Hindawi Publishing Corporation Journal of Energy Volume 2015, Article ID 495418, 8 pages http://dx.doi.org/10.1155/2015/495418

Research Article Recovery of Exhaust Waste Heat for ICE Using the Beta Type Stirling

Wail Aladayleh and Ali Alahmer

DepartmentofMechanicalEngineering,TafilaTechnicalUniversity,P.O.Box179,Tafila66110,Jordan

Correspondence should be addressed to Ali Alahmer; [email protected]

Received 26 August 2014; Accepted 9 December 2014

Academic Editor: Guobing Zhou

Copyright © 2015 W. Aladayleh and A. Alahmer. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

This paper investigates the potential of utilizing the exhaust waste heat using an integrated mechanical device with internal combustion engine for the automobiles to increase the fuel economy, the useful power, and the environment safety. One of the ways of utilizing waste heat is to use a . A Stirling engine requires only an external heat source as wasted heat for its ∘ operation. Because the exhaust gas may reach 200 to 700 C, Stirling engine will work effectively. The indication work, real shaft power and specific fuel consumption for Stirling engine, and the exhaust power losses for IC engine are calculated. The study shows the availability and possibility of recovery of the waste heat from internal combustion engine using Stirling engine.

1. Introduction give largest power at high temperature. Another method now used to recover the heat from exhaust gas is called Today, the energy researches take a wide place in the world; organic Rankin cycle (ORC). Figure 2 is based on the steam the automobile is so significant that it consumes more than generation in a secondary circuit using the exhaust gas half of the total energy used by all types of transportation thermal energy to produce additional power by means of combined. Numerically, the energy consumption of auto- a steam expander. The principle working of the organic mobiles accounts for 52% of all energy used by the entire Rankin cycle is the same as that of Rankin cycle: the working transportation; less than 35% of the energy in a gallon of fluid is pumped to a boiler where it is evaporated, passed gasoline reaches the wheels of a typical car; the remaining through an expansion device (turbine or other expander), heat is expelled to the environment through exhaust gases and then passed through a condenser heat exchanger which and engine cooling systems [1]. Figure 1 illustrates the energy it is finally recondensed [3, 4]. Another method to recover losses of internal combustion engine (ICE). The figure shows exhaust heat is by the use of the Stirling engine technique. the thermal losses take 60% approximately, and 33% of the This method has more activity and it is considered an power is expelled with exhaust gases; in another mean two- external combustion engine to produce mechanical work. thirds of our fuels’ money was spent in the environment. The recovery and utilization of waste heat not only conserve Sincemostoftheenergyconsumedbyaninternalcombus- fuel, usually fossil fuel, but also reduce the amount of waste tion engine is wasted, capturing much of that wasted energy heat and greenhouse gases damped to environment [2]. The can provide more power and efficiency. Many researchers use of Stirling engine has many advantages which can be examine how to utilize that lost energy and many methods summarized as follows [5–7]: high potential efficiency up to were used such as thermoelectric generation, piezoelectric 45%, reversible operation, cleaner emissions, quiet operation, generation, thermionic generation, thermophotovoltaic, and low vibrations, low maintenance, smooth torque delivery, mechanical turbo [2]. But these entire components were and ability to run at different fuels; finally Stirling engine considered as electric or electronic methods and they cannot does not have valves, carburetor, ignition system, or boilers. 2 Journal of Energy

Exhaust 33%

Thermodynamics Total energy losses losses

Cooling 29% Fuel energy 100% Engine 11.5%

Friction Transmission 5% losses 33% Mechanical Rolling resist power 38% 11.5% Energy used to move the Brakes 5% car 21.5% Air drag 5% Air drag 5%

Figure 1: Energy losses of internal combustion engine.

Reduce heat

Heat Heat Power Expender Electric + exchanger Gas (radiator) (turbine) generator $$ Gasifier

Sealed system Gas Liquid

Cooler Pump Liquid (radiator)

Figure 2: Organic Rankin cycle (ORC).

