Helical coil heat echanger1

Helical Coil Heat Exchanger

Thermal Design of Heat Exchangers

ME 436

Fall 2007

Department of Mechanical Engineering

Faculty Advisor: Dr. Abdelmessih

Team Leader: Joel Parker

Team Members: S. Cummings, M. Jorgenson


Table of Contents:

Helical Coil Heat Exchanger Design Report

The Problem Statement. .............. ...... ............ ........ ........ ......3

Acknowledgements............ ........ ........ ............ ........ ........ .. ...3

Background and Scope............. .. ....... . ............ ........ ........ ... ..4

Prel iminary Design............ ........ ........ ............ ........ ........ ......5

Prel iminary Calculations for the Heat Exchanger... ........ .... .. ..6

Final Design..... ..... ............ ........ ........ .......... .. ........ ... ..... .....7

The Apparatus....... ............ ........ ..... ... ............ ........ ........8 -12

Flow Chart and Description ......... ...... ............ ........ ....... 13-14

Revised Calculations for the Heat Exchanger......... .... .... . ....15

Results of the Test Run....... ......... ..... .. .......... ........ ........ ....16

Final Calculations for the Heat Exchanger........ ........ .... ... ....17

Discussion..... ....... ............ ........ ........ ............ ........ .... .... ....18

Concluding Remarks......... ......... ........ ............ ........ ..... ... ...19

Bibl iography......... . ............ ........ ........ ............ ........ ..... ... ...20

Nomenclature....... . ............ ........ ........ ............ ........ ........ ... 21


Appendices.... ....... ... ......... ........ ........ ............ ........ ........ ..... ..22-37

A-1) Budget......... .. .... ........ ........ ........ ............ ........ ........ . ..22

A-2) Laboratory Manual Sample....... ... ............ ........ .... ...23-29

A-3) Contribution of Team Members.... . ........... ........ ........ ...30

A-4) Experimental Data....... .... ..... ..... ............ ........ ........ ....31

A-5) Calculat ions by Hand..... ........ ..... ............ ........ ...... 32-37

Prel iminary..... ...... ............ ........ ........ ........ .... .... ...32-34

Revised....... ........ . ............ ........ ........ ............ ..... ... ...35

Final........ ......... .... ............ ........ ........ ............ ... ...36-37


Helical Coil Heat Exchanger Design Report :

The Problem Statement:

The thermal design of heat exchangers class received the

challenge of designing and building a second heat exchanger

apparatus for the thermal engineering laboratory. The heat

exchanger apparatus currently in the thermal engineering laboratory

is the 1-4 * shell and tube heat exchanger designed and built in

spring semester of 2002. The heat exchanger designed and built by

the thermal design of heat exchangers class wil l give future

mechanical engineering students an opportunity to work with a

helical coil in a hands-on manner. In testing this apparatus, future

students will be able to use their data to calculate Nusselt number,

heat transfer coeff icients and pressure drops for a helical coil.

Acknowledgements:

The Design Team would like to thank the following people for

their assistance in the completion of this project . First, we would

like to thank the school for funding this design project. We would

like to extend a thank you to Ms. Hopie Lopez for her assistanc e

with processing paperwork. We must also thank Otto Jorgenson, as

he has agreed to help make the plaque that we will proudly display

on the apparatus; it is a donation from Jorgenson Manufacturing in

Auburn.

* 1-4 means 1 shell with 4 tube passes


Background & Scope:

Up unti l now, the students in heat transfer classes offered at

Saint Mart in’s University would not have been motivated to study

helical coils and their related equations and correlations. Now

however, they will not only be motivated to study these things, but

there exists a means by which to apply them practically in a

laboratory setting. By test ing our apparatus, they wil l gain

knowledge and experience that may benefit them in their careers.

As a term project, a f inned helical coi l was presented to the

team. The team was instructed to design a laboratory apparatus

featuring the helical coil. Then it was built, tested and an

experiment was created based on it. One of the main concerns for

this experiment was safety based on the maturity levels of the

students who wil l be testing the apparatus in future years . The

goals of the experiment are as follows ; students should be able to

calculate Nusselt number, calculate the heat transfer coeff icient,

calculate the friction factor, and calculate the pressure drop for the

helical coil.


