EXPERIMENTAL INVESTIGATION OF HELICAL COIL AND STRAIGHT TUBE HEAT EXCHANGER

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INTERNATIONAL JOURNAL OF PURE AND

APPLIED RESEARCH IN ENGINEERING AND

TECHNOLOGY

A PATH FOR HORIZING YOUR INNOVATIVE WORK

EXPERIMENTAL INVESTIGATION OF HELICAL COIL AND STRAIGHT TUBE HEAT

EXCHANGER

PRAVIN GAVADE1_{, DR. NEERAJ KUMAR}2

1.Ph. D Scholar, Department of Mechanical Engineering

2.Prof. & HOD, Department of Mechanical Engineering

Accepted Date: 19/03/2018; Published Date: 01/04/2018

Abstract: Heat exchangers are one of the key engineering apparatus used for transmitting heat from one liquid to another. Heat exchangers are commonly used in several types of application such as power plants, nuclear reactors, and refrigeration and air-conditioning systems, mechanical engineering. Helical coil structure is very effective for heat exchangers because they have a large heat transfer area in a small space, with great heat transfer coefficients validate to straight tube heat exchanger. The improved heat transfer coefficients are due to the curvature of the coil, which leads centrifugal forces to act on the fluid, which generates secondary flow. This paper emphasis on the Experimental investigation of helical coil heat exchanger and its study is carried out considering the various parameters such as flow rate of cold water, flow rate of hot water, temperature, effectiveness and overall heat transfer coefficient for both parallel flow and counter flow arrangement.

Keywords: Helical Coil, Overall Heat Transfer Coefficient, Straight Tube, Effectiveness Etc.

Corresponding Author: PRAVIN GAVADE

Access Online On:

www.ijpret.com

How to Cite This Article:

Pravin Gavade, IJPRET, 2018; Volume 6 (8): 224-234_{PAPER-QR CODE}

SPECIAL ISSUE FOR

NATIONAL LEVEL CONFERENCE

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INTRODUCTION

A heat exchanger is known for transferring thermal energy among two or more liquids, at diverse temperatures and in thermal contact. Also the performance of the heat exchanger being enhanced, the heat transfer improvement enables the size of the heat exchanger to be significantly decreased. Helical coil heat exchangers are widely found in many industrial applications. The helically coiled tubes have advantage over straight tubes when working in heat transfer applications. In the coiled tube, the flow adjustment is due to centrifugal forces. The centrifugal forces are acting on the moving fluid due to the curvature ratio of the helical coil leads to the growth of Secondary flow which creates turbulence heat transfer rate increases. The amount of the centrifugal force depends upon axial velocity of flowing liquid and radius of curvature of the helical coil.

HELICAL COIL GEOMETRY

The diagram expresses different factors of the helical coil.

Figure 1: Shell and helical coil heat exchanger.

Where, d= tube diameter, D= shell diameter, Rc = coil radius,

b=Helical coil pitch.

The material of helical coil tube is soft copper. The real helical coil is shown as below:

Organized by G. V. S. E. T., Jaipur. Available Online at www.ijpret.com226  Factors of heat exchangers

The different factors essential for heat exchanger are formulated beneath

Sr. No. Dimensional factors Dimensions (mm)

1 Shell outside diameter [Do] 100.00

2 Shell inside diameter [Di] 96.00

3 Shell Thickness 2.00

4 Outside tube diameter [do] 9.80

5 Inside tube diameter [di] 9.00

6 Tube thickness 0.40

EXPERIMENTAL METHOD AND FABRICATION

A. Experimental Structure

Figure 3 Experimental Structure

Organized by G. V. S. E. T., Jaipur. Available Online at www.ijpret.com227 pump. Flow rate of hot water and cold water is controlled by valve. The inlet and outlet temperatures of hot and cold water were noted by using thermocouples in the inlet and outlet tubes. Also, all the pipes and connections between the temperature measuring stations and heat exchanger are duly insulated.

o Constituents

The different constituents required for Setup are listed below as per specification:

1. Helical coil tube:  Material – Copper  Copper tube length – 2 m  Quantity – 1 no.

2. Heater Specifications:  Power - 2000 Watt  Voltage - 230 V AC/50 Hz

3. Pump:

Pump Specification  Power – 18Watt  Head - 1.5 m  Speed - 1000 rpm  Discharge - LPH  Volt - 220V

4. Thermocouples: For temperature of range 0 to 1200 degree Celsius. For quick response and ease of reading we used this thermometer.

HELICAL COIL DESIGN

The study of the helical coil heat exchanger is carried by following procedure:

Step 1:

Coil length (L) =π×DC×N

Dc= 0.095 m N=6.7

On Exchanging, L = 2 m

Step 2:

Organized by G. V. S. E. T., Jaipur. Available Online at www.ijpret.com228 δ=

=0.0947

Step 3: Pitch Ratio γ =

= 0.1507

Step 4:

Heat transfer rate: Q = mcp [∆T]

Where, Q = Heat transfer rate (kJ⁄s) m = mass flow rate of water (kg⁄s) cp=Specific heat of water ( J⁄kgk)

∆T= Temperature Difference [℃]

Step 5.

