Are you asking about the principle of natural circulation? This is compared to forced circulation.
Take industrial boilers as an example: Most furnace structures include a steam drum (pot shell) and a chute located outside the furnace in an unheated position. The upper part of the descent is connected to the water. space at the bottom of the drum. The lower part of the descender is connected to the collector. There is a heating surface tube in the oven. The upper part of the heating surface tube is connected to the steam space in the upper part of the steam drum, and the lower part of the heating surface tube is also connected to the collector.
The principle of circulation is that after the water in the heating surface tube receives heat in the furnace during operation, especially after steam generation, the specific density average decreases, while the dspecific density of water in the unheated descending tube remains unchanged. First, the density difference causes the steam-water mixture to rise in the heating surface under water pressure from the downcomer tube to the steam space of the steam drum. flows in the downcomer channel to supplement and keep the volume of water in the tube constant, forming a drum of water vapor - ----Downcomer------Head------Pipe heating surface------ The steam drum cycle process. This cycle does not rely on an external force, but on heat. It is the principle of circulation between water and water or a mixture of water and water vapor of different specific density.
The structure of the forced circulation boiler is basically the same as that of natural circulation. It's just that a water pump is installed on the descent channel. The water pump forces the water into the downspout channel and sends it out. on the surface heatednte, and the water pump forces it to proceed. Circulation is the forced circulation of water under the action of external forces.
1. Water on earth comes from the dust of the universe. The main component of cosmic dust is silicate, which contains oxygen. As dust travels through the universe, it encounters the solar wind.
2. The solar wind is a stream of charged particles ejected from the sun. It contains high energy hydrogen ions.
3. Hydrogen ions present in dust meet oxygen ions in the solar wind.
4. Hydrogen ions and oxygen ions react chemically to form water molecules. Water molecules are adsorbed in dust pores and are not easily ionized by high-level rays when covered by dust. When dust falls to the earth, the adsorbed water molecules are also brought back there. This type of waterfalls from the sky, representing tens of tons each year.
5. Another channel: Water-rich comets or asteroids that hit Earth early also brought a lot of water resources to Earth. In fact, the water in comets and asteroids also comes from cosmic dust.
Detailed information
There are five sources of groundwater: infiltration theory, condensation theory, sedimentation theory , the theory of primary generation and the theory of endogenesis.
1. Penetration theory. It was proposed by the ancient Roman architect M.V. Pollio in the 1st century BC. Groundwater is believed to be formed by rain and snow seeping into the ground. This hypothesis was very widespread in the Middle Ages and remained dominant for a long time.
2. Condensation theory. It was proposed by the ancient Greeks in the 4th century BC. At the end ofIn the 19th century, it was strongly recommended by the Austrian engineer O. Folger. Groundwater is believed to be formed by the condensation of water vapor in the air. The fact is that groundwater formed by condensation of water vapor accounts for 10% of groundwater formation, except in arid areas. Except to a certain extent, even if there is condensation water in large wetlands, it represents only a small part of the total groundwater.
3. Sedimentation theory. This proposal was proposed in the early 20th century after people generally discovered the existence of high-temperature brines at depth. The main content of sedimentary theory is that groundwater and aquifer rocks were formed simultaneously in sedimentary basins. The ages of both are the same and this water is called sedimentary water (contemporary water).
4. Lhe theory of birth. It was proposed by the Austrian geologist E. Hughes in 1902. The nascent water is believed to come from the differentiation of magma sources. The basic signs of nascent water are high temperature and special dissolved chemical components related to magma, such as chlorine, silica, sulfur, boron, phosphorus, arsenic, etc. are large. Part of it cannot be obtained by the dissolution of sedimentary rocks.
5. Endogenous theory. Proposed by former Soviet hydrogeologist G.N. Kaminsky. It is believed that any groundwater generated before the infiltration cycle (hydrological cycle) and the sedimentation cycle (geological cycle) can be called endogenous water. This is mainly water from magma and metamorphism (the transformation and change of rocks caused by internal forces). of the earth). composition of the steam.
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