insulating ,Ceramic coating & packing seebeck effect 3/4/2010
KRISHNA'S THERMOEMF IMPLEMENTATION
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“GENERATION OF EMF FROM EXHAUST HEAT” PRESENTED BY AUTHOR : P.KRISHNAKANTH 1
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ABSTRACTWe have developed a solution for using the exhaustheat from the internal combustion engine (4 stroke ) tocharge the battery through a fundamental phenomenonnamely seebeck effect using thermo pile.Here we use the exhaust manifold material of engine(silencer) as hot junction whose temperature is nearly2500C.Due to this temperature difference of the thermo couplethermo emf is produced by see beck effect.This thermo emf is further amplified by means of aprimary and secondary coil arrangement and thisamplified voltage is given to the battery to get charged.2
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INTRODUCTION At present the heat energy, that is the temperature of theengine exhaust gas has been wasted. But through our paper we areadopting a basic thermoelectric process named as seebeck effectwhere the temperature difference is equivalently converted intoelectrical voltage. OBJECTIVE The objective of our paper is to provide a new idea of producing electrical voltage from EGT (exhaust gas temperature) Thus, the produced electrical voltage is used to charge the battery. This is somewhat different from the present way in which the voltage is produced. This is very cheap from the economical point of view and reduces the exhaust gas temperature. 3
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PRINCIPLECurrent flows in an electric circuitmade of two different conductors,when the two junctions in the circuitwere kept at two differenttemperatures.This means that an emf is producedacross two junctions in the circuitcausing the flow of current. The twojunction circuit is called a thermocouple and the emf produced is calledthermo electric emf or setback emf. 4
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The following is a selection from Seebeck s series: bismuth (Bi),nickel (Ni), cobalt (Co), palladium (Pd), platinum (Pt), copper (Cu),manganese (Mn), mercury (Hg), lead (Pb), tin (Sn), gold (Au), silver(Ag), zinc (Zn), cadmium (Cd), iron (Fe), antimony (Sb), tellurium (Te). AUXILLARY COMPONENTS ADDED TO ENGINE •Induction coil. •Constantan •Lead •Ceramic 5. Copper. 5
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WORKINGHere we are considering the four stroke petrol engines but thesame can be applied for the four stroke and also for the dieselengines.Normal exhaust temperature for four stroke engine is 250 C.This is considered to be the hot junction. The atmospheric temperature which is about to be 25 C isconsidered as cold junction.Hence the temperature difference between the 2 ends of thethermo couple is about 225 C.The hot and cold junctions are separated by means of aninsulating(ceramic )material. This temperature difference between hot and cold junction isbeen converted into voltage through seebeck effect. 7
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INVERSIONThe voltage so obtained from a thermo couple is a directcurrent voltage (dc voltage). In order to amplify it , we send itthrough an induction coil. But for the usage in an induction coil , we need to convert itinto an alternating current voltage (ac voltage).For this process , we use a inverter through which the dcvoltage is converted to its equivalent ac voltage. 8
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INDUCTION COILInduction coil is used to check back flow of voltage frombattery to thermo pile Hence through this we convert the wasted engine gastemperature to some useful work.With the help of the primary and secondary coil arrangement,we can amplify the voltage obtained through the step-uptransformer action.9
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CALCULATIONSHere we considered the junction between the constantan and leadand selecting the copper (CU) as the base material. Thus thejunction for the thermocouple has been achieved. Some experimentally tested values: Vseebeck = Vcopper-pb = 0.181mv Vcopper-constantan = 4.436mv Then the voltage produced is given by a standard equation, VAB = αθ + (1/2 βθ^2). Where,A, B – Some two different metals. θ – Temperature difference between hot and cold junction. α, β – Thermo electric coefficients (material parameters forconstantan).α = -38.1µv/ºc β = -0.089µv/ (ºc) ² for temperature range 200K and400K. 10
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Here,Let A be 60% of copper.Let B be 50% of copper.On substituting in above equation,VAB = ((-38.1) ×106×200 )+ (.5×-.089×2002×10-6)VAB = -9.4×10-3 volts. If we use “n” number of couples in series, V= n× (-9.4×10-3) volts. If we use 50 series of couples means voltage can be increased by, V= 50× (-9.4×10-3) volts Vnet = - 0.47 volts.11
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Power :We know that the resistance offered byone thermo-couple = 49 µ ΩResistance for a set of 50 thermocouples = 50 × 49 µ Ω = 2.45 m ΩR = 2.45 m ΩV = -0.47 VPower (P) = V²/RP= ( -0.47)²/ (2.45 ×10-3 )P = 90.16 Watts . 12
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To generate 6 volts we need to make 639 thermo couples Insulation paint BLACK VELVET 738 Rs / l Cost of copper 142m(1mm)=450 Rs(1775 pieces) Cost of iron 190m(.5mm)=100 Rs(2375 pieces) Length of one couple 8 cm Cost of copper in thermo pile Rs162.25 Cost of iron in thermo pile Rs 26.95 Total cost for generating 6 volts =Rs189.2 15
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ADVANTAGES Here the exhaust temperature is effectively used. Serves as an alternate purpose of producing electric voltage. Compatible in size so requires less provision. Easy to operate. Controls the regular charging of batteries.CONCLUSIONThus by our paper we have adapted a different way of utilizing the engine exhaustgas temperature into some useful work without wasting it unnecessarily. 16
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