Whatever you do, remember that the idea is to draw hot air out rather than blow cool air in. For this to be effective you need a second opening which will allow cooler air to be drawn in as the hotter air is expelled. Cold air is heavier than hot air. So, an intake opening near the floor allowing cooler air in, and a fan near, or in, the ceiling to expel the hot air would work best.

Jack

"People generally quarrel because they cannot argue." - G. K. Chesterton