{"id":296215,"date":"2023-08-02T23:47:17","date_gmt":"2023-08-02T23:47:17","guid":{"rendered":"\/forum\/?post_type=topic&#038;p=296215"},"modified":"2023-08-02T23:47:17","modified_gmt":"2023-08-02T23:47:17","slug":"temperature-spike-modeling-melting-in-phase-change-materials-pcm","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/temperature-spike-modeling-melting-in-phase-change-materials-pcm\/","title":{"rendered":"Temperature Spike Modeling Melting in Phase Change Materials (PCM)"},"content":{"rendered":"<p>I&#8217;m trying to build a basic Fluent phase change model simulating a block of paraffin wax with an aluminum casing inside of a duct with hot air blowing over it at 5 m\/s at 350 K. When I run my model, after some time I see a sudden spike\/drop in temperature that causes the PCM to jump to fully melted instantly. <span style=\"font-size: 18.6667px\">The PCM is initialized to 288 K, right below the solidus temperature (I tried varying the temperature to be more subcooled, but still had the same issue).<\/span><\/p>\n<p>I read through the forum thread here to see if I had any similar issues, but it appeared they solved the same issue by switching to the adaptive time control &#8211; CFL based. However, that is the method I&#8217;ve been using since I started. \/forum\/forums\/topic\/convergence-issue-in-pcm-simulation-fluent\/<\/p>\n<p>I checked my CFL number originally and it was 0.31 (@ a time step of 0.1 sec), I then looked at varying my time step to get the CFL number closer to ~1 and still had the same issue. I then looked at refining my mesh to be much more fine at the original 0.1 sec time step, bringing my CFL closer to ~1, but still had the same issue at roughly the same point. This leads me to believe that my material definition for the PCM may not be correct.<\/p>\n<p>Looking at the time step in the transient simulation right before the error, here is what I noticed:<\/p>\n<ul>\n<li>Volume average mass fraction: 0.2<\/li>\n<li>Volume average temperature: 290.52 K<\/li>\n<li>PCM center point temperature 290.15 K (right at solidus temperature, theoretically in the mushy zone)<\/li>\n<li>Max mass fraction is 0.68 right in the hot corners (temperature at this location is 308.8 K, much higher than liquidis temperature of 292.15 K)<\/li>\n<\/ul>\n<p>Is anything that I&#8217;m attempting that is glaringly incorrect? Here is the background on my simulation.<\/p>\n<p>Material properties of paraffin:<\/p>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/02-08-2023-1691019576-mceclip3.png\"><\/p>\n<p>Side walls of duct hidden, PCM block with air flow around it:<\/p>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/02-08-2023-1691019265-mceclip0.png\"><\/p>\n<p>YZ plane view of mass fraction in time step right before error (0.68 mass fraction in the corners, 0 in the center)<\/p>\n<p><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/02-08-2023-1691019311-mceclip1.png\"><\/p>\n<p>Liquid fraction, PCM temperature, average air flow velocity over simulation time, and residuals:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/02-08-2023-1691019407-blobid0.png\" width=\"656\" height=\"432\"><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/02-08-2023-1691019407-blobid1.png\" width=\"649\" height=\"420\"><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/02-08-2023-1691019407-blobid2.png\" width=\"644\" height=\"422\"><img decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/02-08-2023-1691019422-mceclip2.png\"><\/p>\n<p>Simulation controls and material properties for PCM:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/02-08-2023-1691019484-blobid3.png\" width=\"300\" height=\"634\"><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/02-08-2023-1691019485-blobid4.png\" width=\"668\" height=\"565\"><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/02-08-2023-1691019485-blobid5.png\" width=\"581\" height=\"560\"><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/02-08-2023-1691019484-blobid6.png\" width=\"580\" height=\"558\"><img loading=\"lazy\" decoding=\"async\" src=\"\/forum\/wp-content\/uploads\/sites\/2\/2023\/08\/02-08-2023-1691019484-blobid7.png\" width=\"304\" height=\"522\"><\/p>\n<p>(Energy is also Second Order Upwind)<\/p>\n","protected":false},"template":"","class_list":["post-296215","topic","type-topic","status-closed","hentry","topic-tag-conjugate-heat-transfer","topic-tag-melting-simulation-1","topic-tag-pcm"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_author_ip":["23.33.28.199"],"_bbp_subscription":["17059","852"],"_btv_view_count":["1377"],"_bbp_topic_status":["unanswered"],"_bbp_status":["publish"],"_bbp_topic_id":["296215"],"_bbp_forum_id":["27792"],"_bbp_engagement":["852","17059"],"_bbp_voice_count":["2"],"_bbp_reply_count":["2"],"_bbp_last_reply_id":["301223"],"_bbp_last_active_id":["301223"],"_bbp_last_active_time":["2023-08-13 14:24:15"]},"test":"kpmiller1crimson-ua-edu"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/296215","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/topic"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/296215\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=296215"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}