lllucrarea 5 - eforturi induse termic intr-o structura stratificata
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Eforturi induse termic intr-o structura stratificataTRANSCRIPT
Clirea rapid a unei plachete semiconductoare
A truly green car
Bioenergy Energy Systems
AUTORI:Eftenoiu Diana
Diaconu Alexie Petre10.12.20141. Overview: Bioenergy Bioenergy consists of biomass (biological mass) used in the production of energy; http://www.bioproducts-bioenergy.govBiomass
Phototrophs use light to survive and propagate
Chemotrophs (like us) eat phototrophs (vegetables and salads)! Salads topped with biodiesel and acetic acid!
CO2 + H2O >--solar energy and chlorophyll ( CH2O + O2,
or carbohydrate and oxygen
While biomass combustion releases CO2 into the atmosphere, new plants require CO2 to grow, balancing the process for no net CO2 over a long time
2. Bioenergy Map (From Biomass) Direct firing, cofiring, and gasification are forms of biopower ; Ethanol can be made from grain or soybeans, and methanol can be made from cellulose (wood) ; Liquid fuels are essential for transportation vehicles due to high energy density in the tank! ; May be intentionally grown (coppicing) such as poplar trees or might use waste byproducts ; Biomass satisfied 4% of energy demand in 1990 ; Biomass can serve as a bridge from fossil fuels, although it is an inefficient producer of energy (~1%) ;3. Bioenergy Use Changed with Time
4. Bioenergy Definitions Bagasse: Sugar cane refuse left after pressing the juice from the cane
Bioenergy: Energy derived from biomass
Biomass: Mass of plant material formed from solar energy, water, and air; any organic material that is renewable
Cofire: To burn an additional fuel with the primary fuel, such as bagasse or sawdust with coal
IWS: Industrial Waste Stream
Waste wood, plastics, fiber; same kind of discard
MWS: Municipal Waste Stream, or MSW, municipal solid waste
Trash, plant trimmings, garbage (batteries, heavy metals, poisons, chemicals?) contaminate the air.5. Sources and Availability Typical fuels are sugarcane, sugar beets, sorghums, corn, wheat, forage, grasses, kenaf, eucalyptus, short rotation hardwoods, sunflowers, and comfrey. [Blackburn, 1993]
The materials are so cheap that the cost of hauling them determines the overall economics of using them. Truck haulage should not exceed ~70 miles to avoid overall loss of energy from truck fuel consumption
Are the sources sustainable or will there be shortages?
Biomass acts as seasonal peaking, since the growth occurs in time for harvesting for winter heating
6. Energy Extraction and Preparation
Dry biomass may have some residual moisture but only requires physical preparation like chipping to fire it
Some research is being done to see if long trees can be directly fired on a metal conveyor belt
Wet biomass can absorb more heat energy from a furnace than it can supply; the biomass must be externally dried to burn
Small biomass pellets are made from wood scraps and sawdust
There are pellet-burning stoves with a screw conveyor feed
7. Dry Biomass
Dry biomass consists of tree chips, paper, various other plant matter such as corn, soybean, sorghum, sunflower, oats, barley, wheat and hay
When first cut, the sap may absorb energy, and the mass should dry
Spread on fields in the sun
Placed in oven heated by what would otherwise be waste heat
Using solar thermal energy air-heaters8. Municipal Solid Wastes (MSW) Municipal waste streams may have anything in it that people want to throw away -- its a mix
Air blast and magnetic separation can select different streams to go in various piles
Permanent magnets first extract the steel and iron
Alternating current electromagnets use the eddy current effect to remove nonferrous metals (Al, Cu)
Light paper and plastic will stratify in an air column to remove them from heavier substances (metal and bottles)
Hand sorting can pick out some of whats left Without this process, pollutants arent removed
9. Industrial Waste Streams (IWS) Industrial wastes differ from municipal wastes in that they are often separated or categorized as outputs from specific processes
Its relatively easy to have pure waste streams all of one material, like wood strips, pallets, trim scrap
Paper products are a possibility, but dioxin content can cause air pollution
Any wet waste stream will require drying before burning
Could require more energy to dry than can be extracted from it
10. Wet Biomass
Wet biomass tends to be in water or to stay moist
Examples are water plants, animal wastes, and biodiesel oil
Florida has lots of weeds that came from dumped aquariums (also fish that shouldnt be here, like piranha and snakehead will they burn?)