On the other side the main disadvantages and limitations can 2. Stirling Engine Effective Factors be concluded as long start-up time at cold starting, typically not self-starting, and finally being quite large and heavy. Usually the design point of a Stirling engine will be some- The main objectives of this paper could be summarized in where between the two limits of (1) maximum efficiency point two points: using Stirling engine to recover the waste power and (2) maximum power point. There are many factors that through exhaust manifold to generate electrical power and may affect the out power and mechanical efficiency for the also showing the effect of raising the entire operating Stirling efficiency, which can be concise as the following. for Stirling engine to get more power in practical size for the (i) Swept volume: the area under the P-V diagram indicates automobile and internal combustion engine. to the network that if the volume expands the power will The body structure of this paper starts by highlighting be increased; (ii) regenerator efficiency: the regenerator has objectives, advantages, limitations, and related research in mesh wires to store the heat while the working gas transfers Sectionone.Themainfactorsthathaveaneffectonthe between the hot side and cold side; theoretically if the engine performance of Stirling engine were displayed in Section two. does not have a full regenerative, the major trouble will be Thermodynamic model analysis in terms of Schmidt cycle, in the stream flow losses through the regenerator; (iii) mean waste exhaust recovery, Stirling engine power, and exhaust pressure: it is the average pressure inside the engine at the temperature profile were covered in Section three. Our pro- maximum and lower ; the problem appeared posed exhaust’s heat recovery system in Section four follows. when the inside pressure is more than the atmospheric Section five presented the experimental methodology and pressure;unbalanceonthepistonwilloccur;(iv)workinggas: setup. The calculation and results were depicted in Section the type of gas in the Stirling engine takes a major factor; to six. Finally, Section seven summarizes the entire paper and get more power, the filled gas must have high specific heat shows the main conclusion. capacitysothatthegaswillgainandlosetheheatrapidly; Journal of Energy 3

𝑃 𝑃 then the piston is moving rapidly to produce a positive speed The engine pressure basedonthemeanpressure mean,the [5]. The hydrogen has the lowest molecular weight soit minimum pressure 𝑃min, and the maximum pressure 𝑃max is has great efficiency but low safety. Helium (He), N2,and described in [8]: air were considered a working gas for Stirling engine; and 𝑃 √1−𝑐2 𝑃 (1−𝑐) finally (v) temperature difference: as any , the 𝑃= mean = max mechanical efficiency stands upon the hot temperature and 1−𝑐⋅cos (𝜃−𝐴) 1−𝑐⋅cos (𝜃−𝐴) (5) cold temperature so more difference gives more efficiency. 𝑃 (1+𝑐) = min , 1−𝑐⋅cos (𝜃−𝐴) 3. Thermodynamic Analysis where −1 V sin 𝜑 3.1. Schmidt Cycle Analysis. The Schmidt cycle is defined asa 𝐴=tan , Stirlingcycleinwhichthedisplacerandthepowerpistonor 𝑡+cos 𝜑+1 the two power pistons move sinusoidally and dead volumes 4𝑡𝑥 arefound.TheassumptionsuponwhichtheSchmidtanalysis 𝑆=𝑡+2𝑡𝑥 + 𝑅 + V +2𝑥 +1−2𝑥 , 𝐷𝐸 1+𝑡 𝐷𝐶 𝐵 wasbasedareasfollows[8]: (i) sinusoidal motion of parts; (ii)gastemperaturesknownandconstantinallpartsofthe 𝑉 𝑥 = 𝐵 , engine; (iii) absence of gas leakage; (iv) working fluid follow- 𝐵 𝑉𝑆𝐸 ing perfect gas law; and finally (v) at each instant in the cycle (6) the gas pressure being the same throughout the working gas. 2 2 𝐵=√𝑡 +2(𝑡−1) V cos 𝜑+V −2𝑡+1, InthispapertheSchmidtcyclewillbeevaluatednumer- ically.Theperformanceoftheenginecanbecalculatedusing 𝐵 𝑇 𝑉 𝑉 𝑐= ,𝑡=𝐶 , V = 𝑆𝐶 ,𝑥= 𝐷𝐸 , P-V diagram. The volume in the engine is calculated using the 𝐷𝐸 𝑆 𝑇𝐸 𝑉𝑆𝐸 𝑉𝑆𝐸 internal geometry. When the volume, mass of the working gas, and the temperature are decided, then the pressure is 𝑉𝐷𝐶 𝑉𝑅 𝑥𝐷𝐶 = ,𝑥𝑅 = , calculated using an ideal gas method in PV = mRT equation. 𝑉𝑆𝐸 𝑉𝑆𝐸 Firstly, the volumes of the expansion and compression where 𝑡 is temperature ratio, V is a swept volume ratio, and 𝑥 cylinder at a given crank angle will be determined. The in- is dead volume ratio. stantaneous expansion volume 𝑉𝐸 is The net indicated work per cycle8 [ ] is described by

