Comparative study of different exhaust heat exchangers effect on the performance and exergy analysis of a diesel engine

Accepted Manuscript Comparative study of different exhaust heat exchangers effect on the performance and exergy analysis of a diesel engine M. Hatami, M.D. Boot, D.D. Ganji, M. Gorji-Bandpy PII:

S1359-4311(15)00644-4

DOI:

10.1016/j.applthermaleng.2015.06.084

Reference:

ATE 6778

To appear in:

Applied Thermal Engineering

Received Date: 2 March 2015 Revised Date:

19 June 2015

Accepted Date: 21 June 2015

Please cite this article as: M. Hatami, M.D. Boot, D.D. Ganji, M. Gorji-Bandpy, Comparative study of different exhaust heat exchangers effect on the performance and exergy analysis of a diesel engine, Applied Thermal Engineering (2015), doi: 10.1016/j.applthermaleng.2015.06.084. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT 1

Comparative Study of Different Exhaust Heat Exchangers Effect on the

2

Performance and Exergy Analysis of a Diesel Engine

3

M. Hatamia,b,c,1, M.D. Boota, D.D. Ganjic, M. Gorji-Bandpyc a

Combustion Technology, Department of Mechanical Engineering, Eindhoven University of Technology (TU/e), P.O. Box 513, 5600 MB Eindhoven, The Netherlands b Esfarayen University of Technology, Department of Mechanical Engineering, Esfarayen, North Khorasan, Iran c Babol University of Technology, Department of Mechanical Engineering, Babol, Iran

RI PT

4 5 6 7 8 9

Abstract

11

In this research, the effect of three designed heat exchangers on the performance of an

12

OM314 diesel engine and its exergy balance is investigated. Vortex generator heat exchanger

13

(HEX), optimized finned-tube HEX and non-optimized HEX are considered and mounted on

14

the exhaust of diesel engine. Experiments are done for five engine loads (0, 20, 40, 60 and 80

15

% of full load) and four water mass flow rate (50, 40, 30 and 20 g/s) to find the most suitable

16

HEX case for exhaust exergy recovery which has the least effect on the engine performance.

17

Brake specific fuel consumption (BSFC), volumetric efficiency, fuel conversion efficiency

18

and engine exergy balance are discussed parameters in this study.

19

Keywords: Exergy Analysis; Irreversibility; Finned-tube heat exchanger; Vortex generator

20

Heat exchanger; Diesel exhaust.

21

1. Introduction

22

Researchers show that even with advanced engine technologies, around 30–40% of the fuel

23

energy is still lost through the exhaust system. Thus, energy recovery from the exhaust is a

24

promising technology allowing a 4–5% increase in the engine efficiency [1].

AC C

EP

TE D

M AN U

SC

10

1

Corresponding Author: Tel/Fax: +31658758651 E-mails: [email protected]; [email protected] (M. Hatami)

1

ACCEPTED MANUSCRIPT Nomenclature

I& Ke

k L m& Pe p

Q& R

Specific heat in constant pressure (J/kg.K) Specific enthalpy (J/kg) Inner convection coefficient (W/(m2K) Irreversibility (W) Kinetic energy (J) Thermal conductivity (W/m.K)

Length (m) Mass flow rate (kg/s) Potential energy (J) Pressure (Pa) Heat transfer rate (W)

Gas constant (J/kg.K)

S Tj u

Entropy (J/K) Temperature of source j (K) Velocity component

W

Work (J)

Greek symbols

ρ µ ψ

Density (kg/m3) Viscosity (kg/m s) Flow availability (J/kg)

& Φ η

Non-flow availability (W) Second law efficiency (%)

ν

Specific volume (m3/kg)

RI PT

h hi

Surface area (m2) Constants

SC

A C1, C2 Cp

These energy recovery systems are called Waste Heat Recovery (WHR) which efficiency is

26

widely improved by designing a suitable heat exchanger (HEX). Suitable heat exchangers

27

recover as much heat as possible from an engine exhaust at the cost of an acceptable pressure

28

drop. Design of each HEX should offer minimum pressure drop across the device, so that it

29

should not adversely affect the engine performance. Backpressure acting on the engine

30

deteriorates engine and emission performance [2, 3]. Pangavhane et al. [4] investigated the

31

various dimensions of the muffler keeping some dimensions constant to study the

32

backpressure effect and found that backpressure is reduced greatly if the porosity is doubled.

33

Moreover, backpressure increased sharply with increasing hole diameter. Bai et al. [5], in a

34

numerical study, studied the effect of baffles on the heat transfer and pressure drop of a heat

35

exchanger on the exhaust of a gasoline engine and observed more than 190kPa pressure drop

36

in some cases and recommended a bypass for the exhaust in these cases.

37

WHR can be an efficient way to produce useful work. For instance, Wang et al. [6], by means

38

of a multi-objective optimization for an Organic Rankine cycle (ORC), could effectively

39

recover low grade waste heat to electrical power. Maheswari et al. [7] utilized the thermal

40

energy wasted of exhaust gas for desalination using a submerged horizontal tube straight pass

AC C

EP

TE D

M AN U

25

2

ACCEPTED MANUSCRIPT evaporator and a condensing unit, without the aid of any external energy used for pumping

42

system. Some valuable designs for the HEX in WHR systems are proposed in the literature.

43

Banerjee et al. [8] used a porous heat exchanger, Liu et al. [9] applied a new system called

44

‘‘four-TEGs’’, Pandiyarajan et al. [10] designed a finned-tube heat exchanger using phase

45

change material (PCM), Lee and Bae [11] considered a heat exchanger including fins and

46

circulating coolant path, Zhang et al. [12] modeled a finned tube evaporator heat exchanger

47

for an ORC, Ghazikhani et al. [13] used a simple double pipe heat exchanger in the exhaust

48

of a diesel engine using water as coolant, Hossain and Bari [14, 15] applied a shell and tubes

49

HEX to a diesel engine, Mavridou et al. [16] examined a cross-flow plate heat exchanger

50

with finned surfaces on the exhaust gas side, with metal foam material substituting for the

51

fins. An extensive review on different heat exchanger designs can be found in an earlier study

52

[1].

