A heat sink is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium air or a liquid coolant, where it is dissipated away from the device, thereby allowing regulation of the device's temperature at optimal levels. In computers, heat sinks are used to cool central graphics processors. Heat sinks are used with high-power semiconductor devices such as power transistors and optoelectronics such as lasers and light emitting diodes, where the heat dissipation ability of the component itself is insufficient to moderate its temperature. A heat sink is designed to maximize its surface area in contact with the cooling medium surrounding it, such as the air. Air velocity, choice of material, protrusion design and surface treatment are factors that affect the performance of a heat sink. Heat sink attachment methods and thermal interface materials affect the die temperature of the integrated circuit. Thermal adhesive or thermal grease improve the heat sink's performance by filling air gaps between the heat sink and the heat spreader on the device.
A heat sink is made out of copper or aluminium. Copper is used because it has many desirable properties for thermally efficient and durable heat exchangers. First and foremost, copper is an excellent conductor of heat; this means. Aluminium heat sinks are used as a low-cost, lightweight alternative to copper heat sinks, have a lower thermal conductivity than copper. A heat sink transfers thermal energy from a higher temperature device to a lower temperature fluid medium; the fluid medium is air, but can be water, refrigerants or oil. If the fluid medium is water, the heat sink is called a cold plate. In thermodynamics a heat sink is a heat reservoir that can absorb an arbitrary amount of heat without changing temperature. Practical heat sinks for electronic devices must have a temperature higher than the surroundings to transfer heat by convection and conduction; the power supplies of electronics are not 100% efficient, so extra heat is produced that may be detrimental to the function of the device.
As such, a heat sink is included in the design to disperse heat. To understand the principle of a heat sink, consider Fourier's law of heat conduction. Fourier's law of heat conduction, simplified to a one-dimensional form in the x-direction, shows that when there is a temperature gradient in a body, heat will be transferred from the higher temperature region to the lower temperature region; the rate at which heat is transferred by conduction, q k, is proportional to the product of the temperature gradient and the cross-sectional area through which heat is transferred. Q k = − k A d T d x Consider a heat sink in a duct, it is assumed. Applying the conservation of energy, for steady-state conditions, Newton’s law of cooling to the temperature nodes shown in the diagram gives the following set of equations: Q ˙ = m ˙ c p, i n Q ˙ = T h s − T a i r, a v R h s where T a i r, a v = T a i r, i n + T a i r, o u t 2 Using the mean air temperature is an assumption, valid for short heat sinks; when compact heat exchangers are calculated, the logarithmic mean air temperature is used.
M ˙ is the air mass flow rate in kg/s. The above equations show that When the air flow through the heat sink decreases, this results in an increase in the average air temperature; this in turn increases the heat sink base temperature. And additionally, the thermal resistance of the heat sink will increase; the net result is a higher heat sink base temperature. The increase in heat sink thermal resistance with decrease in flow rate will be shown in this article; the inlet air temperature relates with the heat sink base temperature. For example, if there is recirculation of air in a product, the inlet air temperature is not the ambient air temperature; the inlet air temperature of the heat sink is therefore higher, which results in a higher heat sink base temperature. If there is no air flow around the heat sink, energy cannot be transferred. A heat sink is not a device with the "magical ability
Mechanical biological treatment
A mechanical biological treatment system is a type of waste processing facility that combines a sorting facility with a form of biological treatment such as composting or anaerobic digestion. MBT plants are designed to process mixed household waste as well as commercial and industrial wastes; the terms mechanical biological treatment or mechanical biological pre-treatment relate to a group of solid waste treatment systems. These systems enable the recovery of materials contained within the mixed waste and facilitate the stabilisation of the biodegradable component of the material; the sorting component of the plants resemble a materials recovery facility. This component is either configured to recover the individual elements of the waste or produce a refuse-derived fuel that can be used for the generation of power; the components of the mixed waste stream that can be recovered include: Ferrous metal Non-ferrous metal Plastic Glass MBT is sometimes termed biological mechanical treatment, however this refers to the order of processing.
