CO2 Refrigeration Circuit With Intermediate Pressure Relief
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Solution Overview
Problem
The use of CO2 as a refrigerant in commercial refrigeration systems is hindered by the inefficient single-stage cycle process at high air temperatures and the high operating pressures required, which lead to increased material costs and complexity in designing the tubing network, as well as reduced effective volumetric refrigerating power due to transcritical operation and excessive throttling vapor.
Innovation Solution
Incorporating an intermediate relief device between the condenser and the collecting container to relieve refrigerant pressure to a range of 5 to 40 bar, allowing for a lower pressure design of the tubing network and reducing throttling vapor, thereby minimizing the dimensions of suction and liquid lines and enhancing operational efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If CO2 is used as refrigerant in a single-stage cycle process, then the refrigeration system can operate with a simple structure, but the energetic efficiency is insufficient at high air temperatures
Solution Approach 1:
The single-stage compression cycle is divided into two stages: a first compression stage producing refrigerant at 25-50 bar, and a second compression stage producing refrigerant at 70-120 bar. This segmentation allows the system to operate efficiently at high ambient temperatures while maintaining a relatively simple overall structure compared to traditional single-stage high-pressure systems.
2Reliability
If CO2 is used as refrigerant, then natural refrigerant properties are utilized, but high operating pressures up to 100 bar and above are necessary
Solution Approach 1:
The compression process is segmented into two stages with an intermediate pressure level of 25-50 bar. This reduces the peak pressure requirements compared to single-stage compression, allowing the use of CO2 while lowering the maximum operating pressure from over 100 bar to a more manageable 70-120 bar at the highest point.
Solution Approach 2:
The system changes the pressure parameters through two-stage compression, creating an intermediate pressure state that optimizes the balance between CO2 refrigerant properties and practical operating pressure requirements. The intermediate cooler operates at this intermediate pressure to facilitate heat exchange.
3Reliability
If high operating pressures are used, then CO2 refrigeration can be achieved, but material costs and tubing network complexity increase
Solution Approach 1:
The tubing network is divided into different pressure zones: a first network operating at 25-50 bar and a second network operating at 70-120 bar. This segmentation allows each section to be designed with appropriate material specifications, reducing overall material costs and simplifying the design process compared to a single high-pressure network.
Solution Approach 2:
The system changes pressure parameters across different sections of the refrigeration circuit, allowing standard materials to be used in lower-pressure sections while only requiring specialized high-pressure materials in specific areas, thereby reducing overall material costs.
4Temperature
If transcritical operation is used at high air temperatures, then cooling can be maintained, but effective volumetric refrigerating power is reduced due to excessive throttling vapor
Solution Approach 1:
An intermediate cooler is introduced before the final expansion valve to pre-cool the refrigerant and reduce the amount of throttling vapor formed. This preliminary cooling action increases the effective volumetric refrigerating power while maintaining the ability to operate at high ambient temperatures.
Solution Approach 2:
The system changes the temperature and pressure parameters through the two-stage compression and intermediate cooling process, optimizing the refrigerant state to reduce throttling vapor and increase effective refrigerating power while maintaining cooling capability at high ambient temperatures.
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 reduces the required refrigerant filling amount by up to 30%, minimizes throttling vapor, and allows for smaller line dimensions, improving the energetic efficiency and operational safety of the refrigeration circuit while reducing material costs.
Implementation Method 1
an intermediate relief device is arranged between the condenser and the collecting container, in which pressure relief of the refrigerant is effected to a pressure of 5 to 40 bar
Implementation Method 2
The refrigerant compressed in the compressor unit H then is fed via pressure line I to the afore-mentioned condenser A
Implementation Method 3
The refrigerant compressed in the compressor unit H then is fed via pressure line I to the afore-mentioned condenser A
Implementation Method 4
The thus pressure-relieved refrigerant is evaporated in the evaporators of the cold consumers F and F′ and thereby refrigerates the corresponding refrigeration furniture and storage rooms
Implementation Method 5
The thus pressure-relieved refrigerant is evaporated in the evaporators of the cold consumers F and F′ and thereby refrigerates the corresponding refrigeration furniture and storage rooms
Data Source
AI summary
The invention relates to a refrigeration circuit having a mono- or multi-component refrigerant circulating therein, said refrigeration circuit comprising, in the direction of flow, a condenser, a collecting container, a relief device connected upstream of an evaporator, an evaporator and a compressor unit with single-stage compression.According to the invention, there is an intermediate relief device (a) arranged between the condenser (1) and the collecting container (3).Furthermore, there is disclosed a method of operating a refrigeration device in which pressure relief of the refrigerant to an (intermediate) pressure of 5 to 40 bar is effected in the intermediate relief device (a) arranged between the condenser (1) and the collecting container (3).