M AN U

SC

RI PT

41

Recently, Hatami et al. [17] proposed a viscous model for exhaust heat exchanger

54

modeling based on the work of Lee and Bae[11]. The water-based fluids effect on exhaust

55

heat recovery using a finned-tube heat exchanger has been investigated by both the authors

56

[18] and Eftekhar et al. [19], wherein an optimized finned-tube heat exchanger geometry for

57

diesel exhaust heat recovery is proposed [20]. Mokkapati and Lin [21] proposed a heat

58

exchanger with twisted tape inserts and water coolant in a corrugated tube to evaluate its

59

impact on engine performance and economics for heat recovery from the exhaust of a heavy

60

duty diesel generator. The authors showed that the improvement in the rate of heat transfer

61

was about 235.3% for this type of heat exchanger. Recently, Feru et al. [22] developed a

62

dynamic model for a modular two-phase heat exchanger for waste heat recovery from both

63

the exhaust gas recirculation and main exhaust circuits in diesel engines. A low pressure drop

64

vortex generator based heat exchanger (VG-HEX) for diesel exergy recovery has been

AC C

EP

TE D

53

3

ACCEPTED MANUSCRIPT proposed by Hatami et al. [23]. Based on this literature review, the present study will

66

evaluate, with respect to engine performance and exergy equilibrium, three heat exchanger

67

designs: VG-HEX, Optimized finned tube HEX and non-optimized HEX.

68

Experimental setup and procedures

69

For diesel engine exhaust exergy recovery, three different heat exchangers (HEXs) were

70

designed and mounted on the exhaust of an OM314 diesel engine (Fig. 1). In our previous

71

work [18], we optimized the fin geometry by means of numerical ANSYS-FLUENT and a

72

Genetic Algorithm. All HEXs were 70 cm in length, with an inner diameter of 12 cm and

73

outer diameter of 14cm. The inlet and outlet diameters were both 4.8 cm. The HEXs were

74

mounted to the exhaust of an OM314 diesel engine as shown in Fig. 2 (see Table 1 for engine

75

specifications). A schematic overview of the experimental setup is presented in Fig. 3. All

76

temperatures were recorded with K-type thermocouples, at an accuracy of 0.1˚C. A ST-8920

77

differential pressure and velocity meter was used to determine the pressure drop and gas

78

velocity in the exhaust. It could measure the pressures in a range of +/- 5000 Pa at 1 Pa

79

resolution and could record the velocities in a 1.00-80.00 m/s range at 0.01 m/s resolution. In

80

addition, a small ( 175 ×135 × 55mm ) Omega data logger was used to display the temperature

81

values. Experiments were carried out for five loads (0, 20, 40, 60, and 80 %) and for each

82

load, four water flow rates were considered. A manometer and pressure gauge were mounted

83

(Fig. 3) to record the mass flow rate and pressure of the coolant, respectively. Furthermore, a

84

pitot tube was placed in the outlet of the exhaust to measure the exhaust gas flow rate and

85

total/static pressures. To prevent clogging in the tube by exhaust deposits, it was cleaned after

86

each measurement.

87

2. Data analysis

88

In this Section, exergy, engine and HEX performance are treated in in individual subsections.

AC C

EP

TE D

M AN U

SC

RI PT

65

4

ACCEPTED MANUSCRIPT 89

2.1 Exergy

90

Two control volumes are considered for the exergy analysis, namely the heat exchanger alone

91

as well as the whole setup. A. First Control Volume

RI PT

92

In the first control volume, a HEX alone is considered as shown in the Fig. 4-a. By

94

considering the HEX as a control volume, the exergy equations in the HEX can be written as

95

[23],

(1)

M AN U

d Φ cv & + ∑ m& ψ − ∑ m& ψ + W& − I& = ∑Φ Q i i e e act total dt

SC

93

d Φ cv is the non-flow exergy of the control volume, which is zero at steady state dt

where

97

conditions. Since HEX is insulated, the heat transfer to ambient is zero, i.e. first term in right

98

hand side of Eq. (1) is zero too. Also, the work in the control volume (fourth term in RHS Eq.

99

(1) is zero. Accordingly, the exergy equation will become,

TE D

96

I&total = ∑ m& iψ i − m& eψ e = m& water / inletψ water / inlet − m& water / outletψ water / outlet

(2)

EP

+ m& exhaust / inletψ exhaust / inlet − m& exhaust / outletψ exhaust / outlet where the exhaust flow rate is sum of the air and fuel mass flow rates. Also, by definition of

101

the flow exergy,

AC C

100

∆ψ = ∆h − T0 ∆S + ∆K e + ∆Pe 102

(3)

Due to negligible change in kinetic and potential energies, Eq. (3) becomes: ∆ψ = ∆h − T0 ∆S

(4)

103

∆hwater and ∆S water are calculated from thermodynamic tables by using inlet and outlet

104

temperatures and pressures of the coolant. To calculate the enthalpy change of the exhaust

105

gas over the HEX, Eq. (5) can be used: 5

ACCEPTED MANUSCRIPT dh = C P dT

(5)

Since the equivalence ratio in the diesel engine is considerably less than unity (0.5), the

107

combustion products can be assumed to behave as an ideal gas (e.g., air). Consequently, C p

108

can be considered as a function of temperature as presented in Table 2. [20]. Substituting this

109

equation into (5) and integrating between the limits of the prevailing HEX inlet and outlet

110

temperatures , the exhaust gas enthalpy change follows from Eq. (6): Tout

Tin

dh = ∫

Tout

Tin

C p dT

(6)

SC

∆hexhaust = houtlet − hinlet = ∫

RI PT

106

For calculating the change in exhaust gas entropy over the HEX, combustion products need

112

to be considered as air with variable specific heat, ∆Sexhaust =

Tout

∫

Tin

ds =

Tout

∫

Tin

C p dT T

− RLn(

pout ) pin

M AN U

111

(7)

Total irreversibility can be calculated by substituting this equation into Eq. (2). For this

