In air conditioning school they will teach you that heat goes to less heat, cold air is denser, and heavier than hot air, and payday is on friday. (I've been to plumbing school too, but you probably already know that line)
It is easier to move dense air thru thin than vice versa. Put the fan low and blow the cold air. And if you hang the fan off the bottom of a shelf, you might even gain a few square inches of real estate to put more stuff on.
ken