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SORA,CLASSES: IV Sez. A-B TEACHERS: ANNARITA SBARDELLAEMILIANA MANCINIVINCENZO RECCHIA,Power Point Presentation realized by:,Lorenzo Corsetti (Class VA)Cristiano Diamanti (Class VA) Francesco DOrazio (Class VA),LICEO SCIENTIFICO STATALE LEONARDO DA VINCI SORA ITALYCOMENIUS 1.3 “ENCOHAN - ENERGY IN THE CONSUMERS HANDS”2005 - 2008,TEACHERS:ANNARITA SBARDELLAEMILIANA MANCINIVINCENZO RECCHIA,CLASSES: IV Sez. A-B,LICEO SCIENTIFICO STATALE LEONARDO DA VINCI SORA ITALYCOMENIUS 1.3 “ENCOHAN - ENERGY IN THE CONSUMERS HANDS “2005 - 2008,“ENCOHAN” PROJECT MEETING IN HUNGHERY: (6th November / 11th November 2006) Teachers: Emiliana Mancini Vincenzo Recchia,“ENCOHAN” PROJECT MEETING IN POLAND: (25th March / 1st April 2007) Teachers: Annarita Sbardella (Coordinator) Vincenzo Recchia Students: Francesca Fornari (Class IVA) Martina Liburdi (Class IVA) Luca Lombardi (Class IVA) Luigi Recchia (Class IVA) Chiara Iafrate (Class IVB) Alessia Pantano (Class IVB) Ilaria Urbani (Class IVB) Silvia Venditti (Class IVB),DRINKING BIRD,Drinking birds are thermodinamically powered toy heat engines that mimick the motions of a bird drinking from a fountain or other water source. They are also known as happy, dippy, dipping, tippy, tipping, sippy, sipping, dip-dip or dunking birds.Construction and materials:A drinking bird consists of two glass bulbs, joined by a tube (the birds neck). The tube extends nearly all the way into the bottom bulb but does not extend into the top. The space inside is typically filled with coloured dichloromethane(also known as methylene chloride).Air is removed from the apparatus, so the space inside the body is filled by dichloromethane vapour. The upper bulb has a beak attached, which along with the head, is covered in a felt like material. The bird is typically decorated with paper eyes, a blue top hat (plastic) and a single green tail feather. The whole setup is pivoted on a variable point on the neck.The drinking bird illustrates the conversion of thermal energy into mechanical energy. The head of the bird is coated with a fuzzy material, and is initially soaked in water so that it will begin to cool by evaporation.,Drinking birds are thermodinamically powered toy heat engines that mimick the motions of a bird drinking from a fountain or other water source. They are also known as happy, dippy, dipping, tippy, tipping, sippy, sipping, dip-dip or dunking birds.Construction and materials:A drinking bird consists of two glass bulbs, joined by a tube (the birds neck). The tube extends nearly all the way into the bottom bulb but does not extend into the top. The space inside is typically filled with coloured dichloromethane(also known as methylene chloride).Air is removed from the apparatus, so the space inside the body is filled by dichloromethane vapour. The upper bulb has a beak attached, which along with the head, is covered in a felt like material. The bird is typically decorated with paper eyes, a blue top hat (plastic) and a single green tail feather. The whole setup is pivoted on a variable point on the neck.The drinking bird illustrates the conversion of thermal energy into mechanical energy. The head of the bird is coated with a fuzzy material, and is initially soaked in water so that it will begin to cool by evaporation.,This provides the temperature difference from head to tail necessary to run the heat engine. As the head cools, the colored fluid is observed to rise up from the bottom of the bird through the neck, gradually shifting the center of gravity of the bird toward its head. The bird bends at the hips and dips its bill into a glass of water (thus keeping the head wet and cooler than the tail). As the fluid continues to rise into the head, the fluid level in the bottom of the bird eventually drops below the end of the connecting tube. This allows vapor to be pulled up through the neck to equilibrate the pressure. The fluid runs back down into the bottom of the bird, the bird stands up again, and the cycle repeats indefinitely. The drinking bird is basically a heat engine that exploits a temperature differential to convert heat energy to kinetic energy and perform mechanical work. Like all heat engines, the drinking bird works through a thermodynamic cycle. The initial state of the system is a bird with a wet head oriented vertically with an initial oscillation on its pivot.,DRINKING BIRD,DRINKING BIRD,The cycle operates as follows:The water evaporates