# Heat transfer coefficient - local, specfied y+, standard??

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 December 19, 2017, 15:58 Heat transfer coefficient - local, specfied y+, standard?? #1 New Member   Akanksha Rawat Join Date: Apr 2014 Posts: 29 Rep Power: 10 Hi users, I understand the difference between the types of heat transfer coefficients, but I am confused which one to use to get the realistic htc. In the standard htc we can change the reference temperature and have the corresponding value. but should i use the local htc one? or the standard is the right one to use. thanks

 December 20, 2017, 07:56 #2 Senior Member     Ashok Chaudhari Join Date: Aug 2016 Location: Pune, India Posts: 260 Rep Power: 9 Found this in one document. Hope this helps. My doubt are also cleared now. When in doubt, use y+ reference htc. The convective heat transfer coefficient (HTC) is defined as: h= q''wall/(Twall-Tfluid)  The only term not clearly specified is the fluid temperature, i.e. the fluid temperature where?  The choice of fluid temperature may be used to define different heat transfer coefficients  Some definitions may be more useful than others  For turbulent forced convection, we would like the HTC to depend on the Reynolds number, fluid properties and geometry  There may also be some sensitivity to the type of boundary condition (i.e. fixed temperature vs. constant heat flux), but the HTC should not depend on the value of the boundary condition  The above will be true only for particular choices of the fluid temperature Heat Transfer Coefficient:  Uses the computed wall heat flux, wall temperature, and a fluid temperature specified by the user  Does not account for local variations in fluid temperature Local Heat Transfer Coefficient:  Uses definitions from the wall treatment to compute a heat transfer coefficient  These definitions effectively use the near-wall fluid cell temperature  May have some sensitivity to near-wall mesh size Specified y+ Heat Transfer Coefficient:  Uses a fluid temperature at a specified y+ value  Accommodates local fluid temperature variation effects  Eliminates sensitivity to near-wall mesh size  Recommended as best practice - combines the best features of the Heat Transfer Coefficient and the Local Heat Transfer Coefficient Tobi-R, cwl, tisa and 2 others like this.

 December 21, 2017, 05:41 #3 New Member   Akanksha Rawat Join Date: Apr 2014 Posts: 29 Rep Power: 10 @ashokac7 Thank you very much it helped alot!

 Tags htc, y+ htc