Aircraft Environmental Cooling With Loop Heat Pipes and RAM-Air
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Solution Overview
Problem
Current aircraft cooling systems are inefficient, leading to high fuel consumption due to inadequate management of heat sinks, high thermal resistance, and excessive power usage, particularly during flight when significant heat rejection potential is not fully utilized.
Innovation Solution
An integrated environmental control system combining loop heat pipes, skin heat exchangers, and vapor compression cycle machines with a RAM-air subsystem, allowing for smart heat transport and sink utilization, minimizing thermal resistance and power consumption by selectively using different technologies based on operational conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If vapor compression cycle systems are used for cooling aircraft compartments, then cooling capability is provided, but fuel consumption increases due to high power demand
Solution Approach 1:
The patent combines multiple cooling technologies (vapor compression cycle systems, loop heat pipes, and skin heat exchangers) into an integrated environmental control system. This merging allows the system to utilize different cooling mechanisms simultaneously or alternatively, optimizing fuel efficiency by using passive heat rejection through skin heat exchangers when possible, and only activating the power-consuming vapor compression cycle when necessary.
Solution Approach 2:
The integrated system provides multi-functionality by enabling the aircraft to use multiple heat sinks (outside air, fuel, hydraulic fluid) and multiple cooling pathways. The system can adaptively select the most efficient cooling route based on operational conditions, making the cooling system universally applicable across different flight phases and temperature conditions while minimizing fuel consumption.
2Temperature
If cooling systems operate during all flight phases, then continuous cooling is provided, but thermal resistance between compartment and heat sink remains high
Solution Approach 1:
The patent introduces skin heat exchangers as intermediary components that facilitate heat transfer from the compartment to the outside air heat sink. These heat exchangers are integrated into the aircraft skin structure, providing a direct thermal pathway that reduces thermal resistance. The loop heat pipes also act as intermediaries, efficiently conducting heat from internal components to the skin heat exchangers.
Solution Approach 2:
The system dynamically adjusts its operation based on flight phases and thermal conditions. During cruise flight, the system utilizes the large temperature difference between inside and outside air to maximize passive heat rejection through skin heat exchangers. The system continuously monitors thermal conditions and adjusts the operation of vapor compression cycles and loop heat pipes to maintain optimal thermal resistance levels throughout the flight.
3Temperature
If vapor compression cycle machines are used despite available cool outside air, then cooling is provided, but fuel penalty increases due to inadequate heat sink management
Solution Approach 1:
The integrated environmental control system incorporates feedback mechanisms that continuously monitor outside air temperature, compartment temperature, and system operational status. This feedback allows the control system to determine when outside air is sufficiently cool to serve as an effective heat sink, and accordingly activates or deactivates the vapor compression cycle machines. The system learns from operational data to optimize the use of free cooling opportunities, reducing fuel penalty by avoiding unnecessary activation of power-consuming cooling equipment.
4Stability of the object's composition
If electronic equipment is installed in predetermined compartments, then system integration is achieved, but flexibility in utilizing heat sinks is reduced
Solution Approach 1:
The patent segments the cooling system into modular components: multiple independent loop heat pipes, distributed skin heat exchanger units, and separately controllable vapor compression cycle machines. This segmentation allows different portions of the aircraft to be cooled independently using different heat sinks. Electronic equipment can be installed in various compartments while each compartment maintains its own thermal management pathway to appropriate heat sinks, preserving both system integration and flexibility.
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 effectively reduces fuel consumption by optimizing heat management, utilizing available heat sinks, and reducing thermal resistance, thereby enhancing aircraft performance and efficiency across various flight phases.
Implementation Method 1
a loop heat pipe (LHP) heat exchange subsystem having a closed loop heat exchange fluid circuit in heat-exchange relationship with the enclosed space
Implementation Method 2
Loop heat pipes, skin heat exchangers, and vapor compression cycle machines
Implementation Method 3
skin heat exchangers... for dissipating the thermal load from the equipment to the outside air
Implementation Method 4
skin heat exchangers, and vapor compression cycle machines
Implementation Method 5
vapor compression cycle machines with a RAM-air subsystem
Implementation Method 6
vapor compression cycle machines... having a VCM fluid circuit comprising a compressor
Implementation Method 7
RAM-air subsystem having a RAM-air circuit for circulating RAM cooling air
Implementation Method 8
RAM-air subsystem... circulating RAM cooling air
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
Environmental control systems and methods to control environmental temperature of an enclosed space by integrating a passive heat exchange subsystem (e.g., a loop heat pipe (LHP) heat exchange subsystem) having a closed loop heat exchange fluid circuit in heat-exchange relationship with the enclosed space for providing environmental temperature control therewithin, a RAM-air subsystem having a RAM-air circuit for circulating RAM cooling air, and a vapor compression cycle machine (VCM) subsystem having a VCM fluid circuit having a compressor, an evaporator, a condenser and an expansion valve.