Binary refrigeration device
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Solution Overview
Problem
The two-stage refrigeration cycle system experiences performance degradation and increased costs due to inefficient energy conservation at low outdoor-air temperatures, particularly when operating at a low compression ratio, where the temperature difference between the lower-stage condensing and higher-stage evaporating temperatures leads to reduced operating efficiency and wasteful use of components.
Innovation Solution
The system employs an auxiliary radiator that functions as both an aid for the lower-stage condenser in two-stage operation and a main radiator in single-stage operation, allowing for a higher coefficient of performance (COP) selection without adding components, thus maintaining efficiency and reducing costs by switching between operation modes based on outdoor-air temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a two-stage refrigeration cycle system is used to achieve high compression ratio operation, then energy conservation efficiency is improved, but operating efficiency degrades at low compression ratio operations
Solution Approach 1:
The system dynamically switches between two-stage operation mode (for high compression ratio conditions) and single-stage operation mode (for low compression ratio conditions) based on outdoor air temperature and operating conditions. This dynamic adaptation allows the system to optimize energy conservation efficiency when needed while maintaining operating efficiency during low compression ratio operations, resolving the contradiction between these two performance aspects.
2Productivity
If an auxiliary radiator is added to enhance operating efficiency, then heat rejection capability is improved, but device complexity and costs increase
Solution Approach 1:
The auxiliary radiator is designed to serve multiple functions: it acts as a heat rejection device during two-stage operation to enhance operating efficiency, and simultaneously serves as the primary condenser during single-stage operation. This multi-functionality allows the system to improve operating efficiency without proportionally increasing device complexity, as the same component adapts to different operational roles based on system mode.
3Power
If a cascade condenser is used to couple lower-stage and higher-stage cycles, then refrigeration capability is improved, but temperature difference losses increase at low compression ratio
Solution Approach 1:
The system dynamically adjusts the refrigeration cycle configuration by switching between two-stage mode (with cascade condenser) and single-stage mode (without cascade condenser). During low compression ratio operations, the system transitions to single-stage mode, eliminating the cascade condenser from the refrigerant flow path and thereby removing the temperature difference losses associated with the cascade heat exchange, while still maintaining the refrigeration capability through the simplified single-stage cycle.
4Adaptability or versatility
If higher-stage heat exchanger is connected in parallel to lower-stage condenser for single-stage operation, then adaptability is improved, but device complexity and costs increase
Solution Approach 1:
The higher-stage heat exchanger is designed with multi-functionality: it serves as part of the cascade condenser assembly during two-stage operation, and alternatively functions as the primary condenser during single-stage operation. This universal design provides operation mode flexibility without proportionally increasing device complexity, as the same heat exchanger components adapt to different functional roles based on operational requirements.
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 enhances operating efficiency and achieves energy conservation throughout the year by optimizing compressor performance and reducing the need for additional components, thereby avoiding performance degradation and cost increases.
Implementation Method 1
an auxiliary radiator, which transfers heat between a lower-stage refrigerant and outdoor air
Implementation Method 2
a cascade condenser configured to perform heat exchange between a lower-stage condenser in the lower-stage refrigeration cycle and a higher-stage evaporator in the higher-stage refrigeration cycle
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A two-stage refrigeration cycle system includes a higher-stage compressor 21, a higher-stage condenser 22, a higher-stage expansion device 23, and a higher-stage evaporator 24 connected in a higher-stage refrigeration cycle 20 by pipes through which refrigerant circulates therein, a lower-stage compressor 11, an auxiliary radiator 15, a lower-stage condenser 12, a lower-stage expansion device 13, and a lower-stage evaporator 14 connected in a lower-stage refrigeration cycle 10 by pipes through which refrigerant circulates therein, a cascade condenser C including the higher-stage evaporator 24 and the lower-stage condenser 12 and configured to heat exchange between the refrigerant flowing in the higher-stage refrigeration cycle 20 and the refrigerant flowing in the lower-stage refrigeration cycle 10, and a controller 30 configured to switch between a two-stage operation in which both the higher-stage refrigeration cycle 20 and the lower-stage refrigeration cycle 10 operate and a single-stage operation in which the higher-stage refrigeration cycle 20 stops and the lower-stage refrigeration cycle 10 operates, so as to select one of the two-stage operation and the single-stage operation having a higher COP.