![modeling natural convection in solidworks flow simulation modeling natural convection in solidworks flow simulation](https://i.ytimg.com/vi/bNWhaitBPqE/maxresdefault.jpg)
We need the surface temperature of the OD to calculate a more accurate h. We are assuming that the ID of the pipe remains constant at 80 C, but the OD is the surface that is transferring heat to the fluid. Once calculated, Ra is then used to determine which equation is appropriate for calculating the average Nusselt number (Nu) (because of space restrictions a complete list of variable definitions can be found in the table at the end of this blog).Įquation 4: The Nusselt Number for Long CylindersĪnd, finally, the average convection coefficient, h, can be calculated directly with Nu by rearranging Equation 4 to solve for h.īut wait! We are not quite ready to put this number into our thermal analysis. Ra for my copper pipe, where T s = 80 C, T ∞ = 20 C, and L = OD = 0.02, was calculated as Most textbooks will say that fluid properties should be looked-up and/or calculated at an average temperature (skin temperature and ambient temperature), but in my experience it is more accurate to look-up fluid properties at T ∞ (= 20 C).
![modeling natural convection in solidworks flow simulation modeling natural convection in solidworks flow simulation](https://seacadtech.com/shop/image/cache/catalog/products/solidworks-flow-simulation-software-1-650x550-650x550.jpeg)
Where v and α are the kinematic viscosity and thermal diffusivity of the fluid respectively. It is customary to quantify the boundary layer using the Rayleigh number (Ra). The first step in calculating h is to determine if the boundary layer of the fluid is laminar or turbulent, because the boundary layer is the main contributor to the effectiveness of convective heat transfer. To keep things simple, we will assume that the inner surface of the piping will remain constant at 80 C and only simulate a 200 mm section of the length since the results will remain constant in the axial direction. We will also assume the body of water is static and, therefore, the convection is defined as natural rather than forced convection. In this thermal analysis we have a long hollow copper pipe (20 mm OD and 15 mm ID) that is transporting a hot fluid (80 C) through a body of water (20 C). The convection coefficient, formally denoted by h, is what is needed for our thermal analysis in SOLIDWORKS Simulation. They both obey Fourier’s Law īut instead of using the material property, thermal conductivity, this constant depends on many variables that define the boundary layer of the fluid, which is why Equation 1: Fourier’s Law can be simplified to Equation 2: Newton’s Law of Cooling.
![modeling natural convection in solidworks flow simulation modeling natural convection in solidworks flow simulation](https://www.researchgate.net/profile/Oleg-Tashlykov/publication/337817693/figure/fig1/AS:913223310114816@1594740812325/Simulation-results-flow-trajectories-in-conditions-of-natural-convection-a-and_Q640.jpg)
In this blog I will calculate the convection coefficient of a horizontal copper pipe, simulate the temperature distributions of the pipe using a Thermal study, and verify the results using SOLIDWORKS Flow Simulation.Ĭonvection is simply conduction from a solid to a fluid. SOLIDWORKS Simulation will calculate conduction, but it is up to us to define the parameters for convection and radiation. As you may already know, there are three modes of heat transfer conduction, convection, and radiation. I have been asked a few times about calculating and applying a convection boundary condition for SOLIDWORKS Simulation Thermal analyses, because without a CFD software, like SOLIDWORKS Flow Simulation, convection must be calculated by hand.