
Implementing a refrigerant amount balance control system that adjusts the opening degrees of indoor expansion valves to maintain an average refrigerant superheating degree across all units, ensuring sufficient refrigerant distribution and preventing insufficient cooling ability by redistributing refrigerant from units with adequate supply to those with insufficient flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the degree of opening of expansion valves is adjusted to maintain a predetermined reference refrigerant superheating degree (e.g., 2 deg.), then the cooling performance of individual indoor units is optimized, but indoor units installed at higher elevations or farther from the outdoor unit receive insufficient refrigerant flow, resulting in inadequate cooling capacity
Solution Approach 1:
The patent changes the control parameter from a fixed reference superheating degree (e.g., 2 deg.) to a variable target superheating degree that is calculated based on the average superheating degrees of all indoor units. This allows the system to adapt to different installation conditions and redistribute refrigerant flow dynamically, ensuring that units at higher elevations or farther distances receive adequate refrigerant while maintaining overall system efficiency
Solution Approach 2:
The patent implements a feedback mechanism where the superheating degrees of all indoor units are continuously monitored, and the target superheating degree is adjusted based on the average of measured values. This closed-loop control enables the system to detect refrigerant distribution imbalances and automatically correct them by adjusting expansion valve openings, ensuring equitable refrigerant allocation across all indoor units regardless of installation position
2Adaptability or versatility
If indoor units are installed at higher elevations or farther distances from the outdoor unit, then installation flexibility is improved, but pressure loss in refrigerant pipes increases, reducing the amount of refrigerant flowing into these indoor units
Solution Approach 1:
The patent dynamically adjusts the target refrigerant superheating degree parameter based on the average superheating degrees measured from all indoor units. This parameter change compensates for pressure losses in long or vertically-oriented refrigerant pipes by modifying the expansion valve control setpoint, thereby maintaining adequate refrigerant flow to remotely or elevated installed units without requiring physical pipe modifications
Solution Approach 2:
The patent applies different control strategies to different indoor units based on their local conditions. By calculating individual superheating degrees and using their average to determine the target value, the system effectively identifies units with abnormal refrigerant flow (likely due to installation position) and provides them with compensatory control, allowing each unit to operate optimally according to its specific installation environment
3Adaptability or versatility
If the total capacity of multiple indoor units exceeds the capacity of the outdoor unit, then system versatility and cooling coverage are improved, but the refrigerant flow to each individual indoor unit becomes insufficient, reducing cooling ability
Solution Approach 1:
The patent implements comprehensive feedback from all indoor units to the outdoor unit controller. By collecting and averaging superheating degree data from all connected indoor units, the system detects when refrigerant distribution becomes insufficient due to high total capacity configurations. This feedback triggers automatic adjustment of target superheating degrees and expansion valve openings to maximize refrigerant utilization and maintain cooling performance across all units even when total capacity exceeds outdoor unit ratings
Solution Approach 2:
The patent transforms the static expansion valve opening control into a dynamic control system that continuously adapts to changing system conditions. When multiple indoor units operate simultaneously with total capacity exceeding the outdoor unit, the system dynamically adjusts target superheating degrees based on real-time measurements, enabling flexible refrigerant distribution that optimizes cooling performance across varying load conditions and unit combinations
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 ensures each indoor unit receives sufficient refrigerant, maintaining optimal cooling performance even when installation conditions cause uneven refrigerant distribution, thereby ensuring consistent cooling capacity across all units.
Implementation Method 1
the refrigerant flowing from the outdoor unit toward each indoor unit is condensed by the outdoor heal exchanger of the outdoor unit to become liquid refrigerant
Implementation Method 2
the degrees of opening of the plurality of indoor expansion valves are adjusted
Data Source
AI summary
There is provided an air conditioner capable of displaying sufficient cooling ability in each indoor unit by allowing a sufficient amount of refrigerant to flow into indoor units where cooling ability cannot be displayed. By executing refrigerant amount balance control, since degrees of opening of indoor expansion valves are narrowed in indoor units whose refrigerant superheating degrees are smaller than an average refrigerant superheating degree, amounts of refrigerant flowing into the indoor expansion valves are decreased. In the indoor unit where the refrigerant superheating degree is higher than the average refrigerant superheating degree, since refrigerant pressure on a downstream side of the indoor expansion valve is also decreased due to the degrees of opening of the indoor expansion valves being narrowed, the difference in pressure between the upstream side and the downstream side of the indoor expansion valve increases and an amount of refrigerant flowing into the indoor unit is increased.