MBT should not be confused with mechanical heat treatment. The "mechanical" element is an automated mechanical sorting stage; this processes them. It involves factory style conveyors, industrial magnets, eddy current separators, trommels and other tailor made systems, or the sorting is done manually at hand picking stations; the mechanical element has a number of similarities to a materials recovery facility. Some systems integrate a wet MRF to separate by density and flotation and to recover and wash the recyclable elements of the waste in a form that can be sent for recycling. MBT can alternatively process the waste to produce a high calorific fuel termed refuse derived fuel. RDF can be used in cement kilns or thermal combustion power plants and is made up from plastics and biodegradable organic waste. Systems which are configured to produce RDF include the Ecodeco processes, it is a common misconception that all MBT processes produce RDF. The "biological" element refers to either: Anaerobic digestion Composting BiodryingAnaerobic digestion harnesses anaerobic microorganisms to break down the biodegradable component of the waste to produce biogas and soil improver.
The biogas can be used to generate heat. Biological can refer to a composting stage. Here the organic component is broken down by occurring aerobic microorganisms, they breakdown the waste into carbon compost. There is no green energy produced by systems employing only composting treatment for the biodegradable waste. In the case of biodrying, the waste material undergoes a period of rapid heating through the action of aerobic microbes. During this partial composting stage the heat generated by the microbes result in rapid drying of the waste; these systems are configured to produce a refuse-derived fuel where a dry, light material is advantageous for transport and combustion. Some systems incorporate both anaerobic composting; this may either take the form of a full anaerobic digestion phase, followed by the maturation of the digestate. Alternatively a partial anaerobic digestion phase can be induced on water, percolated through the raw waste, dissolving the available sugars, with the remaining material being sent to a windrow composting facility.
By processing the biodegradable waste either by anaerobic digestion or by composting MBT technologies help to reduce the contribution of greenhouse gases to global warming. Usable wastes for this system: Municipal solid waste Commercial and industrial waste Sewage sludgePossible products of this system: Renewable fuel leading to renewable power Recovered recycable materials such as metals, plastics, glass etc. Digestate - an organic fertiliser and soil improver Carbon credits – additional revenues High calorific fraction refuse derived fuel - renewable fuel content dependent upon biological component Residual unusable materials prepared for their final safe treatment and/or landfillFurther advantages: Small fraction of inert residual waste Reduction of the waste volume to be deposited to at least a half, thus the lifetime of the landfill is at least twice as long as Utilisation of the leachate in the process Landfill gas not problematic as biological component of waste has been stabilised Daily covering of landfill not necessary MBT systems can form an integral part of a region's waste treatment infrastructure.
These systems are integrated with kerbside collection schemes. In the event that a refuse-derived fuel is produced as a by-product a combustion facility would be required; this could either be a gasifier. Alternatively MBT solutions can diminish the need for home separation and kerbside collection of recyclable elements of waste; this gives the ability of local authorities and councils to reduce the use of waste vehicles on the roads and keep recycling rates high. Friends of the Earth suggests that the best environmental route for residual waste is to firstly maximise removal of remaining recyclable materials from the waste stream; the amount of waste remaining should be composted or anaerobically digested and disposed of to landfill, unless sufficiently clean to be used as compost. A report by Eunomia undertook a detailed analysis of the climate impacts of different residual waste technologi
A ceramic is a solid material comprising an inorganic compound of metal, non-metal or metalloid atoms held in ionic and covalent bonds. Common examples are earthenware and brick; the crystallinity of ceramic materials ranges from oriented to semi-crystalline and completely amorphous. Most fired ceramics are either vitrified or semi-vitrified as is the case with earthenware and porcelain. Varying crystallinity and electron composition in the ionic and covalent bonds cause most ceramic materials to be good thermal and electrical insulators. With such a large range of possible options for the composition/structure of a ceramic, the breadth of the subject is vast, identifiable attributes are difficult to specify for the group as a whole. General properties such as high melting temperature, high hardness, poor conductivity, high moduli of elasticity, chemical resistance and low ductility are the norm, with known exceptions to each of these rules. Many composites, such as fiberglass and carbon fiber, while containing ceramic materials, are not considered to be part of the ceramic family.
