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heat transfer coefficient - forced convection
Dear Gurus, please help me to solve the following problem:
TARGET: to map the convective heat transfer coefficient (H.T.C., h_cell, [W/m2 K]), without using the energy equation (the "cold" approximation I mean) using a cell by cell formulation, along the frontier of a 3D very complex geometry (many characteristic lengths, confined domain, forced convection) Velocity and pressure field are known everywhere (already computed with a RANS FVM code). Lots of velocity gradients are present inside the whole domain. The flow is incompressible with M << 0.3 and isothermal, Pr = 0.7. Someone told me to use the flat plate approximation computing for each wall cell the local Nusselt relation like this: Nu(x) = c * (Re(x)^n )* Pr^m where c, n and m are the laminar/turbulent coefficient suggested by Schlichting ("B.L. Theory" pag. 298-299) Re(x) = density * vel_cell * x / viscosity and substituting in: h(x) = k * Nu(x) / x to obtain the H.T.C., h(x). The main problem is: > what is "x" for my 3D CFD problem cell by cell based? > Is a correct approximation to choose the wall cell mean length as "x" supposing that this dimension is inside the boundary layer (x=Lmean_cell)? > What is the best choose for vel_cell? Any contribution would be really appreciated. Tes |

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