CO2 Refrigeration Compression Layout With Intercooling
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Solution Overview
Problem
The air-conditioning apparatus using carbon dioxide as a refrigerant faces inefficiencies 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 and reduces operating efficiency.
Innovation Solution
A refrigeration apparatus with a multistage compression mechanism, including two compressors with intercoolers, allows for increased flexibility in refrigerant flow rate adjustment and improved efficiency by cooling the refrigerant before it enters the high-pressure compression elements, reducing heat radiation loss and maintaining a compact size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single compressor is used, then the apparatus size is kept compact, but the degree of freedom for adjusting refrigerant flow rate is limited
Solution Approach 1:
The single compressor is divided into multiple compression elements (first low-pressure, first high-pressure, second low-pressure, second high-pressure compression elements) that can operate independently or in combination. This segmentation allows flexible adjustment of refrigerant flow rates by selectively activating different compression elements while maintaining a compact apparatus structure.
2Power
If the refrigerant is discharged at high temperature from the second-stage compression element, then the compression work is effective, but the heat radiation loss in the outdoor heat exchanger increases significantly
Solution Approach 1:
An intercooler is introduced to cool the refrigerant between the first-stage and second-stage compression elements. This preliminary cooling action reduces the refrigerant temperature before it enters the second-stage compression, thereby reducing the temperature difference with the cooling source in the outdoor heat exchanger and minimizing heat radiation loss while maintaining compression effectiveness.
3Productivity
If the refrigerant temperature is high after compression, then the compression process is efficient, but the temperature difference with the cooling source causes excessive heat radiation loss
Solution Approach 1:
The intercooler acts as an intermediary device between the compression elements and the outdoor heat exchanger. It provides intermediate cooling to the refrigerant, reducing the temperature difference with the cooling source and thereby reducing heat radiation loss in the outdoor heat exchanger while maintaining compression 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
The multistage compression mechanism enhances refrigerant density, reduces heat radiation loss, and improves operating efficiency while maintaining a compact size, addressing the inefficiencies associated with carbon dioxide's low critical temperature.
Implementation Method 1
an intercooler for cooling the refrigerant discharged from the low-pressure compression element
Implementation Method 2
a first low-pressure compression element for increasing the pressure of the refrigerant and a first high-pressure compression element for increasing the pressure of the refrigerant more than the first low-pressure compression element
Data Source
AI summary
A refrigeration apparatus uses a refrigerant that operates in a region including critical processes, and includes a compression mechanism having first and second compressors, a heat-source-side heat exchanger, an expansion mechanism, a utilization-side heat exchanger, an intercooler, and an intermediate refrigerant pipe. The first compressor has a first low-pressure compression element and a first high-pressure compression element to increase pressure of refrigerant more than the first low-pressure compression element. The second compressor has a second low-pressure compression element and a second high-pressure compression element to increase pressure of refrigerant more than the second low-pressure compression element. The intermediate refrigerant pipe causes refrigerant discharged by the first and second low-pressure compression elements to pass through the intercooler and be sucked into first and second high-pressure the compression elements. The intake sides of the first and second low-pressure compression elements are connected. The discharge sides of the first and second high-pressure compression elements merge.