Multistage CO2 Refrigeration Compression With Shared Intercooling
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Solution Overview
Problem
Conventional refrigeration apparatuses using carbon dioxide as a refrigerant face challenges in achieving high operating efficiency due to the low critical temperature of carbon dioxide, leading to high heat radiation loss and limited flexibility in adjusting refrigerant flow rates, which increases the size of the apparatus when trying to improve efficiency.
Innovation Solution
A refrigeration apparatus with a multistage compression mechanism that includes two compressors with low-pressure and high-pressure compression elements, an intercooler, and intermediate cooling pipes, allowing for increased flexibility in refrigerant flow rate adjustment and improved efficiency by reducing refrigerant temperature before it enters high-pressure compression elements, while sharing intercooling resources to minimize size and heat radiation loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single compressor is used, then the apparatus size is kept small, but the degree of freedom for adjusting refrigerant flow rate is limited
Solution Approach 1:
The compression function is segmented into multiple independent compressors (first compressor with first low-pressure and first high-pressure compression elements, second compressor with second low-pressure and second high-pressure compression elements). Each compressor can operate independently or in combination, providing multiple degrees of freedom for adjusting refrigerant flow rates without proportionally increasing apparatus size.
2Adaptability or versatility
If multiple compressors are provided to increase refrigerant flow rate adjustment flexibility, then the degree of freedom for adjusting flow rate is improved, but the apparatus size increases
Solution Approach 1:
The first and second compressors share common components including the intercooler, suction pipe, and discharge pipe. The low-pressure compression elements share a common suction side, and the high-pressure compression elements share a common discharge side. This merging of components allows multiple compressors to operate with reduced apparatus size compared to completely separate compressor systems.
3Loss of energy
If the refrigerant temperature is high after compression, then the compression work is efficient, but the heat radiation loss in the heat source side heat exchanger increases
Solution Approach 1:
The intercooler is positioned between the low-pressure compression elements and the high-pressure compression elements to pre-cool the refrigerant before it enters the high-pressure compression stage. This preliminary cooling action reduces the refrigerant temperature entering the heat source side heat exchanger, thereby reducing heat radiation loss while maintaining effective compression work.
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 solution enhances the degree of freedom in adjusting refrigerant flow rates and improves operating efficiency by reducing refrigerant temperature and heat radiation loss, maintaining a compact apparatus size, and optimizing heat exchange processes.
Implementation Method 1
an intercooler (7) which cools the refrigerant discharged from the low-pressure compression element (3c, 4c)
Implementation Method 2
a first low-pressure compression element (3c) for increasing the pressure of the refrigerant, and a first high-pressure compression element (3d) for increasing the pressure of the refrigerant more than the first low-pressure compression element
Data Source
Figure 1
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Figure 4~5
AI summary
In a refrigeration apparatus using a refrigerant that operates in a region including critical processes, there is provided a refrigeration apparatus capable of increasing the degree of freedom for adjusting the flow rate of refrigerant circulated by multistage compression-type compression elements and improving operating efficiency while suppressing an increase in the size of the apparatus. A compression mechanism (302) includes a first compressor (303) having a compression element (303c) and a compression element (303d) for further increasing the pressure of the refrigerant, and a second compressor (304) having a compression element (304c) and a second high-pressure compression element (304d) for further increasing the pressure of the refrigerant. The intercooler (7) cools refrigerant that passes therethrough. The intermediate refrigerant pipe (8) causes refrigerant discharged by the compression element (303c) and the refrigerant discharged by the compression element (304c) to pass through the intercooler (7) and be sucked into the compression element (303d) and the compression element (304d). The compression element (303c) and the compression element (304c) are connected to the intake side. The compression element (303d) and the compression element (304d) merge on the discharge side.