Recovery Unit Design and ... · 1.2 Waste heat recovery unit A waste heat recovery unit (WHRU) is a heat exchanger that recovers heat from a hot gas stream while transferring it to

Design and Performance analysis of Heat Exchanger Using Waste Heat Recovery Unit

1Manoj N., 2Praveen kumar J., 3Ramki S., and 4Paullinga prakash R.1,2,3Students, Department of Mechanical Engineering, Vel Tech Multi Tech Dr. Rangarajan Dr. Sakunthala

Engineering College, Avadi, Chennai-624Assistant Professor, Department of Mechanical Engineering, Vel Tech Multi Tech Dr.

RangarajanDr.Sakunthala Engineering College, Avadi, Chennai-62Corresponding author e-mail: [email protected]

ABSTRACT In this project, design and performance

analysis of heat exchanger using waste heat recovery unit is done in a attempt to increase the effectiveness of system. In the proposed work a diffuser of required cross section is fixed at the inlet of the shell of the heat exchanger. The diffuser reduces the inlet fluid velocity and increases the pressure at its exit and also it increases the contact time of the high temperature fluid (heat source) with the copper tube carrying the cold fluid (heat sink).

The nozzle reduces the pressure and increases the velocity when the hot fluid leaves the shell chamber. This allows the shell to withstand the high pressure inside, allowing the heat to transfer between hot fluid and the cold fluid to its maximum extent without failure. The shell is a pressure vessel, it is designed to hold the hot fluid (Exhaust gas) until a certain pressure is attained inside. This is important to test the following hypothesis.

“According to thermodynamics, when the pressure increases, the temperature also increases. If the pressure of hot fluid inside the shell of the heat exchanger are increased, the increases of temperature e leading to the increase of heat transfer between the hot fluid and the cold fluid. This results in the increase of effectiveness of heat exchanger”.

Keywords : Heat Exchanger ,Effectiveness ,Waste heat recovery unit.

1. INTRODUCTION A heat exchanger is a device used to transfer heat between one or more fluids. The fluids may be separated by a solid wall or they may be in direct contact. The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant and heats the incoming air.

The most important changes that theoretically influences the performance of the heat exchanger is the introduction of diffuser at the entry and a nozzle at the exit. The shell is sealed shut to act like a pressure vessel, preceding the diffuser is a Non-Return Valve, this is restricts the re-entry of the waste heat carrying gases back into the source system (single cylinder, 4-stroke compression ignition engine).Following the nozzle there is a pressure gauge and a flow control gate valve, to control the pressure inside the shell.

The main aim of this kind of setup is to check the validity of the following Thermodynamics concept in Heat Exchanger units, which states ‘When pressure increases the temperature also increases, so

International Journal of Pure and Applied MathematicsVolume 119 No. 15 2018, 2101-2112ISSN: 1314-3395 (on-line version)url: http://www.acadpubl.eu/hub/Special Issue http://www.acadpubl.eu/hub/

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pressure is directly proportional to temperature of the working fluid in a system’.

To compare the changes in the heat transfer, when the pressure is varied and kept at the normal pressure of the gases at different load condition, this project is carried out.

1.1 Helical coil type heat exchanger

Figure 1.1 Helical coil type heat exchanger

The main advantages of the HCHE, like for the SHE, is its highly efficient use of space, especially when it’s limited and not enough straight pipe be laid. Under conditions of flow rates (or laminar flow), such that the typical shell and tube exchangers have low heat-transfer coefficients and becoming uneconomical. When there is low pressure in one of the fluids, usually from accumulated pressure drop in other process equipment. When one of the fluids has components in multiple phase (solids, liquids and gases), which tends to create mechanical problems during operations, such as plugging of small-diameter tubes. Cleaning of helical coils for these multiple-phases fluids can prove to be more difficult than its shell and

tube counterpart.However helical coil unit would require cleaning less often.

1.2 Waste heat recovery unit A waste heat recovery unit (WHRU) is a heat exchanger that recovers heat from a hot gas stream while transferring it to a working medium, typically water or oil. The hot gas stream can be the exhaust gas from a gas turbine or a diesel engine or a waste gas from industry or refinery.Advantages:

These systems have many advantages which could be direct or indirect.

Direct advantages:1. The revival process will add to the

effectiveness of the process and thus reduce the costs of fuel and energy consumption needed for the process.

