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<span><img alt="Dissertation Defense Announcement at the Cullen College of Engineering" src="https://www.egr.uh.edu/sites/www.egr.uh.edu/files/enews/2022/images/dissertation1.png"></span></div>
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<b>Analysis of Natural Convection Effects in Insulation Layers of Cryogenic Storage Tanks</b></div>
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<b>Swapnil Sharma</b></div>
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June 24, 2024; 10:30 AM - 1:00 PM (CST)<br>
Location: Chemical Engineering Conference Room</div>
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<b>Committee Chair:</b></div>
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Vemuri Balakotaiah, Ph.D.</div>
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Microsoft Teams: <a href="https://urldefense.com/v3/__https://teams.microsoft.com/l/meetup-join/19*3ameeting_ZWQyZmZkYjQtMjkyNS00ZDUwLThkNmYtMDU2NjE2NjhlZGRm*40thread.v2/0?context=*7b*22Tid*22*3a*22170bbabd-a2f0-4c90-ad4b-0e8f0f0c4259*22*2c*22Oid*22*3a*220130d748-c7de-429d-840f-e9da0b68fecc*22*7d__;JSUlJSUlJSUlJSUlJSUl!!LkSTlj0I!ChMNoJO3uj-12GSvJQp2cEJfQf5xoAKddxMZGWDjg_kfe5-yAzuXzu8ATyzKo_qCUyzEGvTDbBTBTF9NqFhnTwXeop4$" id="LPlnk" title="https://teams.microsoft.com/l/meetup-join/19%3ameeting_ZWQyZmZkYjQtMjkyNS00ZDUwLThkNmYtMDU2NjE2NjhlZGRm%40thread.v2/0?context=%7b%22Tid%22%3a%22170bbabd-a2f0-4c90-ad4b-0e8f0f0c4259%22%2c%22Oid%22%3a%220130d748-c7de-429d-840f-e9da0b68fecc%22%7d">
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<b>Committee Members:</b></div>
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T. J. Mountziaris, Ph.D. | R. Krishnamoorti, Ph.D. | B. Dindoruk, Ph.D. | M. Franchek, Ph.D.</div>
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<b>Abstract</b></div>
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Liquid hydrogen (LH2) has one of the highest gravimetric energy densities out of many options available for hydrogen storage and this makes it an attractive candidate for transportation through maritime route. The challenge is to store LH2 at 20K in vessels
of size 40k-100k m3 for extended periods of time. The state-of-the-art technology is the vacuum storage which is not scalable to the commercial size requirement. Current efforts are directed at non-vacuum based insulation, similar to that used in liquified
natural gas (LNG) storage. The non-vacuum insulation layer under large temperature difference can exhibit natural convection inside it, increasing the heat ingress. In this work, we study the natural convection in the insulation layers under different operating
conditions and tank sizes with the aim to minimize convection. In horizontal layers, the stability of the base conduction state with respect to convective perturbations is analyzed to determine the critical permeability (or Rayleigh number) for the onset of
natural convection. A temperature weighted streamfunction is utilized resulting in analytical simplifications and a model that is valid throughout the cryogenic regime. It is shown that in horizontal cryogenic insultation layers with large temperature difference
between the cold and warm boundary, convective solutions emerge by sub-critical bifurcation whereas in spherical insulation layers, the solution branches are disconnected. Furthermore, a novel dual-layer insulation design is proposed for LH2 tanks. The inner
layer is filled with hydrogen gas while the outer layer is filled with nitrogen gas that has lower thermal conductivity. The impermeable barrier separating the two layers is placed such that it is above the liquefaction temperature for nitrogen gas. Linear
stability analysis shows bi-modal neutral curves. The conduction state is stabilized by the barrier and by filling less permeable material in the inner layer. The bifurcation diagrams depict cold boundary migration towards the hot boundary due to convection
which can lead to condensation of nitrogen gas in the outer layer. The dual-layer insulation, designed below the limit point of subcritical pitchfork results in overall thinner insulation system as compared to the single layer design.</div>
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<td style="width:902px; height:129.667px"><span style="font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);"><img alt="Engineered For What's Next" src="https://www.egr.uh.edu/sites/www.egr.uh.edu/files/enews/2022/images/dissertation2.png"></span></td>
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