Lowering the Surrounding Temperature with Mist (Various Places on the EXPO Sites)

Various methods are being considered so that visitors and participants can feel comfortable and a little cooler during Nagoya’s scorching summer. Many people have come to recognize that the surroundings can be made cooler by the sprinkling of water on the ground. At EXPO 2005 there are many facilities that make use of this cooling effect of water. The following is a list of facilities with devices to cool the surrounding area through the artificial emission of mist. Since mist evaporates faster than liquid water, people can feel cooler more quickly in this way. The reason why mist cools down the surrounding area is explained below.

Places at the EXPO sites where you can experience the phenomenon include the following:

(1) Global Common 5: Mist emitted around the whole building

(2) Wonder Circus-Electric Power Pavilion: Dry mist emitted in the admission-waiting area

(3) Tent section of Global Loop: Mist emitted from the poles supporting the tent; 1,824 nozzles used

(4) Mitsubishi Pavilion @Earth: Mist emitted from the green wall part of the viewing exit

(5) Bio Lung: Mist emitted around whole building together with watering of flowers

(6) Earth Tower Nagoya City: Mist emitted from vicinity of tower

(7) Deck section of Global Common 1: Mist emitted from vicinity of entrance deck

(8) Bamboo Planter Bench of Japan Plaza: Mist emitted by sprayer on top of bench

(9) Flower bed on north side of Koi Pond: Mist emitted by several sprayers in the flower bed

(10) Satsuki and Mei's House: Mist emitted from vicinity of bridge near entrance

(11) Aichi Pavilion Nagakute: Mist emitted from edge of roof in the admission-waiting area

(12) Gas Pavilion: Mist emitted from center of rooftop rest area

(13) Seto Gate: Mist emitted from garden area at side of gate

(14) NGO Global Village: Mist emitted from beneath stone at foot of statue of elephant opposite the north entrance

(15) Wind Square: Mist emitted from under slide

Please note that times and conditions for mist emission differ by facility.

Reason Why Mist Lowers the Temperature

You will have learned in elementary school or middle school that water comes in three states: solid, liquid, and gaseous. If these states do not change, the temperature rises only in accordance with the addition of heat. However, at the point in time when there is a change in state (for example, when liquid changes to gas), the temperature of the water itself does not change even when heat is added (or taken away). The heat that is taken away at this time is called the “heat of vaporization.” Mist, which is still water, takes away heat from the surrounding area and changes to vapor (an invisible gaseous state). In other words, the surrounding temperature falls in accordance with the heat that is taken away.

There is a method of experiencing this phenomenon. Hold out both hands with the palms facing upward and lick one of them. Then blow on them both. The palm that you licked feels cooler, doesn't it? The reason is that the licked water takes away heat from the hand and evaporates. When walking in a forest, you feel cool not only because the foliage blocks out the sun's rays but also because the water from the leaves on the trees is evaporating. This is absolutely the same principle.

For dry mist, provide a link to “Experience coolness by dry mist (Wonder Circus-Electric Power Pavilion)” in the “Advanced environmental technology” link.