...I´m using Floworks to simulate natural convection
heat transferon a rectangular finned surface. The heat sink is made
fromaluminum, the fluid is air, i Know the initial temperature of
airand the initial temperature of the heat sink (same as the
airtemperature). I also know the heat fluxon the lower base of
theheat sink.As indicated by Floworks help topics I check the
boxconsidering gravitational effects an started the
transientsimulation.After the simulation I´m able to get the
heat transfercoefficients on the heat sink. This is the point! How
Floworkscansolve a heat transfer problem without knowing the heat
transfercoefficient?? I tried to do the same simulation on
otherFeasoftware and some of them can not start the simulation
without agiven heat transfer coefficient...anyone knows what´s
goingon?thanksfabio
You need to keep in mind, that heat transfer in this instance is by convection. Convection is dependant on the fluid and solid, flow rate, temperature, time, etc. It is very difficult to have accurate convection properties in regular thermal analysis on anything other than a flat plate.
FloWorks actually computes the true convection properties for the heat sink by modeling what happens over time over all regions of the surface and accounting for the different fluid velocities at different areas.
If you think about how do people come up with heat transfer coefficients, it's typically through experimentation (when you get beyond simple geometry). It is done at a global level based on a generic fluid condition (stationary or moving at a specified speed) and then observiing the temperature change as a function of time in the part and air. FloWorks does the same thing, but you can look for local hotspots or cold spots on the heat sink to improve the design.
This is the significant benefit of using FloWorks on thermal problems compared to COSMOSWorks. When you need to look at heat transfer in complex geometry with convection, FloWorks is an excellent tool to use.
Hope this helps,
Ian