𝑃 𝑉𝑆𝐸𝜋𝑐 (1−𝑡) sin 𝐴 𝑉𝑆𝐸 𝑊 = mean 𝑉 = (1− 𝜃) +𝑉 , (1) net √ 2 𝐸 2 cos 𝐷𝐸 1+ 1−𝑐

𝑃min𝑉𝑆𝐸𝜋𝑐 (1−𝑡) sin 𝐴 √1+𝑐 𝑉 𝑉 = ⋅ (7) where 𝑆𝐸 is a swept volume of the expansion piston and 𝐷𝐸 1+√1−𝑐2 √1−𝑐 is an expansion dead volume under the condition. 𝑉 𝑃 𝑉 𝜋𝑐 (1−𝑡) 𝐴 √1−𝑐 The instantaneous compression volume 𝐶 is determined = max 𝑆𝐸 sin ⋅ . by 1+√1−𝑐2 √1+𝑐

𝑉 𝑉 3.2. Waste Heat Energy Calculation. The quantity of waste 𝑉 = 𝑆𝐸 [1− 𝜃) + 𝑆𝐶 [1 − (𝜃−𝜑)]+𝑉 −𝑉, 𝐶 2 cos 2 cos 𝐷𝐶 𝐵 heat contained in an exhaust gas is a function of both the (2) temperature and the mass flow rate of the exhaust gas: ̇ 𝑄 = 𝑚∗𝑐̇ 𝑝 ∗Δ𝑇, (8) 𝑉 𝑉 where 𝑆𝐶 is a swept volume of the compression piston, 𝐷𝐶 𝑄̇ 𝑚̇ is a compression dead volume, and 𝜑 is phase angle. where is the heat loss (kJ/s); istheexhaustgasmassflow rate (kg/s); 𝑐𝑝 is the specific heat of exhaust gas (kJ/kg⋅K); and The total instantaneous volume is calculated in Δ𝑇 is temperature gradient in K. The mass flow rate of exhaust gas 𝑚̇ 𝐸 𝑉=𝑉𝐸 +𝑉𝑅 +𝑉𝐶. (3) 𝑚̇ 𝐸 = 𝑚̇ 𝑓 + 𝑚̇ 𝑎. (9)

Mass flow rate of air𝑚 ( ̇ 𝑎) can be evaluated according to In the Beta type Stirling engine, the displacer piston and the power piston are located in the same cylinder. When both 𝑚̇ 𝑎 =𝜇𝛾 ∗𝜌𝑎 ∗ V𝑠 ∗𝑁∗2. (10) pistonsoverlap,aneffectiveworkingspaceiscreated.The Mass flow rate of fuel (𝑚̇ 𝑓) overlap volume 𝑉𝐵 is 𝑚̇ 𝑚̇ = 𝑎 . 𝑓 (𝐴/𝐹) (11) 2 2 ratio 𝑉𝑆𝐸 +𝑉𝑆𝐶 √ 𝑉𝑆𝐸 +𝑉𝑆𝐶 𝑉𝑆𝐸𝑉𝑆𝐶 𝑉𝐵 = − − cos 𝜑. (4) 2 4 2 The volumetric efficiency (𝜇𝛾)hasarange0.8to0.9. 4 Journal of Energy

0.02 400 C) AB ∘ Large. Well-designed 350 Idle, 700 rpm high-efficiency 300 with good cooling 250 200 )

) 0.015 150 E 100 Ceramic heater parts 50

/(PfV 0 Exhaust temperature ( temperature Exhaust 0 0 20406080100 𝒫 0.01 Limit for conventional Length along exhaust system (inch) stainless steel C)

heater parts ∘ 700 0.008 AB 600 High-alloy heater 500 Beale ( number parts 0.005 400 Smaller. Moderate efficiency 300 engines designed for 200 economy. Long life. Or Accelerated, 2000 rpm 0.002 limited cooling availability 100

