Outdoor Heat Exchanger Switching for Low-Temperature Compressor Startup
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Solution Overview
Problem
Air conditioning apparatuses face issues with refrigerant dissolution in the compressor oil during startup in low temperatures, leading to potential lubrication problems due to increased compressor internal pressure when controlled rotation is maintained.
Innovation Solution
The air conditioning apparatus employs flow passage switching devices and expansion valves, along with a controller, to manage the operation of outdoor heat exchangers and compressors, allowing them to function as evaporators or condensers based on temperature conditions, thereby controlling internal pressure and preventing refrigerant dissolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the compressor is driven on while maintaining its rotation number at a given number during start control, then the compressor is warmed to eliminate refrigerant dissolution, but the compressor internal pressure increases causing refrigerant dissolution
Solution Approach 1:
The patent introduces an intermediary substance (refrigerant) to transfer heat from the compressor discharge side to the suction side, enabling warming of the compressor without directly increasing its rotation number and thus avoiding excessive internal pressure buildup
Solution Approach 2:
The patent implements periodic operation of the compressor with alternating periods of running and stopping, combined with periodic switching of the four-way valve to create cyclic heating cycles that gradually eliminate refrigerant dissolution without sustained high pressure
2Temperature
If the compressor rotation number is increased to warm the compressor quickly, then the warming effect is enhanced, but the compressor internal pressure increases excessively causing refrigerant dissolution
Solution Approach 1:
The patent uses the refrigerant as an intermediary heat transfer medium, routing it through a specific path that allows heat transfer to the compressor without requiring high rotation speeds, thus achieving warming while controlling pressure
Solution Approach 2:
The patent changes the operational parameters of the system by switching the four-way valve to alter refrigerant flow direction and by modulating compressor rotation number dynamically, achieving effective warming while maintaining pressure within safe limits
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 dissolution and maintains compressor lubrication by managing the operation of outdoor heat exchangers and compressors, ensuring efficient startup and operation in low temperatures.
Implementation Method 1
at least two outdoor heat exchangers... the controller executes the switching control of the flow passage switching devices and the valve opening rate control of the outdoor expansion valves
Implementation Method 2
allow it or them to function as an evaporator or evaporators
Implementation Method 3
allow it or them to function as a condenser or condensers
Implementation Method 4
outdoor expansion valves each connected to the other end of each of the outdoor heat exchangers for adjusting the refrigerant flow amount of the outdoor heat exchangers
Implementation Method 5
at least one outdoor unit including at least one compressor... drives the one or more compressors at a predetermined rotation number
Implementation Method 6
flow passage switching devices connected to one end of each of the outdoor heat exchangers for switching the connection of the outdoor heat exchangers to the refrigerant discharge opening or refrigerant suction opening
Data Source
AI summary
An air conditioning apparatus 1 includes first start control and second start control as its start control. In the first start control, first outdoor heat exchangers 24a, 24b are controlled to function as evaporators and second outdoor heat exchangers 25a, 25b are controlled to function as condensers. Thus, even when the compressors 21a, 21b are driven on at a given rotation number, the discharge pressures thereof can be prevented from increasing, thereby being able to prevent the internal pressures of the compressors 21a, 21b from increasing. Also, after end of the first start control, the first outdoor heat exchangers 24a, 24b and second outdoor heat exchangers 25a, 25b are all controlled to function as evaporators, and the compressors 21a, 21b are driven on at a given rotation number. This can shorten the rising time of the heating capacity in the start of the normal heating operation.