Multi-Unit Air Conditioning Subcooling Control for Refrigerant Charging
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Solution Overview
Problem
In air-conditioning apparatuses with multiple heat source units, the uneven distribution of refrigerant due to installation conditions and temperature variations leads to inaccurate determination of the refrigerant charge, causing refrigerant drift and reduced system efficiency.
Innovation Solution
The apparatus includes a controller that adjusts the subcooling levels in each heat source unit's heat exchanger to equalize the refrigerant flow, using sensors to monitor temperature and subcooling degrees, and valves to regulate the refrigerant flow rate, ensuring precise charging and minimizing drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If refrigerant charging is determined based on subcooling degree in multiple heat source units, then refrigerant charging can be performed, but measurement precision deteriorates due to refrigerant drift and uneven distribution
Solution Approach 1:
The system segments the multiple heat source units and identifies a specific target unit with appropriate subcooling conditions. By focusing refrigerant charging determination on a single selected heat source unit rather than averaging or considering all units equally, the system avoids the measurement precision deterioration caused by refrigerant drift in other units. The controller selects one heat source unit as the target based on its subcooling degree, and uses only that unit's data for charging determination.
Solution Approach 2:
The system applies local quality by recognizing that different heat source units have different local conditions (subcooling degrees, refrigerant distribution). Instead of treating all units uniformly, the system identifies and selects the specific local condition (target heat source unit) that provides the most reliable measurement for refrigerant charging determination, thereby improving overall measurement precision despite variations in other units.
2Device complexity
If refrigerant is charged based on subcooling degree without controlling distribution, then charging process is simple, but manufacturing precision deteriorates due to uneven refrigerant distribution
Solution Approach 1:
The system implements feedback by continuously monitoring the subcooling degree in each heat source unit and using this information to control the refrigerant charging process. The controller receives subcooling degree data from multiple units, selects the appropriate target unit based on this feedback, and adjusts the charging amount accordingly. This feedback mechanism enables precise control of refrigerant distribution without significantly increasing system complexity.
Solution Approach 2:
The system uses parameter changes by adjusting the subcooling degree as a control parameter to achieve proper refrigerant distribution. By monitoring and controlling the subcooling degree in the target heat source unit, the system can determine the appropriate refrigerant charge amount. This parameter-based approach improves manufacturing precision while maintaining relatively simple control logic.
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 improves the accuracy of refrigerant charging, reduces refrigerant drift, and maintains consistent system performance across multiple heat source units.
Implementation Method 1
a first heat source-side heat exchanger (4a) and a second heat source-side heat exchanger (4b), each functioning at least as a condenser
Implementation Method 2
the first heat source-side degree of subcooling adjustment means (3a, 8a, 9a) adjusts a first degree of subcooling in an outlet side of the first heat source-side heat exchanger (4a)
Data Source
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AI summary
An air-conditioning apparatus (200) comprising: first through n-th heat source units (101 a, 101b, 101c) having first through n-th heat source-side heat exchangers (104a, 104b, 104c) which function at least as condensers and first through n-th heat source-side flow rate adjustment means (103a, 103b, 103c) for adjusting the flow rate of refrigerant flowing through the first through n-th heat source-side heat exchangers (104a, 104b, 104c); first through n-th determination units (162a, 162b, 162c) for determining first through n-th degrees of subcooling in the outlet sides of the first through n-th heat source-side heat exchangers (104a, 104b, 104c); and a controller (164a, 164b, 164c) for controlling the first through n-th heat source-side flow rate adjustment means (103a, 103b, 103c) so that the first through n-th degrees of subcooling come to be equal when refrigerant is charged into a refrigerant circuit (110) having the first through n-th heat source-side heat exchangers (104a, 104b, 104c) and the first through n-th heat source-side flow rate adjustment means (103a, 103b, 103c).