ChE 304

Chemical engineering laboratory - III Experiment No. 1 Group No. 03 (A2)

Name of the experiment:

Study of heat transfer coefficient in a

double pipe heat exchanger

Submitted by:

Md. Hasib Al Mahbub

Student Id: 0902045

Level: 3; Term: 2

Section: A2

Date of performance: 04/03/2014

Date of submission: 14/03/2014

Partners Student Id. 0902041

0902042

0902043

0902044

Department of Chemical Engineering.

Bangladesh University of engineering and technology, Dhaka.

1

Summary

The objectives of this experiment were to study a double pipe heat exchanger and hence to

obtain individual and overall heat transfer coefficients. Also the variation of heat transfer

coefficient with Reynolds number and fluid velocity and also the experimental and theoretical

heat transfer coefficient was compared. In this experiment, steam was used as the hot fluid

while water was used as the cold fluid. Water was passed through the pipe and steam was

passed through the annulus. Steam pressure was controlled by the valve opening. The inlet and

outlet water temperature was recorded. This same process was done for several steam pressures

of 5, 10 and 15 psig and different flow rate of water. Then by proper mathematical operation,

heat transfer coefficient was determined. In this experiment, the overall theoretical heat transfer

coefficient was found to be varied from 674.1697 W/m2.oC to 1501.875 W/m2.oC while the

experimental values varied from 763.644 W/m2.oC to 1644.788 W/m2.oC. And, the individual

steam side heat transfer coefficient was in the range of 7979.871 W/m2.oC to 8377.854 W/m2.oC

while waterside heat transfer coefficient was from 987.6382 W/m2.oC to 1981.433 W/m2.oC.

Graph of Nusselt number vs. Reynolds number, heat transfer coefficient vs. velocity and

Wilson plot was drawn. The possible discrepancies are discussed at the end of the report.

2

Experimental Setup

Figure 1: Experimental setup of a double pipe heat exchanger.

Saturated

steam inlet

Pressure

Gauge

Outlet

Temperature

Water

Outlet

Steam

Trap

Water

Inlet

Inlet

Temperature

3

Observed data

Tube Length = 7 feet 4 inch

Inner Tube: Nominal Diameter 1 inch; Schedule 40

Table 1: Observed data for double pipe heat exchanger.

Steam

Pressure,

P (psig)

Obs.

No.

Water temperature

(C)

Water Condensate

Inlet Outlet Volume(L) Time(s) Weight(kg) Time(s)

5 01 28 61 1.0 10.19 0.25 60

02 28 59 1.0 8.8 0.3 60

03 28 49 1.0 4.15 0.65 60

04 28 43 1.0 2.94 0.95 60

10 05 28 64 1.0 10.03 0.45 60

06 28 57 1.0 6.78 0.55 60

07 28 50 1.0 4.56 0.65 60

08 28 46 1.0 3.44 0.75 60

15 09 28 68 1.0 12.47 0.35 60

10 28 58 1.0 6.87 0.45 60

11 28 53.5 1.0 5.25 0.55 60

12 28 49.5 1.0 4.06 0.65 60

4

Calculated data

Length of the pipe, L= 7 ft 4 inch = 7.33 ft. = 2.234184 m.

Outer diameter of the pipe, Do=1.32 inch. = 0.033528 m. (Donald Q. Kern, Process Heat

Transfer, page: 843.)

Outside surface area, Ao = D0L = 0.2344 m2.

Table 2: Data for experimental overall heat transfer coefficients.

Obs. No.

Steam

Pressure

(psig)

Saturation

temperature,

TS (oC)

Heat of

condensation,

S (kJ/kg)

Wt. of

condensate,

WC (kg)

Mass flow

rate of

condensate,

Mc

(kg/s)

1

5

108.39

2234.347

0.25 0.0042

2 0.3 0.005

3 0.65 0.0108

4 0.95 0.0158

5

10

115.21

2215.612

0.45 0.0075

6 0.55 0.0092

7 0.65 0.0108

8 0.75 0.0125

9

15

120.97

2199.242

0.35 0.0058

10 0.45 0.0075

11 0.55 0.0092

12 0.65 0.0108

5

Table 3: Data for properties of water at mean temperature.

Obs.

No.

Mean

temperature

of water, TM

(oC)

Tube wall

temperature

on steam

side,Tw

(oC)

Density,

M

(kg/m3)

Mass Flow

rate of

Water

(kg/s)

Viscosity,

M

(kg/m.s)

Prandtl

No.

