Waste heat recovery by using thermoelectric generator

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This paper explains how to convert the lost energy through exhaust system in internal combustion engines “ICE” to electric energy by using thermoelectric generators "TEG" with the benefit of the equipment’s which are already existed in most of the internal combustion engines such as water pump, heat exchanger, and exhaust system.

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Nội dung Text: Waste heat recovery by using thermoelectric generator

International Journal of Mechanical Engineering and Technology (IJMET) Volume 10, Issue 03, March 2019, pp. 188–195, Article ID: IJMET_10_03_019 Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJMET&VType=10&IType=3 ISSN Print: 0976-6340 and ISSN Online: 0976-6359 © IAEME Publication Scopus Indexed WASTE HEAT RECOVERY BY USING THERMOELECTRIC GENERATOR Basel Al Ghabet*, Raymond Kwesi Nutor, Xiaozhen Fan, Sensheng Ren, Yunzhang Fang* Physics Department, Zhejiang Normal University, Jinhua, China. *Corresponding Author ABSTRACT This paper explains how to convert the lost energy through exhaust system in internal combustion engines “ICE” to electric energy by using thermoelectric generators "TEG" with the benefit of the equipment’s which are already existed in most of the internal combustion engines such as water pump, heat exchanger, and exhaust system. The miniature cooler system which is designed in the laboratory to execute the experiment is similar to combustion engines water coolant system to keep the cold side in “TEGs” fixed on ambient temperature. The heat source was applied on the hot side to “TEGs” is came from small candles where the “TEGs” consist of “Bismuth Telluride” material as N-P stripes attached thermally in parallel and electrically in series where it inserted between two porcelain layers. The electric current generated from “TEGs” is direct current “DC” the experiment showed the value of electrical current was proportional to the temperature difference between "TEGs" sides. Key words: TEG; Waste heat recovery; ICE Cite this Article: Basel Al Ghabet, Raymond Kwesi Nutor, Xiaozhen Fan, Sensheng Ren, Yunzhang Fang, Waste Heat Recovery by using Thermoelectric Generator, International Journal of Mechanical Engineering and Technology 10(3), 2019, pp. 188–195. http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=10&IType=3 1. INTRODUCTION Since 1970, conveyances, specifically the ignition of gas and diesel in vehicles, have acquired expanding consideration as a source of air contamination at both neighbourhood and worldwide scales. More than 95% of mechanized transport relies upon oil and records for almost half of world utilization of oil (Woodcock et al., 2007). For the measure of auto use, in the OECD (Economic Cooperation and Development) nations [1]. For these reasons and others, the energy scientists have concentrated on their researchers to solving these problems by using clean energy and developing internal combustion engines to reduce the emission of harmful gases. For these reasons and others, the energy scientists have concentrated in their researchers to solving these problems by using clean energy and developing internal http://www.iaeme.com/IJMET/index.asp 188 editor@iaeme.com
Basel Al Ghabet, Raymond Kwesi Nutor, Xiaozhen Fan, Sensheng Ren, Yunzhang Fang combustion engines to reduce the emission of harmful gases. One of these methods is to use the waste heat in internal combustion engines to generating electricity. Waste warmth through fumes (30% as a motor cooling framework and 30 to 40% as nature through fumes gas). Fumes gases quickly leaving the motor can have temperatures as high as 842-1112°F [450- 600°C]. Therefore, these gases have high heat content, diverting as fumes discharge. Accomplishments can be made to outline more vitality proficient reverberator motor with better heat exchange and lower fumes temperatures; notwithstanding, the laws of thermodynamics put a lower confine on the temperature of fumes gases Figure (1) demonstrate add up to vitality circulations from the inward burning motor. [2]. Figure 1 Total energy distributions from the internal combustion engine 2. THE PRINCIPLE OF “TEG” MODULES Thermoelectric is a device depend on Seebeck effect principle to work wherein 1821 the German physicist Thomas Johann Seebeck found that when two segments of various electrically primary materials were isolated along their length yet merged by two "legs" at their closures, an attractive field created around the legs, gave that a temperature division existed between the two crossings. He distributed his acuities the next year, and the wonder came to be known as the Seebeck impact. Be that as it may, Seebeck did not spot the reason for the attractive