Prel iminary Design:

The original design for the apparatus involved the use of PVC

tubing because it is l ight, inexpensive, resistant to corrosion and

fouling, and easy to maintain. However, i t was dif f icult to f ind

f itt ings compatible with the thermocouples and the selected

industrial gauges.

The helical coi l is housed in a f ive-gallon plastic bucket. The

thermal characteristics of the plastic were considered as hot water

is being used. The risks of deformations over t ime from loading on

the lid of the bucket due to the weight of the helical coi l were also

considered.

The choice was made to work with single -phase condit ions for

the heat exchanger apparatus. Water was chosen as the working

f luid for both the hot side and the cold side for safety reasons. It is

a very safe f lu id to work with. Touching it does not cause chemical

burns although hot water can cause serious scalds and burns if

caution is not taken to avoid contact. It wil l not stain clothing, nor

will it destroy the actual fabric. It is not l ikely to cause i l lness if

ingested and it is not harmful if the vapor is inhaled.


Prel iminary Calculations for the Heat Exchanger:

In this section, a summary of the calculations performed to

size components needed to build the heat exchanger is presented .

For further information, please refer to the Calculat ions section in

the appendices (A-5).

Table 1: Summary of Preliminary Calculations

Parameter Amount Units

Mass Flow Rate 2732.4 lb/hr

Mean Velocity 32346.8 ft/hr

Reynolds Number 53074

Prandtl Number 4.308

Dean Number 21667.4

Radius of Curvature 6.0

Nusselt Number

Straight 276.94

Coil 475.09

Heat Transfer Coefficient

Straight 2429.25 BTU/hr*sq. ft.*F

Coil 4167.38 BTU/hr*sq. ft.*F

Friction Factor

Straight 0.005169

Coil 0.02038

Pressure Drop 3.407 PSI


Final Design:

We mounted the apparatus on a ut il ity cart for the purpose of

mobility and ease of storage. For the f inal design copper tubing and

brass f itt ings were chosen. We housed the helical coi l in a f ive -

gallon plast ic bucket . Furthermore, we took into consideration the

thermal characteristics of the plastic considering we are using hot

water. We also considered the risks of deformations over t ime from

loading on the lid of the bucket due to the weight of the helical coil .

For thermal data acquisit ion, we received two two-channeled Fluke

meters. They process the electrical dif ferential of the type -K

thermocouples and display a temperature reading .

Figure 1: The Complete Apparatus in i ts Final State


The Apparatus:

The following is a piecewise breakdown of the other main

components that went into construct ion of the heat exchanger

apparatus. The prices are noted where applicable. For further

information on the budget please refer to appendix A -1.

The Helical Coil

This is the main component in our apparatus. The helical coi l

is the focus of the heat exchanger; our apparatus wil l be unique in

this aspect.

Figure 2: The Helical Coil Figure 3: CAD drawing of the Helical

Coil with Dimensions


The Hot Water Heater:

The hot water heater is a 3.85 gallon 110 VAC water heater.

The hot water heater has a recovery rate of seven gallons per hour.

It has a maximum pressure of 150 PSI and a temperature range of

65-145˚F. It was purchased at Home Depot for $182.30.

Figure 4: The Hot Water Heater


The Pump:

The pump is a one-half horsepower 110 VAC centrifugal pump

made by Chicago Electric Power tools. It was purchased at Harbor

Freight for $32. It is oversized for the design but due to budget

constraints, options were l imited. I t has a maximum flow rate of 330

Gallons per hour and 115 feet of l if t.

Figure 5: The Pump


The Volumetric Flow Meters:

The volumetric f low meters are from Cole -Palmer. One is a

f if ty-f ive to three hundred gallon per hour f low meter (f igure 5a) for

use with the cooling water and it cost $72. The other is a zero to

sixty gallon per hour f low meter (f igure 5b) for the hot water and it

cost $110. Each Volumetric f low meter has a metering valve built

into it. The volumetric f low meters were chosen based on init ial f low

calculations for each individual f low source.

