Abstract
Multi-foil insulation (MFI) is an advanced insulation technique widely recognized for its ability to achieve ultra-low thermal conductivity, particularly in vacuum environments. This research examines the thermal performance of a cylindrical MFI array, composed of reflective foils and ceramic particle spacers, under varying gas types (helium, xenon, nitrogen). The study explores the performance of the MFI array at interstitial gas pressures ranging from vacuum to 100 kPa and temperatures from 320 K to 520 K. A mathematical model was developed to accurately capture all relevant heat transfer mechanisms, including conduction through the gas, conduction through the particles, and radiation between the foils. MFI can achieve effective thermal conductivities as low as 5 × 10⁻⁴ W/m K in vacuum. At atmospheric pressure, the effective thermal conductivity closely aligns with that of the interstitial gas. The study highlights the versatility of MFI, demonstrating that by adjusting the gas type and pressure within the array, the effective thermal conductivity can be precisely tuned to meet specific insulation requirements. This makes MFI particularly advantageous for applications where space is limited and high insulation performance or variable performance insulation is crucial. The findings are consistent with existing literature and contribute a robust predictive model for optimizing MFI in various practical applications, advancing both theoretical and practical understanding. Experimental results further confirm that the effective thermal conductivity of an MFI array can be controlled by varying the interstitial gas type and pressure, achieving specific values ranging from 5 × 10⁻⁴ W/m K in vacuum to 0.3 W/m K in a helium atmosphere.
Original language | English |
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Pages (from-to) | 63-75 |
Number of pages | 13 |
Journal | Heat Transfer Research |
Volume | 56 |
Issue number | 4 |
DOIs | |
State | Published - 1 Jan 2025 |
Keywords
- controllable thermal insulation
- effective thermal conductivity
- MFI
- multi-foil
ASJC Scopus subject areas
- Condensed Matter Physics
- Mechanical Engineering
- Fluid Flow and Transfer Processes