# UDF to specify heat transfer coefficient

 Register Blogs Members List Search Today's Posts Mark Forums Read

 April 5, 2007, 08:31 UDF to specify heat transfer coefficient #1 jonglee Guest   Posts: n/a Dear users and experts, i am currently modeling combustion flow in small tubes. Would like to use a correlation to specify the heat transfer coefficient at the external wall. For nature convection over vertical cylinder, we have h=1.42[(T-T0)/L]^0.25, T is the average temperature, L is the length of the tube. My idea is very simple, firstly, sum up all the temperature on all faces on the wall. then devided by the number of faces. Following is my UDF code #include "udf.h" DEFINE_PROFILE(HTC, thread, index) { face_t f; real T = 0.0; int n = F_NNODES(f, thread)-1; /* Count of faces */ begin_f_loop(f, thread) /* loops over all faces in the thread passed in the DEFINE macro argument */ { T = F_T(f, thread)+T; /* summation of temperature over all faces */ } end_f_loop(f, thread) F_PROFILE(f, thread, index) = 1.42*(T/n-293.0)^0.25/(27E-3)^0.25; /* 293.0 is the ambient temperature and 27E-3 is the length */ } However this code cannot be interpreted in FLUENT. The error message is "syntax error", which really confused me a lot. I am looking forward to your reply and help. Thanks so much in advance.

 April 5, 2007, 12:40 Re: UDF to specify heat transfer coefficient #2 Andrea Guest   Posts: n/a Hi jonglee, try this in your UDF F_PROFILE(f, thread, index) = pow(1.42*(T/n-293.0),0.25)/pow((27E-3),0.25); I hope it helps andrea

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Alberto Schroth FLUENT 12 January 16, 2014 04:40 Shankar Fluent UDF and Scheme Programming 9 February 18, 2013 10:13 John CFX 3 April 4, 2012 17:50 enigma Main CFD Forum 2 November 1, 2009 23:53 ravi FLUENT 0 July 10, 2004 01:11

All times are GMT -4. The time now is 13:13.