[Shomaz ul Haq]

Dear all,

Hello. Hope all are well. I have been simulating laminar nanofluid single phase flow with constant wall heat flux in a pipe for some time now. I have achieved a high quality mesh, did a grid independence study, and have got enhancement in heat transfer based on heat transfer coefficient (h). The enhancement is more at the inlet and decreases along the pipe till the end. The weird thing is I am getting an almost exactly constant increase of just 3-4 W/(m^2.K^-1) when I increase concentration from 1% to 2% to 3% to 4% to 5%. For each % increase in concentration, the increase in h is almost constant and linear. I know it should increase more at higher concentration according to both experiments and other simulations. I have defined density, specific heat, thermal conductivity, and viscosity as a function of concentration by defining a new variable (by copying material water and changing the properties - I didn't change molar mass and thermal diffusivity though). I have defined both local and average heat transfer coefficient in CFD-Post. I would be grateful if anyone could help me out in figuring what am I doing forgetting and/or doing wrong. Somebody might have faced a similar problem. Hope to hear on this matter. Thanks.