Pr

1 44.5 76.445 990.42447 0.097195728 0.000585 3.7295

2 43.5 75.945 990.83579 0.112594976 0.000596 3.8043

3 38.5 73.445 992.7838 0.239225012 0.000654 4.2178

4 35.5 71.945 993.8621 0.338048333 0.000694 4.5018

5 46 80.605 989.7944 0.09868339 0.00057 3.6217

6 42.5 78.855 991.24 0.14620059 0.000607 3.8816

7 39 77.105 992.5973 0.217674846 0.000648 4.1733

8 37 76.105 993.3316 0.288759186 0.000673 4.3561

9 48 84.485 988.9303 0.079304755 0.00055 3.4857

10 43 81.985 991.0388 0.144256012 0.000601 3.8426

11 40.75 80.86 991.93 0.188939048 0.000627 4.0232

12 38.75 79.86 992.6908 0.244505123 0.000651 4.1954

6

Table 4: Data for properties at mean temperature (Contd)

Obs.No.

Velocity of

Water,

V

(m/s)

Reynolds

No.

Re

Nusselt

No.

Nu

Water side

heat

transfer

coefficients,

hi

(W/m2.oC)

hio

(W/m2.oC)

Film

temperature,

Tf

(oC)

1 0.175932999 7.94E+03 46.99696 1124.823 893.8938 84.43125

2 0.203722416 9.03E+03 52.45477 1253.147 995.8725 84.05625

3 0.431989701 1.75E+04 92.06636 2178.535 1731.276 82.18125

4 0.609781381 2.33E+04 118.3597 2783.741 2212.231 81.05625

5 0.178739508 8.28E+03 48.12093 1154.83 917.74 89.25625

6 0.264418475 1.15E+04 64.13742 1529.407 1215.415 87.94375

7 0.393148522 1.61E+04 85.72424 2030.458 1613.599 86.63125

8 0.521150366 2.05E+04 105.6861 2493.319 1981.433 85.88125

9 0.143765618 6.89E+03 41.01053 987.6382 784.8731 93.60625

10 0.260954478 1.15E+04 63.70505 1520.507 1208.342 91.73125

11 0.341477573 1.44E+04 77.64805 1845.46 1466.581 90.8875

12 0.441565828 1.80E+04 93.88314 2222.617 1766.307 90.1375

7

Table 5: Data for properties at film temperature.

Obs. No. Density, f

(kg/m3)

Viscosity, f104

(kg/m.s)

Thermal

conductivity,

kf (W/m.oC)

Condensation

heat transfer

coefficients, ho

(W/m2.oC)

1 968 3.28 0.67285 8377.854

2 969 3.29 0.67262 8334.933

3 970 3.37 0.67145 8130.011

4 971 3.42 0.67072 8013.865

5 965 3.10 0.67565 8323.548

6 966 3.14 0.67492 8187.492

7 967 3.19 0.67417 8057.763

8 967 3.22 0.67373 7986.179

9 962 2.95 0.67793 8308.74

10 963 3.01 0.67698 8126.193

11 964 3.04 0.67654 8047.844

12 964 3.07 0.67613 7979.871

8

Table 6: Data for experimental heat transfer coefficients.

Observation

No.

Rate of heat

taken-up by

water,

Qw(J/s)

Rate of heat

given-up by

steam,

Qc (J/s)

Mean rate of

heat

transfer,

Qm(J/s)

Log mean

temperature

difference,

Tlm (oC)

Experimental

overall heat

transfer

Coefficient,

UOE

(W/m2 oC)

1 13044.73587 9309.779167 11177.25752 62.4434 763.6442362

2 14195.63681 11171.735 12683.6859 63.6365 850.318422

3 20431.4906 24205.42583 22318.45822 69.36097 1372.749895

4 20627.7093 35377.16083 28002.43507 72.63203 1644.788241

5 14444.87987 16617.09 15530.98493 67.62034 979.8600024

6 17243.33618 20309.77667 18776.55642 71.73568 1116.665483

7 19476.23921 24002.46333 21739.35127 75.67779 1225.520398

8 21144.10264 27695.15 24419.62632 77.86355 1337.972592

9 12898.12542 12828.91167 12863.51854 71.10465 771.7989638

10 17609.33134 16494.315 17051.82317 76.99841 944.7816707

11 19594.58522 20159.71833 19877.15178 79.5399 1066.133263

12 21384.90708 23825.12167 22605.01437 81.74934 1179.676555

9

Table 7: Data for calculation of theoretical heat transfer coefficients

Obs. No.