Figures 6a (left) and 6b (r ight): Volumetric Flow Meters


Pressure Gauges

The Differential Pressure Gauge:

The differential pressure gauge (f igure 7a) is also from Cole-

Palmer, although it is an Ashcroft product. It cost $100. It has a

zero to f if teen pound per square inch dif ferential chosen based on

early calculat ions. After running the experiment, it was discovered

that the dif ferential was too large. With a calculated pressure drop

of 0.18 PSI a smaller dif ferential gauge would work better.

The Standard Pressure Gauges:

These were procured at Grainger for $86.40 for the set of two.

They are the solution to the init ial option not functioning properly.

Figure 7a: The Differential Pressure Gauge

Figure 7b: The Set of Two Standard Pressure Gauges


Flow Chart and Description:

Figure 8: Flow Chart for the Final Design

The f igure above shows the f low paths of the hot water and

coolant, which are the working f luids for the heat exchanger

apparatus. The coolant, which is ordinary tap water, f lows from the

tap through a volumetric f low meter and then into the heat

exchanger that houses the coil. The water entering the system

spli ts off into two f lows, one to the hot water tank and one to the

volumetric f low meter. The cold water enters the exchanger shell

and discharges out the bottom of the exchanger to a drain. The hot

water runs directly through the helical coil into the reservoir, at the

reservoir where it drains to the pump. The f low splits again to the

reservoir and back to the water tank when valve 2 is closed creating

a closed circuit . The configuration dependent f low shown in green


in the above f igure is dependent on whether valve 2 is open or

closed. When valve 2 is open, it allows cold tap water to enter the

hot water tank. When valve 2 is closed, it creates a closed circuit

recycl ing the hot water that is pumping though the system.

Table 2: Valves

Valve 1 Master Drain Valve

Valve 2 Source Inlet to Hot Water Tank

Valve 3 Pump Outlet

Valve 4 Reservoir Overflow Valve


Revised Calculations for the Heat Exchanger:

In the table below is a summation of the results of calculating

with improved measurements. These measurements were taken to

aid in making the CAD drawing of the helical coil. The orange f i l l in

the table below shows what parameters changed. For further

information, please refer to the Calculations section in the

appendices (A-5).

Table 3: Summary of Revised Calculat ions





Prandtl Number 4.308

Dean Number 18882.9


Nusselt Number

Straight 276.94

Coil 457.48


Straight 2429.25 BTU/hr*sq. ft.*F


Friction Factor

Straight 0.005169

Coil 0.02038



Results of the Test Run:

A test run was completed on the apparatus. Once all of the

components were in place, the system was checked thoroughly for

leaks. After f ixing the leaks, the apparatus was prepared for testing.

The test run commenced with the apparatus being tested under

laboratory condit ions. Data was recorded every f ive minutes unti l

the apparatus reached steady state. The hot temperatures fell as

expected; the cold temperatures seemed to be more unpredictable

in one instance rising six degrees in f ive minutes and then on the

next reading fall ing three degrees. The apparatus took 150 minutes

to reach steady state, which can vary based on operating condit ions.

Readings were taken until the three -hour mark; however, the data

became inconsistent, so a steady state set was determined based

on proximity of the readings. The raw data is included in the

appendices for reference (A-4). Full numerical results are

presented in the appendices (A-5) and a summation is given in the

section below. The apparatus is in working order and ready for use

in the laboratory with a few small exceptions (see discussion).


Final Calculations for the Heat Exchanger:

In the tables below, we present our init ial condit ions and a

summation of calculations. We computed these calculat ions after

testing the apparatus under laboratory condit ions.

Table 4: Init ial Conditions

T-hot in T-hot out T-cold in T-cold out (dV/dt)hw (dV/dt)cw P-drop

93.0 84.0 55.5 61.5 58 52 DNF*

Table 5: Summary of Final Calculations





Prandtl Number 5.2

Dean Number 2814


Nusselt Number

Straight 182.6

Coil 292.5


Straight 1569 BTU/hr*sq. ft.*F


Friction Factor

Straight 0.008414

Coil 0.03286


* Did Not Function


Discussion:

These problems were encountered during the course of

working on the design. A reservoir bucket cracked during the

building process and a replacement was purchased. The apparatus

sprung a couple of leaks during the f irst and second trials. The hot

water heater had to be repositioned, as it would not function

properly in the previous position.

