- #MODELING NATURAL CONVECTION IN SOLIDWORKS FLOW SIMULATION PDF#
- #MODELING NATURAL CONVECTION IN SOLIDWORKS FLOW SIMULATION FREE#
Even for this simple system, any value between h\approx 2-25 W/m^2K could be an appropriate heat transfer coefficient, and it’s worth trying out the bounding cases and comparing results. This single-valued heat transfer coefficient represents an approximate and average of all of the local variations in air currents. Where the external air temperature is T ext = 25☌ and h=5 W/m^2K is the heat transfer coefficient. This is modeled using the following boundary condition for the heat flux:
#MODELING NATURAL CONVECTION IN SOLIDWORKS FLOW SIMULATION FREE#
The introductory busbar example assumes free convective heat transfer to an external airspace. The settings for a constant heat transfer coefficient. We then assume that the air temperature far away from the object is a constant, known value. On the other hand, External implies that the object is surrounded by what is essentially an infinitely large volume of air. We then assume that the thermal boundary conditions on the outside of the cavity and at the inlets and outlets are known. Internal means that there is a finite-sized cavity (such as an electrical junction box) around the part within which the air is reasonably well contained, although it might have known air inlets and outlets to an external space. We can classify the surrounding airspace into one of two categories: Internal or External. Convection can, of course, also happen in any other gas or liquid, such as water or transformer oil, but we will center this discussion primarily around convection in air. The air currents depend on the temperature variations as well as the geometry of the part and its surroundings. These free convective air currents increase the rate of heat transfer from the part to the surrounding air. As the air gets hotter, its density decreases, causing the hot air to rise relative to the cooler surrounding air. Thus, the transfer of heat to the air is via natural, or free, convection.Īs the part heats the surrounding air, the air gets hotter. The example also initially assumes that there isn’t any fan forcing air over the busbar. We assume that there is only heat transfer to the surrounding air, neglecting any conductive heat transfer through the bolts and radiative heat transfer. This leads to resistive heating, which in turn causes the temperature of the busbar to rise. In this example, we model electric current flowing through a busbar.
#MODELING NATURAL CONVECTION IN SOLIDWORKS FLOW SIMULATION PDF#
You may recognize this as an introductory example to COMSOL Multiphysics, but if you haven’t already modeled it, we encourage you to review this model by going through the Introduction to COMSOL Multiphysics PDF booklet.Įlectric currents (arrow plot) flowing through a metal busbar lead to resistive heating that raises the temperature (color surface plot). Let’s start by considering a model of the electrical heating of a busbar, shown below. Starting Simple: The Heat Transfer Coefficient Today, we will look at several different ways of modeling these types of convection in the COMSOL Multiphysics® software. The movement of the air can be either forced, via a fan, or free, as a result of the natural buoyancy variations due to changes in the air temperature.
Whenever we have a heated or cooled part exposed to air, there is some transfer of heat from the part to the air via convection.