Theoretical

Overall heat

transfer

coefficients,

UOT (W/m2.oC)

OTU

1

OEU

1 8.0

1

MV

1 753.6054 0.001327 0.00131 4.015338

2 824.378 0.001213 0.001176 3.570828

3 1266.447 0.00079 0.000728 1.957137

4 1501.857 0.000666 0.000608 1.485459

5 770.0179 0.001299 0.001021 3.964821

6 967.2557 0.001034 0.000896 2.898455

7 1200.727 0.000833 0.000816 2.110351

8 1390.981 0.000719 0.000747 1.684339

9 674.1697 0.001483 0.001296 4.719282

10 961.9187 0.00104 0.001058 2.929194

11 1117.201 0.000895 0.000938 2.362165

12 1281.277 0.00078 0.000848 1.923108

10

Table 8: Data for the heat loss calculation and % of heat loss calculation.

Observation No.

Rate of heat

taken-up by

water,

Qw(J/s)

Rate of heat

given-up by

steam,

Qc (J/s)

Heat loss

QL (J/s)

% of heat loss

1 13044.73587 9309.779167 -3734.96 -40.11863911

2 14195.63681 11171.735 -3023.9 -27.06743229

3 20431.4906 24205.42583 3773.935 15.59127799

4 20627.7093 35377.16083 14749.45 41.69201594

5 14444.87987 16617.09 2172.21 13.07214518

6 17243.33618 20309.77667 3066.44 15.09834664

7 19476.23921 24002.46333 4526.224 18.85733166

8 21144.10264 27695.15 6551.047 23.65413208

9 12898.12542 12828.91167 -69.2138 -0.539513838

10 17609.33134 16494.315 -1115.02 -6.760003926

11 19594.58522 20159.71833 565.1331 2.803278816

12 21384.90708 23825.12167 2440.215 10.2421915

11

Sample Calculation

For observation No. 10:

Inlet water temperature, T1 =28oC

Outlet water temperature, T2 =58oC

Volume of water collected, V1 =0.001m3

Time for water collection, tw = 6.87 s

Weight of condensate collected, WC = 0.45 Kg

Time for condensation, tc = 60s

Density of water at 37 oC = 991.0388 Kg/m3

Weight of water collected, Ww = 0.001 991.0388

= 0.9910388 Kg

Mass flow rate of water, Mw = Ww/tw = (0.99103886.87) Kg/s

= 0.1442560116 Kg/s

Mass flow rate of condensate, Mc = WC/tc

= (0.45 60) kg/s

= 0.0075 kg/s

Mean temperature of water, Tm = (T1+ T2)/2 = (58+28)/2 =43 oC

Heat capacity of water at 43 oC, Cp = 4069 J/kg. oC

Rate of heat taken by water, Qw = Mw Cp (T2-T1)

=0.1442560116 4069 (58-28)

= 17609.33134 J/s

Heat of condensation of steam at 15 psig (29.7 psia), s =2199.242 KJ/kg

(Ref: Richard M. Felder, Ronald W. Rousseau, Element Principles of Chemical Processes,

3rd ed.)

Rate of heat given by steam,

QC = MC s = (0.0075 2199242) J/s =16494.315 J/s

Mean rate of heat flow,

Qm = 2

CW QQ = 2

315.16494 417609.3313 = 17051.82317 J/s

Saturation temperature of steam at 15 psig (29.7 psia), Ts = 120.97 oC

(Ref: Richard M. Felder, Ronald W. Rousseau, Element Principles of Chemical Processes,

3rd ed.)

12

Temperature difference at inlet,

T1 = Ts - T1 = (120.97 28) oC = 92.97 oC

Temperature difference at outlet,

T2 = Ts - T2 = (120.97 58) oC =62.97 oC

Log mean temperature difference,

Tlm =

2

1

21

lnT

T

TT

=

97.62

97.92ln

97.6297.92 oC =77 oC

The outside surface per linear feet = 0.344 ft2/ft

Inside diameter (ID) of the pipe, Di = 1.049 in. = 0.02665 m. (Donald Q. Kern, Process

Heat Transfer, page: 843.)

