Two-Stage Heat Pump Oil Equalizing for Stable Compressor Operation
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Solution Overview
Problem
In two-stage compression refrigeration cycles, maintaining independent rotational speeds for lower and higher stage compressors is crucial for high efficiency, and ensuring uniform refrigerant oil levels between them is essential to prevent operational complications and inefficiencies.
Innovation Solution
A heat pump system with an oil equalizing mechanism that connects the lower and higher stage compressors, allowing refrigerant oil to flow between them, and a refrigerant path switching mechanism that switches between two-stage and one-stage compression operations based on temperature and pressure conditions, ensuring appropriate oil levels without stopping the compressors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If two independent compressors are connected in series for two-stage compression, then compression efficiency is improved, but maintaining uniform refrigerant oil levels between compressors becomes difficult
Solution Approach 1:
The patent merges the oil management functions of two independent compressors by introducing an oil equalizing line that connects both compressors. This allows refrigerant oil to flow freely between compressors, automatically equalizing oil levels and ensuring both compressors maintain adequate oil levels for reliable operation while benefiting from two-stage compression efficiency.
2Reliability
If refrigerant oil levels are equalized between compressors, then operational reliability is improved, but system complexity increases due to additional piping and control mechanisms
Solution Approach 1:
The oil equalizing line operates passively based on pressure and level differences between compressors. When one compressor has lower oil level, oil automatically flows from the other compressor through the equalizing line without requiring active control mechanisms, pumps, or complex instrumentation. This self-regulating approach ensures reliable oil level maintenance while minimizing system complexity.
3Loss of energy
If differential pressure between compressors is reduced during two-stage compression, then energy efficiency is improved, but refrigerant oil return becomes insufficient
Solution Approach 1:
The oil equalizing line acts as an intermediary pathway that decouples oil return from the refrigerant flow path. Instead of relying on refrigerant pressure differential to return oil (which is reduced for energy efficiency), the equalizing line provides a dedicated route for oil to flow between compressors based on oil level differences, ensuring adequate oil return even when refrigerant pressure differential is minimized for energy efficiency.
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 allows for stable and efficient operation of the heat pump system by maintaining uniform refrigerant oil levels between compressors, enabling efficient switching between two-stage and one-stage compression modes, thus ensuring continuous and high-efficiency hot water supply.
Implementation Method 1
an oil equalizing path that connects the lower stage-side compressor to the higher stage-side compressor and allows refrigerant oil to flow between the lower stage-side compressor and the higher stage-side compressor
Implementation Method 2
an expansion valve that decompresses and expands the refrigerant flowing out of the first heat exchanger
Implementation Method 3
a first heat exchanger that exchanges heat between the refrigerant compressed by the compression mechanism and an object to be subjected to heat exchange
Implementation Method 4
a first heat exchanger that exchanges heat between the refrigerant compressed by the compression mechanism and an object to be subjected to heat exchange
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3
AI summary
Provided is a two-stage compression heat pump with which the amount of refrigerant oil in the two compressors is easily kept uniform. The system is provided with: a compression mechanism (10) provided with a lower stage-side compressor (10a) and a higher stage-side compressor (10b), for compressing and discharging a refrigerant; a water-refrigerant heat exchanger (11) for heat exchange between a target to undergo heat exchange and the refrigerant compressed by the compression mechanism (10); an expansion valve (12) for decompression and expansion of the refrigerant outflowing from the water-refrigerant heat exchanger (11); a heat source-side heat exchanger (13) for heat exchange between a target to undergo heat exchange and the refrigerant decompressed and expanded by the expansion valve (12); an oil equalizing mechanism (20) connecting the lower stage-side compressor (10a) and the higher stage-side compressor (10b), through which a refrigerant oil flows; and a four-way switching valve (14) for selectively switching between a two-stage compression path in which the refrigerant flows in order to the lower stage-side compressor (10a) and the higher stage-side compressor (10b), and a one-stage compression path in which it flows either to the lower stage-side compressor (10a) or the higher stage-side compressor (10b) only.