Compressor Startup Bypass Control to Prevent Oil Dilution
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Solution Overview
Problem
Air conditioners face the issue of refrigerant dilution of the compressor oil due to the inflow of a large amount of refrigerant from the accumulator during startup, leading to potential discharge and foaming.
Innovation Solution
Incorporating a variable speed compressor, four-way valve, outdoor and indoor heat exchangers, a decompression device, an accumulator, and a bypass pipe with a two-way valve, controlled by a compressor temperature sensor to manage the compressor's operating frequency and valve opening/closing based on temperature thresholds, preventing refrigerant inflow during startup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the two-way valve is closed after startup to enable rapid operation, then productivity is improved, but the dilution of refrigerator oil occurs due to large amount of refrigerant flowing into the compressor
Solution Approach 1:
The system performs preliminary action by extending the low-frequency operation time during the first startup of the compressor. This preliminary operation allows the two-way valve to remain open for a predetermined time, preventing refrigerator oil discharge before the system transitions to normal operation. The preliminary action ensures that when the two-way valve is later closed for rapid operation, the compressor is already prepared and less susceptible to oil dilution.
Solution Approach 2:
The system applies dynamics by implementing variable low-frequency operation times based on startup sequence. The first startup uses an extended low-frequency operation time with the two-way valve open, while subsequent startups use shortened low-frequency operation times. This dynamic adjustment allows the system to balance between preventing oil discharge during initial startup and enabling rapid operation during subsequent startups, resolving the contradiction between productivity and reliability.
2Reliability
If the two-way valve is opened during first startup to prevent refrigerator oil discharge, then reliability is improved, but the operation time is extended
Solution Approach 1:
The system applies partial action by opening the two-way valve for only a predetermined amount of time during the first startup, rather than keeping it open indefinitely. This partial opening duration is sufficient to prevent refrigerator oil discharge during the critical initial operation phase, while avoiding excessive time extension. The valve is closed after the predetermined time elapses, allowing the system to transition to normal operation without unnecessary delay.
3Reliability
If the compressor operates at low frequency for extended period, then refrigerator oil discharge is prevented, but productivity is reduced
Solution Approach 1:
The system implements periodic action by using different operation patterns for different startup phases. During the first startup, the compressor operates at low frequency with the two-way valve open for a predetermined period to prevent oil discharge. After this initial period, the system transitions to normal operation with shortened low-frequency time. This periodic variation in operation mode allows the system to maintain reliability during critical phases while restoring productivity during normal operation.
Data Source
AI summary
An air conditioner according to an embodiment of the invention includes a refrigerator cycle unit having a variable speed compressor, an outdoor heat exchanger, a decompression device, an indoor heat exchanger, and an accumulator sequentially connected to one another, a bypass pipe that connects the discharge side of the compressor and an outlet of the accumulator and has a two-way valve in the middle thereof, a discharge temperature sensor that detects the temperature of the compressor, and a controller that opens or closes the two-way valve, and limits the number of rotations of the compressor to a predetermined value or less, on the basis of the temperature detected by the discharge temperature sensor when the compressor starts.