from the head.Evaporation lowers the temperature of the glass head. The temperature drop causes some of the dichloromethane vapor in the head to condense.The lower temperature and condensation together cause the pressure to drop in the head (ideal gas law). The pressure differential between the head and base causes the liquid to be pushed up from the base. As liquid flows into the head, the bird becomes top heavy and tips over during its oscillations. When the bird tips over, the bottom end of the neck tube rises above the surface of the liquid. A bubble of vapor rises up the tube through this gap, displacing liquid as it goes Liquid flows back to the bottom bulb, and vapor pressure equalizes between the top and bottom bulbs The weight of the liquid in the bottom bulb restores the bird to its vertical position.,If a glass of water is placed so that the beak dips into it on its descent, the bird will continue to absorb water and the cycle will continue as long as there is enough water in the glass to keep the head wet. However, the bird will continue to dip even without a source of water, as long as the head is wet, or as long as a temperature differential is maintained between the head and body. This differential can be generated without evaporative cooling in the head - for instance, a heat source directed at the bottom bulb will create a pressure differential between top and bottom that will drive the engine. The ultimate source of energy is heat in the surrounding environment - the toy is not a perpetual motion machine.,DRINKING BIRD,1) Heat engineA heat engine is a physical or theoretical device that converts thermal energy to mechanical output. The mechanical output is called work, and the thermal energy input is called heat. Heat engines typically run on a specific thermodynamic cycle. Heat engines are often named after the thermodynamic cycle they are modeled by. They often pick up alternate names, such as gasoline/petrol, turbine, or steam engines. Heat engines can generate heat inside the engine itself or it can absorb heat from an external source. Heat engines can be open to the atmospheric air or sealed and closed off to the outside (Open or closed cycle).In engineering and thermodynamics, a heat engine performs the conversion of heat energy to mechanical work by exploiting the temperature gradient between a hot source and a cold sink. Heat is transferred from the source, through the working body of the engine, to the sink, and in this process some of the heat is converted into work by exploiting the properties of a working substance (usually a gas or liquid).,THE PHISICS AROUND :,THE PHISICS AROUND :,Figure 1: Heat engine diagram,Heat engines are often confused with the cycles they attempt to mimic. Typically when describing the physical device the term engine is used. When describing the model the term cycle is used.In thermodinamics, heat engines are often modeled using a standard engineering model such as the Otto cycle (4-stroke/2-stroke). Actual data from an operating engine, one is called a indicator diagram, is used to refine the model. All modern implementations of heat engines do not exactly match the thermodynamic cycle they are modeled by. One could say that the thermodynamic cycle is an ideal case of the mechanical engine. One could equally say that the model doesnt quite perfectly match the mechanical engine. However, much benefit is gained from the simplified models, and ideal cases they may represent.,THE PHISICS AROUND :,In general terms, the larger the difference in temperature between the hot source and the cold sink, the larger is the potential thermal efficiency of the cycle. On Earth, the cold side of any heat engine is limited to close to the ambient temperature of the environment, or not much lower than 300 kelvins, so most efforts to improve the thermodynamic efficiencies of various heat engines focus on increasing the temperature of the source, within material limits. The efficiency of various heat engines proposed or used today ranges from 3 percent (97 percent waste heat) for the OTEC ocean power proposal through 25 percent for most automotive engines, to 35 percent for a supercritical coal plant, to about 60 percent for a steam-cooled combined cycle gas turbine. All of these processes gain their efficiency (or lack thereof) due to the temperature drop across them.,OTEC uses the temperature difference of ocean water on the surface and ocean water from the depths, a small