114

control volume (C.V.1), the Second Law efficiency is defined as,

ηC .V .1 =

m& (ψ −ψ in ) water Recovered exergy = water out Input exergy m& exhaust (ψ in −ψ 0 ) exhaust

(8)

B. Second Control Volume

EP

115

TE D

113

In the second control volume, the whole system (i.e., HEX, diesel engine and generator) is

117

considered. Accordingly, output work is not equal to zero and considering the system inlets

118

of fuel and air, Eq. (1) will become;

AC C

116

I&total = W&act + ∑ m& iψ i − m& eψ e = Pb + m& water / inletψ water / inlet − m& water / outletψ water / outlet + m& air / inletψ air / inlet − m& exhaust / outletψ exhaust / outlet + m& fuel a fch 119

where a fch is the fuel exergy which for hydrocarbons in form of CzHy is [24, 25];

6

(9)

ACCEPTED MANUSCRIPT y 0.042   a fch = QLHV 1.04224 + 0.011925 −  z z  

(10)

120

Based on Table 3, the molecular weight of the fuel is considered to 175.0 g/mol, with the

121

molecular formula being C12.8H22.824 and

RI PT

22.824 0.042   a fch = 43.2 1.04224 + 0.011925 −  = 45.8MJ / kg = 45801.6kJ / kg 12.8 12.8  

(11)

Other terms in Eq. (9) can be calculated analogous to the approach performed for the first

123

control volume. In this work, the mass flow of exhaust gas, which is sum of fuel and air mass

124

flows, is calculated by with assumption (φ=0.5) obtained from earlier experimental work on

125

this engine in current constant engine speed with equivalence ratio of φ=0.5 and considering

126

stoichiometric combustion as,

M AN U

SC

122

and

F  A actual φ= F  A  st 128

So,

EP

127

TE D

y y y   Cx H y +  x +  ( O2 + 3.76 N 2 ) ⇒ CO2 + H 2O + 3.76  x +  N 2 4 2 4  

F F 1 1 = φ  = 0.5 × =  A actual A st 14.54 29.1 Which

A 22.824  28.9 kg air  =14.54  = 12.8+  × 4.76 × F st  4  175 kg fuel 130 131

(13)

(14)

AC C

129

(12)

The second law efficiency for second control volume is defined by

7

(15)

ACCEPTED MANUSCRIPT ηC .V .2 =

Useful output exergy m& water (ψ out −ψ in ) water + Pb = Input exergy m& fuel a fch

132

2.2 Engine performance

133

A. Brake Specific Fuel Consumption (BSFC)

(16)

BSFC is the fuel flow rate per unit brake output power and is an indicator of overall engine

135

efficiency, i.e., conversion of chemical energy into mechanical work[26]:

136

m& f ( g / h) Pb (kW )

B. Brake Mean Effective Pressure (BMEP)

(17)

SC

BSFC ( g / kW .h) =

RI PT

134

BMEP is an indicator of thermal efficiency, i.e. conversion of chemical energy into pressure.

138

(18) Pb (kW )nR ×103 BMEP (kPa ) = Vd (dm3 ) N (rev / s ) where nR is the number or crank revolutions for each power stroke per cylinder, which is2 in

139

the case, as a four-stroke engine is used. Vd is the cumulative displacement volume for all

140

cylinders. For this engine, based on the data in Table 1) this volume equals: Vd = 4 ×

4

B 2 L = 3.14 × 2352.25 × 128=3781665.28 mm 3 =3.781 665 28 dm 3

(19)

C. Volumetric Efficiency

EP

141

π

TE D

M AN U

137

Volumetric efficiency is defined as the volume flow rate of air into the intake system divided

143

by the rate at which volume is displaced by the piston and is an indicator for the engine’s

144

efficiency as an air pump [26]:

AC C

142

ηv =

2m& a ρ a ,iVd N

(20)

145

where ρ a ,i is the inlet air density, calculated at the prevailing air temperature at the height of

146

the inlet (Table 2).

147

D. Fuel Conversion Efficiency 8

ACCEPTED MANUSCRIPT 148

The ratio of the work produced per cycle to the amount of fuel energy supplied per cycle that

149

can be released in the combustion process is commonly named fuel conversion efficiency and

150

and follows from (Eq. (17)) [26]:

E. Friction Factor

152

2.3 HEX Performance

RI PT

151

The friction factor (f) in the HEX can be calculated by,

f =

∆P 1 L ρ V2   2 D

(22)

M AN U

153

(21)

3600 BSFC ( g / kW .h) QLHV ( MJ / kg )

SC

ηf =

With respect to heat transfer, the Nusselt number and friction factor are two important non-

155

dimensional parameters which will be discussed here. A Wilson plot is used to calculate the

156

convection heat transfer coefficient and Nusselt number [27]. The overall thermal resistance

157

(Rov) for the current heat exchangers is,

TE D

154

(23)

EP

D  ln  o  D 1 1 Rov = +  i + hi Ai 2π kw Lw ho Ao

Wilson revealed that when the mass flow of the cooling liquid is modified, the change in

159

overall thermal resistance would be mainly due to the variation of the in-tube convection

160

coefficient, with the remaining thermal resistance remaining nearly constant. Moreover,

161

Wilson determined that,

AC C

158

hi = C2Vrn

(24)

162

where C2 is a constant, Vr is the reduced fluid velocity and n is a velocity exponent (0.89 in

163

this study). By comparing Eq. (23) with the following experimental formula for Rov, 9

ACCEPTED MANUSCRIPT Rov =

(25)

LMTD m& water C p (Tc ,out − Tc ,in )

164

and depicting the linear function of Rov versus 1/(Vr)n from Eq. (29), C1 and C2 constants can

165

be obtained from the slope and intercept of Figure xx (refer to Figure in question here) [28].