The earliest ceramics made by humans were pottery objects or figurines made from clay, either by itself or mixed with other materials like silica and sintered in fire. Ceramics were glazed and fired to create smooth, colored surfaces, decreasing porosity through the use of glassy, amorphous ceramic coatings on top of the crystalline ceramic substrates. Ceramics now include domestic and building products, as well as a wide range of ceramic art. In the 20th century, new ceramic materials were developed for use in advanced ceramic engineering, such as in semiconductors; the word "ceramic" comes from the Greek word κεραμικός, "of pottery" or "for pottery", from κέραμος, "potter's clay, pottery". The earliest known mention of the root "ceram-" is the Mycenaean Greek ke-ra-me-we, "workers of ceramics", written in Linear B syllabic script; the word "ceramic" may be used as an adjective to describe a material, product or process, or it may be used as a noun, either singular, or, more as the plural noun "ceramics".
A ceramic material is an inorganic, non-metallic crystalline oxide, nitride or carbide material. Some elements, such as carbon or silicon, may be considered ceramics. Ceramic materials are brittle, strong in compression, weak in shearing and tension, they withstand chemical erosion that occurs in other materials subjected to acidic or caustic environments. Ceramics can withstand high temperatures, ranging from 1,000 °C to 1,600 °C. Glass is not considered a ceramic because of its amorphous character. However, glassmaking involves several steps of the ceramic process, its mechanical properties are similar to ceramic materials. Traditional ceramic raw materials include clay minerals such as kaolinite, whereas more recent materials include aluminium oxide, more known as alumina; the modern ceramic materials, which are classified as advanced ceramics, include silicon carbide and tungsten carbide. Both are valued for their abrasion resistance and hence find use in applications such as the wear plates of crushing equipment in mining operations.
Advanced ceramics are used in the medicine, electronics industries and body armor. Crystalline ceramic materials are not amenable to a great range of processing. Methods for dealing with them tend to fall into one of two categories – either make the ceramic in the desired shape, by reaction in situ, or by "forming" powders into the desired shape, sintering to form a solid body. Ceramic forming techniques include shaping by hand, slip casting, tape casting, injection molding, dry pressing, other variations. Noncrystalline ceramics, being glass, tend to be formed from melts; the glass is shaped when either molten, by casting, or when in a state of toffee-like viscosity, by methods such as blowing into a mold. If heat treatments cause this glass to become crystalline, the resulting material is known as a glass-ceramic used as cook-tops and as a glass composite material for nuclear waste disposal; the physical properties of any ceramic substance are a direct result of its crystalline structure and chemical composition.
Solid-state chemistry reveals the fundamental connection between microstructure and properties such as localized density variations, grain size distribution, type of porosity and second-phase content, which can all be correlated with ceramic properties such as mechanical strength σ by the Hall-Petch equation, toughness, dielectric constant, the optical properties exhibited by transparent materials. Ceramography is the art and science of preparation and evaluation of ceramic microstructures. Evaluation and characterization of ceramic microstructures is implemented on similar spatial scales to that used in the emerging field of nanotechnology: from tens of angstroms to tens of micrometers; this is somewhere between the minimum wavelength of visible light and the resolution limit of the naked eye. The microstructure includes most grains, secondary phases, grain boundaries, micro-
Energy recovery includes any technique or method of minimizing the input of energy to an overall system by the exchange of energy from one sub-system of the overall system with another. The energy can be in any form in either subsystem, but most energy recovery systems exchange thermal energy in either sensible or latent form. In some circumstances the use of an enabling technology, either diurnal thermal energy storage or seasonal thermal energy storage, is necessary to make energy recovery practicable. One example is waste heat from air conditioning machinery stored in a buffer tank to aid in night time heating. Another is an STES application at a foundry in Sweden. Waste heat is recovered and stored in a large mass of native bedrock, penetrated by a cluster of 140 heat exchanger equipped boreholes that are 150m deep; this store is used for heating an adjacent factory as needed months later. An example of using STES to recover and utilize natural heat that otherwise would be wasted is the Drake Landing Solar Community in Alberta, Canada.
