Selection Of Closed Cooling Towers
Influence of Heat Radiation on Type Selection of Closed Cooling Tower
Thermal radiation refers to the phenomenon that an object radiates electromagnetic waves due to its temperature. One of 3 ways of heat transfer. All objects with a temperature higher than absolute zero can produce thermal radiation. The higher the temperature, the greater the total energy radiated, and the more short-wave components. The spectrum of thermal radiation is a continuous spectrum, and the wavelength coverage range can theoretically range from 0 to infin; general thermal radiation is mainly transmitted by visible light and infrared rays with longer wavelengths. Since the propagation of electromagnetic waves does not require any medium, thermal radiation is the only way to transfer heat in a vacuum. When the temperature is low, it mainly radiates with invisible infrared light. When the temperature is 300°C, the strongest wavelength of thermal radiation is in the infrared region. When the temperature of the object is above 500°C to 800°C, the strongest wavelength component in the thermal radiation is in the visible light region.
With regard to thermal radiation, there are four important laws: Kirchhoff's radiation law, Planck's radiation distribution law, Stefan-Boltzmann's law, and Wien's displacement law. These four laws are sometimes collectively referred to as the laws of thermal radiation. While an object radiates outward, it also absorbs energy radiated from other objects. The energy radiated or absorbed by an object is related to its temperature, surface area, blackness and other factors. A black body is a special radiator whose absorption ratio to all wavelengths of electromagnetic radiation is always 1. The black body does not exist under natural conditions, it is only an idealized model, but it can be artificially produced to be close to the analogue of the black body. That is, a small hole is opened on the wall of a closed cavity. After light of any wavelength enters the cavity through the small hole, it is repeatedly reflected on the inner wall of the cavity, and the chance of passing through the small hole again is extremely small, even if there is a chance Passing out, most of the energy is lost due to multiple reflections. For observers outside the cavity, the absorption ratio of the small hole to any wavelength of electromagnetic radiation is close to 1, so it can be regarded as a black body. Apply Kirchhoff's radiation law to black bodies, that is, the spectral radiance emission of black bodies.
www.gwbrefrigeration.com