2.4 Error Analysis

RI PT

166

The uncertainty associated with a measurement should include factors that affect both the

168

accuracy and precision of the measurement. Experimental precision s can be determined as

169

follows. Let N measurements be called x1 , x2 ,..., xN . Let the average of the N values be called

170

x , with each deviation represented by δ xi = xi − x , for i = 1, 2,..., N . s then follows from:

s=

171

(δ x

2 1

+ δ x22 + ... + δ xN2 )

( N − 1)

=

∑δ x

2 i

( N − 1)

M AN U

SC

167

(26)

Uncertainly for a function of variable factors such as f(a,b,c,d) can be defined as:  ∂f   ∂f   ∂f   ∂f  u f =   ua2 +   ub2 +   uc2 +   ud2  ∂a   ∂b   ∂c   ∂d  2

2

2

(27)

TE D

2

where ua-ud denote the uncertainly in measurement variables a-d, which can be found via the

173

rectangular distribution:

accuracy of instrument ( a − d )

(28)

3

AC C

ua − d =

EP

172

174

By using the above approach, the uncertainly in temperature, pressure and velocity

175

measurements were found to be 0.268˚C, 1.43Pa and 0.377m/s, respectively.

176

3. Results and discussions

177

After recording the data of all three heat exchangers, the average recovered heat is used to

178

evaluate which HEX is the most efficient pertaining to exhaust heat recovery from the test

179

diesel engine. As can be seen in Fig. 5, for nearly all engine loads and coolant flow rates, the 10

ACCEPTED MANUSCRIPT optimized HEX has about twice the amount of recovered heat compared to the VG-HEX and

181

Non-Optimize case. Moreover, this Figure confirms that the VG-HEX is more suitable than

182

the non-optimize finned HEX for the investigated experimental conditions. The main reason

183

for this is believed to be caused the large surface area available for heat transfer in the case

184

of the optimized HEX, which has 10 lengthy fins, while in non-optimize case 5 thicker fins

185

were used. In the VG-HEX, heat transfer improved by creating vortices in the tube. Its

186

surface area is the same as that of a simple double pipe HEX. As described in the previous

187

Section, two control volumes are considered (Fig. 4). Fig. 6 illustrates the exergy recovery

188

from water in different HEXs. From this Figure becomes clear that at high engine loads and

189

optimized HEX, the maximum recovered exergy is about 150 W. The difference between the

190

HEXs pertaining to recovered exergy is mainly related to the aforementioned heat transfer

191

considerations. Because heat exchangers result in create exhaust back pressure it will affect

192

the engine performance. This effect is visualized in Fig. 7. One of the main objectives in

193

HEX optimization is minimizing the pressure drop. It can be seen that the optimized HEX

194

has a lower pressure drop than both the VG-HEX and non-optimized case. The former due

195

to thinner fins which manifests in a smaller surface area, while in the non-optimized and

196

VG-HEX, thicker fins and angle of the vortex generators make a more obstacle in exhaust

197

gases flow. The HEX irreversibility minimum (C.V.1) can be found for the VG-HEX (Fig.

198

8). The optimized-HEX has a higher total irreversibility due to higher exhaust mass flow

199

rates compared to the non-optimized case which has thicker fins. Second Law efficiency for

200

the first control volume (C.V.1) - as defined by Eq. (8) - for all three HEXs can be seen in

201

Fig. 9. At higher engine loads, the optimized HEX yields a higher efficiency due to a larger

202

surface area and temperature gradient.

AC C

EP

TE D

M AN U

SC

RI PT

180

11

ACCEPTED MANUSCRIPT As described before, for calculating the Nusselt number, a Wilson-Plot is used (Fig. 10). The

204

graph of overall resistance versus reduced velocity is depicted in Fig. 10 to find the

205

associated constants. The linear fit equations are presented on the graph to calculate the C1

206

and C2 constants for Nusselt number as defined in section 3.3. After the calculations, Fig.

207

11-a presents the Nusselt number when the water mass flow rate is 50 g/s and Fig. 11-b

208

shows the friction factor calculated by Eq. (22). The Optimized HEX and VG-HEX result in

209

the highest Nusselt number and minimum friction factor, respectively.

210

To compare the effect of HEXs on engine performance, BSFC and volumetric and fuel

211

conversion efficiencies are determined. With respect to BSFC, it can be seen in (Fig. 12) that

212

the optimized-HEX has the best performance. This is most likely due to the lower back

213

pressure (Fig. 7). Figs. 13 and 14 confirm that the maximum volumetric and fuel conversion

214

efficiency are found for the VG-HEX and optimized-HEX, respectively. This is due to lower

215

back pressure and enhanced induction process in both cases. The exergy balance for the

216

second control volume (C.V.2) is shown in Table 4 and data are depicted graphically in Figs.

217

15, 16 and 17. These pie-charts are plotted at different engine loads for the VG-HEX,

218

Optimized-HEX and Non-Optimized-HEX, respectively. From the charts can be learnt

219

which fraction of input fuel exergy converts to water exergy, work, irreversibility or is lost

220

as exhaust exergy. Finally, Second Law efficiency for the second control volume (C.V.2) is

221

depicted in a bar-chart via Fig. 18, calculated from Eq. (16). From this chart becomes

222

evident that the most effective HEX is the optimized HEX, owing to a higher efficiency, less

223

flow blockage and enhanced heat transfer.

224

4. Conclusion

AC C

EP

TE D

M AN U

SC

RI PT

203

225

A comparative study of different heat exchangers (HEXs) applied for the diesel engine

226

exhaust exergy recovery is performed in this paper. The vortex generator HEX, Optimized

12

ACCEPTED MANUSCRIPT finned HEX and non-optimized HEX are the three HEX types that are subject of

228

investigation. Results are presented in the form of an exergy balance and engine performance

229

parameters such as BSFC, volumetric efficiency, fuel conversion efficiency and Second Law

230

efficiency. The main conclusion of this paper is that the Optimized HEX configuration yields

231

the best overall results with respect to exergy recovery and engine performance.

RI PT

227

Acknowledgements

233

Authors would like to acknowledge the Iranian heavy diesel company (DESA), especially

234

Dr. Bahram Jafari, Mr. Maziyar Rezaee, Mr. Fahimi and Mr. Farajollahi for providing the

235

experimental setup. Also, authors gratefully acknowledge Mr. Kazem Gholami for his help

236

in designing and constructing the heat exchangers.