Treated with hydrogasification at high pressure and low temperatures to produce a gas or biofuel oil
11. Animal Wastes Average manure production for fully bred cows and pigs is 40 kg and 2.3 kg wet weight per day [Sorensen, 2000](a thing I never wanted to know)
Manure lagoons at Consolidated Animal Feeding Operations (CAFO) pose a stored pollution problem
Lagoon dam breaches have poisoned nearby streams and killed thousands of fish in NC
Anaerobic digestion allows methane gas recovery
12. Municipal Sewer Plants The same processes for farm animal wastes can be used at city sewer plants
40 billion Btus of methane per 100,000 people per year
Florida methane could yield 20 trillion Btus per year
Cost would be $6 to $8 per million Btu
At present, filtered sewage sludge is often bulk dumped (sprayed) on agricultural pastures
The methane gas from a sewage lagoon can be recovered by a bioenergy process, reducing the sludge before disposal
A cruise ship is like a small city -- where does the sewage go?
13.Gaseous Biomass
Methane is the primary biogas
Aside from sewage, theres termites, livestock flatulence, swamps, etc.
Landfill gas is primarily methane but contains CO2 and other gases from plastics, etc.
80% of odors humans find offensive are the result of nitrogen- or sulfur-bearing compounds. The nitrogen and sulfur atoms are rearranged into smaller molecules that give off odor when they're volatilized as gases into the air, as little as one part per billion - needs to be present for sensitive noses to notice
14. Landfill Gases
Conversion from biomass to heat requires some extraction if the fuel stream is contaminated with polluting substances
Typical processes are the following:
Direct combustion
Anaerobic Digestion
Fermentation
Pyrolysis
Other less-used techniques
Energy Conversion Conversion from biomass to heat requires some extraction if the fuel stream is contaminated with polluting substances
Typical processes are the following:
Direct combustion
Anaerobic Digestion
Fermentation
Pyrolysis
Other less-used techniquesConversion: Direct Combustion Refuse Derived Fuel (RDF) can be fired (burned) directly or in combination with conventional fuels
Some processing, such as cleaning, chopping, etc. may be needed for handling or air pollution avoidance
Fluidized grate furnaces blow air in beneath the grate, and this keeps the burning mass in seething flotation as it burns
Conversion: Anaerobic Digestion Bacteria produce acetic acid (found in vinegar)
Methane gas 50% to 80%, $2.50/kft3 (1976)
Microgy Cogeneration Systems, Inc. is building a 25 MW digestion plant
Essex Junction Wastewater Treatment facility in Essex Junction, Vermont treats 1.7 million gallons of waste water per day and will produce 400 MW electricity per year to reduce plant costs
Price of electricity is estimated at $0.02 per kWh
Conversion: Fermentation Enzymes can change cellulose into sugars, which can then be fermented into alcohol
Cane sugar, C6H12O6 ( 2C2H5OH + 2CO2 Fermentation of corn or other biomass will produce ethanol
The use of food stocks in this way might be seen as a poor use of food
Brewery spillage or waste and outdated soda can be filtered, cleaned, and reprocessed to produce fuel
It is denatured with 15% gasoline to discourage drinking and avoid Federal liquor law taxes
Fermentation of stillage refuse can also produce methane
Conversion: Pyrolysis Fast pyrolysis is heating biomass without oxygen to decompose it into vapors, aerosols and char
The liquid has ~one-half the heating value of fuel oil
The process is tuned to produce liquid rather than charcoal
Low-quality producer gas can be cleaned to remove CO2 and N2, then this synthesis gas reacted as 2H2 + CO ( CH3OH to yield methanol
Conversion: Other Hydrogasification
Low temperature and high pressure produces ethane & methane plus CO2 A catalyst aids the process
Hydrogenation
Waste + Steam and CO forms low-sulfur oil having 16000 Btu/pound heating value
Used to make peanut butter and margarine
Issues and Trends Environmental considerations
Biomass conversion plants are often fought by some as a source of pollutants
Less polluting than a coal plant
MSW may contain heavy metals and should not be burned
Paper colored inks often contain heavy metals
Trash production can be decreased by careful purchases, conservation, reusing, and recycling
If these waste reduction practices are followed, there is less available for bioenergy
3 Parcurgerea paiilor modelului de analiz Pasul 1:
n primul pas, se coboar temperatura de la o valoare iniial de 800 C la 150 C, ceea ce are ca i impact principal , afectarea stratului superior (stratul de manta) , respectiv a substratului.! Stratul purttor nu este activ n acest pas.Colul din stnga jos a substratului este fix, iar colul din dreapta jos a substratului este constrns n direcia y. Acest lucru previne micrile corpului rigid, dar nu afecteaz distribuia solicitrii.