Exhaust temperature ( temperature Exhaust 0 0 600 800 1000 1200 0 20406080100 363 Heater temperature (K) Length along exhaust system (inch) Predicted Figure 3: Graph of vs. heater temperature for a range Actual of Stirling engines [5]. Figure 4: Illustration of the exhaust gas temperature versus tailpipe length [9]. 3.3. Engine Power Output. Power output can be estimated using a variety of methods which takes into consideration many things like temperature difference, operating speed and through the exhaust system are required to determine the pressure, expansion and compression space volumes, and most effective location for Stirling engine placement. Figure 4 regenerator effectiveness. The Beale and West numbers were shows the comparison of the estimated and measured tem- used to determine the Stirling engine power. peratures for almost identical runs along the exhaust line of the test vehicle for both idling and accelerated engine 3.3.1. Beale Number. It is an empirical number that char- speeds [9]. The surface temperature measurements method acterizes the performance of Stirling engine. It is used to wasusedinnearlystableconditionsafterinitialwarm- estimate the power output of Stirling through relating an up. Exhaust temperatures for idling conditions were much indicated power, P𝑜 (W), to mean pressure 𝑃 (bar), operating lower compared to accelerated conditions. When moving 3 frequency 𝑓 (Hz), and expansion space volume 𝑉𝐸 (cm )with away from the exhaust valve, the gases temperatures will the Beale number 𝐵𝑛: be decreased. Exhaust temperature varies with engine load; more loads or speed means more exhaust temperature due to P𝑜 =𝐵𝑛𝑃𝑓𝑉 𝐸. (12) decreasing in expansion cooling.

Beale number can be estimated from Figure 3,showinga 4. Proposed Exhaust’s Heat Recovery System graph plotted by measuring data from many Stirling engines. The solid line in the middle is typical of most Stirling engines Figure 5 presents the unit of heat recovery for exhaust sys- while the upper and lower lines denote unusually high or low tem (3D/section) views. Stirling engine components are (1) performing engines [5]. exhaust gases outlet; (2) exhaust gases inlet; (3) hot heat exchanger; (4) displacer piston cylinder; (5) coolant jacket; 3.3.2. . ItissimilartotheBealenumberexcept (6) crank case container (to keep high pressure behind power ittakesdirectaccountofthetemperaturedifference.The piston); (7) displacer; (8) power piston; and finally (9) crank formula is expressed as shaft and flywheel. Afterwards, the exhaust gases leave the combustion 𝑇 −𝑇 ℎ 𝑐 chamber, they will enter through hot exchanger’s pipe 1, and P𝑜 =𝑊𝑛𝑃𝑓𝑉 𝐸 ( ), (13) 𝑇ℎ +𝑇𝑐 then they leave from heat exchanger pipe 2 and then to cat- alytic converter, muffler, and tailpipe. 𝑊 where 𝑛 is the West number, which has an average value of Hot heat exchanger must be near to exhaust valve or 0.25–0.35, and a higher number represents a more efficient isolatetheinletpipeinRockwooltopreventtheexhaust engine. gases’ heat escaping before it entered the heat exchanger. The coolantjacketisusedtogetdifferenceinenginetemperature 3.4.TemperatureProfileinAutomotiveExhaustSystems. The also, to improve good contraction for working fluid for flow rate and temperature profile of the burnt gases passing Stirling engine in cold side of Stirling engine; coolant jacket Journal of Energy 5

1 Table 1: Specifications and parameters of the internal combustion 3 4 engine.

5 ICE specifications 7 Brand Robin engines single cylinder 2 Model EX13D-4 stroke 8 Displacement 126 CC 6 9 Max. output 3.2 KW at 4000 rpm Max. torque 8 N.m at 2500 rpm Fuel Unleaded gasoline Spark plug NGK B4 (recommended) Cooling Air cooling Lubricant API/SEorSAE10W-30 Figure 5: Exhaust’s heat recovery unit. ICE parameters Bore 58 mm Stroke 48 mm Air intake duct diameter 54.8 mm Exhaust manifold diameter 64 mm

Table 2: Readings of ICE powered by Jordanian gasoline/octane rate 95 after 135 seconds at beginning of the engine operation.

