Performance Analysis of Shell and Tube Heat Exchanger

Performance Analysis of Shell and Tube Heat Exchanger

S. G. Sangashetty,

Professor, Dept. of Mechanical Engg.

RajaRajeswari College of Engg, Bangalore-560074, India.

Lakshmikant Gurumurthy, Asst., Prof., Dept., of Mech.,Engg., Appa Institute of Technology, Kalburgi, India.

N. Sreenivasalu Reddy,

AssociateProfessor, Dept. of Mechanical Engg.

RajaRajeswari College of Engg, Bangalore-560074, India.

M. S. BhagyaShekar,

Professor and Principal, Dept. of Mechanical Engg.

RajaRajeswari College of Engg, Bangalore-560074, India.

Abstract:- The main aim of the present work is achieved by calculating heat transfer coefficient using water as a base fluid

.The kerns method is simplest and easy to understand as compared to the other methods. The poor heat transfer properties of the employed fluids in the industries are obstacles for using different types of heat exchangers. Hence using Nano fluids, improves Heat Transfer and Stability, Reduced Pumping Power, Minimal Clogging, Miniaturized Systems & Cost and Energy Saving.

Keywords Heat exancher, heat transfer coefficient, nano fluids.

properties, phenomena, and processes due to their nanoscale size

1. INTRODUCTION

   Heat exchangers are devices used for effective transfer of heat energy from one or more fluids to another across a solid surface, usually for both cooling and heating large/small scale industrial processes. Globally, they are extensively used in numerous industries, namely, petrochemical, power generation and food processing. Industrial heat exchangers, in essence, are categorized in accordance to various parameters including type of transfer process, size, flow configurations and arrangements, pass arrangements and heat-transfer mechanisms. Examples of these heat exchangers include shell and tube, compact, double pipe and plate.

   A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another as shown in figure 1. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power plants, chemical plants, petrochemical plants, petroleum refineries, natural gas processing, and sewage treatment. One such type is shell & tube Heat exchanger.

   L.B. Mapa, Sana Mazhar[1], analyses that the nanotechnology is concerned with the materials and systems whose structures and components exhibit novel and significantly improved physical, chemical, and biological

   Fig. 1. Shell and tube heat exchanger

   Young-Seok Son", J ee-Young Shin[2] proposes conventional shell-and-tube heat exchanger, fluid contacts with tubes flowing up and down in a shell, therefore there is a defect in the heat transfer with tubes due to the stagnation portions. Masoud haghshenas fard , Mohammad reza talaie , Somaye nasr[3] analysed with plate and concentric tube heat exchangers are tested by using the water–water and nanofluid-water streams. M. Raja, R.M. Arunachalam and S. Suresh[4] evaluated the heat transfer characteristics of Alumina/water nanofluid in a STHE with the aid of coil insert is being studied. Investigations were made on the effects of Peclet number and the effect of the Alumina/water nanofluid concentration on the heat transfer and pumping power characteristics. H. D. Li, V. Kottke[5] determined the local heat transfer coeffcients on the shell side of shell-and-tube heat exchangers for in-line tube arrangement are visualized and determined from mass transfer measurements. Navid Bozorgan, Mostafa Mafi, and Nariman Bozorgan[6] focuses on the potential mass flow rate reduction in exchanger with a given heat exchange capacity using nano fluids. A.N. Mahure and , V.M. Kriplani[7] In this paper, heat transfer augmentation techniques refer to different methods used to increase rate of heat transfer without affecting much the

   overall performance of the system. Ye Yao , Xingyu Zhang

   ,Yiying Guo [8] In this paper, a high-intensity ultrasound can induce cavitation bubbles and acoustic streaming in liquid, which makes it possible for power ultrasonic to be applied to the improvement of heat transfer process. Nenad Radojkovicl, Gradimir Ilic1, Zarko Stevanovic, Mica Vukic1, Dejan Mitrovic1, Goran Vuckovic1[9,10 and 11] has been carried out experimental investigations were done to identify influence of thermal and flow quantities and shell side geometry on STHE's heat exchange intensity.

   In the present work, a stainless steel shell and tube heat exchanger is used to study the various parameters of the heat exchanger such as heat transfer coefficient, Reynoldss number, pressure drop, Overall heat transfer coefficient etc using water as a heat transfer medium

2. EXPERIMENTAL SET UP

   Fig. 2. Shows the experimental setup of Shell and tube heat exchanger consisting of a calming section, test section, rotameters, overhead water tank for supplying cold water & a constant temperature bath for supplying hot water with in- built heater, pump & the control system. The test section is a smooth stainless tube with dimensions of 800mm length, Inner diameter of tube-16mm ID, and Outer diameter of tube- 19mm OD. These tubes are arranged in triangular pitch in the shell. Two calibrated rotameters, with the flow ranges, are used to measure the flow of cold water. The water, at room temperature is drawn from an overhead tank using gravity flow. Similarly a rotameter is provided to control the flow rate of hot water from the inlet hot water tank. Four thermo- couples are used measure the inlet & outlet temperature of hot water & cold water (T1 T4) through a multipoint digital temperature indicator. Sensors are inserted to measure the mass flow rate in shell and as well tubes sides.