Pasul 2:
n aceast etap toate cele trei straturi sunt active i se scade temperatura de la 150 C pn la o temperatur a camerei de 20 C. Acest pas include i solicitrile iniiale de la Pasul 1.
n acelai mod ca i la Pasul, 1 colul din stnga jos al stratului de transport este fixat, iar colul din dreapta-jos al stratului de transport este restrictionat n direcia y.
Observaii:
Presiunea normal n direcia x din prima etap de analiz este reprezentat n Figur 2. Materialul de substrat are un coeficient de dilatare termic mai mare dect materialul de acoperire.
Acest lucru denot faptul c substratul se micoreaz mai mult dect stratul de acoperire(manta) , avand drept efect tensiuni de ntindere n zona de lng substrat de acoperire respectiv , tensiuni de compresie n stratul de acoperire(manta).
Figura 2. Tensiunea normal n direcia x pentru analiza primului pas.
Figura de mai jos (nr.3) prezint rezidul termic x de stres n etapa final, ce a avut c principala aciune coborrea temperaturii pn la o valoare de 20 C.
Nivelurile de presiune au crescut oarecum n zona de lng substratul de acoperire, aa cum i nivelul de compresiune n stratul de acoperire a crescut, comparativ cu primul pas al procesului.
Principala contribuie a tensiunii este n mod clar tensiunea adugat iniial n primul pas al procesului.
Figura 3. Solicitari reziduale termice pe directia x la temperatura camerei4.Concluzii
Odat cu finalizarea pasului 1, din graficul rezultat (vezi fig.2) stratul purttor nu mai este activ!
n ceea ce privete distribuia eforturilor n stratul manta, aceasta este net mai mic, cu excepia colturilor din dreapta, respectiv stnga sus, n aceste zone, distribuia eforturilor fiind ceva mai mari comparativ cu restul stratului.
Din punct de vedere al mrimilor eforturile, cele mai mari ca valoare se regsesc la partea superioar a substratului, acestea scznd considerabil ctre partea de jos.
Dup parcurgerea pasului 2, stratul purttor este activ. O parte din eforturile aflate n acest substrat se transfera n stratul purttor, la o valoare semnificativ mai mare dect cea de dinaintea activrii statului purttor, lucru ce se poate vizualiza n figura 3.
5 Bibliografie
1. www.ce.tuiasi.ro/~vrabie/rez2008.pdf
2. www.resist.pub.ro/Cursuri_master/SMC/CAP.4.DOC
3. instal.utcb.ro/site/Teza_Paun_Virgil.pdf
4. http://lege5.ro/Gratuit/geydemjqha/reglementarea-tehnica-normativ-privind-proiectarea-si-executia-invelitorilor-subtiri-de-beton-armat-si-precomprimat-monolite-si-prefabricate-indicativ-np-119-06-din-21092006/2
5. http://www.oltplast-onesti.ro/Caracteristici%20tehnice%20ale%20sticlei.pdf.
6. http://www.spatiulconstruit.ro/storproc/fisier_atasabil/h1/f119/119_zidarie_curs_1a_caracteristici_generale.pdf.
7. Lucrarea de laborator
6 LI ST D E F IGURIFigura 1 Geometria placii........................................................................................................................3Figura 2 Tensiunea normal n direcia x pentru analiza primului pas........................................................4Figura 3 Solicitari reziduale termice pe directia x la temperatura camerei....................................................57 CONINUT1 Introducere....................................................................................................................................22 Definirea modelului...................................................................................................................23 Parcurgerea paiilor modelului de analiz...............................................................................34 Concluzii .......................................................................................................................................65 Bibliografie...............................................................................................................................66 List de figuri........................................................................................................................................7