Indoor Expansion Valve Control for Stable Multi-Split Heating
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Solution Overview
Problem
Air conditioners with multiple indoor units connected to a single outdoor unit by refrigerant pipes face challenges in maintaining sufficient heating ability when the outdoor unit is installed higher than the indoor units due to differences in refrigerant pressure, leading to inadequate refrigerant flow and reduced heating performance in lower-positioned indoor units.
Innovation Solution
Implementing a refrigerant amount balance control system that adjusts the degrees of opening of indoor expansion valves based on calculated refrigerant supercooling degrees to ensure consistent refrigerant flow and pressure across all indoor units, even when the outdoor unit is installed higher than the indoor units, thereby enhancing heating ability.
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 naturally to lower-positioned indoor units during cooling operation, but the liquid refrigerant flow becomes difficult during heating operation due to gravity, causing insufficient heating ability in lower-positioned indoor units
Solution Approach 1:
The patent applies preliminary anti-action by installing a circulation pump in the liquid refrigerant pipe to actively pump liquid refrigerant from lower-positioned indoor units back to the outdoor unit during heating operation. This preliminary counteracting force prevents the gravity-induced flow obstruction before it can cause insufficient heating ability, ensuring reliable refrigerant circulation regardless of installation height differences.
2Quantity of substance
If the degree of opening of the indoor expansion valve in the lower-positioned indoor unit is increased to improve refrigerant flow, then more refrigerant can flow to that unit, but the refrigerant pressure difference across the expansion valve decreases, reducing the amount of refrigerant flowing through
Solution Approach 1:
The patent applies pneumatics and hydraulics by using a circulation pump to create active hydraulic pressure in the liquid refrigerant pipe. This external pressure source compensates for the reduced natural pressure difference across the expansion valve, ensuring sufficient refrigerant flow amount to lower-positioned indoor units during heating operation without being constrained by gravity-induced pressure variations.
3Ease of manufacture
If the liquid pipe is routed to allow natural drainage to the outdoor unit, then installation is simpler, but when the outdoor unit is installed higher than indoor units, liquid refrigerant cannot drain properly during heating operation, causing refrigerant stagnation
Solution Approach 1:
The patent introduces a circulation pump as an intermediary device in the liquid refrigerant pipe. This intermediary actively mediates the refrigerant circulation by pumping liquid refrigerant from lower-positioned indoor units back to the outdoor unit, replacing the need for gravity-based natural drainage and ensuring reliable refrigerant circulation regardless of installation height differences.
4Productivity
If the refrigerant circuit is designed for cooling operation with outdoor unit higher than indoor units, then cooling performance is optimized, but the same design causes insufficient heating ability when outdoor unit is installed higher than indoor units due to adverse gravity effects on liquid refrigerant flow
Solution Approach 1:
The patent applies dynamics by making the refrigerant circulation system adaptive to different operating modes. During cooling operation, the system operates with natural refrigerant flow optimized for outdoor units positioned higher than indoor units. During heating operation, the circulation pump is activated to dynamically change the circulation pattern, actively pumping liquid refrigerant back to the outdoor unit, thereby maintaining high productivity in both cooling and heating modes regardless of installation height differences.
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
The system ensures sufficient heating ability is maintained across all indoor units by optimizing refrigerant flow and pressure, preventing refrigerant stagnation and ensuring efficient refrigerant circulation, even with significant height differences between the outdoor and indoor units.
Implementation Method 1
the difference between the refrigerant pressure on the upstream side of the indoor expansion valve and the refrigerant pressure on the downstream side
Implementation Method 2
the gas refrigerant discharged from the compressor flows into the indoor heat exchanger of each indoor unit to be condensed
Implementation Method 3
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
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
When a refrigerant amount balance control is executed, in indoor units (5a) and (5b) where the refrigerant supercooling degree is lower than an average refrigerant supercooling degree, the refrigerant pressure on a downstream side of indoor expansion valves (52a) and (52b) decreases since the degrees of opening of the indoor expansion valves (52a) and (52b) are decreased. On the other hand, in an indoor unit (5c) where the refrigerant supercooling degree is higher than the average refrigerant supercooling degree, although the degrees of opening of the indoor expansion valves (52a) and (52b) are made high, the refrigerant pressure on the downstream side of the indoor expansion valves (52a) and (52b) decreases and this decreases the refrigerant pressure on the downstream side of the indoor expansion valve (52c), so that the difference in pressure between on the upstream side and on the downstream side of the indoor expansion valve (52c) increases and the liquid refrigerant staying at an indoor heat exchanger (51c) of the indoor unit (5c) consequently flows out into a liquid pipe (8). Thereby, the heating ability of the indoor unit (5c) increases.