   Fig. 2. Experimental setup

3. EXPERIMENTAL PROCEDURE

   1. Water is collected upto some volume in the tanks provided in the experimental set up of shell and tube heat exchanger.

   2. All the rotameters & RTD are calibrated.

   3. Shell and tube heat exchanger set up is made ON and heater provided is connected to the red water tank.

   4. Temperature is taken into consideration as water is started to heat.

   5. Pumps of shell side and tube side are started and flow takes place. Hot water at about 60°C is allowed to pass through the tube side of heat exchanger.

   6. Cold water is now allowed to pass through the shell side of heat exchanger in counter current direction at a desired flow rate.

   7. The water inlet and outlet temperatures for both hot water & cold water (T1-T4) are recorded only after temperature of both the fluids attains a constant value.

   8. The procedure was repeated for different cold water flow rates

   9. Temperatures are noted through the display. Temperatures for shell inlet and out let and tube side inlet and outlet are calibrated using thermocouples connected at every inlets and outlets.

   10. Minimum five readings are taken for every flow.

   11. The values are noted down through the computer connected to the experimental set up.

   12. Values are logged in for every reading using the software interface.

   13. Graphs are generated for every flow and temperatures in the excel sheets.

   14. Properties of fluids used is to be enter if different fluid is used other than water as waters properties are already been induced in the software provided.

   15. After completion of logging many readings, the log sheet of results is enerated which is to be saved for calibration

   16. Pressure drop is measured for each flow rate with the help log sheet.

   17. Over all heat transfer rate is measured.

   18. Discuss your results, by

   19. Commenting on the results and possible reasons for discrepancies,

   20. Reporting on the possible sources of errors in the experiment, and

   21. Analyzing the assumptions made during the experiment and their effects on the results in detail.

4. DESIGN PROCEDURE

Shell and tube heat exchanger is designed by trial and error calculations. The procedure for calculating the shell-side heat- transfer coefficient and pressure drop for a single shell pass exchanger is given below The main steps of design following the Kern method are summarized as follows:

STEP 1: Calculating the area of cross flow As, for hypothetical row of tubes at the shell Equator, given by

As = {(Pt Do)*Ds*Lb} /Pt

STEP 2: Calculate shell side mass velocity Gs and linear velocity Us.

Gs = ms / As or Us = Gs / s

STEP 3: Calculate the shell side equivalent diameter De.

For square pitch:

De = [4*(Pt2 {(/4)* Do2}] / (* Do) For triangular pitch:

De = [4*{(Pt2*3)/4} {(* Do2)/8}] / [(*Do)/2] STEP 4: Calculate shell side Reynolds number Res.

Res = (Gs* De) / s Or Res = (Us* De* s) / s STEP 5: Calculate shell side Prandtl number Prs.

Prs = (Cps*s) / Ks

STEP 6: Calculate the shell side heat transfer coefficient hs hs = 0.36*( Ks / De)* (Re^0.55)*(Pr^0.33)*{(s / w)^0.14}

Note: The value of (s / w) ^0.14 = 1, for water.

CALCULATION OF SHELL SIDE PRESSURE DROP

STEP 7: Calculate the number of baffles on shell side Nb.

Nb = {Ls / (Lb + tb)} 1 STEP 8: Calculate the friction factor f.

f = exp {0.576 (0.19*Ln Res)}

STEP 9: Calculate the shell side pressure drop Ps.

Ps = [4* f* Gs2* Ds*( Nb+1)] / [2* *De*×{(s / w)^0.14}]

V RESULTS AND DISCUSSIONS

The shell and tube heat exchanger is analyzed using Kerns method and heat transfer coefficient, Reynolds number, pressure drops, overall heat transfer coefficient etc are calculated for various mass flow rates and the results are shown in the graphs from figures 3 to 11. It is found that, shell side heat transfer coefficient increases with increasing mass flow rate. Also the shell side pressure increases rapidly with increasing flow rate.

Fig. 3. Reynolds Number V/S Mass Flow Rate

PRESSURE DROP

PRESSURE DROP

Fig. 4. Mass Flow Rate V/S Heat Transfer Coefficient

0.1

0.08

0.06

0.04

0.02

0

0

0.1

0.2

0.3

0.1

0.08

0.06

0.04

0.02

0

0

0.1

0.2

0.3

HEAT TRANSEFR COEFFICIENT

HEAT TRANSEFR COEFFICIENT

Fig. 5. Pressure Drop V/S Heat Transfer Coefficient

Fig. 6. Reynolds number V/s Over All Heat Transfer Coefficient on Shell and Tube Side

