Cooling system with oil return to accumulator
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Solution Overview
Problem
Cooling systems using certain primary refrigerants like carbon dioxide face issues where oil gets stuck in low side heat exchangers, leading to compressor failure and efficiency loss, as the oil is not effectively cycled back to the compressor.
Innovation Solution
The cooling system operates in three modes: normal, oil drain, and oil return modes, where oil from low side heat exchangers is drained into vessels and then pushed back to the compressor using compressed refrigerant, ensuring efficient oil circulation and prevention of oil buildup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If certain primary refrigerants (e.g., carbon dioxide) are used in the cooling system, then the cooling system can effectively cool various spaces, but the oil gets stuck in the low side heat exchanger leading to compressor failure
Solution Approach 1:
A vessel is introduced as an intermediary component between the low side heat exchanger and the compressor. The vessel collects oil that drains from the low side heat exchanger and allows compressed refrigerant to push the oil back toward the compressor, preventing oil accumulation in the heat exchanger while maintaining cooling efficiency
Solution Approach 2:
The system operates in periodic cycles alternating between normal cooling mode and oil return mode. During normal mode, cooling operates as usual; during oil return mode, the refrigerant flow is redirected to push oil from the vessel back to the compressor, creating a periodic action that prevents oil buildup
2Reliability
If oil is allowed to drain from the low side heat exchanger to a vessel, then oil accumulation in the heat exchanger is prevented, but additional components and operational complexity are introduced
Solution Approach 1:
The vessel serves multiple functions: it acts as an oil collection reservoir, a flow distribution chamber, and a pressure equalization chamber. The same vessel that collects oil also facilitates the oil return process by allowing compressed refrigerant to push oil back to the compressor, reducing the need for additional dedicated components
Solution Approach 2:
The oil drainage and oil return functions are merged into a single integrated system using the same vessel for both purposes. The vessel combines oil collection during normal operation with oil return capability during dedicated return cycles, simplifying the overall system architecture
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 drains and returns oil to the compressor, improving the efficiency and lifespan of low side heat exchangers and compressors by maintaining proper oil circulation, thus preventing breakdowns and maintaining system performance.
Implementation Method 1
the first low side heat exchanger uses primary refrigerant from the flash tank to cool a secondary refrigerant
Implementation Method 2
directs primary refrigerant from the second compressor to the vessel. The primary refrigerant from the second compressor pushes the oil in the vessel to the oil reservoir
Data Source
AI summary
A cooling system drains oil from low side heat exchangers to vessels and then uses compressed refrigerant to push the oil in the vessels back towards a compressor. Generally, the cooling system operates in three different modes of operation: a normal mode, an oil drain mode, and an oil return mode. During the normal mode, a primary refrigerant is cycled to cool one or more secondary refrigerants. As the primary refrigerant is cycled, oil from a compressor may mix with the primary refrigerant and become stuck in a low side heat exchanger. During the oil drain mode, the oil in the low side heat exchanger is allowed to drain into a vessel. During the oil return mode, compressed refrigerant is directed to the vessel to push the oil in the vessel back towards a compressor.