Indirect advantages:1. Reduction in pollution: Thermal

and air contamination will dramatically decreases the costs.

2. Reduction in pollution due to less flue gas are emitted from the plants, since most of the energy is reused.

3. Reduction in secondary power consumption : Reduction in apparatus sizes means another reduction in energy fed to those systems like pumps, filters, fans, etc.,

Disadvantages: Capital cost to implement a waste heat

recovery system may outweigh the benefit gained in heat recovered.

Additional equipment is required for additional maintenance cost.

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On a biological scale, all organisms will die if ambient temperature is too high.

1.3 Literature ReviewB. Chinna Ankanna, B. Sidda Reddy (2014)[1] has proved that helical coil configuration is very effective for hest exchangers and chemical reactors because they can accommodate a large heat transfer area in a small space, with high heat transfer coefficient.An attempt has been made by Kapil Dev, Kuldeep Singh pal, Suhail A, Siddiqui(2014)[2] to study the parallel flow and counter flow of inner higher temperature fluid flow and lower temperature fluid flow , which are separated by copper surface in a helical coil heat exchanger. Helical geometry allows the effective handling at higher temperature and extreme temperature differentials without any highly induced stress or expansion of joints.Gavade Pravin P, Prof.Kulkarni P.R[3] stated from their experiments that te helical pipe is having te greater surface area which allows the fluid to be in contact for greater period of time period so that there is an enhanced heat transfer compared to that of straight pipe.Vimal Kumar, pooja Gupta and K.D.P.Nigam[6] reported that helically coiled tubes find applications in various industrial processes like solar collectors, combustion systems, heat exchangers and distillation processes because of their simple and effective means of enhancement in heat and mass transfer.Salimpour[7] investigation tree heat exchanger with different coil pitched and found that the shell-side heat transfer coefficient of coils with larger pitches is higher than those with smaller pitches for the counter-flow configuration.

2. DESIGN AND MODELLING

Prior to the fabrication process the project has been digitally designed using design software CREO PARAMETRIC 2.0, developed by PTC Corporation.2.1 Part Modelling

The different designed and Modeled Parts are;

Shell Diffuser & Nozzle Copper Coil Tube Heat Exchanger

2.1.1 Copper Coil Tube

Figure 2.1 Copper tube coil2.2.2 Heat exchanger Setup

ShellLs : 500mmDs : 120mmTs : 1.2mm

Copper CoilDc : 100mmLfree : 480mmCoilpitch : 20mmna : 24Lwire : 8200mm

Copper Tubed1 : 8mmd2 : 9.8mm

Non-Return Valve, Gate ValveDiameter : 40mm

DiffuserHd : 200mmTd : 2mmDid : 40mmDod : 120mm

NozzleHn : 200mmTn : 2mmDin : 40mmDon : 120mm


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Figure 2.2 Heat Exchanger 3. MATERIAL SELECTION

The materials selected for shell and Tube are SS304 and copper respectively. The properties that led to the selection of these materials are given below.3.1 Stainless Steel 304

SS304 is the most versatile and the most widely used of all stainless steels. Its chemical composition, mechanical properties, weldability. It is a corrosion resistance when compared to aluminum. 3.1.1 Typical Applications

SS304 is used in all industrial, commercial and domestic fields because of its good corrosion and heat resisting properties.3.1.2 Chemical Composition

The chemical composition in terms of the materials present.

Table 3.1 Chemical composition of SS304SS 0C Mn P S Si Cr Ni

304 0.08 max

2.0 0.045 0.03 1.0 18.0 8.0 to 10.50

3.1.3 Mechanical PropertiesVarious mechanical properties of SS304 at

room temperatureTable 3.2 Mechanical Properties of SS304

SS304

Typical Minimum

Tensile Strength, MPa 600 515

Proof strength(0.2%), MPa 310 205

Elongation ( % in 50 mm) 60 40

Hardness (Brinell) 170 -

Endurance limit, MPa 240 -

3.1.4 Properties at Elevated TemperaturesThe Tensile strength of SS304 at Elevated

temperatures areTable 3.3 Temperature Vs Tensile Strength

Temperature, 0c 600 700 800 900Tensile

strength,MPa380 270 170 90

3.1.5 Atmospheric The performance of SS304 compared with

other metals in various environments is shown in the following table. The corrosion rates are based on a 10 year exposure.

