Multi-Split System Defrost Control for Indoor Temperature Stability
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Solution Overview
Problem
In multi-split air conditioning systems, the defrost mode can cause rapid indoor temperature drops in rooms where indoor units are operating, affecting user experience and potentially leading to compressor damage and inefficient defrosting due to uniform expansion valve settings.
Innovation Solution
A defrosting control method that dynamically adjusts the opening degrees of expansion valves based on the capacity of working and off-state indoor units, closing working units and adjusting off-state units to maintain a balanced refrigerant flow, ensuring the defrosting requirement is met while minimizing indoor temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the expansion valves of all indoor units are maintained at the same opening degree during defrost mode, then the defrosting process is simplified and the outdoor unit can be effectively defrosted, but the indoor temperature of rooms where indoor units are working decreases rapidly, affecting user experience
Solution Approach 1:
The patent applies local quality by differentiating the control strategy for expansion valves based on the operational status of indoor units. Working indoor units have their expansion valves closed to maintain indoor temperature, while off-state indoor units have their expansion valves opened to a calculated degree (Off_PLS) to enable defrosting. This localized differentiation resolves the contradiction by allowing defrosting functionality without compromising indoor temperature stability in occupied rooms.
Solution Approach 2:
The patent implements dynamic control of expansion valve opening degrees based on real-time system conditions. The opening degree for off-state indoor units is dynamically calculated using the formula Off_PLS = ALL_HP×Avg_PLS/Off_HP, where ALL_HP is total system capacity, Avg_PLS is average opening degree, and Off_HP is total capacity of off-state units. This dynamic adjustment enables the system to adaptively balance defrosting requirements with indoor temperature maintenance.
2Productivity
If the expansion valves of off-state indoor units are opened to maximum degree during defrost mode, then the defrosting efficiency is improved, but the refrigerant flow becomes unbalanced which may lead to compressor damage
Solution Approach 1:
The patent changes the parameter of expansion valve opening degree from a fixed maximum value to a dynamically calculated value (Off_PLS). This parameter transformation ensures that the opening degree is optimized based on system capacity distribution, achieving sufficient defrosting efficiency while maintaining balanced refrigerant flow to protect the compressor from damage due to refrigerant imbalance.
3Reliability
If the expansion valves of working indoor units are kept open during defrost mode, then the indoor temperature is maintained, but the defrosting requirement cannot be satisfied due to insufficient refrigerant flow to the outdoor unit
Solution Approach 1:
The patent extracts the defrosting function from the working indoor units by closing their expansion valves, and assigns this function to off-state indoor units by opening their expansion valves to Off_PLS. This extraction allows the working indoor units to maintain indoor temperature while off-state units provide the necessary refrigerant flow for defrosting the outdoor unit, resolving the contradiction between temperature maintenance and defrosting effectiveness.
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 method effectively prevents significant indoor temperature drops, ensures efficient defrosting, and reduces the risk of compressor damage by optimizing expansion valve settings, thereby improving user experience and system performance.
Implementation Method 1
an expansion valve is disposed on each of connecting pipes between one of the indoor units and the outdoor unit... adjusting the opening degree of each of the expansion valves
Implementation Method 2
the indoor exchanger transfer heat with the outside
Implementation Method 3
the multi-split system is running at a cold mode... to defrost the outdoor unit
Data Source
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AI summary
A defrosting control method for a multi-split system is provided. A multi-split system comprises an outdoor unit and multiple indoor units. An expansion valve is provided on a connecting pipeline between each of the indoor units and the outdoor unit. When the expansion valve of each activated indoor unit is closed and the degree of opening of the expansion valve of each off-state indoor unit is less than or equal to a maximum set degree of opening, the system satisfies a defrosting requirement, and as a result the method controls the expansion valve of each activated indoor unit to remain closed, thereby resolving the issue of a dramatic temperature drop in a room having an activated indoor unit during defrosting and improving user satisfaction. The degree of opening of the expansion valve of a off-state indoor unit is Off_PLS, and is controlled such that Off_PLS = ALL_HP ∗ Avg_PLS / Off_HP. The invention satisfies a defrosting requirement and reduces the degree of opening of the expansion valves as much as possible, thereby preventing damage to a compressor without affecting defrosting.