M AN U

SC

232

References

238

[1] M. Hatami, D.D. Ganji, M. Gorji-Bandpy, A review of different heat exchangers designs

239

for increasing the diesel exhaust waste heat recovery, Renewable and Sustainable Energy

240

Reviews 37 (2014) 168–181.

241

[2] B. Balakrishna, S. Mamidala, Design Optimization of Catalytic Converter to reduce

242

Particulate Matter and Achieve Limited Back Pressure in Diesel Engine by CFD,

243

International Journal of Current Engineering and Technology 2 (2014) 651-658.

244

[3] A.A. Patil, L.G. Navale, V.S. Patil, Simulative Analysis of Single Cylinder Four Stroke

245

C.I. Engine Exhaust System, international journal of science, spirituality, business and

246

technology 2(1) (2013) 2277—7261.

247

[4] S.D. Pangavhane, A.B. Ubale, V.A. Tandon, D.R. Pangavhane, Experimental and CFD

248

Analysis of a Perforated Inner Pipe Muffler for the Prediction of Backpressure, International

249

Journal of Engineering and Technology 5(5) (2014) 3940-3950.

AC C

EP

TE D

237

13

ACCEPTED MANUSCRIPT [5] S. Bai, H. Lu, T. Wu, X. Yin, X. Shi, L. Chen, Numerical and experimental analysis for

251

exhaust heat exchangers in automobile thermoelectric generators, Case Studies in Thermal

252

Engineering 4 (2014) 99-112.

253

[6] J. Wang, Z. Yan, M. Wang, M. Li, Y. Dai, Multi-objective optimization of an organic

254

Rankine cycle (ORC) for low grade waste heat recovery using evolutionary algorithm,

255

Energy Conversion and Management 71 (2013) 146–158.

256

[7] K.S. Maheswari, K. Kalidasa Murugavel, G. Esakkimuthu, Thermal desalination using

257

diesel engine exhaust waste heat — An experimental analysis, Desalination 358 (2015) 94–

258

100.

259

[8] A. Banerjee, R. Bala Chandran, J.H. Davidson, Experimental investigation of a reticulated

260

porous alumina heat exchanger for high temperature gas heat recovery, Applied Thermal

261

Engineering 75 (2015) 889-895.

262

[9] X. Liu, Y.D. Deng, Z. Li, C.Q. Su, Performance analysis of a waste heat recovery

263

thermoelectric generation system for automotive application, Energy Conversion and

264

Management 90 (2015) 121–127.

265

[10] V. Pandiyarajan, M. Chinna Pandian, E. Malan, R. Velraj, R.V. Seeniraj, Experimental

266

investigation on heat recovery from diesel engine exhaust using finned shell and tube heat

267

exchanger and thermal storage system, Applied Energy 88 (2011) 77–87.

268

[11] S. Lee, C. Bae, Design of a heat exchanger to reduce the exhaust temperature in a spark-

269

ignition engine, International Journal of Thermal Sciences 47 (2008) 468–478

270

[12] H.G. Zhang, E.H. Wang, B.Y. Fan, Heat transfer analysis of a finned-tube evaporator for

271

engine exhaust heat recovery, Energy Conversion and Management 65 (2013) 438–447

AC C

EP

TE D

M AN U

SC

RI PT

250

14

ACCEPTED MANUSCRIPT [13] M. Ghazikhani, M. Hatami, D.D. Ganji, M. Gorji-Bandpy, Gh. Shahi, A. Behravan,

273

Exergy recovery from the exhaust cooling in a DI diesel engine for BSFC reduction purposes,

274

Energy 65 (2014) 44–51

275

[14] S.N. Hossain, S. Bari, Waste heat recovery from the exhaust of a diesel generator using

276

Rankine Cycle, Energy Conversion and Management 75 (2013) 141–151.

277

[15] S. Bari, S.N. Hossain, Waste heat recovery from a diesel engine using shell and tube

278

heat exchanger, Applied Thermal Engineering 61 (2013) 355-363.

279

[16] S. Mavridou, G.C. Mavropoulos, D. Bouris, D.T. Hountalas, G. Bergeles, Comparative

280

design study of a diesel exhaust gas heat exchanger for truck applications with conventional

281

and state of the art heat transfer enhancements, Applied Thermal Engineering 30 (2010) 935–

282

947.

283

[17] M. Hatami, D.D. Ganji, M. Gorji-Bandpy, Numerical study of finned type heat

284

exchangers for ICEs exhaust waste heat recovery, Case Studies in Thermal Engineering 4

285

(2014) 53–64.

286

[18] M. Hatami, D.D. Ganji, M. Gorji-Bandpy, CFD simulation and optimization of ICEs Exhaust

287

Heat Recovery using Different Coolants and Fin Dimensions in Heat Exchanger, Neural

288

computing and applications 25 (7-8) (2014) 2079-2090.

289

[19] M. Eftekhar, A. Keshavarz, A. Ghasemian, J. Mahdavinia, The Impact of Nano-fluid

290

Concentration Used as an Engine Coolant on the Warm-up Timing, International Journal of

291

Automotive Engineering 3(1) (2013) 336-347.

292

[20] M. Hatami, M. Jafaryar, D.D. Ganji, M. Gorji-Bandpy, Optimization of finned-tube heat

293

exchangers for diesel exhaust waste heat recovery using CFD and CCD techniques,

294

International Communications in Heat and Mass Transfer 57 (2014) 254–263

AC C

EP

TE D

M AN U

SC

RI PT

272

15

ACCEPTED MANUSCRIPT [21] V. Mokkapati, C.S. Lin, Numerical study of an exhaust heat recovery system using

296

corrugated tube heat exchanger with twisted tape inserts, International Communications in

297

Heat and Mass Transfer 57 (2014) 53–64

298

[22] E. Feru, B. de Jager, F. Willems, M. Steinbuch, Two-phase plate-fin heat exchanger

299

modeling for waste heat recovery systems in diesel engines, Applied Energy 133 (2014) 183–

300

196.

