Can taping a cooling fan to the outside of my desktop case help cool the computer down?

Can taping a cooling fan to the outside of my desktop case help cool the computer down?
Added (1). It may sound dumb, but I don't dare to open the case yet.
Plus, I don't have any spare external cooling pads/devices I can add to the desktop case.
So until I get one, is it okay if I do just that?

My rig is not a external machine. The monitor and case and all the parts are mounted together in a display.

Lenovo Ideacentre AIO 700

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