Indoor Expansion Valve Control for Multi-Split Heating Balance
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Solution Overview
Problem
Air conditioners with multiple indoor units connected to a single outdoor unit face challenges in maintaining sufficient heating ability when the outdoor unit is installed in a higher position than the indoor units, due to differences in refrigerant pressure and flow, leading to inadequate heating performance in lower-positioned indoor units.
Innovation Solution
An air conditioner equipped with a compressor, discharge pressure detector, and indoor units featuring indoor heat exchangers and temperature detectors, utilizing a controller to adjust indoor expansion valve openings based on average refrigerant supercooling degrees and heat exchange exit temperatures to ensure balanced refrigerant flow and maintain sufficient heating ability across all indoor units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outdoor unit is installed in a higher position than the indoor units, then the refrigerant can flow down to the indoor units by gravity during cooling operation, but during heating operation the liquid refrigerant cannot flow back to the outdoor unit, causing insufficient heating ability in lower-positioned indoor units
Solution Approach 1:
The patent applies dynamics by making the expansion valve opening degree adjustable and variable based on operational conditions. The control device dynamically changes the opening degree of expansion valves in response to detected refrigerant temperatures and supercooling degrees, optimizing refrigerant flow for both heating and cooling operations regardless of installation position differences.
Solution Approach 2:
The patent changes the parameter of expansion valve opening degree based on detected refrigerant conditions. By measuring refrigerant temperature and supercooling degree, the control device adjusts the opening degree parameter to maintain proper refrigerant flow and heating/cooling performance across different installation configurations.
2Ease of manufacture
If the outdoor unit is installed on the ground floor while indoor units are installed on upper floors, then installation space is optimized, but refrigerant pressure differences cause insufficient cooling ability in upper-floor indoor units
Solution Approach 1:
The patent changes the expansion valve opening degree parameter based on detected refrigerant conditions and installation position differences. By measuring refrigerant temperature and supercooling degree, the control device adjusts the opening degree to compensate for pressure differences caused by height variations, ensuring adequate cooling performance in upper-floor indoor units while maintaining the beneficial ground-floor outdoor unit installation.
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 that each indoor unit achieves sufficient heating ability even when the outdoor unit is positioned higher than the indoor units, by optimizing refrigerant flow and pressure balance through the adjustment of indoor expansion valve openings, thereby preventing refrigerant stagnation and ensuring consistent heating performance.
Implementation Method 1
since the liquid refrigerant condensed at the outdoor unit and having flown from the outdoor unit into the liquid pipe flows to each indoor unit against gravity
Implementation Method 2
the liquid refrigerant condensed at the outdoor unit
Implementation Method 3
the gas refrigerant discharged from the compressor flows into the indoor heat exchanger of each indoor unit to be condensed
Implementation Method 4
the difference between the refrigerant pressure on the upstream side of the indoor expansion valve and the refrigerant pressure on the downstream side thereof
Data Source
AI summary
When a refrigerant amount balance control is executed, in indoor units where the refrigerant supercooling degree is lower than an average refrigerant supercooling degree, the refrigerant pressure on a downstream side of indoor expansion valves decreases since the degrees of opening of the valves are decreased. On the other hand, in an indoor unit where the refrigerant supercooling degree is higher than the average refrigerant supercooling degree, although the degrees of opening of the valves are made high, the refrigerant pressure on the downstream side of the valves decreases and this decreases the refrigerant pressure on the downstream side of the indoor expansion valve, so that the difference in pressure between on the upstream side and on the downstream side of the indoor expansion valve increases and the liquid refrigerant staying at an indoor heat exchanger of the indoor unit consequently flows out into a liquid pipe.