Table 3.4 Environment Vs Corrosion RateEnvironment Corrosion Rate (µm/year)

SS304 Aluminium-3S

Mild Steel

Rural 0.0025 0.025 5.8Marine 0.0076 0.432 34.0Marine

Industrial0.0076 0.686 46.2

3.2 Copper3.2.1 General and Atomic Properties of Copper

The general chemical properties of copper is as follows :

Table 3.5 Chemical Composition of CopperAtomic Number 29Atomic Weight 63.546

Atomic diameter 2.551 x 10-10mElectronic Structure 3d 104S

Valences States 2.1Fermi Energy 7.0 eVFermi surface Spherical, necks at [111]

Hall Coefficient -5.12 x 10-11 m3/(A S)Magnetic State DiamagneticHeat of Fusion 134 J/g

Heat of Vaporization 3630 J/g


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Heat of Sublimation @ 1299 K

3730 J/g

3.2.2 Physical PropertiesBoiling Point : 2567 0CDensity @ 20 0C : 8.96 g/cm2

Melting point : 1083 0C3.2.3 Mechanical propertiesMaterial condition HardHardness- Vickers 87Tensile strength (MPa) 314Young’s modulus(GPa) 129.83.2.4 Thermal propertiesLatent Heat of Evaporation : 4756 J/gLinear Expansion Coefficient @ 0 – 100 0C : 17.0 x 10-6 m/m-KSpecific Heat @ 25 0C : 385 J/Kg-KThermal Conductivity, @ 0 – 100 0C : 401 W/m-K3.3 Coolant Oil3.3.1 Physical PropertiesDensity @ 20 0C : 903 kg/m3

Boiling Point : 175 0C3.3.2 Thermal PropertiesSpecific Heat @ 20 0C : 1.838 j/kg 0C 3.4 Silicon Transformer Oil3.4.1 Physical PropertiesDensity @250C : 960 kg/m3

Flash Point : >3000CFire Point : 3700C3.4.2 Thermal PropertiesSpecific Heat @ 25 0C : 1.51 kj/kg K3.5 Water4.5.1 Physical PropertiesDensity @20 0C : 1000 kg/m3

3.5.2 Thermal PropertiesSpecific Heat @25 0C : 4.186 kj/kg KThermal Conductivity : 0.6065 W/mK

4. FABRICATION AND EXPERIMENTAL SETUP

Complete setupThe completely fabricated unit is coupled

with a Compression Ignition Engine as shown below. The engine is a single cylinder, 4-stroke, slow speed diesel engine made by Kirloskar.

Figure 4.1 Engine

5. PERFORMANCE TESTING AND CALCULATIONS

5.1 Testing 5.1.1 Counter flow setup (coolant oil)

At no load condition, in this hot gas and coolant flow in the opposite direction.Table 5.1 Counter flow observation for coolant at no

load

Figure 4.2 Engine Specifications


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Figure 4.3 Non – Return valve

Figure 4.4 Pressure Gauge & Gate Valve

Figure 4.5 Complete Unit

5.1.2 Counter flow setup (coolant oil)At 25% load condition, in this hot gas and

coolant flow in the opposite direction.Table 5.2 Counter flow observation for coolant at

25% loads.no

P bar

T1 0C

T20

Ct1

0C)

t20C

mc (kg/s)

mh (kg/s)

1 0 153 80 30 46 0.0053 0.0012

2 0.5 203 83 30 55 0.0053 0.0012

3 1 210 95 30 69 0.0053 0.0012

4 1.5 233 110 30 74 0.0053 0.0012

5.1.3 Counter flow setup (silicon transformer oil)At no load condition, in this hot gas and

silicon transformer oil flow in the opposite direction.Table 5.3 Counter flow observation for STO-50 at no

load

s.no

P bar

T1 0C

T20C

t10C

t20C

mc (kg/s)

mh (kg/s)

1 0 126 70.8

27 41 0.0053 0.0012

2 0.5 168 54 27 49 0.0053 0.0012

3 1 250 81 27 64 0.0053 0.0012

4 1.5 267 110 27 75 0.0053 0.0012


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5.1.4 Counter flow setup (silicon transformer oil)At 25% load condition, in this hot gas and

silicon transformer oil flow in the opposite direction.Table 5.4 Counter flow observation for STO-50 at

