How to Find Surface Temperature during Transient Conduction due to Sudden Convection

[@gabbypang]

I'm a Mechanical engineering student of IIT Bhubaneswar and i have an exam tomorrow afternoon on heat transfer you are literally saving my life right now.........i should have found your channel way earlier thanks for your work keep doing it!

[@BrianBernardEngineering]

Good luck on your test! I've got 5 more heat transfer videos coming, on convection and radiation, that should be released over the next month so hopefully they'll be ready for when you get to those next sections of the course. They'll be added to my Heat Transfer playlist when they are published, so if you bookmark that, they'll be easy to find.

[@terra2218]

Helpful video but I'm confused by the last step. When do you need to consider intersecting geometries?? I thought that the equations used in the last step only consider one dimension of heat transfer in the solid, and that you need to consider each dimension separately, at least for cylinders and cubes which are not symmetrical in all dimensions like a sphere.

[@BrianBernardEngineering]

You're right, the methods in this video are only 1 dimensional. The steak is modeled as a 1D wall, not as a cube. And the cylinder only looks at heat radiating in 1 direction, outwards from the center through the side, not through the flat ends of the cylinder. There are a lot of times where objects are large enough in 1 direction that the surface area in the 1D direction is much larger than the surface area in other directions, so those other directions can be neglected without introducing too much error. Directly - when do you need to consider intersecting geometries - when you think the amount of heat transfer through the other surfaces is large enough to be relevant. If I were to make up numbers, since there's so much error in calculating convection anyway which you'll learn later in the course when you calculate nusselt number, I probably wouldn't bother if you think the extra heat is < maybe 20% of the total? It would totally depend on the application though. If I really needed as perfectly accurate answer as possible, then I suppose I would always include every direction. But often, good enough is good enough.

[@terra2218]

Thank you for the response! Very clear :))

[@connorsimmons5779]

Why do you use 2.02 for the bessel function. Im trying other problems that require to find that value and I can't figure out where it comes from

[@connorsimmons5779]

Nvm rewatched and realized it is our zeta1 from the second biot calculation

[@BrianBernardEngineering]

Great work, glad I could help! This must be how TA Indy feels when I thank all the time when all he does is play and try to distract me.