Compressor oil injection cooling
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Solution Overview
Problem
The use of A2L refrigerants in HVACR systems results in higher discharge temperatures due to their higher heat of compression, which can damage compressors and is not effectively addressed by existing cooling methods without impacting the working fluid circuit's cooling capacity.
Innovation Solution
An oil injection system is introduced into the compressor suction pathway to cool the working fluid, utilizing an oil pump and restriction to inject oil at a higher pressure, liberating dissolved gaseous refrigerant for cooling, and optionally using an oil cooler to further reduce discharge temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If A2L refrigerant is used in the working fluid circuit, then the cooling capacity is improved, but the discharge temperature increases causing compressor damage
Solution Approach 1:
The system performs preliminary cooling of the refrigerant before it enters the compression chamber by injecting cooled oil into the suction pathway. This pre-cools the refrigerant, reducing the discharge temperature while maintaining cooling capacity.
Solution Approach 2:
Oil serves as an intermediary cooling medium. It is cooled separately in an oil cooler and then injected into the suction pathway to transfer cooling effect to the refrigerant, mediating between the cooling system and the compression process.
2Reliability
If existing cooling methods are applied to reduce discharge temperature, then the compressor is protected, but the working fluid circuit's cooling capacity is impacted
Solution Approach 1:
The cooling function is segmented into separate oil cooling and refrigerant cooling pathways. The oil is cooled in a dedicated oil cooler, then injected into the suction pathway to cool the refrigerant, separating the cooling function from the main refrigerant circulation.
Solution Approach 2:
The injected oil serves multiple functions: it cools the refrigerant in the suction pathway, lubricates the compressor components, and is then separated and reused in the oil sump, creating a multi-functional system that protects the compressor without compromising cooling capacity.
3Temperature
If oil is injected into the suction pathway to cool the working fluid, then the discharge temperature is reduced, but the oil circulation may be affected
Solution Approach 1:
The system discards the injected oil into the main refrigerant stream after it has served its cooling purpose, then recovers it through the oil separator and returns it to the oil sump for reuse, preventing oil loss while maintaining cooling effect.
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 discharge temperature of the compressor is reduced by 2.8K to 16.7K without affecting the working fluid circuit's mass flow or oil circulation, effectively managing higher heat of compression issues with A2L refrigerants.
Implementation Method 1
the oil pathway is configured to inject the oil from the oil sump into the suction pathway
Implementation Method 2
injecting the oil from the oil pathway into the suction pathway and liberating gaseous refrigerant dissolved in the oil from the oil to provide cooling
Implementation Method 3
optionally using an oil cooler to further reduce discharge temperatures
Data Source
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AI summary
A working fluid circuit includes a compressor (10), an oil sump (56), and an oil injection system. The compressor compresses working fluid into a compressed working fluid. The oil injection system has an oil pathway that is connected to the oil sump and to a suction pathway of the compressor. The oil pathway injects the oil from the oil sump into the suction pathway to cool the working fluid in the suction pathway. A method of controlling a working fluid circuit includes suctioning working fluid into a compressor, compressing the working fluid, and discharging the working fluid from the compressor. The method also includes separating oil from the working fluid and supplying and injecting, via an oil pathway, the oil into a suction pathway of the compressor. Gaseous refrigerant dissolved in the oil is liberated from the oil to provide cooling to the working fluid in the suction pathway.