25% loads.no

P bar

T1 0C

T2 0C

t10C

)

t20

Cmc

(kg/s)mh

(kg/s)

1 0 181 83 40 61 0.0057 0.0012

2 0.5 220 88 40 87 0.0057 0.0012

3 1 254 101 40 104 0.0057 0.0012

4 1.5 300 115 40 119 0.0057 0.0012

5.1.5 Counter Flow Setup (Water)At no load condition, in this hot gas and

water flow in the opposite direction.Table 5.5 Counter flow observation for Water at no

load

5.1.6 Counter flow setup (Water)At 25% load condition, in this hot gas and

water flow in the opposite direction.Table 5.6 Counter flow observation for Water at 25%

loads.no

P bar

T1 0C

T2 0C

t10C

t2 0C

mc (kg/s)

mh (kg/s)

1 0 200 150.33

32 55 0.0065 0.0012

2 0.5

200 145.03

32 59 0.0065 0.0012

3 1 200 140.3

32 62 0.0065 0.0012

4 1.5

200 130.3

32 65 0.0065 0.0012

5.2 FormulaCounter flow

Heat Transfer

NTU Method

s.no

P bar

T1 0C

T20C

t10C

t20C

mc (kg/s)

mh (kg/s)

1 0 168 105 40 62 0.0057 0.0012

2 0.5 230 111 40 75 0.0057 0.0012

3 1 265 131 40 90 0.0057 0.0012

4 1.5 272 145 40 97 0.0057 0.0012

s.no

P bar

T1 0C

T20C

t10C

t2 0C

mc (kg/s)

mh (kg/s)

1 0 200 154.33 31.5 52 0.0065 0.0012

2 0.5 200 149.88 31.5 54 0.0065 0.0012

3 1 200 145.42 31.5 56 0.0065 0.0012

4 1.5 200 143.20 31.5 58 0.0065 0.0012


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The above formula are taken from the HMT data book.

5.3 Heat Exchanger CalculationsThe Calculations are done for the test rig

after running a test.U = 20 – 300 W/m2K.

5.3.1Counter flow (coolant oil at no load)i. For P = 0 bar

To find ( T)lm∆

( )lm = 42/0.68∆𝑇( )lm = 61.6 0C∆𝑇

To find QQ = UA( )lm∆𝑇 = 200 x 0.0113 x 61.76Q = 139.58 W To find 𝜀

= 1.22[14/99]𝜀

= 1.22[0.14]𝜀 = 0.17𝜀

5.3.2 Counter flow (coolant oil at 25% load)i. For P = 0 bar

To find ( T)lm∆

( )lm = 57/0.76∆𝑇( )lm = 74.92 0C∆𝑇To find QQ = UA( )lm∆𝑇 = 200 x 0.0113 x 74.92Q = 169.32 W To find 𝜀

= 1.22[16/123]𝜀

= 1.22[0.130]𝜀 = 0.16𝜀

5.3.3 Counter flow (STO 50 oil at no load)i. For P = 0 bar

To find ( T)lm∆


= 1.40[22/128]𝜀

= 0.25𝜀


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5.3.4 Counter flow (STO 50 oil at 25% load)i. For P = 0 bar

To find ( T)lm∆


= 1.40[21/141]𝜀

= 0.21𝜀

5.3.5 Counter flow (water at no load)i. For P = 1 bar

To find ( T)lm∆

( )lm = 153.22 0C∆𝑇To find QQ = UA( )lm∆𝑇 = 200 x 0.0113 x 131.786Q = 297.67 W To find 𝜀

= 297.67/2032.11𝜀 = 0.152𝜀

5.3.6 Counter flow (water at 25% load)i. For P = 1 bar

To find ( T)lm∆

( )lm = 134.19 0C∆𝑇To find QQ = UA( )lm∆𝑇 = 200 x 0.0113 x 134.19Q = 303.28 W To find 𝜀

