Looking back over my heat transfer (for actual field applications, not homework), is it correct that for forced convection there seems to be no differentiation between a vertical hot plate and a horizontal hot plate*? Is this strictly a concern for free convection alone? Hopefully, the SD can validate that this correct. (I wager the air speed is the governing factor for forced convection, and the plate’s orientation has little or no bearing on the matter.)

*broken down further by a hot surface face up or face down.

As long as your free stream velocity is significantly higher than any buoyancy-driven flow would generate, then no, it doesn’t matter whether the plate is horizontal or vertical. If you look at the equations governing forced convection over a hot plate, I expect gravity isn’t in there.

Hereare the equations for heat transfer for free convection over a hot plate at different angles. As you can see, the heat transfer is a function of angle to the direction of gravity.

For forced convection, the heat transfer depends on the direction of the flow compared to the plate. It can get complicated if there is flow separation for particular orientations.

For field applications, the closest I can think of is solar heat collectors - and for that case, the angle does not matter. cite