Two-Stage CO₂ Refrigeration Compressor with Intermediate Cooling
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Solution Overview
Problem
Existing refrigeration systems face challenges in being constructed and operated efficiently, particularly for transport refrigeration systems using CO2 as a refrigerant, where optimizing the compression of refrigerant flows to achieve optimal pressure levels and efficient cooling is difficult.
Innovation Solution
The refrigerant compressor unit is designed with a first stage for compressing refrigerant to medium pressure and a second stage for compressing to high pressure, with the auxiliary mass flow entering the second stage, and a medium-pressure-side heat exchanger is used to cool the refrigerant before the second compression stage, allowing for efficient compression and cooling of CO2 refrigerant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-stage compressor is used to compress refrigerant from low pressure to high pressure, then the device complexity is reduced, but the mechanical loading on compressor components increases and efficiency decreases
Solution Approach 1:
The compressor is divided into two separate compression stages: a first compression stage that compresses refrigerant from low pressure to medium pressure, and a second compression stage that compresses from medium pressure to high pressure. This segmentation reduces the mechanical loading on each stage while achieving the overall compression goal, resolving the contradiction between device simplicity and power requirements.
2Device complexity
If refrigerant is compressed directly to high pressure without intermediate cooling, then the number of heat exchangers is reduced, but the compression efficiency and system performance deteriorate
Solution Approach 1:
A medium-pressure heat exchanger is introduced between the first and second compression stages to cool the refrigerant before it enters the second stage. This preliminary cooling action improves compression efficiency by reducing the temperature of the refrigerant entering the second stage, resolving the contradiction between device simplicity and compression efficiency.
3Ease of manufacture
If CO2 is used as refrigerant with traditional single-stage compression, then the system is simpler to construct, but optimal compression and cooling performance cannot be achieved
Solution Approach 1:
The compression system is segmented into two stages with an intermediate cooling phase, allowing CO2 to be compressed and cooled in controlled steps. This enables optimal compression performance for CO2 refrigerant while maintaining a relatively simple overall system construction, resolving the contradiction between ease of manufacture and cooling performance.
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 configuration enables optimal compression of both the principal and auxiliary mass flows to high pressure, effectively utilizing CO2 as a refrigerant while minimizing mechanical loading on compressor components and maintaining efficient operation.
Implementation Method 1
a first compressor stage for compressing, to a medium pressure, the refrigerant of the principal mass flow supplied at low pressure
Implementation Method 2
the first compressor stage of the refrigerant compressor unit is connected to a medium-pressure-side heat exchanger, which cools the principal mass flow that has been compressed to a medium pressure
Implementation Method 3
a second compressor stage for compressing, to a high pressure, the refrigerant of the principal mass flow that has been compressed to a medium pressure
Implementation Method 4
an expansion member, which is arranged in the refrigerant circuit following on from the high-pressure-side heat exchanger and in the active state cools the total mass flow of the refrigerant by expansion
Implementation Method 5
a high-pressure-side heat exchanger arranged in the refrigerant circuit and cooling refrigerant compressed to a high pressure
Data Source
AI summary
A refrigeration system, in particular a transport refrigeration system, comprising: a refrigerant circuit, which in particular works using CO2 as the refrigerant and in which there is guided a total mass flow of the refrigerant; a high-pressure-side heat exchanger arranged in the refrigerant circuit and cooling refrigerant compressed to a high pressure; at least one cooling stage which expands the principal mass flow from the intermediate-pressure collector to a low pressure in at least one cooling expansion member and in so doing makes refrigeration capacity available at a low-pressure-side heat exchanger; and a refrigerant compressor unit which compresses the principal mass flow from a low pressure to a high pressure, wherein the refrigerant compressor unit has a first compressor stage for compressing, to a medium pressure, the refrigerant of the principal mass flow supplied at low pressure, and a second compressor stage for compressing, to a high pressure, the refrigerant of the principal mass flow that has been compressed to a medium pressure.