The community uses a cluster of boreholes in bedrock for interseasonal heat storage, this enables obtaining 97 percent of the year-round space heating from solar thermal collectors on the garage roofs. Another STES application is recovering the cold of winter by circulating water through a dry cooling tower, using that to chill a deep aquifer or borehole cluster; the chill is recovered from the storage for summer air conditioning. With a coefficient of performance of 20 to 40, this method of cooling can be ten times more efficient than conventional air conditioning. A common application of this principle is in systems which have an exhaust stream or waste stream, transferred from the system to its surroundings; some of the energy in that flow of material may be transferred to the make-up or input material flow. This input mass flow comes from the system's surroundings, being at ambient conditions, are at a lower temperature than the waste stream; this temperature differential allows heat transfer and thus energy transfer, or in this case, recovery.
Thermal energy is recovered from liquid or gaseous waste streams to fresh make-up air and water intakes in buildings, such as for the HVAC systems, or process systems. Energy consumption is a key part of most human activities; this consumption involves converting one energy system to another, for example: The conversion of mechanical energy to electrical energy, which can power computers, motors etc. The input energy propels the work and is converted to heat or follows the product in the process as output energy. Energy recovery systems harvest the output power and provide this as input power to the same or another process. An energy recovery system will close this energy cycle to prevent the input power from being released back to nature and rather be used in other forms of desired work. Heat recovery is implemented in heat sources like e.g. a steel mill. Heated cooling water from the process is sold for heating of homes and offices in the surrounding area. Regenerative braking is used in electric cars, heavy cranes etc. where the energy consumed when elevating the potential is returned to the electric supplier when released.
Active pressure reduction systems where the differential pressure in a pressurized fluid flow is recovered rather than converted to heat in a pressure reduction valve and released. Energy recovery ventilation Energy recycling Water heat recycling Heat recovery ventilation Heat recovery steam generator Cyclone Waste Heat Engine Hydrogen turboexpander-generator Thermal diode Thermal oxidizer Thermoelectric Modules Waste heat recovery units Electric Turbo Compounding is a technology solution to the challenge of improving energy efficiency for the stationary power generation industry. Fossil fuel based power generation is predicted to continue for decades in developing economies; this is against the global need to reduce carbon emissions, of which, a high percentage is produced by the power sector worldwide. ETC works by making gas and diesel-powered gensets work more and cleaner, by recovering waste energy from the exhaust to improve power density and fuel efficiency. Helps developing economies with unreliable or insufficient power infrastructure.
Gives independent power providers, power rental companies and generator OEMs a competitive advantage and potential increased market share. Improves overall efficiency of the genset, including fuel input costs and helping end-users reduce amount of fuel burned. 4-7% less fuel consumption for both diesel and gas gensets. Fewer carbon emissions. Increased power density. Capability to increase power output and capacity, with improved fuel efficiency. ETC system integration offers a step change in efficiency without increasing service or maintenance requirements; the cost of generating power through waste heat recovery is less than burning more fuel with low diesel prices. Upfront costs incur an additional expense for businesses; the need to update existing turbomachinery and recertification of the unit adds additional costs and can be time consuming. There will be additional weight to add an ETC to a current unit. Process still uses fossil fuels, thus still has a carbon footprint in a renewable age, they are bespoke to each generator so the design and implementation can be a lengthy process.
