Aircraft cooling system
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Solution Overview
Problem
Current aerospace cooling systems face challenges in efficiently operating over a wide range of ambient conditions, as vapor compression cycles are limited to lower temperatures and gas-based systems are less efficient and bulkier, making them unsuitable for high ambient temperatures and varying aircraft operations.
Innovation Solution
The proposed cooling system employs a refrigerant like CO2 that can operate in trans-critical, sub-critical, and super-critical modes, using valve-controlled refrigerant flow paths and multiple expansion circuits to manage pressure and vapor quality, allowing for efficient heat rejection and absorption across varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a vapor compression cycle is used, then cooling efficiency is improved at lower temperatures, but the system cannot operate effectively at high ambient temperatures
Solution Approach 1:
The system dynamically switches between sub-critical and trans-critical operating modes based on ambient temperature conditions. The refrigerant cycle adapts its pressure-temperature relationship dynamically, operating below the critical point at lower temperatures and above the critical point at higher temperatures, thereby maintaining optimal cooling efficiency across the full operating range.
Solution Approach 2:
The system changes the operating parameters of the refrigerant cycle by transitioning between sub-critical and trans-critical modes. This involves adjusting the pressure and temperature parameters of the refrigerant to match ambient conditions, allowing the system to maintain efficient heat rejection at both low and high ambient temperatures.
2Adaptability or versatility
If a gas-based system is used, then adaptability to wide ambient conditions is improved, but system size and weight increase
Solution Approach 1:
The system uses parameter changes to transition between sub-critical and trans-critical modes, allowing a compact refrigerant-based system to adapt to wide ambient conditions without requiring the large duct passages and high mass flow rates needed by gas-based systems.
3Productivity
If a gas-based system is used, then cooling capacity is maintained across conditions, but system volume increases
Solution Approach 1:
The system utilizes phase transitions of the refrigerant in sub-critical mode (liquid-vapor transitions in the evaporator and condenser) to achieve high cooling capacity in a compact volume. The latent heat of vaporization provides efficient heat transfer, allowing the system to maintain high productivity without the large volume required by gas-based systems.
4Volume of stationary object
If vapor compression cycle is used, then compact size is achieved, but operation at high ambient temperatures becomes inefficient
Solution Approach 1:
The system dynamically adapts its operating mode based on ambient temperature. At high ambient temperatures, it transitions to trans-critical mode where the refrigerant operates above its critical point, changing the heat rejection mechanism from phase change to sensible heat transfer in a gas cooler, thereby maintaining compact size while preserving cooling efficiency.
Solution Approach 2:
The system changes the thermodynamic parameters of the refrigerant cycle by operating in trans-critical mode at high temperatures, where the refrigerant pressure exceeds the critical pressure. This parameter change allows efficient heat rejection at high ambient temperatures while maintaining the compact size characteristic of refrigerant-based systems.
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 system provides efficient cooling across a wide range of temperatures and pressures, optimizing performance by switching between sub-critical, trans-critical, and super-critical operations, thus enhancing the cooling capacity and reducing system size and weight.
Implementation Method 1
Vapor compression cycles pass a refrigerant through two-phase operation and can operate efficiently and take advantage of the thermal carrying capacity of a liquid, as opposed to a gas, as well as take advantage of the heat of vaporization of the liquid refrigerant.
Implementation Method 2
Vapor compression cycles pass a refrigerant through two-phase operation and can operate efficiently and take advantage of the thermal carrying capacity of a liquid, as opposed to a gas, as well as take advantage of the heat of vaporization of the liquid refrigerant.
Implementation Method 3
Vapor compression cycles pass a refrigerant through two-phase operation
Data Source
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AI summary
A cooling system includes a first heat exchanger (1106), an evaporator (1130) coupled to a thermal load of an aircraft. First and second cooling circuits (1100, 1112) are coupled to the heat exchanger (1106), the first and second cooling circuits (1100, 1112) selectable via a set of cooling circuit valves (1122, 1124, 1126) that are arranged to direct a refrigerant through the first circuit (1100), the second circuit (1112), or both the first and second circuits (1100, 1112) based on air passing through the first heat exchanger (1106) at ambient conditions of the aircraft, and a receiver (1134) configured to accumulate reserve refrigerant to provide flexibility in system operation as the cooling system operates in sub-critical, trans-critical, and super-critical modes of operation.