Multi-Split Defrost Control to Prevent Compressor Liquid Return
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Solution Overview
Problem
Multi-split air conditioning systems face challenges in defrosting efficiently while ensuring safe and reliable operation, particularly under low temperature and high humidity conditions, where frost buildup reduces heat transfer efficiency and increases the risk of liquid refrigerant return to the compressor.
Innovation Solution
A control method that includes a shunt device with a throttling element, which detects gas discharge pressure, gas return pressure, and gas discharge temperature to adjust the throttling element's open degree, closing it for a pre-set period before switching to defrosting mode to reduce refrigerant return to the outdoor unit, thereby preventing liquid return to the compressor and improving defrosting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the four-way valve is switched to refrigerating mode for defrosting, then the outdoor heat exchanger is defrosted by high-temperature gaseous refrigerant, but liquid refrigerant may instantaneously return to the low-pressure gas-liquid separator causing liquid return to the compressor
Solution Approach 1:
The patent applies preliminary action by closing the throttling element before switching the four-way valve to defrosting mode. This prevents liquid refrigerant from returning to the low-pressure gas-liquid separator during the mode transition, eliminating the harmful liquid return effect before it can occur.
Solution Approach 2:
The patent applies preliminary anti-action by closing the throttling element in advance to counteract the potential liquid return that would occur during defrosting mode switching. This preemptive measure creates resistance against the harmful flow of liquid refrigerant toward the compressor.
2Reliability
If the throttling element is closed for a pre-set period before defrosting, then liquid return to the compressor is prevented, but defrosting efficiency may be reduced
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the throttling element's opening degree based on real-time detection of gas discharge pressure, gas return pressure, and gas discharge temperature. This allows optimization of both compressor protection and defrosting efficiency under varying operating conditions.
Solution Approach 2:
The patent applies dynamics by making the throttling element's opening degree adjustable rather than fixed. The control system dynamically modifies the throttling element position according to detected pressure and temperature parameters, enabling adaptive balance between safety and efficiency.
3Productivity
If the outdoor heat exchanger operates in low temperature and high humidity conditions, then heat transfer efficiency is reduced due to frost buildup, but system complexity increases with additional control measures
Solution Approach 1:
The patent applies universality by utilizing the existing throttling element, which normally controls refrigerant flow during heating operation, to also serve the additional function of preventing liquid return during defrosting. This multi-functionality avoids adding separate control components, maintaining system simplicity.
Solution Approach 2:
The patent applies self-service by using the system's own existing components (throttling element, pressure sensors, temperature sensors) to achieve liquid return prevention during defrosting. The system leverages its inherent elements rather than requiring external auxiliary devices.
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 ensures efficient defrosting while preventing liquid return to the compressor, enhancing the safety and reliability of the multi-split air conditioning system by adjusting the throttling element based on pressure and temperature thresholds.
Implementation Method 1
controlling the throttling element to close for a pre-set period by the shunt device to reduce an amount of a refrigerant returned to the outdoor unit
Implementation Method 2
the compressor is used to discharge gas at a high temperature to exchange heat with indoor air
Implementation Method 3
The gas transfers the heat to the indoor air and thus is condensed as a fluid
Implementation Method 4
The gas transfers the heat to the indoor air and thus is condensed as a fluid
Implementation Method 5
the outdoor heat exchanger is converted to a condenser, the indoor unit is converted to an evaporator
Implementation Method 6
a four-way valve is used to switch the system to a refrigerating mode
Data Source
AI summary
A multi-split system and a liquid return prevention control method thereof during defrosting of the multi-split system. The method includes the following steps: when the multi-split system is in heating operation, detecting gas exhaust pressure (PC), gas return pressure (PE) and gas exhaust temperature (TP) of a compressor in real time; if an outdoor unit receives a defrosting instruction, sending a defrosting signal to a diverter and heating indoor units in multiple indoor units, controlling, by means of the diverter, a throttling element (EXV2) to close before first reversing of a four-way valve and last for a pre-set time, so as to reduce the amount of a refrigerant returned to the outdoor unit; and regulating the opening of the throttling element (EXV2) according to the gas exhaust pressure (PC), gas return pressure (PE) and gas exhaust temperature (TP) during defrosting operation of the multi-split system, so that the risk of liquid return occurred to the compressor during a defrosting process, and the safety and reliability of the system are greatly improved.