field. This attractive field comes about because of equivalent however inverse electric streams in the two metal-strip legs. These streams are caused by an electric potential distinction over the intersections instigated by heat contrasts between the materials. On the off chance that one intersection is open however the temperature differential is kept up, current never again streams in the legs yet a voltage can be predictable over the open circuit. This created voltage (V) is the Seebeck voltage and is identified with the distinction in temperature (ΔT) between the heated intersection and the open intersection by a proportionality factor (α) called the Seebeck coefficient, or V = αΔT. The inducement for α is subject to the sorts of material at the intersection. While there is a Seebeck impact in intersections between various metals, the impact is little. A significantly bigger Seebeck impact is accomplished by utilization of p-n intersections between p-sort and n-type semiconductor materials [3]. The figure (2) demonstrates p-sort and n-type semiconductor legs between a heat source and a heat sink with an electrical power heap of protection RL associated over the low-temperature closes. A practical thermoelectric gadget can be comprised of numerous p-sort and n-type semiconductor legs associated electrically in arrangement and thermally in parallel between a typical heat source and a heat sink http://www.iaeme.com/IJMET/index.asp 189 editor@iaeme.com
Waste Heat Recovery by using Thermoelectric Generator Figure 2 N-type and P-type semiconductor legs between the heat sink and a heat source 3. TEG PROFICIENCY AND FIGURE OF MERIT Figure (3) represents a thermoelectric circuit (or couple) comprising of two distinct homogeneous materials A and B, their intersections kept up at hot intersection temperature Th and cold intersection temperature Tc (Th > Tc), and the terminals 1 and 2 of the circuit are associated with an outside load RL. The heat proficiency, ηg, of the circuit, appeared in figure (3) can be considered as (1) Where P is the electrical power which conveyed to the outer load RL and qh is the heat input required to keep up the hot intersection temperature at Th. Figure 3 Thermoelectric circuit The electrical power, , is defined as (2) In equation (2) is the present coursing through the circuit and is characterized as the proportion of emf created over the circuit to the cumulative shield of the circuit. (3) where α is the combined Seebeck coefficient of the materials A and B, ΔT is the temperature contrast between the hot and cool intersections and R is the collection electrical protection of the materials A and B. The heat contribution at the hot intersection, Th, is given by (4) http://www.iaeme.com/IJMET/index.asp 190 editor@iaeme.com
Basel Al Ghabet, Raymond Kwesi Nutor, Xiaozhen Fan, Sensheng Ren, Yunzhang Fang Where is the combined Heat conductance of the materials A and B. The terms (κΔT) and (- 1/2 I^2 R) in condition (4) result from the two irreversible impacts of Heat exchange because of Heat conduction and Joule heating. While the term (αT_h) is because of the reversible Peltier impact. Combining equalities (2), (3), (4), and lead to: (5) ( )( ) ( ) For a fixed , , and , the can be improved when the term (Rκα2 ) in the denominator of condition (5) is limited. This gathering of properties, called the thermoelectric figure of merit (Z), is characterized as (6) Where: (̅ ̅ ) (̅ ̅ ) (̅ ̅ ) Where is the quantity of (series associated) couples in the gadget or generator, ̅ and ̅ are the Seebeck coefficients of the n and p write material arrived at the midpoint of over the temperature run to . ̅ And ̅ are the electrical resistivity and ̅ and ̅ are the heat conductivities averaged similarly. is the aspect ratio of the legs and assumed uniform over the device or generator.[4] 4. DESCRIPTION OF EXPERIMENT The proposed system in the laboratory was four thermoelectric modules attached as parallel in thermally way and electrically in series way generate electrical power, where each module has specifications shown in the table (1). The heat source was candles put under aluminium heat sink which it touches TEGs in hot side and transfer the heat by conduction process, while the cold side of TEGs is connected with an aluminium plate to dissipating the heat through water flow inside it. The water was pumped by using a small water pump located between small water tank and small heat exchanger, where the purpose of heat exchanger is scattering the heat immersed from cold way of TEGs and keep the water temperature equal to ambient temperature, therefore the water is flowing from water tank to heat exchanger to arrive aluminum plate have ambient temperature and come back to water tank in through closed circuit as shown in 3D drawing in figure (4). Table 1 Specifications of TEG module Dimensions 40 * 40 * 3.7mm component pairs 127 Lead Specifications Lead length 300 ± 5mm RV standard lead 5mm single tin Inner resistance 2.0 ~ 2.2Ω (ambient temperature 23 ± 1 ℃, 1kHZ Ac test) Temperature variance △ Tmax (Qc = 0) 62 ℃ above. Working current Imax = 6 Rated voltage DC12V (Vmax: 15.5V) Cooling control Qcmax 60W Assemblage pressure 85N / cm2 N-P material type Bismuth Telluride http://www.iaeme.com/IJMET/index.asp 191 editor@iaeme.com
