Definition
Convection
Fluid (gas or liquid) to achieve heat transfer process through the macro flow of each of themselves. Due to the small thermal conductivity of the fluid, the heat transferred by heat transfer is small, and the convection is the main heat transfer method of the fluid. The convection can be divided into natural convection and forced convection. The temperature gradient in the fluid causes a density gradient, and if a low-density fluid is under, high-density fluid is on, natural convection will be naturally convected under gravity. Winter indoor heating is the heat transfer of natural convection, atmospheric and oceans with natural convective in the air of indoor air. It is forced convection to heat the fluid circulation.
Atmospheric convection
Atmospheric Convection
A group of air in the atmosphere is vertically rising in thermal or dynamic. Through atmospheric convection, the heat, momentum, and water vapor exchange between the atmospheric low layer and the high layer can be generated, and the water vapor coagulation caused by the flow may produce precipitation. The atmospheric convection under thermal action is mainly in the atmosphere of the lack of unstable, and the density of a group of air is less than the density of the ambient air, and the buoyancy it is greater than gravity, then in the net Aqui Mid < / B> The rising motion formed under the action of the buoyancy . A small, short-term, burst and precipitation formed by cumulus hanging clouds, often caused by the atmosphere of thermal action. Under the dynamic action, atmospheric convection is mainly an increase in the rising motion formed under the radiation or terrain of airflow. A wide range of precipitation in the atmosphere is often formed by a front and accompanying airflow horizontal radiation lifting, while precipitation produced in fixed regions near the mountain range is often caused by terrain forcing. Some special terrain (such as a flam-like terrain) The atmospheric convection of the atmospheric convection existing terrain is lifted, and there is also a terrain that irradiates the airflow level.
One aspect The thermal and dynamic action can form atmospheric convection , on the other hand, the atmospheric convection can also affect the thermal and power structure of the atmosphere, which is the feedback of the atmospheric convection. This feedback effect is particularly important in the tropics where the atmosphere is located, and the water vapor condensation of the atmospheric convection formation is often an important energy source of large-scale atmospheric movements in the region.
Troposphere
Troposphere
is located at the lowest layer of the atmosphere, a concentration of about 75% atmospheric mass and more than 90% of water quality. The lower boundary is connected to the ground, and the upper height varies with geolocation and season. The average height in the low latitude region is 17 ~ 18 kilometers, and the average in the mid-latitude region is 10 ~ 12 kilometers, and the average is 8 ~ 9 kilometers; the summer is higher than in winter.
Introduction, the temperature decreases with height, with an average of 100 meters, and the temperature is reduced by 0.65 ° C. Due to the large influence of the surface, the horizontal distribution of meteorological elements (temperature, humidity, etc.) is uneven. Air regular vertical motion and unregistered chaos are quite strong. The upper and lower layers of water, dust, and heat exchange mix. Since more than 90% of water gases are concentrated in the stream, there are many weather phenomena such as clouds, fog, rain, and snow.
The first layer from the ground from the ground to 1 to 2 kilometers is greatly affected by the ground, dry and wet, and the warmth is high, called the friction layer (or atmospheric boundary layer). The friction layer is less affected by the ground condition, called the free atmosphere. There is a transition layer between the flow layers and the atrial layer thereon, called the top of the convection layer, with a thickness of about several hundred meters to 2 kilometers. The temperature in the vicinity of the stream is mutated as the height increase, or the increase in temperature decreases with a high degree of temperature reduction, or the temperature increases with the height increase, or increases with a high increase in temperature. There is a strong blocking effect on vertical motion.
mantle convection
Mantle Convection Hypothesis
a hypothesis that explains the internal material movement and interpretation of the interior of the earth or rock ring. It believes that there is a substance of the substance in the mantle. In the heating center of the mantle, the material is dimensioned, and the rise is slowly formed to form an upflow, and the soft flow ring is turned back to reverse. After a certain distance from another phase, it will become a downward stream, which will continue again. The bottom of the rising flow is fixed, and the rising flow is added to form an annular pair of fluid. The rock ring plates that are flat with the upper part of the fluid are a large-scale slow level movement. Forming a foreign ridge in the rising flow, the down-down flowhouse causes the dive and the continental collision between the plates.
