I am planning to use the ducts as outlets to let the hot air exit the room , the flexible duct will connect the Y connector to the existing solid HVAC duct , for the intake , I will leave some of the false cieling tiles open , so that Air can flow in to the room , Air temp is around 25 C to 30 C this time of year.
Why do you think this will overheat the miners ? and what do you suggest instead ?