heat transfer coefficients

I'd like to know more about the heat transfer coefficients present in the material library.
I see that it depends from the surface temperature, from the temperature at infinite distane and from a geometric parameter (height for a vertical surface, area/parameter ratio for an horizontal surface, isnt't it?).
But i suppose that in reality also the surrounding conditions influence this parameter.

For example the superior face of a box suspended in the middle of a room full of air is cooled differently respect to a box placed on the floor of the same room.
Or the same face of that box can be cooled in a differant way if that box is alone, or is laterally surrounded by other identical boxes.

Since there is no way of considering those situations in the setting of the parameter h from the library, I suppose that those effects are considered secondary effects, neglected, and whose effects have to be considered in a different way if the results of the simulations are not compatible with experimental data for this reason.

But I'd like to know in which situation the library coefficient is the one exactly correct to use, and if there is a 'rule of thumb' for considering it incorrect when experimental data, or multipysics simulations including the ai flow inside the volume of air are not available.




In addition I'd like to know how I should behave when I have to consider not a single surface, but when a surface is composed by different boundaries: can i still use the library heat transfer coefficient? which geometric parameter should I consider, the one relative to the whole surface, or, for every boundary, I should use the one relative to that surface?


Thanks for the attention, I hope of being clear, if I wasn't , please ask.
Francesco