CO2 Refrigeration Cycle Layout for Dual-Mode Heat Exchanger Use
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Solution Overview
Problem
Conventional super critical refrigeration cycles using CO2 refrigerant face inefficiencies due to large pressure differences, leading to insufficient cooling, poor COP, and increased manufacturing costs, particularly because of suboptimal heat exchanger designs and complex circuit structures.
Innovation Solution
A refrigeration cycle device with a series connection of compressors, optimized heat transfer area ratios, and integral or divided heat exchanger structures, utilizing the second heat source side heat exchanger during both cooling and heating operations, and considering air speed distribution for enhanced efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the second heat source side heat exchanger is disposed in a flow path between the low pressure main compressor and the high pressure sub compressor, then the compression work is reduced and COP is improved during cooling operation, but the heat transfer area of the evaporator is decreased and refrigerant efficiency is degraded
Solution Approach 1:
The patent applies dynamic operation by switching the second heat source side heat exchanger between two functional modes: during cooling operation it serves as an intermediate cooler in the compression path, and during heating operation it serves as part of the evaporator. This dynamic reconfiguration allows the system to optimize performance for each operation mode, resolving the contradiction between compression work reduction and refrigerant efficiency maintenance.
Solution Approach 2:
The second heat source side heat exchanger is designed with multi-functionality, serving different purposes in different operation modes. In cooling mode it functions as an intermediate cooler to reduce compression work, while in heating mode it functions as an evaporator component to maintain refrigerant efficiency. This universal design allows a single component to address multiple system needs.
2Power
If the heat transfer area ratio of the first heat source side heat exchanger and the second heat source side heat exchanger is not optimized against the volume ratio of the expansion machine volume and the second compressor volume, then the expansion machine has poor recovery efficiency
Solution Approach 1:
The patent optimizes specific parameters including the heat transfer area ratio between the first and second heat source side heat exchangers, and the volume ratio of the expansion machine to the second compressor. By establishing quantitative relationships between these parameters, the system achieves optimal power recovery efficiency while maintaining manageable device complexity through standardized design ratios.
3Loss of energy
If the heat dissipation amount of the second heat source side heat exchanger is not optimized in accordance with environmental conditions, then the efficiency is not high
Solution Approach 1:
The system incorporates feedback control by detecting environmental conditions (outdoor temperature, indoor temperature, air conditioner load) and adjusting the heat dissipation amount of the second heat source side heat exchanger accordingly. This feedback mechanism allows the system to adapt to varying environmental conditions and maintain high efficiency across different operating scenarios.
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 improves refrigeration efficiency by optimizing heat transfer areas and volume ratios, simplifying circuit structures, and reducing manufacturing costs, while maintaining high efficiency across varying environmental conditions.
Implementation Method 1
optimized heat transfer area ratios
Implementation Method 2
different from the fluid of the vapor-liquid phase
Implementation Method 3
an intermediate cooler is utilized. An explanation will now be made as to a conventional example in which a second heat source side heat exchanger (second gas cooler) is used in the refrigeration cycle utilizing the second compressor driven by an expansion power recovered by an expansion machine
Data Source
AI summary
In order to provide a refrigeration cycle device that is compact and efficiently utilizing an expansion machine and reduced in manufacturing cost through the use of a first compressor and second compressor driven by an expansion machine, a heat radiator and an on-off valve are disposed between the first and the second compressors and the second heat radiator is utilized irrespective of the operating mode such as the cooling or heating operation. Also, the heat transfer area ratio, which is a ratio of the heat transfer area of the second heat source side heat exchanger relative to the total heat transfer area of the heat transfer areas of said first and second heat source side heat exchangers, is set, according to the air speed distribution, within a range at which the COP is at its peak. Thus, the second heat source side heat exchanger can be utilized even during the heating operation, providing a high efficiency refrigeration cycle device.