301

[23] M. Hatami, D.D. Ganji, M. Gorji-Bandpy, Experimental and thermodynamical analyses

302

of the diesel exhaust vortex generator heat exchanger for optimizing its operating condition,

303

Applied Thermal Engineering 75 (2015) 580-591.

304

[24] M. Ghazikhani, M. Hatami, B. Safari, The effect of alcoholic fuel additives on exergy

305

parameters and emissions in a two stroke gasoline engine, Arabian Journal for Science and

306

Engineering 39 (3) (2014) 2117–2125

307

[25] M. Ghazikhani, M. Hatami, B. Safari, Effect of speed and load on exergy recovery in a

308

water-cooled two stroke gasoline-ethanol engine for the BSFC reduction purposes, Scientia

309

Iranica 21 (1) (2014) 171–180

310

[26] J. Heywood, Internal combustion engine fundamentals, McGraw-Hill Education, 1988.

311

[27]

312

investigation of shell and coiled tube heat exchangers using Wilson plots, International

313

Communications in Heat and Mass Transfer 35 (2008) 84– 92.

314

[28] J. Fernandez-Seara, J. Francisco, J. Sieres, A. Campo, A general review of the Wilson

315

plot method and its modifications to determine convection coefficients in heat exchange

316

devices, Applied Thermal Engineering 27 (2007) 2745–2757.

M AN U

TE D M.R.

EP

Shokouhmand,

Salimpour,

M.A.

Akhavan-Behabadi,

AC C

H.

SC

RI PT

295

317 318

16

Experimental

ACCEPTED MANUSCRIPT Figures

M AN U

SC

RI PT

319

AC C

EP

TE D

(a)

(b) Fig. 1 a) Vortex generator (VG-HEX), b) Optimized finned HEX 320

17

TE D

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

322

AC C

321

EP

Fig. 2 Experimental setup, OM314 diesel engine and measurement instruments

18

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

Fig. 3 Schematic overview of the experimental setup 323

327 328 329 330 331 332

EP

326

AC C

325

TE D

324

19

M AN U

SC

(a)

RI PT

ACCEPTED MANUSCRIPT

335 336 337 338 339

EP

334

AC C

333

TE D

(b) Fig. 4 a) Control volume 1 (C.V.1): Heat exchanger, b) Control volume 2 (C.V.2): engine, generator and HEX

340 341 342 343 20

ACCEPTED MANUSCRIPT

2.5

2

1.5

1

0.5

Non-Optimized HEX Optimized HEX VG-HEX

3

Average recovered heat (kW)

Average recovered heat (kW)

3

2.5

2

1.5

1

0

20

40

60

0.5

80

0

20

Engine load (%)

80

SC

Non-Optimized HEX Optimized HEX VG-HEX

Non-Optimized HEX Optimized HEX VG-HEX

Average recovered heat (kW)

M AN U

3

2

1.5

1

0

20

40

TE D

Average recovered heat (kW)

60

(b)

2.5

0.5

40

Engine load (%)

(a)

3

RI PT

Non-Optimized HEX Optimized HEX VG- HEX

60

80

Engine load (%)

2.5

2

1.5

1

0.5

0

20

40

60

80

Engine load (%)

345 346 347

AC C

344

EP

(c) (d) Fig. 5 Average recovered heat at different engine loads and coolant mass flow rates of a) 50g/s, b) 40g/s, c) 30g/s and d) 20 g/s

348 349 350 351 21

ACCEPTED MANUSCRIPT 60

160

Non-Optimized HEX Optimized HEX VG-HEX

50

Non-Optimized HEX Optimized HEX VG-HEX

140

40

30

20

100 80 60 40

10 20

0

0

20

40

60

0

80

0

20

40

60

80

Engine load (%)

SC

Engine load (%)

(a)

(b)

120 Non-Optimized HEX Optimized HEX VG-HEX

Non-Optimized HEX Optimized HEX VG-HEX

100

M AN U

100

RI PT

Recovered exergy (W)

Recovered exergy (W)

120

Recovered exergy (W)

80

60

40

20

0

0

20

40

TE D

Recovered exergy (W)

80

60

80

Engine load (%)

60

40

20

0

0

20

40

60

80

Engine load (%)

354 355 356

AC C

353

EP

(c) (d) Fig. 6 Recovered exergy at different engine loads and exhaust gas flow rates of a) 50g/s, b) 40g/s, c) 30g/s and d) 20 g/s 352

357 358

22

ACCEPTED MANUSCRIPT 500

500

Non-Optimized HEX Optimized HEX VG-HEX

450

450

400

400

350

300

250

200

350

300

250

0

20

40

60

200

80

Engine load (%)

0

60

80

(b)

SC

(a) 500

Non-Optimized HEX Optimized HEX VG-HEX

Non-Optimized HEX Optimized HEX VG-HEX

450

M AN U

450

Pressure drop (Pa)

400

350

300

250

0

20

40

TE D

Pressure drop (Pa)

40

Engine load (%)

500

200

20

RI PT

Pressure drop (Pa)

Pressure drop (Pa)

Non-Optimized HEX Optimized HEX VG-HEX

60

80

Engine load (%)

400

350

300

250

200

0

20

40

60

80

Engine load (%)

360 361 362 363

AC C

359

EP

(c) (d) Fig. 7 Exhaust pressure drop for the optimized , non-optimized and VG- HEX at a) 50g/s, b) 40g/s, c) 30g/s and d) 20 g/s of coolant

364 365 366

23

ACCEPTED MANUSCRIPT 700

600

Total Irreversibility (W)

500

400

300

200

500

400

300

200

100

100

0

Non-Optimized HEX Optimized HEX VG-HEX

0

0

20

40

60

80

0

Total Irreversibility (W)

300

200

40

TE D

Total Irreversibility (W)

600

400

20

Non-Optimized HEX Optimized HEX VG-HEX

M AN U

Non-Optimized HEX Optimized HEX VG-HEX

0

80

(b)

700

500

0

60

SC

(a) 700

100

40

Engine load (%)

Engine load (%)

600

20

RI PT

600

Total Irreversibility (W)

700

Non-Optimized HEX Optimized HEX VG-HEX

60

80

Engine load (%)

