Adaptive trans-critical CO2 cooling system
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Solution Overview
Problem
Current aerospace cooling systems face inefficiencies and bulkiness due to limitations in ambient temperature operation, with vapor compression cycles being ineffective at high temperatures and gas-based systems being less efficient and larger in size, while trans-critical CO2 systems suffer from start-up thermal inertia.
Innovation Solution
A thermal management system incorporating a dynamic vapor cycle system, a steady-state vapor cycle system, and a thermal energy storage device, with a controller managing refrigerant flow and operating modes based on ambient conditions and thermal loads, utilizing CO2 as a refrigerant to span operating conditions and optimize system efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If vapor compression cycles are used, then system compactness is improved, but high ambient temperature operation capability deteriorates
Solution Approach 1:
The system changes the operating parameters of CO2 refrigerant by operating in trans-critical mode rather than traditional sub-critical vapor compression, allowing the system to maintain compactness while adapting to high ambient temperatures up to 47°C
Solution Approach 2:
The cooling system is designed to universally handle both high and low ambient temperature conditions by using CO2 trans-critical cycle that can adapt its operation across a wide temperature range, eliminating the need for separate systems for different temperature conditions
2Adaptability or versatility
If gas-based systems are used, then high ambient temperature operation capability is improved, but system efficiency deteriorates
Solution Approach 1:
The system changes from single-phase gas-based operation to trans-critical CO2 cycle that utilizes two-phase operation and heat of vaporization, dramatically improving thermal efficiency while maintaining high temperature operation capability
Solution Approach 2:
The system exploits phase transitions of CO2 refrigerant between liquid and vapor states during evaporation and condensation processes, utilizing the latent heat of vaporization to achieve high efficiency cooling even at elevated ambient temperatures
3Adaptability or versatility
If gas-based systems are used, then adaptability to wide ambient conditions is improved, but system size deteriorates
Solution Approach 1:
The system uses CO2 trans-critical cycle with optimized pressure and temperature parameters that allow compact component design while maintaining adaptability across wide ambient conditions from -40°C to 47°C
Solution Approach 2:
By utilizing two-phase CO2 refrigerant operation with efficient heat exchangers that leverage phase change heat transfer, the system achieves high cooling capacity in a compact form factor, eliminating the need for large duct passages required by gas-based systems
4Loss of energy
If trans-critical CO2 systems are used, then system efficiency is improved, but start-up thermal inertia deteriorates
Solution Approach 1:
The system pre-charges the CO2 refrigerant circuit and pre-heats the refrigerant before startup to minimize thermal inertia effects, enabling faster system response and reduced delays in initiating cooling operation
Solution Approach 2:
The system maintains continuous refrigerant circulation and thermal energy transfer during startup by optimizing the sequence of component activation, eliminating idle time and reducing overall start-up duration while preserving the high efficiency benefits of trans-critical operation
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 system effectively manages both dynamic and steady-state thermal loads, reducing system size and weight, improving efficiency, and addressing start-up delays through strategic refrigerant flow control and thermal energy storage.
Implementation Method 1
a thermal energy storage device... addressing start-up delays through strategic refrigerant flow control and thermal energy storage
Implementation Method 2
carbon dioxide (CO2) as a refrigerant which, when operated in trans-critical mode (i.e., spanning operation between super-critical to sub-critical)
Implementation Method 3
take advantage of the heat of vaporization of the liquid refrigerant
Data Source
AI summary
A cooling system includes a heat exchanger through which a refrigerant flows, the heat exchanger having a fluid passing therethrough such that heat is rejected to the fluid, an evaporator, a refrigerant piping split point that receives the refrigerant at a given pressure from the heat exchanger and splits the refrigerant flow into a first circuit and a second circuit, the first circuit having an expansion valve that receives the refrigerant at the given pressure, and the second circuit having a first turbine coupled to a first compressor, wherein the first turbine receives the refrigerant at the given pressure, and a set of valves arranged to direct the refrigerant through the first circuit, the second circuit, or both the first and second circuits based on ambient conditions of the cooling system.