There are challenges with high speed turbo generators such as high stress in the rotors, heat generation of the electrical machine and rotordynamics of the turbo generator system. There is a large potential for energy recovery in
Fluidized bed concentrator
A fluidized bed concentrator is an industrial process for the treatment of exhaust air. The system uses a bed of activated carbon beads to adsorb volatile organic compounds from the exhaust gas. Evolving from the previous fixed-bed and carbon rotor concentrators, the FBC system forces the VOC-laden air through several perforated steel trays, increasing the velocity of the air and allowing the sub-millimeter carbon beads to fluidize, or behave as if suspended in a liquid; this increases the surface area of the carbon-gas interaction, making it more effective at capturing VOCs. The fluidized bed concentrator consists of five primary components: Adsorption tower Desorption tower Thermal oxidizer Carbon transport system Process fans: Inlet Adsorber, Inlet Desorber, Outlet Oxidizer to Stack Industrial Processes requiring ventilation, including paint booths and chemical production, exhaust the ventilated air to the fluidized bed concentrator at room temperature; the air first passes into the Adsorption tower, where it moves through six perforated trays of clean carbon beads.
The 0.7 mm captures the VOCs as they intermix. The saturated carbon beads are passed from the Adsorber tower to the Desorber tower, where the beads are heated to 350 °F and the VOCs are released; the Adsorber tower is many times larger than the Desorber tower, leading to an air volume reduction and an increase in VOC concentration. The ratio of Adsorber size to Desorber size is called the Concentration Ratio, ranges from 10:1 to 100:1; the concentrated VOC gas stream is sent from the Desorb tower to a thermal oxidizer, where the organic compounds are heated to 1400 °F and oxidized, or broken down into Carbon Dioxide, by-products. In some cases, small amounts of Carbon Monoxide, Nitrogen Oxide, other gases are produced; the primary advantage of the FBC over traditional rotor concentrators lies in its ability to achieve any concentration ratio up to the lower explosive limit. This allows Honda Alabama's paint shop to switch from oxidizing 100,000 CFM of VOCs in a Regenerative Thermal Oxidizer, to oxidizing only 1,500 CFM of VOCs in a small thermal oxidizer, at a much higher concentration.
Reducing the volume of air to be oxidized from 100,000 CFM to 1,500 CFM, allows for a much lower energy usage and fewer CO2 and NOX emissions. "Despite an increase in Line 2 production, Honda is realizing a reduction in plant VOC emissions of nearly 60 metric tons annually as a result of the installation of the FBC system. The new system uses 20% of the energy of an RTO system." - Honda Manufacturing of Alabama Paint Finishing Automotive Aerospace Heavy Machinery Transportation Printing Chemical production Semiconductor Food Processing Environmental C&CCustomers: Sony, Akzo Nobel, Lucent, Panasonic TKS Industrial Customers: Toyota, Ford PEI Customers: Nail Polish Manufacturer Volatile organic compound National Emissions Standards for Hazardous Air Pollutants Air pollution in the United States Activated Carbon Air pollution Clean Air Act plus further links to relevant rules and programs. Organic NESHAP
A thermal oxidizer is a process unit for air pollution control in many chemical plants that decomposes hazardous gases at a high temperature and releases them into the atmosphere. Thermal oxidizers are used to destroy hazardous air pollutants and volatile organic compounds from industrial air streams; these pollutants are hydrocarbon based and when destroyed via thermal combustion they are chemically oxidized to form CO2 and H2O. Three main factors in designing the effective thermal oxidizers are temperature, residence time, turbulence; the temperature needs to be high enough to ignite the waste gas. Most organic compounds ignite at the temperature between 590 °C and 650 °C. To ensure near destruction of hazardous gases, most basic oxidizers are operated at much higher temperature levels; when catalyst is used, the operating temperature range may be lower. Residence time is to ensure; the turbulence factor is the mixture of combustion air with the hazardous gases. The simplest technology of thermal oxidation is direct-fired thermal oxidizer.
