# Adjust the internal heat transfer coefficient?

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• Last Post 17 October 2017
admin posted this 27 September 2017

How can I adjust the internal heat transfer coefficient?

cbhavsar posted this 17 October 2017

Heat flux to be supplied to the external wall as a boundary condition is available through the DEFINEPROFILE macro on the fluid-side wall. The heat transfer coefficient can be defined with the DEFINEHEATFLUX macro. This macro calculates the heat flux by the following equation. qid = cid[0] + cid[1]*CT(c0,t0) - cid[2]F_T(f,t) - cid[3]pow(FT(f,t),4) qir = cir[0] + cir[1]*CT(c0,t0) - cir[2]F_T(f,t) - cir[3]pow(FT(f,t),4) qid: convective heat flux qir: radiant heat flux To specify the heat transfer coefficient, one can be set the same value for the cid [1] and cid [2] within the UDF. For example, if you want to fix the heat transfer coefficient in a wall as 10 SI units, it can be realized as the follows. DEFINEHEATFLUX(flux,f,t,c0,t0,cid,cir) { if(THREADID(t) == wallid){ /* specify boundary heat transfer coefficient */ cid[1] = 10.; cid[2] = 10.; } } wallid is the zone ID of the wall you want to fix.