This disambiguation page lists articles associated with the title Cool Cool Water PDF. If an internal link led you here, you may wish to change the link to point directly to the intended article. There is some evidence that evaporative cooling was used as early as the Old Kingdom of Egypt, around 2500 B. Frescos show slaves fanning water jars, which would increase air flow around the porous jars and aid evaporation, cooling the contents.
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These jars exist even today and are called « zeer », hence the name of the pot cooler. Many clay pots were discovered in Indus Valley Civilization around 3000 BC which were probably used for storing as well as cooling water similar to the present-day ghara and matki used in India and Pakistan. Despite being developed in Northern Africa, the technology appears to have been forgotten with the advent of modern electrical refrigerators. However, in the Indian Subcontinent, ghara, matka and surahi, which are different types of clay water pots are used to cool water. In the 1890s gold miners in Australia developed the Coolgardie safe, based on the same principles. In rural northern Nigeria in the 1990s Mohamed Bah Abba developed the Pot-in-Pot Preservation Cooling System, consisting of a small clay pot placed inside a larger one, and the space between the two filled with moist sand.
The inner pot is filled with fruit, vegetables or soft drinks and covered with a wet cloth. Abba, who hails from a family of potmakers, tapped into the large unemployed local workforce and hired skilled pot makers to mass-produce the first batch of 5,000 Pot-in-Pots. 75,000 award to make the invention available throughout Nigeria. After the millennium several international NGOs started to work on the dissemination of this technology in various African countries: Practical Action in Sudan and Humanity first in Gambia and Movement e. Extensive research has also been done in Mali by D-Lab in partnership with World Vegetable Center. A zeer is constructed by placing a clay pot within a larger clay pot with wet sand in between the pots and a wet cloth on top. The device cools as the water evaporates, allowing refrigeration in hot, dry climate.
It must be placed in a dry, ventilated space for the water to evaporate effectively towards the outside. Evaporative coolers tend to perform poorly or not at all in climates with high ambient humidity, since the water is not able to evaporate well under these conditions. If there is an impermeable separation layer between the food and the porous pots, undrinkable water such as seawater can be used to drive the cooling process, without contaminating the food. Extended operation is possible if the pots are able to draw water from a storage container, such as an inverted airtight jar, or if the pots are placed in a shallow pool of water. A strap can be used to tie the inner pot down instead of using sand to prevent it from floating. Alternatives to the Pot-in-Pot construction include various versions of a simple Pot-in-Dish. The same basic operating principles apply.
Detailed information on construction materials and methods can be found in the D-Lab best practices guide. Several key considerations are important for determining if an evaporative cooling device will provide effective cooling and storage. The effectiveness of evaporative cooling varies with the temperature, humidity and airflow. Documented tables show the minimum temperature that can be achieved at different starting temperatures and percent humidities.