Temperature-Controlled ULD with Cryogenic Cooling and Stirling Power
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Solution Overview
Problem
Current Unit Load Devices (ULDs) lack temperature control, which damages perishable items during air transport, and existing temperature-controlled ULDs require inconvenient and time-consuming methods for recharging, such as replacing ice or using power sources for extended periods.
Innovation Solution
A temperature-controlled ULD system using cryogenic coolant and a heat exchanger for temperature regulation, powered by a gas turbine generator and Stirling engine, with Vacuum Insulated Panels for thermal isolation, and autonomous operation for up to 10 days, including alternative cooling methods like Direct Inject and safety features like blowout panels to prevent explosion in case of decompression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ice or dry ice is used for temperature control, then perishable items are protected from temperature damage, but the system requires frequent manual intervention for replacement and recharging
Solution Approach 1:
The system uses an autonomous temperature control mechanism with a heat exchanger, cryogenic coolant storage, and electrical heating elements that automatically maintain setpoint temperatures without manual intervention. The controller activates cooling or heating based on temperature sensor feedback, eliminating the need for frequent ice replacement or power box recharging.
Solution Approach 2:
The patent replaces manual mechanical operations (ice replacement, power box connection) with an automated electromechanical system featuring electronic temperature sensing, controller logic, and electrically actuated components that autonomously maintain temperature control throughout the shipping duration.
2Reliability
If power box connection is used for recharging, then temperature control is maintained, but the system requires 6 hours per recharge which is time-consuming
Solution Approach 1:
The system pre-charges deep cycle batteries before shipping using external power sources at the origin facility. The batteries are fully charged in advance, allowing the ULD to operate autonomously for the entire shipping duration without requiring time-consuming power box connections during transit or at intermediate stops.
Solution Approach 2:
The autonomous power system with pre-charged batteries enables the ULD to self-sustain temperature control throughout the journey without external power interventions, eliminating the 6-hour recharging wait time associated with power box connections.
3Reliability
If liquid nitrogen is stored and used during flight, then active cooling is provided, but safety risks increase due to potential decompression explosions
Solution Approach 1:
The patent incorporates a blowout panel as a safety feature that is pre-positioned to fail safely in the event of rapid decompression. This panel allows controlled rupture to prevent catastrophic explosion, providing beforehand protection against the harmful effects of pressure differential during flight.
Solution Approach 2:
The system extracts the cryogenic coolant storage and active cooling operation from the in-flight environment. Liquid nitrogen is stored and used only on the ground before shipping, and the ULD operates in passive shipping mode during flight, eliminating the decompression explosion risk while maintaining temperature control through pre-established cooling and insulation.
4Device complexity
If standard insulation is used, then the ULD structure is simple, but heat transfer from the harsh cargo area environment damages temperature control
Solution Approach 1:
The patent employs composite insulation construction combining rigid foam insulation boards with reflective insulation barriers. This multi-layer composite structure provides superior thermal resistance against the harsh cargo area temperature extremes while maintaining a manageable structural profile, significantly improving temperature control stability compared to single-material insulation.
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
Provides a reliable, efficient, and convenient temperature-controlled environment for perishable goods, maintaining setpoint temperatures from -40°C to 50°C for extended periods without the need for frequent power hookups or ice replacement, with reduced weight and cost through the use of fiberglass beams and efficient cooling/heating capabilities.
Implementation Method 1
a heat exchanger to cool the ULD payload bay
Implementation Method 2
Vacuum Insulated Panels (VIPs) thermally isolate the payload bay from the harsh, rapid, and extreme temperature changes typically experienced in airline cargo areas
Implementation Method 3
providing electrical power to a storage device by means of a gas turbine generator and a Stirling engine
Implementation Method 4
An additional source of electrical power is provided by a gas turbine generator that is powered by the exhaust from both the heat exchanger and the Stirling engine
Implementation Method 5
an electric heating element is placed in the same airflow path as the heat exchanger
Data Source
AI summary
Systems and methods are disclosed for transporting products with an airplane by controlling temperature in a payload bay using cryogenic coolant and a heat exchanger to cool the payload bay and heat from a heater; recycling exhaust from the heat exchanger to power a Stirling engine; charging a storage device with power from the Stirling engine; and housing the payload bay in an enclosure with an angled side below one or more cryogenic tanks to fit the airplane.