{"id":453922,"date":"2026-03-07T06:11:22","date_gmt":"2026-03-07T06:11:22","guid":{"rendered":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/fluent-outlet-temperature-does-not-increase-despite-mass-flow-inlet-in-straight\/"},"modified":"2026-03-07T06:11:22","modified_gmt":"2026-03-07T06:11:22","slug":"fluent-outlet-temperature-does-not-increase-despite-mass-flow-inlet-in-straight","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/fluent-outlet-temperature-does-not-increase-despite-mass-flow-inlet-in-straight\/","title":{"rendered":"Fluent: Outlet Temperature Does Not Increase Despite Mass Flow Inlet in Straight"},"content":{"rendered":"

<p>\"the<\/p><p data-start=”224″ data-end=”250″>Hi everyone,<\/p><p data-start=”252″ data-end=”338″>I am trying to simulate <\/strong>water flow in a straight pipe in ANSYS Fluent. My setup:<\/p><ul data-start=”340″ data-end=”641″><li data-section-id=”ooy2pq” data-start=”340″ data-end=”404″><p data-start=”342″ data-end=”404″>Straight pipe with identical inlet and outlet cross-sections<\/p><\/li>\n

<li data-section-id=”zk0p7h” data-start=”405″ data-end=”452″><p data-start=”407″ data-end=”452″>Mass Flow Inlet = 0.0083 kg\/s (30 kg\/h)<\/p><\/li>\n

<li data-section-id=”sltzir” data-start=”453″ data-end=”489″><p data-start=”455″ data-end=”489″>Pressure Outlet = 0 Pa gauge<\/p><\/li>\n

<li data-section-id=”1may2n” data-start=”490″ data-end=”535″><p data-start=”492″ data-end=”535″>Walls set with heat flux or adiabatic<\/p><\/li>\n

<li data-section-id=”1gyh1r6″ data-start=”536″ data-end=”641″><p data-start=”538″ data-end=”641″>Inlet Temperature: using an Expression to mimic a “closed-loop” temperature cycle<\/p><\/li>\n<\/ul>\n

<p data-start=”643″ data-end=”655″>The issue:<\/p><ul data-start=”656″ data-end=”951″><li data-section-id=”1jazvnc” data-start=”656″ data-end=”742″><p data-start=”658″ data-end=”742″>The fluid flows correctly, but the outlet temperature does not increase at all<\/p><\/li>\n

<li data-section-id=”1pzpqoe” data-start=”743″ data-end=”865″><p data-start=”745″ data-end=”865″>The Expression I used tries to set inlet = outlet, but it seems Fluent cannot read the outlet temperature in real-time<\/p><\/li>\n

<li data-section-id=”d2i9q” data-start=”866″ data-end=”951″><p data-start=”868″ data-end=”951″>I cannot use a UDF, and Periodic BC does not appear in the boundary type dropdown<\/p><\/li>\n

<li data-section-id=”d2i9q” data-start=”866″ data-end=”951″>I use 1000 W\/m2 for the heat flux input properties<\/li>\n<\/ul>\n

<p data-start=”953″ data-end=”968″>My questions:<\/p><\/p>\n

    <li data-section-id=”kjqyou” data-start=”969″ data-end=”1052″><p data-start=”972″ data-end=”1052″>Is it expected that Expressions alone cannot make the inlet follow the outlet?<\/p><\/li>\n

    <li data-section-id=”auumvh” data-start=”1053″ data-end=”1175″><p data-start=”1056″ data-end=”1175″>What is the best approach to create a straight pipe closed-loop thermal setup without using a UDF or Periodic BC?<\/p><\/li>\n

    <li data-section-id=”1puqmmd” data-start=”1176″ data-end=”1328″><p data-start=”1179″ data-end=”1328″>Are there any common settings for flow or boundary conditions that I might be missing, which could cause the outlet temperature to remain stagnant?<\/p><\/li>\n<\/ol>\n

    <p>Thanks in advance for your help!<\/p><\/p>\n","protected":false},"template":"","class_list":["post-453922","topic","type-topic","status-publish","hentry","topic-tag-ansys-fluent","topic-tag-fluent","topic-tag-fluid-flow","topic-tag-heat-flux"],"aioseo_notices":[],"acf":[],"custom_fields":[{"0":{"_bbp_forum_id":["27792"],"_bbp_topic_id":["453922"],"_bbp_subscription":["641045","8124"],"_bbp_author_ip":["118.99.73.154"],"_bbp_last_reply_id":["454041"],"_bbp_last_active_id":["454041"],"_bbp_last_active_time":["2026-03-10 08:24:22"],"_bbp_reply_count":["5"],"_bbp_reply_count_hidden":["0"],"_bbp_voice_count":["2"],"_bbp_engagement":["641045","8124"],"_btv_view_count":["81"],"_bbp_topic_status":["unanswered"],"_edit_lock":["1773057729:641045"]},"test":"mattindrawijayagmail-com"}],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/topics\/453922","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\/453922\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=453922"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}