difference of perhaps 25 degrees Celsius, and so the efficiency must be low. The combined cycle gas turbines use natural-gas fired burners to heat air to near 1530 degrees Celsius, a difference of a large 1500 degrees Celsius, and so the efficiency can be large when the steam-cooling cycle is added in:,THE PHISICS AROUND :,Figure 1: Heat engine diagram,Examples of everyday heat engines include: the steam engine, the diesel engine, and the gasoline (petrol) enginein an automobile. A common toy that is also a heat engine is a drinking bird. All of these familiar heat engines are powered by the expansion of heated gases. The general surroundings are the heat sink, providing relatively cool gases which, when heated, expand rapidly to drive the mechanical motion of the engine.It is important to note that although some cycles have a typical combustion location (internal external), they often can be implemented as the other combustion cycle. For example, John Ericsson developed an external heated engine running on a cycle very much like the earlier Diesel cycle. In addition, the externally heated engines can often be implemented in open or closed cycles.What this boils down to is there are thermodynamic cycles and a large number of ways of implementing them with mechanical devices called engines.,THE PHISICS AROUND,2) Evaporation and condensation EVAPORATION:,Water condenses into visible droplets after evaporating from a cup of hot tea,Evaporation is the process whereby atoms or molecules in a liquid state gain sufficient energy to enter the gaseous state (the equivalent process in solids is known as sublimation). It is the opposite process of condensation. Evaporation is exclusively a surface phenomena and should not be confused with boiling. Most notably, for a liquid to boil, its vapor pressure must equal the ambient pressure, whereas for evaporation to occur, this is not the case.The vapor pressure of a liquid is the pressure exerted by its vapor when the liquid and vapor are in dynamic equilibrium.,THE PHISICS AROUND,In chemistry and physics, vapor pressure is the pressure of a vapor in equilibrium with its non-vapor phases. All solids and liquids have a tendency to evaporate to a gaseous form, and all gases have a tendency to condense back. At any given temperature, for a particular substance, there is a partial pressure at which the gas of that substance is in dynamic equilibrium with its liquid or solid forms. This is the vapor pressure of that substance at that temperature. In meteorology, the term vapor pressure is used to mean the partial pressure of water vapor in the atmosphere, even if it is not equilibrium, and the equilibrium vapor pressure is specified as such. Meteorologists also use the term saturation vapor pressure to refer to the equilibrium vapor pressure of water or brine above a flat surface, to distinguish it from equilibrium vapor pressure which takes into account the shape and size of water droplets and particulates in the atmosphere.,THE PHISICS AROUND,Vapor pressure is an indication of a liquids evaporation rate. It relates to the tendency of molecules and atoms to escape from a liquid or a solid. A substance with a high vapor pressure at normal temperatures is often referred to as volatile. The higher the vapor pressure of a material at a given temperature, the lower the boiling point.The vapor pressure of any substance increases non-linearly with temperature according to the Clausius-Clapeyron relation. The boiling point of a liquid is the temperature where the vapor pressure equals the ambient atmospheric pressure. At the boiling temperature, the vapor pressure becomes sufficient to overcome atmospheric pressure and lift the liquid to form bubbles inside the bulk of the substance. Evaporation is a critical component of the water cycle, which is responsible for clouds and rain. Solar energy drives evaporation of water from oceans, lakes, moisture in the soil, and other sources of water. In hydrology, evaporation and transpiration (which involves evaporation within plant stomata) are collectively termed evapotranspiration.,THE PHISICS AROUND,CONDENSATION:,Condensation is the change in matter of a substance to a denser phase, such as a gas (or vapor) to a liquid. Condensation commonly occurs when a vapor is cooled to a liquid, but can also occur if a vapor is compressed (i.e., pressure on it increased) into a liquid, or undergoes a combination of cooling and compression. Liquid which has been