Multi-Outdoor AC Refrigerant Balancing in Two-Phase Operation
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Solution Overview
Problem
Existing air conditioning systems with multiple outdoor units face challenges in stably judging the refrigerant amounts between units, especially when one unit is in a two-phase state, leading to inaccuracies in refrigerant specific enthalpy variations and temperature differences.
Innovation Solution
The system balances refrigerant amounts by controlling the degree of opening of outdoor expansion valves, compressor frequencies, and outdoor fan speeds, ensuring uniform specific enthalpy and subcooling levels across units, using thermistors to monitor and adjust these parameters to maintain equilibrium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the degree of subcooling at the condenser outlet is measured to judge refrigerant amount, then refrigerant balancing between outdoor units can be achieved, but the method becomes ineffective when the condenser outlet is in a two-phase state where temperature changes are absent
Solution Approach 1:
The patent changes the measurement parameter from temperature-based subcooling degree to pressure-based refrigerant specific enthalpy. By measuring the pressure at the condenser outlet and calculating refrigerant specific enthalpy from it, the system can accurately judge refrigerant amounts even when the outlet is in a two-phase state where temperature measurements would be ineffective.
2Reliability
If outdoor expansion valve openings are adjusted to balance refrigerant amounts between units, then refrigerant distribution can be improved, but the control complexity increases
Solution Approach 1:
The patent implements a feedback control mechanism where the refrigerant specific enthalpy calculated from condenser outlet pressure is continuously monitored. Based on this feedback, the control device automatically adjusts the outdoor expansion valve openings to balance refrigerant amounts between units, achieving reliable refrigerant distribution through a systematic feedback loop rather than complex manual control.
3Reliability
If compressor frequencies are adjusted to achieve refrigerant balancing, then refrigerant distribution between units can be optimized, but energy consumption increases
Solution Approach 1:
The patent applies local quality adjustment by individually controlling each outdoor unit's expansion valve based on its specific refrigerant condition. Instead of uniformly adjusting all compressors' frequencies which would increase overall energy consumption, the system locally adjusts only the expansion valve openings of units that need refrigerant balancing, optimizing refrigerant distribution with minimal energy impact.
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 approach allows for stable and accurate refrigerant balancing across outdoor units of different capacities, even when in a two-phase state, reducing errors in refrigerant judgment and maintaining system efficiency.
Implementation Method 1
A refrigerant detection unit is disposed upstream of the outdoor expansion valve and detects the amount or the amount-related value of refrigerant accumulated upstream of the outdoor expansion valve
Implementation Method 2
The opening of the expansion valve of the outdoor unit with a smaller degree of subcooling is made smaller than the opening of the expansion valve of the outdoor unit with a larger degree of subcooling, thus attaining the balance
Implementation Method 3
an outdoor heat exchanger functions as a condenser of the refrigerant compressed in a compressor
Implementation Method 4
the degree of subcooling (supercooling) at the condenser outlet of each outdoor unit is judged
Implementation Method 5
an outdoor heat exchanger functions as a condenser of the refrigerant compressed in a compressor
Data Source
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AI summary
An air conditioner including plural outdoor units (10a, 10b), indoor units (40a, 40b, 40c) each having an indoor heat exchanger, and control circuits (71a, 71b). Each of the outdoor units has an outdoor heat exchanger (14a, 14b), an outdoor expansion valve (15a, 15b), a subcooling circuit (21a, 21b), and a thermistor (61a, 61b) connected in turn, the thermistor acting to sense the temperature of refrigerant. The control circuits compare the sensed temperatures of the refrigerant in the outdoor units, respectively. After the temperatures of the refrigerant passed through the subcooling circuits of the outdoor units are sensed by their respective thermistors, an operation for judging the amounts of the refrigerant in the outdoor units is carried out.