After testing the apparatus, some possible modif icat ions to the

system are suggested. One such suggestion is to procure a better

pressure gauge that f its our f inal design , one that can detect a

pressure drop of 0.18 PSI. This problem was so lved by using two

standard pressure gauges one for the inlet and one for the outlet.

Another suggestion is at some point replacing the probe

thermometer with a thermocouple to obtain the cold entrance

temperature more accurately. The thermocouple has been procured

and has been mounted and functioned properly .

The calculat ions went through mult iple runs, as new

information was discovered that changed what the results calculated

previously. A majority of the needed information for the calculations

was found in textbooks for previous courses or current courses.

The Konakov correlation for frict ion factor for the helical tube was

found in volume two of the Heat Exchanger Design Handbook.


Concluding Remarks:

The future students will benef it from the hands-on study of the

helical coil heat exchanger apparatus. This apparatus will be a

valuable addition to the thermal engineering laboratory for years to

come.


Bibl iography:

Heat Exchanger Design Handbook, Begell House, 2002 Ed. Volume

2 Section 5 Equation 42

Heat Exchangers: Select ion, Rating and Thermal Design, Kakac &

Liu 2nd Ed. Pgs 95 and 119

Fundamentals of Fluid Mechanics, Munson et . al. 5 t h Ed. Appendix

B Table 1

Fundamentals of Heat and Mass Transfer, Incropera, DeWit t,

Bergman & Lavine, 6 th Ed. Page 949,Table A.6 and Conversion

Factors, End pages

Thermal Engineering Laboratory Manual, Abdelmessih, 6 t h Ed. Heat

Exchanger, Chapter 17, Pages 58-63

Thermodynamics: An Engineering Approach, Boles and Cengel, 5 th

Ed. Page 938 Table A-3E


Nomenclature:

Roman Symbols:

D= Coil diameter, inches

d= Tube diameter, inches

(dV/dt)cw=Cold Water Volumetric f low rate, Gallons per Hour

(dV/dt)hw= Hot Water Volumetric f low rate, Gallons per Hour

LL= long straight leg of the coil, inches

SL= short straight leg of the coil, inches

P-drop= pressure drop, PSI

Greek Symbols:

λ= curvature ratio (D/d)

Subscripts:

c= Coiled tube property

cw= cold water

hw= hot water

i= inner dimension

o= Outer dimension

s= Straight tube property


Appendix A-1

Budget:

Our init ial budget allotted was $400. We ended up spending

approximately $830, which was definitely in excess of our init ial

budget. The approximated amounts were paid in cash and the

receipts have been submitted to the secretary of the Engineering

department. The exact budget is dif f icult to compute at this t ime, as

some of the receipts are not in the team’s possession.

Table 6: List of Expenditures

Part Source Unit Cost Quantity Total Cost

Ariston Water Heater Home Depot $ 182.30 1 $ 182.30

Galvanized Steel Bucket Lowe's $ 8.00 1 $ 8.00

Clearwater Pump Harbor Freight $ 32.00 1 $ 32.00

Differential Pressure Gauge Cole-Palmer $ 100.00 1 $ 100.00

Volumetric Flow meter (55-300 GPH) Cole-Palmer $ 72.00 1 $ 72.00

Volumetric Flow meter (0-60 GPH) Cole-Palmer $ 110.00 1 $ 110.00

Tax from Cole-Palmer purchases Cole-Palmer $ 23.69 1 $ 23.69

Copper tubing Lowe's $ 17.00 2 $ 42.00

Blue Bucket Lowe's $ 4.00 1 $ 4.00

Ball Valves Lowe's $ 7.00 4 $ 28.00

Compression Fit Spigot Lowe's $ 8.00 1 $ 8.00

Utility Cart Harbor Freight $ 43.35 1 $ 43.35

Clear 1/16th inch plexiglass DK Boos Glass $ 5.42 1 $ 5.42

Thermocouple shield Omega $ 22.50 1 $ 22.50

Pressure Gauge Grainger $ 43.20 2 $ 86.40

Sundry Fittings and Miscellany Various $ 174.66

Total $ 942.32

Table 7: List of Donations

Part Source

Duct Tape Peter Jorgenson

Commemorative Plaque Jorgenson Manufacturing

White Bucket Saint Martin's University Maintenance

Surge Protector Saint Martin's University

Helical Coil Thermal Engineering Laboratory


Appendix A-2

(Draft)

Chapter ___

Helical Coil Heat Exchanger Experiment

Foreword:

In fall semester of 2007, Thermal Design of Heat Exchangers

class (Jorgscumpark Industries) created this laboratory experiment

for not only your enlightenment but also your entertainment. We

would like to take this opportunity to remind you to keep safety in

mind as you work through this experiment. So, remember have fun

and be safe.

