a pot-in-pot refrigerator , clay pots cooler or zeer (Arabic: ??? ?) is an evaporative cooling cooler that does not use electricity. It uses a porous outer pots vessel (coated with wet sand) containing an inner pot (which can be glazed to prevent penetration by the liquid) where food is placed. Evaporation of the outer liquid draws heat from the inner pot. This tool can be used to cool any substance, and requires only relatively dry airflow and water sources.
Video Pot-in-pot refrigerator
Histori
There is some evidence that evaporative cooling was used as early as Egypt's Old Kingdom, about 2500 BC. Frescos shows the slave fanning the water jar, which will increase the airflow around the porous jar and help evaporate, cooling its contents. This jar is even today and is called "zeer", so the pot's name is colder.
Many pottery pots are found in the Indus Valley Civilization of about 3000 BC which may be used for storing as well as cooling water similar to the present day ghara and matki used in India and Pakistan.
Although developed in North Africa, the technology seems to have been forgotten with the advent of modern electric refrigerators. However, in Subbenua India, ghara, matka and surahi, which are different types of pottery pots used to cool water. In Spain, botijos is very popular. Botijo ​​is a porous clay container used for storing and cooling water; they have been used for centuries, and are still relatively broad. Botijos is most favored by the low Mediterranean climate; locally, the cooling effect is known as the "botijo ​​effect".
In the 1890s gold miners in Australia developed the Coolgardie safes, based on the same principle.
In rural northern Nigeria in the 1990s Mohamed Bah Abba developed the Pot-in-Pot Preservation Cooling System, which consisted of small pots of pots placed inside a larger one, and a space between two filled with wet sand. The inner pot is filled with fruit, vegetables or soft drinks and covered with a damp cloth.
Abba, who comes from a family of pot manufacturers, taps into a large unemployed local workforce and hires skilled potmakers to mass-produce the first batch of 5,000 Pot-in-Pots. He received the Rolex Award for Enterprise in 2001 and used the $ 75,000 award to make this discovery available throughout Nigeria. Abba designed educational campaigns tailored to village life and illiterate populations featuring video games-record by local actors to dramatize the benefits of desert refrigerators. Pots sell at 40 US cents a pair.
After the millennium several international NGOs began working on the deployment of this technology in various African countries: Practical Actions in Sudan and the First Humanity in Gambia and the Movement e.V. in Burkina Faso.
Maps Pot-in-pot refrigerator
Construction
A zeer was constructed by placing a clay pot in a larger clay pot with wet sand between the pot and the wet cloth above.
The device cools as water evaporates, allowing cooling in hot and dry climates. It should be placed in a dry, ventilated space in order for the water to evaporate effectively outwardly. Evaporative coolants tend to perform poorly or not at all in a climate with high air humidity, because water can not evaporate well under these conditions.
If there is an impermeable separation layer between food and porous pots, water that can not be drunk like seawater can be used to encourage the cooling process, without polluting the food. This is useful in dry locations near the ocean where drinking water is a limited commodity, and can be achieved by using pots that have waterproof glazes or cement applied to the inner wall of the food stored.
Expanded operations are possible if the pots can take water from a storage container, such as an airtight bottle upside down, or if the pot is placed in a shallow water pool. The rope can be used to tie the inner pot downwards rather than using sand to prevent it from floating.
Effectiveness
The effectiveness of evaporative cooling varies with temperature, humidity and airflow. With a constant stream of cool, dry air, the inner pot can reach temperatures as low as 4.5 ° C (40 ° F), which is the temperature below which the mesophilic bacteria ("middle temperature") of the food rot bacteria significantly slows down. growth.
Impact
Pot-in-pot refrigeration has some positive effects on populations that use them beyond the simple ability to keep fresh food for longer periods and reduce the incidence of food-related diseases.
- Increased profits from food sales: Since there is no rush to sell food to avoid decay, farmers can sell their products on demand and can order higher prices.
- Increased opportunities for women: Women can sell food directly from their homes, reducing their dependence on their husbands as a single provider. Also, since girls traditionally bring food to the market for sale, and since the food in zeer remains fresh for long enough so that they can go to the market once a week rather than once a day, there is more time for them to attend school.
- Rural employment opportunities: Farmers can support themselves with their increased profits in the market, slowing the transition to cities. Also, making pots themselves produces job opportunities.
- Increased dietary variation because food is available longer in a year.
- The ability to store vaccines and medicines that should not be available in an area without cooling facilities.
A zeer cost about 150 naira (about US $ 1.00 in 2011) to be made in Nigeria, and they sell for 180-200 naira ( US $ 1.20 to US $ 1.30 in 2011).
See also
- Solar powered refrigerator
- Evaporative cooler
- Coolgardie is safe
People
- Mohammed Bah Abba
References
External links
- Media related to Egyptian Zeer on Wikimedia Commons
Bibliography
- Oluwemimo Oluwasola: Pot-in-pot Company: Refrigerator for the Poor. United Nations Development Program, New York 2011. (Online pdf)
- Peter Rinker: Der TonkrugkÃÆ'¼hler - eine angepasste KÃÆ'¼hlmÃÆ'¶glichkeit. Bau- und Nutzungsanleitung. Movement e. V., Teningen 2014. (Online article (pdf file in German/English/French is also linked))
Source of the article : Wikipedia
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