عنوان مقاله [English]
Investigation of effective factors on water production system using land cooling
Introduction Water scarcity has been a worrying issue and one of the obstacles to economic growth of countries, despite various water supply sources such as groundwater, seas, rivers and rainfall. Today, in many parts of the world, due to the scarcity of water resources, disputes over access to water resources have crossed national borders and access to these resources has become a strategic goal in the interaction between countries. According to statistics released by the World Resources Institute in recent years, about 35 countries will face water stress in 2040, of which Iran ranks 13th. Considering the average rainfall in Iran and also considering the amount of water resources and per capita consumption in the country, Iran is considered among the countries that are at risk of lack of physical water resources. The purpose of this study was to provide safe water for domestic use and drinking water without using fresh water sources and only with the benefit of the air humidity. In fact, the goal is to provide fresh water from the humidity, especially for remote areas and villages with small populations that do not have access to water. In this method, there is no need to use fossil and electrical energy and only wind energy, air humidity and depth of the earth are the factors of its production, and so it is also economically viable. The system considered in this research reduces the air temperature and cools it until the saturation phase by blowing the outside hot air into a buried pipe underground. In this way, some part of the air moisture is separated and appeared in the form of water droplets on the pipe wall; then the obtained water is stored in a tank and used.
Materials and Methods In this research, a system was used that was partly underground and partly out of the soil. Buried sections include the copper pipes, the circuit breakers and connections, and a water tank and the sections on the ground include a cubic chamber with dimensions of 2×2 m, temperature and humidity sensors, fans, inlet air supply section, valves control levers, air conditioners, heaters and humidifiers. During the tests, the temperature and humidity inside the chamber were controlled by a microcontroller board and the effect of changes in air humidity (30, 50, 70 and 90%), air temperature (20, 30, 40 and 50 °C), inlet air flow (2.5, 5 and 7.5 m3/h , equal to the speeds of 1, 2 and 3 m/s , respectively) and the pipe effective length (2 and 4 m with a fixed diameter of 30 mm and a thickness of 1 mm) on the amount of extracted water was evaluated. The burial depth of the pipe was about 1 m and the soil temperature was measured by a sensor next to the buried pipes. The used statistical design was the split plots design in the form of completely randomized blocks and the results were analyzed and compared using SPSS software. In order to create and control different atmospheric conditions inside the chamber, it was necessary to consume electrical energy, while in the open space water can be produced from this system without the need for electrical energy.
Results and Discussion the studied factors, including the pipe length, air humidity, air temperature and air flow rate (inside the pipe), affected on the amount of produced water significantly. By increasing of the air humidity, the air flow rate, the chamber air temperature and the pipe length, the amount of produced water was increased. The air temperature of 50 °C, the air velocity in 3 m/s, the humidity of 90% and 4 m length of the copper pipe had the maximum water production in a certain period of time.
Conclusion The results of the present study show that water production from air humidity can be used as a method to produce fresh water, especially in remote and low populated areas with high air humidity that do not have access to the fresh water. Although the volume of water production by this method is not comparable with methods such as the multi-stage distillation, but it is economical and does not require any energy.