Transcritical Refrigeration Subcooling for High Ambient Efficiency
Solution Overview
Problem
Transcritical refrigeration systems face inefficiencies at high ambient temperatures, leading to increased power consumption due to the formation of flash gas when refrigerant is expanded, which is not effectively managed by existing technologies.
Innovation Solution
Incorporating a heat exchanger between the gas cooler and high pressure expansion valve to subcool the refrigerant, reducing flash gas formation and enhancing the system's coefficient of performance (COP) by utilizing a processor-controlled valve to direct refrigerant flow based on ambient temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If refrigerant is expanded directly from the gas cooler to the flash tank, then the system structure is simple, but flash gas formation increases power consumption
Solution Approach 1:
A heat exchanger is introduced as an intermediary component between the gas cooler and the flash tank. This heat exchanger enables subcooling of the refrigerant by exchanging heat between the high-pressure refrigerant from the gas cooler and the low-pressure refrigerant from the flash tank, thereby reducing flash gas formation and power consumption without significantly complicating the overall system structure
2Use of energy by moving object
If a heat exchanger is added for subcooling, then power consumption decreases, but device complexity increases
Solution Approach 1:
The heat exchanger serves multiple functions: it subcools the high-pressure refrigerant to reduce flash gas formation, pre-cools the low-pressure refrigerant before it enters the evaporator, and enables heat recovery between different parts of the system. This multi-functionality justifies the added complexity by providing multiple benefits from a single component
3Ease of operation
If refrigerant flow is not controlled at high ambient temperatures, then the system operates continuously, but COP decreases
Solution Approach 1:
A four-way valve is introduced to dynamically control the refrigerant flow direction based on ambient temperature conditions. When ambient temperature exceeds a predetermined threshold, the valve directs refrigerant flow through the heat exchanger for subcooling; otherwise, it allows direct flow. This dynamic adaptation optimizes system performance and maintains high COP under varying operating conditions
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 subcooling process reduces flash gas formation, lowers power consumption, and increases the system's COP by 9.5% at high ambient temperatures, making the refrigeration system more efficient without the need for additional compressors.
Implementation Method 1
The heat exchanger is operable to cool the refrigerant flowing from the first refrigerant inlet to the first refrigerant outlet using the refrigerant flowing from the second refrigerant inlet to the second refrigerant outlet
Implementation Method 2
The high pressure expansion valve is coupled to the flash tank and reduces a pressure of the refrigerant flowing from the heat exchanger to the flash tank
Data Source
AI summary
In certain embodiments, a transcritical refrigeration system provides refrigeration by circulating refrigerant through the system. The system includes a gas cooler, a heat exchanger, a high pressure expansion valve, a flash tank, refrigeration cases, and compressors. The gas cooler cools the refrigerant to a first temperature. The heat exchanger cools the refrigerant flowing from the gas cooler to the high pressure expansion valve to a second temperature. The high pressure expansion valve is coupled to the flash tank, which is coupled to the refrigeration cases. The refrigeration cases are coupled to the compressors, which are coupled to the gas cooler. An expansion valve between the gas cooler and the heat exchanger may cool the refrigerant flowing to the heat exchanger. A high pressure vapor compressor between the heat exchanger and the gas cooler may compress the refrigerant flowing from the heat exchanger to the gas cooler.