Nanoporous Surface Layer for Cryogenic Chilldown Heat Transfer
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Solution Overview
Problem
Cryogenic fluid systems face inefficiencies during the chilldown process, characterized by lengthy chilldown times and low heat transfer rates, particularly in microgravity environments, due to conventional heat transfer technologies reaching their limits.
Innovation Solution
The implementation of a nanoporous surface layer, specifically anodized aluminum oxide on an aluminum substrate, which enhances heat transfer by creating a superhydrophilic surface with controlled pore density and distribution, optimizing boiling and quenching characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional heat transfer surfaces are used in cryogenic systems, then system simplicity is maintained, but chilldown time increases and heat transfer rates remain low
Solution Approach 1:
The patent applies porous materials by creating a nanoporous surface layer on the system component. The nanopores (10-100 nm in diameter) with controlled density (10^10-10^12 pores/cm²) enable enhanced heat transfer during chilldown by facilitating improved nucleate boiling and phase change, reducing chilldown time by approximately 20% compared to smooth surfaces.
Solution Approach 2:
The patent changes surface parameters by transforming a smooth surface into a nanoporous structure with specific pore size distributions (10-100 nm), pore densities (10^10-10^12/cm²), and surface chemistry modifications through anodization. These parameter changes optimize the surface for enhanced heat transfer coefficients and improved wetting characteristics during cryogenic operation.
2Power
If conventional heat transfer surfaces are used, then manufacturing simplicity is maintained, but heat transfer rates are insufficient during phase change
Solution Approach 1:
The nanoporous surface layer enhances heat transfer rates during phase change by providing numerous nucleation sites for bubble formation and improved liquid-vapor interface contact. The controlled pore structure increases the heat transfer coefficient by enhancing nucleate boiling, achieving higher power transfer capability.
Solution Approach 2:
The patent uses composite materials by combining the base system component material (e.g., aluminum) with anodized aluminum oxide forming a nanoporous surface layer. This composite structure integrates the bulk material properties with enhanced surface characteristics to achieve superior heat transfer performance.
3Temperature
If smooth surfaces are used in cryogenic systems, then surface uniformity is maintained, but Leidenfrost temperature and critical heat flux remain low
Solution Approach 1:
The nanoporous surface structure modifies the Leidenfrost effect by providing capillary channels that facilitate liquid penetration and enhanced contact between the cryogenic fluid and surface. This results in increased Leidenfrost temperature and higher critical heat flux values compared to smooth surfaces, as the porous structure prevents premature film formation.
Solution Approach 2:
The patent applies local quality by creating a nanoporous surface layer with specific local characteristics (pore size, density, and distribution) that are optimized for heat transfer enhancement. The surface uniformity is maintained at the macro level while the micro/nano level structure provides enhanced thermal performance through localized nucleation and phase change phenomena.
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 approach significantly reduces chilldown time by approximately 20% and enhances heat transfer rates, increasing the Leidenfrost temperature and critical heat flux, thereby improving the efficiency of cryogenic fluid systems in both terrestrial and microgravity conditions.
Implementation Method 1
heat transfer to a cryogenic fluid is accomplished via a nanoporous surface layer of a component or device
Implementation Method 2
Chilldown is the process of adjusting the system to the low temperature scale, which is usually several hundred degrees below the room temperature
Implementation Method 3
The implementation of a nanoporous surface layer, specifically anodized aluminum oxide on an aluminum substrate, which enhances heat transfer by creating a superhydrophilic surface
Implementation Method 4
optimizing boiling and quenching characteristics
Implementation Method 5
Chilldown is the process of adjusting the system to the low temperature scale, which is usually several hundred degrees below the room temperature
Implementation Method 6
increasing the Leidenfrost temperature and critical heat flux
Data Source
AI summary
Various methods and systems are provided for cryogenic heat transfer by nanoporous surfaces. In one embodiment, among others, a system includes a cryogenic fluid in a flow path of the system; and a system component in the flow path that includes a nanoporous surface layer in contact with the cryogenic fluid. In another embodiment, a method includes providing a cryogenic fluid; and initiating chilldown of a cryogenic system by directing the cryogenic fluid across a nanoporous surface layer disposed on a surface of a system component.