condensed from a vapor is called condensate. A device or unit used to condense vapors into liquid is called a condenser. Condensers are typically coolers or heat exchangers which are used for various purposes, have various designs, and come in many sizes ranging from rather small (hand-held) to very large.Condensation of vapor of liquid is the opposite of evaporation or boiling and is an exothermic process, meaning it releases heat. The water seen on the outside of a cold glass on a hot day is condensation.,THE PHISICS AROUND,THE PHISICS AROUND,CONDENSATION OF WATER IN NATURE:,Dew on a spider web,Water vapor from air which naturally condenses on cold surfaces into liquid water is called dew. Water vapor will only condense onto another surface when that surface is cooler than the temperature of the water vapor, or when the water vapor equilibrium in air, i. e. saturation humidity, has been exceeded. When water vapor condenses onto a surface, a net warming occurs on that surface.,The water molecule brings a parcel of heat with it. In turn, the temperature of the atmosphere drops very slightly. In the atmosphere, condensation of water vapour is what produces clouds. The dew point of an air parcel is the temperature to which it must cool before condensation in the air begins to form.Also, a net condensation of water vapor occurs on surfaces when the temperature of the surface is at or below the dew point temperature of the atmosphere. Deposition is a type of condensation. Frost and snow are examples of deposition (or sublimation). Deposition is the direct formation of ice from water vapor.,THE PHISICS AROUND,Condensation on a cold bottle of water,APPLICATIONS OF CONDENSATION:,Because condensation is a naturally occurring phenomenon, it can often be used to generate water in large quantities for human use. In fact, there are many structures that are made solely for the purpose of collecting water from condensation, such as fog fences, air wells and dew ponds. Such systems can often be used to retain soil moisture in areas where active desertification is occurring. In fact, certain organizations use education about water condensers in efforts to effectively aid such areas.,THE PHISICS AROUND,CONDENSATION IN BUILDINGS:,Condensation is the most common form of dampness encountered in buildings. In buildings the internal air can have a high level of relative humidity due to the activity of the occupants (e.g. cooking, drying clothes, breathing etc.). When this air comes into contact with cold surfaces such as windows and cold walls it can condense, causing dampness.,3) Ideal gas law,THE PHISICS AROUND,The ideal gas law is the equation of state of a hypothetical ideal gas, first stated by Benot Paul mile Clapeyron in 1834.,The state of an amount of gas is determined by its pressure, volume, and temperature according to the equation:,where:,is the pressure PAL,is the volume m ,3,is the amount of substance of gas mol,is the gas constant 8.3143 m3PaK-1mol-1, and,is the temperature in kelvins K.,The ideal gas constant (R) is dependent on what units are used in the formula. The value given above, 8.314472, is for the SI units of pascal-cubic meters per mole-kelvin. Another value for R is 0.082057 L atm mol-1 K-1)The ideal gas law is the most accurate for monatomic gases and is favored at high temperatures and low pressures. It does not factor in the size of each gas molecule or the effects of intermolecular attraction. The more accurate Van der Waals equation takes these into consideration.,THE PHISICS AROUND,Alternate formsConsidering that the number of moles (n) could also be given in mass, sometimes you may wish to use an alternate form of the ideal gas law. This is particularly useful when asked for the ideal gas law approximation of a known gas. Consider that the number of moles (n) is equal to the mass (m) divided by the molar mass (M), such that:,Then, replacing n gives: in statistical mechanics, and is often derived from first principles:,THE PHISICS AROUND,Here, kb is Boltzmanns constant, and N is the actual number of molecules, in contrast to the other formulation, which uses n, the number of moles. This relation implies that Nkb = nR, and the consistency of this result with experiment is a good check on the principles of statistical mechanics. From here we can notice that for an average particle mass of times the atomic mass of Hydrogen,THE PHISICS AROUND,and since = m / V, we find that the ideal gas law can be re-writte