1928 British Geologist A. Homs believes that the rising flow space is cracked, forming a new ocean, and the crust is extruded into the mountain range. In 1939, D. T. Grigs proposed that due to poor thermal conductivity, the aggregation of radioclast is caused. After the establishment of sector structure in the late 1960s, mantle convection motion was generally considered to be the driving force of the plate movement.
The soft flow ring under the Earth's rock ring has 10% of the melt melt. The solid mage of the rock ring is expressed as a high temperature high pressure, and the same toughness is like viscous liquid and can generate flow. In the mantle, heat is heat-warmed due to heat, and the density is small, so that the light substance is upward, the heavy material is moved downward to reach the lowest position, which is the mantle convection, the speed is very slow, its rise stream can continue Tens of millions to hundreds of millions of years.
The anisotropy of seismic wave velocity, and the hypothetical hypothesis caused by the mantle convection caused by the convection of the transistor, and strongly supports the convection of the mantle. J. Morgan proposed a single-axis feather mantle convection mode in the 1970s. The fluid is raised from the bottom of the mantle at a few centimeters per year to form a cylindrical pair of fluids such as a shaft and a downstream flow. The crust area of the rising flow is hot.
Thermal convection
Thermally constrained stream refers to the phenomenon that the heat is transmitted through the flow medium and is propagated from a space to another. The bigger the area of the ventilation hole in the fire, the faster, the faster, the higher the position where the ventilation hole is, the faster the flow rate is faster. Thermalistic flow is an important way of thermal transmission and is the most important factor affecting the development of the initial fire. The main factors affecting heat conduction are: temperature difference, thermal conductivity and thickness and cross-sectional area of thermal conductive objects. The healing coefficient is bigger, the smaller thickness, the more the heat of the conduction is more.
(1) The process of defining or explaining heat transfer within a substance (system) is called heat transfer.
(2) Description heat transfer is achieved by heat conduction, flow and heat radiation. In the actual heat transfer process, these three methods are often accompanied by.
1 heat transfer: heat from a part of the system to another or by a system to another system called heat transfer. Thermal conduction is the main way of heat transfer in the solid. In gas or liquid, the heat transfer process tends to occur simultaneously with convection. The thermally conductive properties of various substances are different, and general metals are hotleneguardizers, glass, wood, cotton milk products, feathers, fur, and gas and gases are hot poor conductors, and the thermal conductivity of asbestos is extremely poor, often as thermal insulation materials.
2 convection: The temperature tends to be uniform through the cycle flow between the heat or gas in the liquid or gas. Convection is a unique manner of heat transfer in liquid and gas, and the convection of gas is significantly higher than liquid. The convective can be divided into two kinds of natural convection and forced convection. Natural convections are often naturally caused by uneven temperature. Forced convection is formed by the influence of the outside. Increase the flow rate of liquid or gases, and speed up the heat transfer.
3 thermal radiation: The object has the ability to emit energy outward due to its own temperature, which is called thermal radiation. The heat radiation is also a way of heat transfer, but it is different from heat transfer, convection. It can not rely on the media to pass heat directly from one system to another system. Heat radiation emits energy in the form of electromagnetic radiation, the higher the temperature, the stronger the radiation. The wavelength distribution of radiation also varies with temperature, as the temperature is low, mainly in an invisible infrared light, and at 500 ° C and higher temperatures, visible light is emitted sequentially to ultraviolet radiation. Thermal radiation is the main way of long-distance heat transfer. For example, the heat of the sun is in the form of heat radiation, and the space is passed to the earth.