ICE reading ∘ Exhaust gas temperature 200 C ∘ Ambient temperature 24.5 C Oil temperature 85.8 C Fuel temperature 23.8 C Engine speed 2585 rpm Figure 6: SI Robin engine single cylinder, air cooled and with direct- Engine power 2.3 KW injection. Air flow speed 1.5 m/s must be connected directly with a separated radiator. The displacer owns a vertical hole with mesh material because of Table 3: Parameters and specifications of Stirling engine. brief in engine size; the container also has compensated valve to modify entire pressure of the engine. Stirling engine parameters Engine configuration Stirling engine-Beta type 5. Experimental Setup Hot swept volume 200 CC Cold swept volume 150 CC A number of experiments were carried out in Tafila Technical Hot dead volume 25 CC University in the automotive laboratories. A Robin engine Cold dead volume 20 CC single cylinder, air cooled and with direct-injection engine, Regenerator volume 30 CC wasusedinthisworkasshowninFigure6.Theengine Mean pressure 20 bars specifications are listed in Table 1.Tomeasurethegasoline ∘ Hot side temperature 200 C engine torque, the engine was coupled to dynamometer. The ∘ reading of engine parameters was recorded after 135 sec of Cold side temperature 35 C ∘ engine operation and depicted in Table 2. The Stirling engine Phase angle 90 was coupled to ICE. The specification of Stirling engine was Engine speed 1500 rpm (25 Hz) listed in Table 3. Working fluid Air

6. Results and Calculations To evaluate the wasted exhaust power, the air and fuel flow fuel and air flow are 0.16 g/s and 4.32 g/s, respectively. The through the combustion process should be estimated. From brake power and recovery exhaust power are 0.901 kW and the recorded information during experiment in Table 2,the the percentage difference for exhaust and brake power is 61%. fuel consumption is 21.6 g in interval 135 seconds. So the The result of availability of heat recovery by Robin engine is 6 Journal of Energy

3000 450 400 2500 350 300 2000 250 200 1500 150 Total volume (cc) volume Total

Pressure (kPa) Pressure 100 1000 50 0 0 50 100 150 200 250 300 350 400 500 ∘ 200 250 300 350 400 450 Crank angle (𝜃 ) Volume (cc) Figure 9: Changing of the total volume versus the crank angle for Figure 7: Relation between entire and changing in volume Stirling engine. for Stirling engine.

3000 350 2500 300 2000 250

) 1500 3 200 1000 Pressure (kpa) Pressure 150 500 Volume (cm Volume 100 0 50 0 50 100 150 200 250 300 350 400 ∘ Crank angle (𝜃 ) 0 0 50 100 150 200 250 300 350 400 Figure 10: Changing of the pressure versus the crank angle for 𝜃∘ Crank angle ( ) Stirling engine.

e c total pressure versus crank angle is depicted in Figure 10. Figure 8: Relation for volume changing of expansion and contrac- The relation between pressure and total volume is inverse tion space versus crank angle. here. The expansion and contraction intervals cannot be determined precisely from P-V diagram. But on the other side, the expansion and contraction can be easily evaluated similar to 04 Prius 1NZ-FEX and BMW M135i which give from V-𝜃 or P-𝜃 diagram. (58% and 56%, resp.) percentage difference. According to the Schmidt cycle, the ideal expansion work, Figure 7 represents the relation between entire pressures pumping work, total network, and ideal net power are 88.5 J, andchanginginvolumeforStirlingengine,thecurvebeing −56.6 J, 31.9 J, and 0.772 kW at 1500 rpm, respectively. For formed as cam lobe due to dead volume affected and non- estimation the real output (shaft power) for Stirling engine sinusoidal motion for the drive mechanism; Schmidt cycle is0.42kWbasedontheBealemethod.FromFigure3,the ∘ givesidealassumption,elsedeadvolumeandnonsinusoidal Bealenumberisnearly0.0042atheatertemperature200C. motion, too. The area enclosed in P-V curve was indicated So, mechanical efficiency for Stirling engine is 51.8%. work per one cycle. Figure 8 illustrates the relation for volume To determine the specific fuel consumption using Stirling changing of expansion and contraction space with crank engine, the following equation was used: angle. From this diagram the location of the volumes of . . . expansion can be determined and contraction space must be s f c without Stirling s.f.c. = , (14) equal relatively to crank angle. Also it can be provided as an with Stirling 1+h indication for critical point when the volume was converted where h is lowering percentage for brake power; in this case or changed from increasing to decreasing or inverting versus it is equal to 18%, so the s.f.c. with Stirling engine will lower crank angle. Figure 9 shows the relation between total to 15% of s.f.c. without Stirling engine. h canbecalculatedby volumes for Stirling engine versus crank angle. From this dividing real brake power for Stirling engine on brake power diagram the total volume changing relatively to crank angle for IC engine: can be determined; also the flow rate of working gas inside P Stirling engine can be estimated at any instant. After that h = br.sti . P (15) the flow losses through the engine can be evaluated. The br.IC Journal of Energy 7

