In the summer you would keep the upstairs windows closed , open the roof vent , and the downstairs windows , and you had convection airflow .

Household furniture must be positioned and/or elevated to allow adequate air flow underneath and between furnishings and adjacent walls.

My team and I are working on a mid 70s 150 unit apartment rehab and our hallways smell like must and old smoke due to limited/low airflow in the 4 feet wide by 200 feet long enclosed hallways.

Getting air flow is key to remove any condensation.  

Air Flow - There is a window in the room and I have been advised that an AC unit can be added to this to keep the room cool 2.

This is commonly accomplished by adding "approved" material(s), detailed in the building code, to contain air flow.

The door to the room is also louvered to allow for airflow to the mechanicals. 

Also check from both ends of the heating element to ground (the metal chassis of the dryer), some elements can break apart and short to ground that way.A "classic" dryer will have at least one regular thermostat, located somewhere in the air flow, that switches the heat off and on as the dryer runs. 

Also, for comfortable living, air flow, and ventilation, it is a good idea to have windows that can open well enough to allow stale air out and fresh air in. 

Give Ron Vital of Airflow AC and HVAC a call.