Cryogenic Transfer Line Chilldown Using Pulse Flow and Thermal Coating
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Solution Overview
Problem
Chilldown processes for cryogenic propellant transfer in microgravity environments are inefficient due to poor heat transfer and increased propellant consumption, exacerbated by the lack of buoyancy forces, leading to prolonged chilldown times and vapor ingestion issues.
Innovation Solution
Employing low-thermal conductivity coatings on the inner surfaces of metallic pipes combined with pulse flow to enhance heat transfer efficiency, reducing propellant consumption and chilldown time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional continuous flow is used for chilldown in microgravity, then propellant transfer is maintained, but heat transfer efficiency is poor and propellant consumption is high
Solution Approach 1:
The patent implements pulse flow (periodic action) where cryogenic propellant is flowed in intermittent pulses rather than continuously. This periodic flow pattern enhances heat transfer efficiency during the pulse phases while allowing thermal equilibrium to be maintained during off-periods, thereby reducing overall propellant consumption for chilldown while maintaining effective heat transfer.
Solution Approach 2:
The patent changes the flow parameter from continuous to pulsed mode, and introduces variable duty cycles (ratio of pulse duration to total period). By adjusting these parameters, the system optimizes the balance between heat transfer effectiveness and propellant consumption, achieving superior chilldown efficiency with reduced propellant loss.
2Loss of substance
If low-thermal conductivity coating is applied to pipe inner surface, then heat transfer to propellant is reduced, but propellant consumption decreases
Solution Approach 1:
The patent applies a low-thermal-conductivity coating specifically to the inner surface of the transfer line pipe, creating a localized thermal barrier. This coating (with thermal conductivity 0.1-1.0 W/m·K) is applied only where needed to reduce heat transfer from the pipe wall to the cryogenic propellant, thereby preventing propellant boil-off and reducing consumption while maintaining acceptable overall heat transfer rates.
3Loss of substance
If pulse flow is used instead of continuous flow, then propellant consumption is reduced, but chilldown time may increase
Solution Approach 1:
The pulse flow system uses periodic flow pulses that are strategically timed and sized to achieve efficient chilldown. The intermittent nature of the pulses allows the propellant to absorb heat during flow and then maintain temperature during off-periods, achieving comparable or faster chilldown times with significantly reduced propellant consumption compared to continuous flow.
Solution Approach 2:
By optimizing pulse parameters including duty cycle, pulse duration, and flow rate, the system achieves the desired chilldown performance with reduced propellant consumption. The variable parameters allow tuning of the balance between cooling effectiveness and propellant usage, overcoming the potential time penalty.
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 combination of low-thermal conductivity coatings and pulse flow achieves up to 75% reduction in propellant consumption and significantly shortens chilldown times in microgravity conditions.
Implementation Method 1
an inner surface of the metallic pipe comprises a low thermal conductivity thin-filmed coating layer. The low conductivity thin-filmed coating layer can have a thermal conductivity in a range of 0.1 Watt per meter-Kelvin to 1.0 Watt per meter-Kelvin
Implementation Method 2
a feed system that is configured to use a pulse flow for transferring the cryogenic propellent fuel from the fuel storage tank to the nozzle of the combustion chamber
Data Source
AI summary
The enabling of in-space cryogenic engines and cryogenic fuel depots for future space exploration missions begins with development of cryogenic fluid management systems upstream in the propellant feed system. Before single-phase liquid can flow to the engine or customer spacecraft receiver tank, the connecting transfer line can be chilled down to cryogenic temperatures. In some examples, a method to quench the line is to use the cold propellant itself. When a cryogenic fluid is introduced into a warm transfer system, two-phase flow quenching ensues. Due to the projected cost of space exploration, it is desired to perform this chilldown process using the least amount of propellant. The embodiments include enhancements that reduce the amount of propellant consumed during chilldown while in a microgravity environment. Experiments were performed to examine the effects of using low thermally conductive coatings and pulse flow on the chilldown process.