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- Title
Theoretical investigation of heat transfer in structurally graded silica aerogels with pores diameter changing.
- Authors
Noroozi, Mina; Panahi-Sarmad, Mahyar; Bahramian, Ahmad Reza; Sharif, Alireza
- Abstract
In graded structure aerogels, change of pores diameter through the thickness affects the effective thermal conductivity as the most important parameter. As the diameter of the pores is reversely correlated to the density, the effective thermal conductivity (λeff) of aerogel is often normalized to the apparent density (ρ) and it is expressed as the B (λeffρ) parameter. Lower values of B would be the optimum conditions for the insulation performance of resulting aerogel. The objective of this work is to simulate the heat transfer of the optimum structure and to compare it with functionally graded structures that pore diameter varies through the thickness. For this purpose, the structural characteristics and properties of silica aerogel along with the effect of coupling thermal conductivity have to be taken into consideration. The heat transfer and time-temperature history diagram were modeled for an optimum structure (OPT) having a minimum value of the B parameter. The results were compared to the structurally graded aerogels in which the density was varied in two fashions, from higher to lower values (HtL) density and from lower to higher values (LtH) density. The change of temperature with time was tracked for all the cases. Results indicated that the minimum value of heat transfer was obtained for the structurally graded aerogel of the type of LtH (2% increase in efficiency for LtH compared to OPT). Therefore, this structure introduces as the best candidate for producing a thermal insulator.
- Subjects
HEAT transfer; AEROGELS; THERMAL conductivity; TEMPERATURE measurements; PARAMETER estimation
- Publication
Journal of Thermal Analysis & Calorimetry, 2019, Vol 135, Issue 3, p1713
- ISSN
1388-6150
- Publication type
Article
- DOI
10.1007/s10973-018-7315-7