A process stream with hazardous gases is introduced into a firing box through or near the burner and enough residence time is provided to get the desired destruction removal efficiency of the VOCs. Most direct-fired thermal oxidizers operate at temperature levels between 980 °C and 1,200 °C with air flow rates of 0.24 to 24 standard cubic meters per second. Called afterburners in the cases where the input gases come from a process where combustion is incomplete, these systems are the least capital intensive, can be integrated with downstream boilers and heat exchangers to optimize fuel efficiency. Thermal Oxidziers are best applied where there is a high concentration of VOCs to act as the fuel source for complete combustion at the targeted operating temperature. One of today’s most accepted air pollution control technologies across industry is a regenerative thermal oxidizer referred to as a RTO. RTOs use a ceramic bed, heated from a previous oxidation cycle to preheat the input gases to oxidize them.
The preheated gases enter a combustion chamber, heated by an external fuel source to reach the target oxidation temperature, in the range between 760 °C and 820 °C. The final temperature may be as high as 1,100 °C for applications; the air flow rates are 2.4 to 240 standard cubic meters per second. RTOs are versatile and efficient – thermal efficiency can reach 95%, they are used for abating solvent fumes, etc. from a wide range of industries. Regenerative Thermal Oxidizers are ideal in a range of low to high VOC concentrations up to 10 g/m3 solvent. There are many types Regenerative Thermal Oxidizer on the market with the capabitlity of 99.5+% Volatile Organic Compound oxidisation or destruction efficiency. The ceramic heat exchanger in the towers can be designed for thermal efficiencies as high as 97+%. Ventilation air methane thermal oxidizers are used to destroy methane in the exhaust air of underground coal mine shafts. Methane is a greenhouse gas and, when oxidized via thermal combustion, is chemically altered to form CO2 and H2O.
CO2 is 25 times less potent than methane when emitted into the atmosphere with regards to global warming. Concentrations of methane in mine ventilation exhaust air of coal and trona mines are dilute. VAMTOX units have a system of valves and dampers that direct the air flow across one or more ceramic filled bed. On start-up, the system preheats by raising the temperature of the heat exchanging ceramic material in the bed at or above the auto-oxidation temperature of methane 1,000 °C, at which time the preheating system is turned off and mine exhaust air is introduced; the methane-filled air reaches the preheated bed, releasing the heat from combustion. This heat is transferred back to the bed, thereby maintaining the temperature at or above what is necessary to support auto-thermal operation. A less used thermal oxidizer technology is a thermal recuperative oxidizer. Thermal recuperative oxidizers have a primary and/or secondary heat exchanger within the system. A primary heat exchanger preheats the incoming dirty air by recuperating heat from the exiting clean air.
This is done by a plate heat exchanger. As the incoming air passes on one side of the metal tube or plate, hot clean air from the combustion chamber passes on the other side of the tube or plate and heat is transferred to the incoming air through the process of conduction using the metal as the medium of heat transfer. In a secondary heat exchanger the same concept applies for heat transfer, but the air being heated by the outgoing clean process stream is being returned to another part of the plant – back to the process. Biomass, such as wood chips, can be used as the fuel for a thermal oxidizer; the biomass is gasified and the stream with hazardous gases is mixed with the biomassgas in a firing box. Sufficient turbulence, retention time, oxygen content and temperature will ensure destruction of the VOC's; such biomass fired thermal oxidizer has been installed at New Hampshire. The inlet concentrations are between 3000-10.000 ppm VOC. The outlet concentration of VOC are below 3 ppm, thus having a VOC destruction efficiency of 99.8%-99.9%.
