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:
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.