= 303.28/2026.08𝜀

= 0.157𝜀

6. RESULT AND DISCUSSION

Table 6.1 Comparison between the Coolant Vs STO 50 Vs Water at No load

Q (W) WITHOUT LOAD

E WITHOUT LOADS. NO

P Bar

Coolant STO 50

Water Coolant

STO 50

Water

1 0 139.216 189.489

153.51 0.17 0.25 0.076

2 0.5 140.17 241.82

228.51 0.18 0.26 0.112

3 1 241.2 290.31

303.28 0.202 0.31 0.152

4 1.5 293.73 309.31

376.29 0.244 0.34 0.185


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0 0.5 1 1.50

0.1

0.2

0.3

0.4

coolantSTO 50water

Effectiveness of coolant Vs STO 50 Vs Water at no load

EFF

EC

TIV

EN

ESS

PRESSURE

6.1 Pressure Vs Effectiveness at no load

Table 6.2 Comparison between the Coolant Vs STO 50 Vs Water at 25% load

0 0.5 1 1.50

0.2

0.4

0.6

CoolantSTO 50Water

Effectiveness of Coolant Vs STO 50 Vs Water at 25% load

EFF

EC

TIV

EN

ESS

PRESSURE

Figure 6.2 Pressure Vs Effectiveness at 25% load

Thus from the result obtained after testing, it is proved that the proposed hypothesis is true and valid in case of heat exchanger.

The graph between pressure and effectiveness clearly shows that both are directly proportional to each other because when the pressure increases, the temperature also increases. If temperature increases then effectiveness is also increases. Copper having high thermal conductivity to be effectively heat conductor then other material. The Stainless Steel shell emitted very less amount of heat to the atmosphere due to low thermal conductivity, when the gas is stored inside the shell to attain high pressure. The helical coil increased the heat transfer between the hot fluid and cold fluid when compared to linear tube bundles.

From the above graph the effectiveness is greater to the STO 50 oil compared to the Coolant and Water. The STO 50 oil has the greater heat transfer rate compared to the Coolant and Water.

REFERNCES1. B.Chinna Ankanna. B. Sidda Reddy (2014), “Performance Analysis Of Fabricated Helical Coil

Q (W) WITH 25% LOAD

E WITH 25% LOADS. NO

P Bar Coola

ntSTO

50Water Coola

ntSTO

50Wate

r1 0 169.32 169.5

62158.63 0.16 0.21 0.078

2 0.5 209.07 188.49

236.72 0.18 0.36 0.116

3 1 221.81 223.54

318.38 0.26 0.42 0.157


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HeatExchanger”International Journal Of Engineering Research , Volume No.3 issue No: Special 1. Pp:33.2. Dev, Kuldeep Singh pal, Suhail A, Sidd iqui (2014) “An Empirical Study Of Helical Coil Heat Exchanger Used In Liquid Evaporization And Droplet Disengagement For a Laminar Fluid Flow” International Journal Of Engineering Sciences & Research Technology.3. Gavade Pravin P , Prof. Kulkarni P.R “ Experimental Evaluation Of Helical Coil Tube In Tube Heat Exchanger”. 4. P.E .Minton “Designing Spiral-Plate Heat Exchanger” , Union carbide corp.5. Achmad Nursyamsu , Dr . Ir . Ahmad Indra S (2007) “Analysis of fluid flow in pipes with spiral on the variation pitch computational fluid dynamics using (CFD)”: Undergraduate Program, Gunadarma University.6. Kumar V, Mridha M , Gupta , A.K Nigam (2007) , coiled flow inverter as a heat exchanger , pergamon-Elservier science Ltd , Vol 62.00 , Issue .9 pp, 2386-2396,2007.7. Salimpour M.R. , “Heat Transfer Coefficients Of Shell And Coiled Tube Heat Excangers” , Experimental thermal and Fluid Science.2009.8. Guo L , Chen , Feng , and Bai B(1998) Transient convective heat transfer in a helical coiled tube with pulsating fully developed turbulent flow. International journal of heat and mass transfer , Vol . 41 ,pp.2867-2875. 9. Kervin M , Lunsford , “ Increase heat Exvhanger performance” , Bryan Research And Engineering . Inc. – Technical papers ( March 1998) , Vol 2 ISSN -2278-0181.10. S C Bhatia, “ Fundamentals of Heat and Mass Transfer” CBS Publishers and Distributors, Feb 1, 2002. 11. C.P. Kothandaraman, S. Subramanyan “Heat and Mass Transfer Data book”.


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Recovery Unit Design and ... · 1.2 Waste heat recovery unit A waste heat recovery unit (WHRU) is a heat exchanger that recovers heat from a hot gas stream while transferring it to

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