Indoor Unit Valve Control to Prevent Refrigerant Accumulation
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Solution Overview
Problem
In multi-type air conditioners, refrigerant accumulation in inactive indoor units can lead to increased costs and safety hazards, particularly with flammable refrigerants, and can cause users to mistakenly believe the system has failed due to noise during operation cessation.
Innovation Solution
The air conditioner incorporates on-off valves upstream of expansion valves in indoor units and a control unit that manages these components to equalize pressure and prevent refrigerant accumulation by controlling the indoor fan and expansion valve, ensuring safe operation and user confidence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the refrigerant circuit is charged with a higher amount of refrigerant to ensure sufficient refrigerant circulation for all indoor units operating simultaneously, then the air conditioning capabilities of respective indoor units can be exercised at the same time, but the cost increases and safety hazards arise with flammable refrigerants
Solution Approach 1:
The refrigerant circuit is segmented into multiple independent zones by providing on-off valves at the entrances and exits of each indoor unit. This allows the refrigerant circuit to be divided into separate segments that can be independently controlled, so that refrigerant is only charged in the segments where indoor units are installed, rather than charging the entire circuit for all possible units.
Solution Approach 2:
The patent applies local quality by charging refrigerant only in the specific segments of the refrigerant circuit where indoor units are actually installed, rather than uniformly charging the entire circuit. This localized refrigerant charging approach ensures sufficient refrigerant is available for operating units while avoiding unnecessary refrigerant accumulation in segments without units.
2Reliability
If the on-off valve corresponding to the indoor unit that has stopped operating is shut to prevent refrigerant accumulation, then refrigerant accumulation in the indoor unit is prevented, but a refrigerant in the liquid phase accumulates in the liquid pipe upstream of the expansion valve
Solution Approach 1:
The patent applies preliminary action by driving the indoor fan of the stopping unit for a predetermined period after closing the on-off valve. This preliminary fan operation creates a pressure difference that draws the liquid phase refrigerant from the liquid pipe through the expansion valve into the indoor unit, preventing liquid refrigerant accumulation in the pipe before the unit is fully stopped.
3Productivity
If the indoor fan is stopped immediately when the indoor unit stops operating, then the operation cessation is efficient, but noise of refrigerant causes a situation such that a user mistakenly thinks that the air conditioner has failed
Solution Approach 1:
The patent applies preliminary action by driving the indoor fan for a predetermined period after the indoor unit stops operating. This preliminary fan operation completes the refrigerant drainage process from the liquid pipe, preventing abnormal noise that would occur if the fan were stopped immediately. The fan continues running until the liquid refrigerant is fully drained, eliminating the source of abnormal noise.
Solution Approach 2:
The patent applies the skipping principle by rushing through the refrigerant drainage process by maintaining fan operation for a predetermined period after unit stoppage. This ensures the liquid refrigerant is quickly and completely drawn through the expansion valve and into the indoor unit, preventing the refrigerant from accumulating in the liquid pipe and causing abnormal noise during the transition period.
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 effectively prevents refrigerant accumulation in inactive indoor units, reducing costs and safety risks while minimizing user concerns about system failure during cooling operations.
Implementation Method 1
driving an indoor fan in the stopping unit until pressure in a part between an on-off valve that corresponds to the stopping unit and an expansion valve and pressure in a part downstream of the expansion valve are equalized
Implementation Method 2
flows via an expansion valve into a heat exchanger then functioning as an evaporator to evaporate therein
Implementation Method 3
the outdoor unit including a compressor, a reversing valve, and an outdoor heat exchanger, the indoor units each including an indoor heat exchanger
Implementation Method 4
A refrigerant that has been discharged from the compressor and then flowed into a heat exchanger then functioning as a condenser to condense therein
Implementation Method 5
flows via an expansion valve into a heat exchanger then functioning as an evaporator to evaporate therein
Implementation Method 6
A refrigerant that has been discharged from the compressor and then flowed into a heat exchanger then functioning as a condenser to condense therein
Data Source
AI summary
An air conditioner includes an outdoor unit, a plurality of indoor units, a plurality of expansion valves which are provided upstream of indoor heat exchangers, a plurality of on-off valves which are provided upstream of the expansion valves, and control unit wherein when the indoor units include a stopping indoor unit and an operating indoor unit currently operating, and when a stopping of the stopping unit is due to thermostat-off operation, the control unit performs a procedure to stop the stopping unit, the procedure including closing an on-off valve that corresponds to the stopping unit and driving an indoor fan in the stopping unit until pressure in a part between the on-off valve and an expansion valve that corresponds to the stopping unit and pressure in a part downstream of the first expansion valve are equalized, fully opening the expansion valve, and stopping the indoor fan.