500

400

300

200

100

0

0

20

40

60

80

Engine load (%)

368 369 370

AC C

367

EP

(c) (d) Fig. 8 Total irreversibility at different engine loads and coolant mass flow rate of a) 50g/s, b) 40g/s, c) 30g/s and d) 20 g/s

371 372 373 374 24

ACCEPTED MANUSCRIPT Non-Optimized HEX Optimized HEX VG-HEX

14

10

8

RI PT

Second law efficiency (%)

12

6

4

0

0

20

40

Engine load (%)

SC

2

60

80

M AN U

Fig. 9 Average Second Law efficiency for C.V.1 and different HEXs 375 376 377 378

382 383 384 385 386 387

EP

381

AC C

380

TE D

379

388 389 390

25

ACCEPTED MANUSCRIPT Non-Optimized HEX Optimized HEX VG- HEX

0.18 0.16 0.14

0.1

y = 0.1605x + 0.0038

RI PT

Rov (K/W)

0.12

0.08 0.06

y = 0.064x + 0.0132

0.04

0

0.2

0.4

n

1/Vr

0.6

SC

y=0.1211x-0.0324

0.02

0.8

1

M AN U

Fig. 10 Linear function of overall resistance versus reduced velocity for Wilson plot method 391 392 393 394

398 399 400 401 402 403

EP

397

AC C

396

TE D

395

404 405

26

ACCEPTED MANUSCRIPT 0.8

200

Non-Optimized HEX Optimized HEX VG- HEX

180

Non-Optimized HEX Optimized HEX VG- HEX

0.7

160

0.6

120 100 80

0.5 0.4 0.3

60 0.2

40 0.1

20 0

20

40

60

0

80

Engine load (%)

0

20

RI PT

Friction factor

Nusselt number

140

40

60

Engine load (%)

SC

(a) (b) Fig. 11a) Nusselt number and b) friction factor for different HEXs at 50g/s coolant mass flow rate 406

M AN U

407 408 409 410

414 415 416 417 418 419 420

EP

413

AC C

412

TE D

411

421 422 423 27

80

ACCEPTED MANUSCRIPT 1000

800

700

700

600 500

600 500

400

400

300

300

200

200 100

20

40

60

80

(a) 1000

80

60

80

VG-HEX Optimized-HEX Non-Optimized-HEX

M AN U

VG-HEX Optimized-HEX Non-Optimized-HEX

900

800

800

BSFC (g/kW.h)

700 600 500 400 300 200

20

40

TE D

BSFC (g/kW.h)

60

(b)

1000

100

40

Engine load (%)

Engine load (%)

900

20

RI PT

BSFC (g/kW.h)

800

100

VG-HEX Optimized-HEX Non-Optimized-HEX

900

SC

900

BSFC (g/kW.h)

1000

VG-HEX Optimized-HEX Non-Optimized-HEX

60

80

EP

Engine load (%)

700 600 500 400 300 200 100

20

40

Engine load (%)

424 425 426 427

AC C

(c) (d) Fig. 12 Brake Specific Fuel Consumption (BSFC) for a) 50g/s, b) 40g/s, c) 30g/s and d) 20 g/s of coolant

428 429

28

ACCEPTED MANUSCRIPT 100

100

Non-Optimized HEX Optimized HEX VG- HEX

Non-Optimized HEX Optimized HEX VG- HEX 80

60

40

40

20

20

0

0

20

40

60

80

0

(a)

60

80

60

80

(b)

100

100

Non-Optimized HEX Optimized HEX VG- HEX

M AN U

Non-Optimized HEX Optimized HEX VG- HEX

60

20

0

20

40

TE D

40

60

80

EP

Engine load (%)

Volumetric Efficiency (%)

80

80

Volumetric Efficiency (%)

40

Engine load (%)

Engine load (%)

0

20

SC

0

60

RI PT

Volumetric Efficiency (%)

Volumetric Efficiency (%)

80

60

40

20

0

0

20

40

Engine load (%)

430 431 432 433

AC C

(c) (d) Fig. 13 Volumetric efficiency at a) 50g/s, b) 40g/s, c) 30g/s and d) 20 g/s coolant mass flow rate

434 435 436 437 29

ACCEPTED MANUSCRIPT 60

60

VG-HEX Optimized-HEX Non-Optimized-HEX

20

0

40

20

0

20

40

60

80

(a)

M AN U 60

80

EP

Engine load (%)

Fuel Conversion Efficiency (%)

TE D

Fuel Conversion Efficiency (%)

40

40

40

20

0

20

40

60

Engine load (%)

439 440 441

AC C

(c) (d) Fig. 14 Fuel conversion efficiency for a) 50g/s, b) 40g/s, c) 30g/s and d) 20 g/s of coolant 438

80

VG-HEX Optimized-HEX Non-Optimized-HEX

VG-HEX Optimized-HEX Non-Optimized-HEX

20

60

(b)

60

60

0

40

Engine load (%)

Engine load (%)

20

20

RI PT

40

SC

Fuel Conversion Efficiency (%)

Fuel Conversion Efficiency (%)

VG-HEX Optimized-HEX Non-Optimized-HEX

442 443 444

30

80

RI PT

ACCEPTED MANUSCRIPT

(b)

M AN U

SC

(a)

447 448 449 450 451 452 453

EP

446

AC C

445

TE D

(c) (d) Fig. 15 Fuel exergy balance for the VG-HEX at a) 20%, b) 40%, c) 60% and d) 80% of full load

454 455 456 457 31

RI PT

ACCEPTED MANUSCRIPT

(b)

M AN U

SC

(a)

(c) (d) Fig. 16 Fuel exergy balance for the Optimized-HEX at a) 20%, b) 40%, c) 60% and d) 80% of full load

461 462 463 464 465 466

EP

460

AC C

459

TE D

458

467 468 469 470 32

RI PT

ACCEPTED MANUSCRIPT

(b)

M AN U

SC

(a)

473 474 475 476 477 478 479

EP

472

AC C

471

TE D

(c) (d) Fig. 17 Fuel exergy balance for the Non-Optimized-HEX at a) 20%, b) 40%, c) 40% and d) 80% of full load