Problem Statement:

The Heat Transfer Company is seeking your participation in a

program for the investigation of the Helical Coil Heat Exchanger

designed and built by Jorgscumpark Industries in the fall of 2007.

They donated their t ime creating this apparatus for the Thermal

Engineering Laboratory as well as for the generations of future

employees of the Heat Transfer Company. It is now up to you to

test it.

Purpose:

From your experimental data, you should be able to make

various calculations. You can calculate Nusselt number, heat

transfer coeff icient, and pressure drops for the helical coi l. You

should be able to f ind all the information you require in your Heat

Transfer textbook or within this laboratory manual. If you should

need any other information, you may perform a literature search for

it and cite the sources you used.


Equipment:

Gauges:

Three Thermocouples and a probe thermometer

Two Volumetric f low meters- Cole Palmer

One Differential pressure meter- Ashcroft

Pump:

Clearwater Pump- Chicago Electr ic Power tools Model #01479

Buckets:

Five gallon white bucket- housing for the coil

Three-gallon bucket- overf low reservoir and trapped air removal

method

Hot Water Heater:

Four-gallon water heater- Ariston- It is imperative that you avoid

gett ing excess water on the hot water heater.

Data Acquisit ion:

2 two channeled Fluke meters

Miscellany:

A mop and mop bucket- for any spil ls and the leaky fresh water

supply

Rags or paper towels- also for spi l lage

Reservoir Cover


Dimensions of the Helical Coil:

Figure 1: Dimensions of the Helical Coil

Experimental Procedure:

Experimental Phase:

1. First, as to not damage the circuit

breaker, turn off any equipment you

are not using for this laboratory

exercise.

2. Perform a safety check on the

apparatus. Check the device for

exposed wires and other such

dangers. This is also a good time to

check the connections on the

apparatus. Make sure that al l valves

are closed. Plug in the surge

protector.


3. If the pump has not been used in

more than f ive days, remove the

cover and turn the fan with a

screwdriver.

4. Connect the source hose to the

source spigot, making sure that the

spigot is closed. Place the

discharge hose into the f loor drain.

5. Open valve 2 and Turn on source

water. Al low the water level to r ise

to a point where the helical coil is

fully submerged before. Use the

view port on the heat exchanger lid

to verify, visually, the water level.

While the heat exchanger is f i l l ing

up, turn on the hot water heater.

6. Once desired temperature is

reached, open the metering valve on

hot water volumetric f low meter and

begin f i l l ing the reservoir

approximately halfway.

7. Note: Make sure that the valves are

opened in the proper order specif ied.

8. Close valve 2

9. Open valve 3 and turn on pump by

plugging into the surge protector

(Make sure water in reservoir is at

least halfway full as fail ing to do so

will burn out the pump). This will


create a closed circuit for the hot

water.

10. Adjust hot water f low rate as

desired.

11. Adjust valve 1 and cold water

f low rate (via the volumetric f low

meter) such that the cold water

entering the heat exchanger is in

synch with the cold water exit ing out

the discharge.

12. Connect the three

thermocouples to the Fluke meters.

Make note of thermocouple

orientat ion.

13. Insert the type-K temperature

probe into the hole on the top of the

heat exchanger until it makes

contact with the cold-water inlet f low.

Then connect it to the Fluke meter

port.

14. Begin taking readings at

desired intervals until steady state

conditions.

15. Keep an eye on water level in

the reservoir, if overf low is imminent

open valve 4 to discharge.

