Air conditioner
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Solution Overview
Problem
During defrosting operations in air conditioners, increasing the compressor's rotational speed to enhance defrosting efficiency can lead to reduced suction pressure, potentially below the compressor's performance lower limit, risking damage and prolonging heating operation restoration due to installation conditions such as differing sizes of outdoor and indoor heat exchangers and refrigerant pipe lengths.
Innovation Solution
The air conditioner is configured to drive the compressor at a rotational speed corresponding to the total capacity of indoor units and refrigerant pipe length during the initial defrosting operation, preventing significant suction pressure reduction and thus avoiding compressor damage and low-pressure protection control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the compressor's rotational speed is increased to enhance defrosting efficiency, then the defrosting operation time is shortened, but the suction pressure is significantly reduced and may fall below the compressor's performance lower limit
Solution Approach 1:
The patent applies dynamics by making the compressor's activation rotational speed variable rather than fixed. The control unit determines the activation rotational speed based on installation conditions (outdoor heat exchanger size, refrigerant pipe length, indoor unit capacity) before starting the defrosting operation. This allows the system to dynamically adjust the compressor speed to match the specific installation configuration, preventing suction pressure from falling below the performance lower limit while still achieving effective defrosting.
Solution Approach 2:
The patent changes the parameter of compressor activation rotational speed based on installation conditions. By calculating and setting an appropriate activation rotational speed before the defrosting operation starts, the system optimizes the balance between defrosting efficiency and suction pressure maintenance. This parameter adjustment ensures that the compressor operates at a speed that prevents harmful pull-down effects while maintaining adequate defrosting performance.
2Temperature
If the compressor is activated at a high rotational speed at the start of defrosting operation, then the amount of high-temperature refrigerant discharged is increased, but the suction pressure is abruptly reduced due to pull-down
Solution Approach 1:
The patent applies preliminary action by determining and setting the appropriate activation rotational speed before the defrosting operation begins. The control unit calculates the optimal rotational speed based on installation conditions (outdoor heat exchanger size, refrigerant pipe length, indoor unit capacity) and stores this value for use when the defrosting operation starts. This preliminary determination prevents the harmful pull-down effect by ensuring the compressor starts at a speed that maintains adequate suction pressure from the beginning.
3Length of stationary object
If the refrigerant pipe length is long or the outdoor heat exchanger size is large, then the refrigerant circulation amount is reduced, but the suction pressure reduction becomes more significant
Solution Approach 1:
The patent changes the activation rotational speed parameter based on refrigerant pipe length and outdoor heat exchanger size. The control unit receives installation condition information including pipe length and heat exchanger size, then determines an appropriate activation rotational speed that compensates for the reduced refrigerant circulation amount. This ensures that even with long pipes or large heat exchangers, the suction pressure remains above the performance lower limit during the defrosting operation.
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 approach prevents suction pressure from falling below the compressor's performance lower limit, preventing damage and ensuring uninterrupted defrosting and heating operations by maintaining optimal compressor performance.
Implementation Method 1
a compressor (21) that compresses a refrigerant
Implementation Method 2
an outdoor heat exchanger (23) that exchanges heat with outdoor air
Implementation Method 3
a four-way valve (22) that switches an operation mode of the air conditioner
Implementation Method 4
a high-temperature refrigerant discharged from the compressor flows into the outdoor heat exchanger and melts frost formed on the outdoor heat exchanger
Data Source
Figure 1(A)~1(B)
Figure 2
Figure 3
AI summary
An outdoor unit control unit 200 has a defrosting operation condition table 300a that defines an activation rotational speed Cr in accordance with a total sum of rated capacity of indoor units 5a to 5c and a refrigerant pipe length that is lengths of a liquid pipe 8 or a gas pipe 9. The outdoor unit control unit 200 uses the total sum of the rated capacity of the indoor units 5a to 5c and refers to the defrosting operation condition table 300a, so as to determine the activation rotational speed Cr. Then, the outdoor unit control unit 200 activates a compressor 21 at the determined activation rotational speed Cr when starting a defrosting operation, maintains this activation rotational speed Cr for a predetermined time (one minute) from the start of the defrosting operation, and drives the compressor 21.