480 481 482

33

ACCEPTED MANUSCRIPT 483 50 Non-Optimized HEX Optimized HEX VG-HEX

30

RI PT

Second law efficiency (%)

40

20

0

0

20

40

60

M AN U

Engine load (%)

SC

10

80

Fig. 18 Average Second Law efficiency for C.V.2 and different HEXs 484 485 486

490 491 492 493 494 495

EP

489

AC C

488

TE D

487

496 497 498 499 34

ACCEPTED MANUSCRIPT

501

Table 1. Specifications of the OM314 diesel engine

Engine Engine type Number of cylinder Combustion chamber Bore × stroke (mm) Piston displacement (cc) Compression ratio Maximum power (hp) Maximum torque(N. m) Maximum speed (rpm) Mean effective pressure (bar)

SC

502 503

M AN U

504 505 506 507

512 513 514 515 516

EP

511

AC C

510

TE D

508 509

specification 4 stroke diesel engine 4 Direct injection 97 × 128 3784 17:01 85 235 2800 6.8 @ 2800 rpm

RI PT

500

517 518 519 520 35

ACCEPTED MANUSCRIPT Table 2. Temperature-dependent properties of exhaust gases when modelled as air [23]

521

A + B ×T + C ×T 2 + D ×T

Exhaust gas properties

3

B

C

D

ρ (kg/m )

2.504012288761e+00

-5.958486188418e-03

5.578942358587e-06

-1.772600918994e-09

Cp (J/kg.K)

1.015580935928e+03

-1.512248401853e-01

4.544870294058e-04

-1.785063817137e-07

µ (kg/m s)

1.325186910351e-06

6.740061370040e-08

-3.749043579926e-11

1.110074961972e-14

k (W/m.K)

-3.182421851331e-03

1.185847825677e-04

-7.706004236629e-08

2.939653967062e-11

522 523

SC

524

M AN U

525 526 527 528 529

534 535 536 537 538

EP

533

AC C

532

TE D

530 531

RI PT

A

3

539 540 541

36

ACCEPTED MANUSCRIPT Table 3. Detailed Properties of light diesel fuel [26]

542

Fuel

Formula

Molecular weight

Density (kg/dm3)

Specific heat (kJ/kg.K)

Light diesel

CnH1.8n

≈ 170

0.78-0.84

2.2

Higher Heating Value (MJ/kg) 46.1

Lower Heating Value (MJ/kg) 43.2

RI PT

543 544 545

SC

546 547

M AN U

548 549 550 551

555 556 557 558 559 560

EP

554

AC C

553

TE D

552

561 562 563 564 37

(A/F)s

14.5

ACCEPTED MANUSCRIPT Table 4 Second Law analysis for second C.V.2 Fuel Exergy (kW)

Exhaust Exergy (kW)

Water Exergy (kW)

Irreversibility (kW)

Work Exergy (kW)

46.24403 44.33765 44.54393 43.97293 42.99727 39.28967 34.92862 36.526 33.77276 34.42797 37.16892 36.8738 40.12365 38.66811 44.3508

0.237339 0.322468 0.330112 0.462623 0.545482 0.122073 0.13429 0.185052 0.221136 0.269265 0.023934 0.020858 0.031812 0.037162 0.066145

0.033906 0.044862 0.031734 0.041893 0.058525 0.033703 0.031809 0.042274 0.09315 0.102861 0.003683 0.006489 0.007681 0.00449 0.021938

45.97279 39.97032 36.18208 31.46842 26.39326 39.13389 30.76252 28.29867 21.45847 18.05585 37.14131 32.84645 32.08415 26.62646 28.26271

0 4 8 12 16 0 4 8 12 16 0 4 8 12 16

566 567

571 572 573 574 575 576

EP

570

AC C

569

TE D

568

RI PT

% of full load 0 VG-HEX 20 40 60 80 0 Optimized Finned20 HEX 40 60 80 0 NonOptimized 20 Finned 40 HEX 60 80

SC

HEX Type

M AN U

565

577 578 579

38

ACCEPTED MANUSCRIPT Figure Caption

582 583 584

Experimental setup, OM314 Diesel engine and measurement instruments

Fig. 3

Schematic of the experimental setup

Fig. 4

Control volumes

Fig. 5

Average recovered heat in different engine loads

Fig. 6

Recovered exergy for different engine loads and exhaust gases amount

Fig. 7

Exhaust pressure drop for optimized , non-optimized and VG- HEX

Fig. 8

Total irreversibility in different engine load

Fig. 9

Average second law efficiency for C.V.1 and different HEXs

Fig. 10

Linear function of overall resistance versus reduced velocity

Fig. 11

Nusselt number and friction factor of different HEXs

Fig. 12

Brake Specific Fuel Consumption (BSFC) of engine

Fig. 13

Volumetric efficiency of diesel engine

Fig. 14

Fuel conversion efficiency of diesel engine

Fig. 15

Fuel exergy balance for VG-HEX

Fig. 16

Fuel exergy balance for Optimized-HEX

Fig. 17

Fuel exergy balance for Non-Optimized-HEX

Fig. 18

Average second law efficiency for C.V.2 and different HEXs

TE D

M AN U

SC

RI PT

Fig. 2

EP

581

Different designed heat exchangers

AC C

580

Fig. 1

585 586 587

39

ACCEPTED MANUSCRIPT Table Caption Specifications of OM314 diesel engine

Table. 2

Temperature-dependent properties of exhaust gases

Table. 3

Detailed Properties of light diesel fuel

Table. 4

Second law analysis for second C.V.2

RI PT

Table. 1

AC C

EP

TE D

M AN U

SC

588

40

ACCEPTED MANUSCRIPT

Highlights Three different heat exchangers are used for diesel exhaust heat recovery.

•

Exergy analysis and engine performance are discussed.

•

Nusselt number and friction factor are compared for heat exchangers.

•

Optimized Finned Tube is introduced as the best heat exchanger.

AC C

EP

TE D

M AN U

SC

RI PT

•