Logarithmic mean temp difference:

=

Where, Parallel flow:

Tco

Counter flow:

are temperature differences

= Inlet temperature of hot Water = Outlet temp of hot water = Inlet temperature of cold Water

= Outlet temperature of cold water Step 6:

Overall heat transfer coefficient:

Organized by G. V. S. E. T., Jaipur. Available Online at www.ijpret.com229 Where,

U = Overall heat transfer coefficient (W/m2 ₎

Q = Heat transfer rate ( ) F = friction factor (1) A = Area of helical coil ( )

= LMTD ( )

Step 7: Effectiveness:

Where,

Effectiveness

RESULT TABLE

Result Tables for Helical coil heat exchanger in constant flow rate

 Helical coil heat exchanger

(Constant mass flow rate in parallel flow):

Sr. No _{Temp( ) (kg/s)} Q (KJ/S) _{U (W/m}2 ₎

1. 65 0.0167 0.9035 357.8 0.37

2. 60 0.0167 0.7045 321.18 0.3566

3. 55 0.0167 0.5560 255.44 0.32

 Helical coil heat exchanger

(Constant mass flow rate in counter flow):

Result Tables for Straight tube heat exchanger in constant flow rate  Straight tube heat exchanger

[For constant mass flow rate in parallel flow]

Sr. No. _{Temp( ) (kg/s)} Q (KJ/S) _{U (W/m}2 ₎

1. 65 0.0167 0.9730 366.86 0.40

2. 60 0.0167 0.8645 326.52 0.366

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Sr. No. _{Temp ( ) (kg/s)} Q (KJ/S) _{U (W/m}2 ₎

1. 65 0.0167 0.7632 112.65 0.334

2. 60 0.0167 0.4857 91.14 0.25

3. 55 0.0167 0.4132 104 0.2173

 Straight tube heat exchanger

[For constant mass flow rate in counter flow]

Sr. No.

Temp ( )

(kg/s) Q (KJ/S) U

(W/m2 ₎

1. 65 0.0167 0.8326 270.71 0.3636

2. 60 0.0167 0.6255 219.38 0.3214

3. 55 0.0167 0.4894 205.25 0.304

Result Tables for Helical coil heat exchanger for varying mass flow rate  Helical coil heat exchanger:

 (varying mass flow rate in parallel flow)

Sr. No.

Temp( ) (kg/s) Q (KJ/S) U (W/m2 ₎

1. 65 0.0167 0.695 235.89 0.2857

2. 65 0.01428 0.6576 214.13 0.3142

3. 65 0.0125 0.6803 213.19 0.3714

 Helical coil heat exchanger:

(Varying mass flow rate in counter flow)

Sr. No. Temp( ) (kg/s) Q (KJ/S) U (W/m2 ₎

1. 65 0.0167 0.977 346.64 0.4

2. 65 0.0142 0.8968 306.95 0.42

3. 65 0.0125 0.8374 294.22 0.48

Result Tables for Straight tube heat exchanger in varying flow rate

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Sr. No.

Temp( ) (kg/s) Q (KJ/S) U

(W/m2 ₎

1. 65 0.0167 0.5583 169.01 0.2424

2. 65 0.01428 0.5381 157.89 0.2727

3. 65 0.0125 0.4710 138.14 0.2727

 Straight tube heat exchanger for varying mass flow rate in counter flow

Sr. No.

Temp( ) (kg/s) Q (KJ/S) U (W/m2 ₎

1. 65 0.0167 0.628 186.06 0.2772

2. 65 0.01428 0.590 174.38 0.3030

3. 65 0.0125 0.524 151.42 0.3030

GRAPHS

o Varying mass flow rate:

Variation of Mass flow rate vs. Temperature drop

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Variation of heat transfer coefficient vs mass flow rate

Variation of effectiveness vs. mass flow rate

o Constant mass flow rate:

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Temperature Vs. Effectiveness:

Temperature Vs heat transfer rate

CONCLUSION

The helical pipe has the greater surface so the time period of fluid contact with surface is greater which results into improved heat transfer compared to that of straight pipe. Effectiveness is greater in counter flow arrangement for both helical and straight heat exchangers compare to parallel flow arrangement. When temperature increases there is a slow rise in the heat transfer rate in both straight tube and helical coil but it is extreme in helical coil. Also effectiveness increases by temperature increases and decreases when mass flow rate is increased. The temperature drop for helical coiled tube is higher than the straight tube. From this experimental investigation for same space and volume in industry the helical heat exchangers are more efficient than normal straight heat exchangers.

REFERENCE

1. N. D. Shirgire (2014), “Comparative Study and Analysis between Helical Coil and Straight Tube Heat Exchanger” International Journal of Engineering Research & Technology (IJERT) Vol 4 Issue 8.

Organized by G. V. S. E. T., Jaipur. Available Online at www.ijpret.com234 3. B. ChinnaAnkanna, B. Sidda Reddy (2014),”Performance Analysis of Fabricated Helical Coil Heat Exchanger” International Journal of Engineering Research, Volume No.3 Issue No: Special 1, pp: 33-39.

4. Mr. Dhiraj D. Shinde (2015), “Experimental Study of Heat Transfer Parameters using internal threaded pipe fitted with inserts of different materials” International Journal of Engineering Research & Technology (IJERT) Vol. 1 Issue 8.

5. MadhuriTayde (dec2014),”Heat Transfer Analysis of a Helically Coiled Heat Exchange” International Journal of Engineering Research & Technology (IJERT) Vol 4 Issue 14

6. Namrata D. Ranaware (2015),”A Review on Comparison between Shell and Tube Heat Exchanger and Helical Coil Heat Exchanger” International Journal of Engineering Research & Technology (IJERT vol 2 Issue 2).

7. Swapnil Ahire (2015),”Fabrication and Analysis of Counter Flow Helical Coil Heat Exchanger” International Journal of Engineering Research & Technology (IJERT) Vol 15