Science and technology of the Tang dynasty
The inventor Ding Huan (fl. 180 AD) of the Han dynasty invented a rotary fan for air conditioning, with seven wheels 3 m (10 ft) in diameter and manually powered. In 747, Emperor Xuanzong had a "Cool Hall" built in the imperial palace, which the "Tang Yulin" (唐語林) describes as having water-powered fan wheels for air conditioning as well as rising jet streams of water from fountains. During the subsequent Song dynasty, written sources mentioned the air conditioning rotary fan as even more widely used.
Packaged terminal air conditioner
Although PTACs are used mostly to heat or cool a single living space using only electricity (with resistive and/or heat pump heating), there are cooling-only PTACs with external heating through a hydronic heating coil or natural gas heating. Typical PTAC heating and cooling capacity values range from 2 to 5.5 kilowatts (7,000–19,000 BTU/h) nominal. One characteristic of PTACs is that condensate drain piping is not required because the condensate water extracted from the air by the evaporator coil is drawn by the condenser fan onto the condenser coil surface where it evaporates. Conventional PTACs still require condensate drain piping to be installed. The first practical semi-portable air conditioning unit was invented by engineers at Chrysler Motors and offered for sale starting in 1935.