Parallel Oil Return Circuit for R32 Compressor Oil Temperature Control
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Solution Overview
Problem
Refrigerating cycles using R32 refrigerant face challenges in suppressing oil temperature rises and maintaining efficient oil separation due to high discharge gas temperatures, leading to increased oil circulation rates and reduced performance, especially when compared to R410A refrigerant systems.
Innovation Solution
An oil return circuit with a parallel configuration that includes a direct return path and a cooling path, where the oil return circuit switches from direct to cooling mode based on detected discharge temperature or oil viscosity thresholds, using an oil cooler to maintain oil temperature within specified limits, preventing re-mixing with refrigerant gas and minimizing performance impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If R32 refrigerant is used instead of R410A, then environmental burden is reduced (lower GWP), but discharge gas temperature rises by 10-20°C causing oil temperature increase and viscosity decrease
Solution Approach 1:
The patent extracts the oil from the high-temperature discharge gas stream using an oil separator, separating it from the refrigerant. This allows the oil to be cooled independently in a dedicated cooling passage before returning to the compressor, preventing the oil temperature rise that would otherwise occur from direct exposure to high-temperature discharge gas.
Solution Approach 2:
The patent introduces a cooling passage as an intermediary element between the oil separator and the compressor. This cooling passage acts as a mediator that transfers heat away from the separated oil, lowering its temperature before it returns to the compressor, thus resolving the temperature issue without affecting the R32 refrigerant's environmental benefits.
2Temperature
If oil is cooled by returning it through the suction circuit where it remixes with refrigerant gas, then oil temperature is lowered, but oil separation efficiency decreases and oil circulation rate increases
Solution Approach 1:
The patent segments the oil return path into a separate dedicated cooling passage that is independent from the refrigerant circulation path. This segmentation prevents remixing of oil and refrigerant by providing separate channels: one for refrigerant flow and another for cooled oil return, thereby maintaining oil separation efficiency while still achieving oil temperature reduction.
Solution Approach 2:
The cooling passage serves as an intermediary structure that enables oil cooling without requiring the oil to travel through the suction circuit. By introducing this intermediate cooling channel, the system achieves oil temperature reduction while avoiding the harmful effect of oil-refrigerant remixing that would occur in the suction circuit approach.
3Temperature
If a direct bypass flow path is used to cool refrigerant containing oil from the oil separator, then oil temperature rise is suppressed, but the piping structure becomes complicated and expensive
Solution Approach 1:
The patent merges the oil cooling function with the existing compressor structure by incorporating cooling passages directly into the compressor housing or casing. This integration eliminates the need for separate external cooling pipes and complex bypass flow paths, as the cooling function is built-in to the compressor itself, thereby reducing piping complexity while maintaining effective oil cooling.
Solution Approach 2:
The compressor structure provides self-service cooling for the returned oil by incorporating dedicated cooling passages within its own housing. The compressor essentially cools its own lubricating oil through integrated cooling channels, eliminating the need for external cooling systems or complex piping arrangements, thus simplifying the overall system structure.
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 limits oil temperature rises in compressors, maintains efficient oil separation, and secures an allowable operating range equivalent to R410A refrigerant systems, reducing oil circulation rates and minimizing performance impacts on refrigerating cycles.
Implementation Method 1
a cooling circuit which cools oil by an oil cooler and returns the cooled oil to the oil reservoir
Implementation Method 2
an oil separator provided in a discharge circuit from the compressor
Data Source
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AI summary
The purpose of the present invention is to make it possible to minimize any increase in oil temperature within a compressor and to ensure a permissible operating range and conditions comparable to those for R410A refrigerant, even when a R32 refrigerant having a high discharge gas temperature is used, as well as to minimize any increase in the oil circulation rate and the effects on the refrigerating cycle capacity and performance. The present invention is provided with a refrigerating cycle (1) equipped with a low-pressure housing-type compressor (2) and filled with R32 refrigerant, an oil separator (3) provided to the discharge circuit (13A) of the compressor, and an oil return circuit (31) for returning the oil separated by the oil separator to an oil reservoir inside the housing of the compressor. The oil return circuit is a parallel circuit comprising a direct circuit (32) for direct return of oil to the oil reservoir in the housing, and a cooling circuit (35) for return of oil having been cooled by an oil cooler (37), and is provided with an oil temperature control unit (42) for detecting at least one parameter among the discharge temperature of the refrigerant, and the oil temperature or oil viscosity within the compressor, and when the parameter exceeds a threshold value, switching the oil return circuit from the direct circuit to the cooling circuit, and returning the oil once the oil temperature is brought to a prescribed temperature or lower.