Waste Heat Recovery by using Thermoelectric Generator Figure 4 3D drawing of an experiment 5. PRACTICAL EXPERIMENT AND RESULTS The figure (5) shows the practical experiment implementation with all equipment used. Figure 5 Practical experiment implementation The experiment shows that when the difference in temperature between "TEGs" both sides increase the electrical power output from "TEGs" increase as shown in tables (2) which illustrates the measurements are taken and results. http://www.iaeme.com/IJMET/index.asp 192 editor@iaeme.com
Basel Al Ghabet, Raymond Kwesi Nutor, Xiaozhen Fan, Sensheng Ren, Yunzhang Fang Table 2 The measurements are taken and results Cold side Hot side Temperature Output ( Output Output temperature(°c) temperature(°c) variance(°c) V) (A) (W) 21.5 24.3 2.8 0.28 0.05 0.014 21.5 30 8.5 2 0.12 0.24 21.5 40 18.5 3.63 0.24 0.8712 21.5 50 28.5 5.31 0.38 2.0178 21.5 60 38.5 6.79 0.48 3.2592 21.5 70 48.5 8.06 0.6 4.836 21.5 80 58.5 9.66 0.69 6.6654 21.5 90 68.5 12 0.77 9.24 21.5 100 78.5 12.4 0.93 11.532 21.5 110 88.5 13.1 0.97 12.707 Figure 6 "TEG" output(V, A, W) vs temperature difference The figure (6) shows the changing of “TEGs” output voltage, current, and power with the temperature difference respectively. 6. APPLYING “TEG” SYSTEM ON INTERNAL COMBUSTION ENGINES “ICE” A concept of power generation system by using thermoelectric generators which are designed for waste heat recovery in combustion engines based on the high temperature of rejected gases from the combustion chambers which flow inside a duct connected with the exhaust pipe to allow gases heat the internal sides of the duct while the TEGs based on external sides, the hot side of TEGs will absorbing heat from duct surface by conduction thermal process while the other side of TEGs will dissipating the heat through water flow inside aluminum plates fixed on the TEGs cold side by conduction thermal process too. The water which reasonable about absorbing the heat from cold side of TEGs came from the coolant combustion system existed in the most of engines by adding water circuit with small pipes diameter connected with the heat exchanger exit pipe and water pump inlet pipe where it enters the aluminum plates cold and exit hot after absorbs the heat from TEGs to enter the engine heat exchanger through water pump to cold back in closed circuit as shown in figure (7) while the figure (8) shows the water coolant connections of “TEG” system. http://www.iaeme.com/IJMET/index.asp 193 editor@iaeme.com
Waste Heat Recovery by using Thermoelectric Generator Figure 7 Fixing "TEG" system with "ICE" exhaust pipe Figure 8 Water coolant connections of “TEG” system 7. CONCLUSIONS This research illustrated one of the useful methods to benefit from waste heat in combustion engines and generate electric current by using thermoelectric generators with equipment exist already in most of the combustion engines, the main benefit of this system is reducing the fuels used in combustion engines which are leading to reduce the released emissions gases from engines and environmental conservation. http://www.iaeme.com/IJMET/index.asp 194 editor@iaeme.com
Basel Al Ghabet, Raymond Kwesi Nutor, Xiaozhen Fan, Sensheng Ren, Yunzhang Fang ACKNOWLEDGEMENTS This work was held by the Pioneering group of the Zhejiang Solid State Photo-electronic Plans Laboratory, Project 973 of the National Key Basic Research Program (No.2012CB825705) of China. REFERENCES [1] LU JIE, Professor Lars -Gunnar Franzén, Environmental Effects of Vehicle Exhausts Global and Local Effects – A Comparison between Gasoline and Diesel, Halmstad University, Halmstad 2011 [2] J. S. Jadhao, D. G. Thombare. Review of Exhaust Gas Heat Recovery for I.C. Engine. International Journal of Engineering and Innovative Technology (IJEIT) Volume 2, Issue 12, June 2013, ISSN: 2277-3754, Automobile Engineering Department, R.I.T., Sakharale, Dist. Sangali, (MS). [3] https://www.britannica.com/technology/thermoelectric-power-generator#ref48989. [4] Madhav A Karri, Wallace H. Coulter, Thermoelectric power generation system optimization studies a dissertation, NY 13699 – 5725, department of mechanical and aeronautical engineering School of Engineering Clarkson University Potsdam. http://www.iaeme.com/IJMET/index.asp 195 editor@iaeme.com

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