In a flameless thermal oxidizer system waste gas, ambient air, auxiliary fuel are premixed prior to passing the combined gaseous mixture through a prehea
Atmospheric aerosol particles – known as atmospheric particulate matter, particulate matter, particulates, or suspended particulate matter – are microscopic solid or liquid matter suspended in the atmosphere of Earth. The term aerosol refers to the particulate/air mixture, as opposed to the particulate matter alone. Sources of particulate matter can be anthropogenic, they have impacts on precipitation that adversely affect human health. Subtypes of atmospheric particles include suspended particulate matter and respirable particles, inhalable coarse particles, which are coarse particles with a diameter between 2.5 and 10 micrometers, fine particles with a diameter of 2.5 μm or less, ultrafine particles, soot. The IARC and WHO designate airborne particulates a Group 1 carcinogen. Particulates are the deadliest form of air pollution due to their ability to penetrate deep into the lungs and blood streams unfiltered, causing permanent DNA mutations, heart attacks, respiratory disease, premature death.
In 2013, a study involving 312,944 people in nine European countries revealed that there was no safe level of particulates and that for every increase of 10 μg/m3 in PM10, the lung cancer rate rose 22%. The smaller PM2.5 were deadly, with a 36% increase in lung cancer per 10 μg/m3 as it can penetrate deeper into the lungs. Worldwide exposure to PM2.5 contributed to 4.1 million deaths from heart disease and stroke, lung cancer, chronic lung disease, respiratory infections in 2016. Overall, ambient particulate matter ranks as the sixth leading risk factor for premature death globally; some particulates occur originating from volcanoes, dust storms and grassland fires, living vegetation and sea spray. Human activities, such as the burning of fossil fuels in vehicles, stubble burning, power plants, wet cooling towers in cooling systems and various industrial processes generate significant amounts of particulates. Coal combustion in developing countries is the primary method for heating homes and supplying energy.
Because salt spray over the oceans is the overwhelmingly most common form of particulate in the atmosphere, anthropogenic aerosols—those made by human activities—currently account for about 10 percent of the total mass of aerosols in our atmosphere. The composition of aerosols and particles depends on their source. Wind-blown mineral dust tends to be made of mineral oxides and other material blown from the Earth's crust. Sea salt is considered the second-largest contributor in the global aerosol budget, consists of sodium chloride originated from sea spray. In addition, sea spray aerosols may contain organic compounds; the drift/mist emissions from the wet cooling towers is source of particulate matter as they are used in industry and other sectors for dissipating heat in cooling systems. Secondary particles derive from the oxidation of primary gases such as sulfur and nitrogen oxides into sulfuric acid and nitric acid; the precursors for these aerosols—i.e. The gases from which they originate -- may have a natural biogenic origin.
In the presence of ammonia, secondary aerosols take the form of ammonium salts. Secondary sulfate and nitrate aerosols are strong light-scatterers; this is because the presence of sulfate and nitrate causes the aerosols to increase to a size that scatters light effectively. Organic matter can be either primary or secondary, the latter part deriving from the oxidation of VOCs. Organic matter influences the atmospheric radiation field by both absorption. Another important aerosol type is elemental carbon: this aerosol type includes light-absorbing material and is thought to yield large positive radiative forcing. Organic matter and elemental carbon together constitute the carbonaceous fraction of aerosols. Secondary organic aerosols, tiny "tar balls" resulting from combustion products of internal combustion engines, have been identified as a danger to health; the chemical composition of the aerosol directly affects. The chemical constituents within the aerosol change the overall refractive index.
The refractive index will determine how much light is absorbed. The composition of particulate matter that causes visual effects such as smog consists of sulfur dioxide, nitrogen oxides, carbon monoxide, mineral dust, organic matter, elemental carbon known as black carbon or soot; the particles are hygroscopic due to the presence of sulfur, SO2 is converted to sulfate when high humidity and low temperatures are present. This causes yellow color. Aerosol particles of natural origin tend to have a larger radius than human-produced aerosols such as particle pollution; the false-color maps in the third image on this page show where there are natural aerosols, human pollution, or a mixture of both, monthly. Among the most obvious patterns that the size distribution time series shows is that in the planet’s most southerly latitudes, nearly all the aerosols are l