Fig. 7. Pressure Drop V/s Mass Flow Rate On Tube Side

500

400

300

200

100

500

400

300

200

100

shell

tube

shell

tube

0

0

0

0

0.1

0.1

0.2

0.2

0.3

0.3

OVER ALL HEAT TRANSFER COEFFICIENT

OVER ALL HEAT TRANSFER COEFFICIENT

0

-0.2 0

-0.4

-0.6

-0.8

-1

-1.2

0

-0.2 0

-0.4

-0.6

-0.8

-1

-1.2

2

2

4

4

6

6

Pressure drop

Pressure drop

heat transfer co efficient

heat transfer co efficient

REYNOLDS NO

REYNOLDS NO

Fig. 8. Heat Transfer Co efficient V/s Pressure Drop

Fig. 11. Reynolds number V/s Over All Heat Transfer Coefficient on Shell and Tube Side

VI CONCLUSIONS

It is found that among the all method, the Kern method provided a simple method for calculating shell side pressure drop and heat transfer coefficient. However, this method cannot adequately account the baffle to shell and tube to baffle leakage. By this experimentation it is clear that heat transfer co-efficient and various thermal parameters can be calculated and analyzed up to higher accurate as compared to the other methods.

ACKNOWLEDGMENT

HEAT TRANSFER

COEFFICIENT

HEAT TRANSFER

COEFFICIENT

Fig. 9. Mass Flow rate V/s Overall Heat Transfer Coefficient on Shell and Tube Side

0.25

0.2

0.15

0.1

0.05

0

33.6 33.8 34 34.2 34.4

AVERAGE COLD WATER TEMPERAT

0.25

0.2

0.15

0.1

0.05

0

33.6 33.8 34 34.2 34.4

AVERAGE COLD WATER TEMPERAT

Fig. 10. Heat Transfer Coefficient V/s Average Cold Water Temperature

The Authors are grateful to VTU PG Center, Kalburgi and RajaRajeswari college of Engg, Bangalore for providing support.

REFERENCES

1. L.B. Mapa, Sana Mazhar Heat transfer in mini heat exchanger using nanofluids American Society for Engineering Education April 1-2, 2005 Northern Illinois University, DeKalb, Illinois. 2005 IL/IN Sectional Conference.

2. Young-Seok Son", J ee-Young Shin Performance of a Shell-and- Tube Heat Exchanger with Spiral Baffle Plates Dong-Eui University, Busan 614-714, Korea KSME International Journal, Vol. 15. No. n. pp. 1555-1562, 2001

3. Masoud haghshenas fard , mohammad reza talaie , and somaye nasr Numerical and experimental investigation of heat transfer of zno/water nanofluid in the concentric tube and plate heat exchangers thermal science, year 2011, vol. 15, no. 1, pp. 183-194

4. M. Raja , R.M. Arunachalam and S. Suresh Experimental studies on heat transfer of alumina /water nanofluid in a shell and tube heat exchanger with wire coil insert International Journal of Mechanical and Materials Engineering (IJMME), Vol. 7 (2012), No. 1, 1623.

5. H. D. Li, V. Kottke Visualization and determination of local heat transfer coefficients in shell-and-tube heat exchangers for in-line tube arrangement by mass transfer measurements Heat and Mass Transfer 33 (1998) 371±376 Ó Springer-Verlag 1998

6. Navid Bozorgan,1 MostafaMafi,2 and Nariman Bozorgan1 Performance Evaluation of AI2O3/Water Nanofluid as Coolant in a Double-Tube Heat Exchanger Flowing under a Turbulent Flow Regime Hindawi Publishing Corporation Advances in Mechanical Engineering Volume 2012, Article ID 891382, 8 pages doi:10.1155/2012/891382

7. A.N. Mahure and V.M. Kriplani Review of Heat Transfer Enhancement Techniques International Journal of Engineering Research and Technology. ISSN 0974-3154 Volume 5, Number 3 (2012)

8. Yao, Ye; Zhang, Xingyu; and Guo, Yiying, "Experimental Study on Heat Transfer Enhancement of Water-water Shell-and-Tube Heat Exchanger Assisted by Power Ultrasonic". International Refrigeration and Air Conditioning Conference (2010)

9. Nenad Radojkovic1, Gradimir Ilic1, Zarko Stevanovic, Mica Vukic1, Dejan Mitrovic1, Goran Vuckovic1 Experimental study on thermal and flow processes in shell and tube heat exchangers Mechanical Engineering Vol. 1, No 10, 2003, pp. 1377 1384

10. Sunilkumar Shinde, Mustansir Hatim Pancha Comparative Thermal Performance Analysis Of Segmental Baffle Heat Exchanger with

    Continuous Helical Baffle Heat Exchanger using Kern method. International Journal of Engineering Research and Applications (IJERA), July-August 2012

11. A.R. Moghadassi1, S.M. Hosseini1, F. Parvizian1, F. Mohamadiyon1,

    1. Behzadi Moghadam1 and A. Sanaeirad2 An expert model for the shell and tube heat exchangers analysis by artificial neural networks ARPN Journal of Engineering and Applied Sciences vol. 6, no. 9, september 2011 .