Table 1: Note on valves:

Valve 1 Master Drain Valve

Valve 2 Source Inlet to Hot Water Tank

Valve 3 Pump Outlet

Valve 4 Reservoir Overflow Valve


Post Experimental Phase:

1. Secure the apparatus; close al l

valves unplug the pump, hot water

heater and anything else you

plugged in. Also, please leave the

thermal engineering lab as clean as

you found it.

2. From the volumetric f low rates,

calculate mass f low rates. Do this

with your steady state data

3. Predict the fouling factors for the

apparatus.

4. Begin your calculat ions for the

following…

a. Nusselt numbers

b. Heat transfer coeff icients

c. Pressure drops

Useful Correlations:

Petukhov’s Correlation for Nusselt number (2)

Nus=((f/2)*Re*Pr)/(1.07+12.7*(f/2)^(1/2)*(Pr^(2/3) -1))

Where f=(1.58*ln(Re)-3.28)^-2

Schmidt’s Correlat ion for Nusselt number (2)

Nuc=(1.0+3.6*(1-(1/ λ))*(1/ λ)^0.8)* Nus

Konakov’s Correlat ion for frict ion factor (1)

f=(1.8*log(Re)-1.5)^-2


References:

(1) Heat Exchanger Design Handbook, Begell House, 2002 Ed.

(2) Heat Exchangers: Selection, Rating and Thermal Design, Kakac

& Liu 2nd Ed.

(3) Thermal Engineering Laboratory Manual, Abdelmessih, 6 th Ed.


Appendix A-3:

Contribution of Team Members:

J. Parker: Team Leader & Treasurer

Overall design and construction of heat exchanger apparatus

Development of experimental procedure

Maintained budget records

General research

S. Cummings: Production Assistant & Draftsman

Construct ion of thermocouple units

Computer Drafting of f low chart and helical coil

Assisted in design and construction of the apparatus

Photography

General research

M. Jorgenson: Secretary & Principal Photographer

Calculat ions

Correlat ion research

Photography

Compiled f inal report

Scholar’s Day Liaison


Appendix A-4:

Exper imental Data

Volumetr ic f low rates: Hot: 58 GPH Cold: 52 GPH

Table 8: Data Spreadsheet

Time (sec) time (min) T-hot in T-hot out T-cold in T-cold out

0 0 93.9 84.0 55.5 61.5

300 5 93.7 83.9 54.5 61.5

600 10 93.8 84.1 53.4 61.7

900 15 93.5 83.9 53.1 61.6

1200 20 93.2 83.7 53.4 61.6

1500 25 93.3 83.7 54.0 61.2

1800 30 93.1 83.5 52.5 61.2

2100 35 93.3 83.6 53.3 61.4

2400 40 93.3 83.5 53.4 61.6

2700 45 92.9 83.1 54.3 61.9

3000 50 93.1 83.3 54.3 61.7

3300 55 92.8 83.1 54.5 61.5

3600 60 92.9 83.1 54.9 61.6

3900 65 92.6 82.7 55.2 61.9

4200 70 92.8 82.9 54.0 61.9

4500 75 92.5 82.8 54.5 61.5

4800 80 92.7 82.8 55.4 61.6

5100 85 92.7 82.9 56.4 61.5

5400 90 92.7 82.7 56.9 61.6

5700 95 92.6 83.1 51.5 61.1

6000 100 92.7 83.3 51.8 61.4

6300 105 93.0 82.8 57.0 61.7

6600 110 92.7 82.7 55.3 62.3

6900 115 92.5 82.9 51.7 61.4

7200 120 92.5 82.9 51.9 61.4

7500 125 92.7 82.9 51.9 61.4

7800 130 92.9 83.0 51.9 61.5

8100 135 92.8 83.0 51.4 61.1

8400 140 92.8 83.1 51.6 61.4

8700 145 92.9 83.3 51.5 61.4

9000 150 92.9 83.3 51.5 61.4

9300 155 93.1 83.7 51.5 60.9

9600 160 93.3 83.6 51.5 61.7

9900 165 93.4 83.4 51.5 61.7

10200 170 93.3 83.3 51.5 61.7

10500 175 93.1 82.7 51.5 61.9

10800 180 92.9 82.5 51.5 61.9

The yel low highl ight indicates the values used for steady state calculat ions.

Helical coil heat echanger1

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