{"id":319003,"date":"2023-11-22T10:31:04","date_gmt":"2023-11-22T10:31:04","guid":{"rendered":"\/forum\/forums\/reply\/319003\/"},"modified":"2023-11-22T10:31:04","modified_gmt":"2023-11-22T10:31:04","slug":"319003","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/319003\/","title":{"rendered":"Reply To: Energy source term related with chemical reaction in UDF"},"content":{"rendered":"<p>&lt;p&gt;Chemicals have a formation energy, but also energy associated with state. In Fluent these two components are lumped together as enthalpy. That&#8217;s fine for separate models with reactions OR phase change but can be a little messier when it&#8217;s AND. So, use some caution.&nbsp;&lt;\/p&gt;&lt;p&gt;I assume your reaction is actually A = B + C + energy?&nbsp; The energy term will come from the enthalpy. However, you&#8217;re also adding and removing mass from the domain against a reference of 298.15K so will need to add and remove heat from the phases.&nbsp;&lt;\/p&gt;&lt;p&gt;Do A and C mix? Ie is the liquid a species mixture or two separate phases?&nbsp;&lt;\/p&gt;&lt;p&gt;R19.2 is around 5 years old now, and multiphase saw significant improvements in the 2019-2021 period that will make a difference. Changes since are equally useful but may be less obvious.&nbsp;&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-319003","reply","type-reply","status-publish","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t<!-- All in One SEO 4.9.10 - aioseo.com -->\n\t<meta name=\"description\" content=\"Chemicals have a formation energy, but also energy associated with state. In Fluent these two components are lumped together as enthalpy. That&#039;s fine for separate models with reactions OR phase change but can be a little messier when it&#039;s AND. So, use some caution. 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