The mechanical fatigue behavior of perlite insulation under cyclic thermal loading conditions is studied in this research.
Reliability of cryogenic systems depends on the ability of perlite insulation to withstand repeated temperature fluctuations.
The laboratory results show the following findings.
1. Test Protocol
Temperature range used in the study was between –196 °C and +20 °C. The test involved 1 000 full temperature cycles between cooling and heating phases.
The dwell time at each extreme point was 30 minutes.
2. Pore-Structure Evolution
Initial mean pore size was 50 µm.
The mean pore diameter decreased by –8 % after 500 cycles.
Total shrinkage reached –12 % after 1 000 cycles which indicates progressive micro-collapse.
3. Settling Behavior
The measured compaction reached 2 mm after 100 cycles.
Total settlement reached 20 mm after 1 000 cycles.
The fill grade requires periodic top-up or re-compaction procedures.
4. Long-Term
R-Value Retention The baseline R-value was measured at 0.036 W/m·K.
The R-value measurement after 1 000 cycles showed an increase to 0.038 W/m·K which represents a +5.5 % Δ.
R-value retention will exceed 95 % of its initial value when the insulation operates under cyclic conditions for one year.
The R-value stability of perlite remains above 95 % even though it experiences minor pore collapse and settling during severe cycling which makes it a suitable material for cryogenic insulation applications in dynamic thermal environments.
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