Fluids

Fluids

Confused about evaluating Nuavg for constant heat flux based

    • mariamsar
      Subscriber
      Hello I am trying to evaluate average Nusselt number on an isosceles triangular with a fixed heat flux from the base while the oblique walls kept with cold temperature. The triangle is filled with Cu-Water nanofluid and the reference temperature that should be used for the nanofluid is unknown, I tried evaluate Nuavg from surface integrals> Wall fluxes>surface Nusselt number with setting reference temperature as 298 but it give me minus Nuavg? is there another way to predict Nuavg? any suggestions?.
    • Karthik R
      Administrator
      What is your wall temperature? Also, what is the plot of surface heat transfer coefficient look like? nIn addition to T_ref, the Nusselt number definition uses the reference length.nThanks.nKarthikn
    • mariamsar
      Subscriber
      Many thanks for the answer. The wall is exerted to constant heat flux not temperature? I do not need local heat transfer coefficient just want the average Nusselt number at the heated wall. I used the characteristics length which represent in my case the triangle height (H) as the reference length.nThe geometry and the boundary conditions as below, as it seen the base is partially heated and I want to estimate Nuavg on the heated part of the base.nnn n
    • Karthik R
      Administrator
      The Nusselt number definition uses the local surface heat transfer coefficient, which in turn uses the wall and reference temperatures. This is why you to check these values.nThanks.nKarthikn
    • mariamsar
      Subscriber
      Thanks for the reply. May you tell me how I can estimate the wall temperature of the heated wall in Fluent? Besides how I can choose the reference temp?.Mariamn
    • Rob
      Ansys Employee
      Wall temperature can be found in the reporting functions. The reference temperature is something you need to determine for your operating conditions. The equation for the Nusselt Number is explained in the Fluent User's Guide, and you use that to guide the reference setting you'll need. n
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