450 7. Conclusion 400 The utilization of the exhaust waste heat for ICE by the use 350 of Stirling engine was investigated. The study results can be summarized into the following points.

h) 300 ·

250 (i) Waste heat of internal combustion engine is consid- ered great problem; two-thirds of that energy which 200 entered through the engine was lost to the environ-

bs.f.c. (gm/kW 150 ment. 100 (ii) Waste heat recovery takes great benefits as raising fuel mileage and reducing greenhouse gases and fuel con- 50 sumption, so that the IC efficiency will be increased. 0 0 20 40 60 80 100 120 (iii) Around 15% can be improved in vehicle fuel econ- Engine load (%) omy through installing Stirling engine cross exhaust manifold to recover waste heat in internal combustion With Stirling engine Without Stirling engine engines. (iv) The recovered power through Stirling engine can be Figure 11: Showing brake specific fuel consumption without Stirling converted to charge vehicle’s batteries or to operate engine and with Stirling engine. themechanicalauxiliarysuchasoilpump,water pump, A/C compressor, and power steering pump. (v) Applications’ range for this project is not trapped on 3000 theautomobileonly,butitcanbeapplicableonelec- tricity generation planets, mining application cement 2500 planets, and factories.

2000 (vi) Three obstacles to using Stirling engine are as follows: (1) adding some weights to the automobile which is 1500 going to decrease its fuel efficiency, so in order to be viable it must be light; (2) backpressure through the

Pressure (kPa) Pressure 1000 exhaust system; (3) additional pumping power losses.

500 Conflict of Interests 0 0 100 200 300 400 500 The authors declare that there is no conflict of interests 3 Volume (cm ) regarding the publication of this paper. 1 bar 10 bars 5 bars 15 bars References

Figure 12: P-V diagram at different operating pressures. [1] J. Halderman, Automotive Technology, Prentice Hall, 4th edi- tion, 2011. [2]J.JadhaoandD.Thombare,“Reviewonexhaustgasheat recovery for I.C. engine,” International Journal of Engineering and Innovative Technology,vol.2,no.12,pp.93–100,2013. The brake specific fuel consumption without Stirling engine [3]N.Galanis,E.Cayer,P.Roy,E.S.Denis,andM.Desilets,´ “Elec- and with Stirling engine is displayed in Figure 11.Atbegin- tricity generation from low temperature sources,” Journal of ning of engine loading, bs.f.c. for internal combustion engine Applied Fluid Mechanics,vol.2,no.2,pp.55–67,2009. with and without Stirling engine are identical due to lowering [4] K. K. Srinivasan, P. J. Mago, and S. R. Krishnan, “Analysis of in exhaust temperature (low load); subsequently when the exhaust waste heat recovery from a dual fuel low temperature engine load was increased, exhaust temperature will also combustion engine using an Organic Rankine Cycle,” Energy, increase, so Stirling engine will work effectively to reduce vol.35,no.6,pp.2387–2399,2010. specific fuel consumption. So at those moments bs.f.c. curves [5] C. Lloyd, A low temperature differential stirling engine for are not identical. power generation [M.S. thesis], Department of Electrical and Figure 12 displays the P-V diagram at different operating Computer Engineering, University of Canterbury, 2009. pressures. The indicated work is represented by the area of [6] U. Ramesh and T. Kalyani, “Improving the efficiency of marine enclosed curve for each operating pressure. As shown in the power plant using stirling engine in waste heat recovery sys- figure as the operating pressure increases, the area enclosed tems,” International Journal of Innovative Research and Devel- willincreaseanditwillincreasetheindicatedwork. opment,vol.1,no.10,pp.449–466,2012. 8 Journal of Energy

[7] J. Ruiz, Waste heat recovery in automobile engines: potential solu- tions and benefits [Master dissertation], Department of Mechan- ical Engineering, Massachusetts Institute of Technology, 2007. [8] K. Hirata, “Schmidt theory for Stirling engines,” Tech. Rep., National Maritime Research Institute, 1997. [9]M.Ehsan,M.Shah,H.Hasan,andS.Hasan,“StudyofTemper- ature Profile in automotive exhaust systems for retrofitting cat- alytic converters,”in Proceedings of the International Conference on Mechanical Engineering (ICME ’05), Dhaka, Bangladesh, 2005. Journal of Journal of International Journal of Rotating Energy Wind Energy Machinery

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