Outside diameter (OD) of the pipe, Do = 1.32 in. = 0.033528 m. (Donald Q. Kern, Process

Heat Transfer, page: 843.)

Tube length = 7 ft. 4 in. = 88 in. = 7.33 ft.

Outside area available for heat transfer, Ao = 0.3447.33 ft2 = 0.2344 m2.

Experimental overall heat transfer coefficient, UOE = 0.AT

Q

lm

m

= 2344.077

717051.8231

W/m2.oC

= 944.78167 W/m2.oC

Tube wall temperature on steam side,

Tw = 2

mS TT oC = 2

4397.120 oC =81.985 oC

Properties at mean temperature, Tm= 43 oC

Density of water, m =991.0338 kg/m3

Viscosity of water, m =0.00060102 kg/m.s

Prandtl no. of water,Pr = 3.8426

Thermal conductivity of water, km = 0.63608 W/m.oC (Ref: J P Holman, Suvik Bhattacharyya,

Heat Transfer, page no.: 609)

Inner flow area, Ai = 0.0005576 m2

Velocity of water, vm = im

W

A

M

=

0005576.00338.991

160.14425601

m/s = 0.260954478 m/s

13

Reynolds no. of water,

Re = m

mmi vD

.. =

00060102.0

260954478.00338.99102665.0 = 11468.05

Water side heat transfer coefficient for turbulent flow

Using Dittus-Boelter equation, hi = 0.023 i

m

D

k (Re)

0.8 (Pr)1/3

= 0.02302665.0

63608.0 (11468.05)0.8 (3.8426)1/3

= 1520.507 W/m2.oC

Film temperature,

Tf = Ts-0.75 (Ts-Tw)

= 120.97- 0.75 (120.97- 81.985) oC

= 91.73125 C

Properties of condensate at film temperature, Tf = 97.73125 C

Density, f =963.21 kg/m3

Viscosity of condensate, f = 0.00030103 kg/m.s

Thermal conductivity of condensate, kf = 0.67698 W/m.oC (Ref: J P Holman, Suvik

Bhattacharyya, Heat Transfer, page no.: 609)

Steam side heat transfer coefficient using Nusselt equation for film type condensation,

ho = 25.0

0

23

])(

...[725.0

fWS

Sff

TTD

gk

=25.0

23

]00030103.0)985.8197.120(033528.0

2199.242 81.9)21.963()67698.0([725.0

W/m2.oC

= 8126.193 W/m2.oC

Now, xw= mDD i .003439.0

2

02665.0033528.0

2

0

Carbon-steel metals thermal conductivity, KM = 43 W/m.oC

Log-mean diameter, Dlm =

i

i

D

D

DD

0

0

ln

= m.03.0

02665.0

033528.0ln

02665.0033528.0

Theoretical overall heat transfer coefficient,

14

UOT = 100

0

).

.

.

1(

lmm

W

ii DK

Dx

hD

D

h

= 1)03.043

033528.0003439.0

1520.50702665.0

033528.0

8126.193

1(

W/m2.oC

= 961.9187 W/m2.oC

Now, 0.001058944.78167

11

OEUm2.oC/W

0.00104961.9187

11

OTU m2.oC/W

2.929194)750.26095447(

118.08.0

v (s/m)0.8

Heat loss, QL = Qc-Qw = 1649.315- 17609.331341 = -1115.02 J/s

% of heat loss = (Qc-Qw)*100/Qc = -6.76%

15

Graphs

Figure 2: Log-log plot of Nusselt number vs. Reynolds number plot for 10 psig steam

pressure.

Figure 3: Log-log plot of Nusselt number vs. Reynolds number for 5 psig steam pressure.

y = 0.019x0.8686

10

100

1000

7000

Nuss

elt

Num

ber

,Nu

Reynolds Number,Re

10 psig

Power (10 psig)

y = 0.0214x0.8569

10

100

1000

6000

Nuss

elt

Num

ber

,Nu

Reynolds Number, Re

5 psig

Power (5 psig)

16

Figure 4: Log-log plot of Nusselt number vs. Reynolds number for 15 psig pressure steam.

Figure 5: Log-log plot of water side head transfer coefficient vs. velocity for 5 psig steam

pressure

y = 0.0197x0.8646

10

100

5000

Nuss

elt

Num

ber

,Nu

Reynolds Number, Re

15 psig

Power (15 psig)

y = 3842.6x + 469.57

100

1000

10000

0.1 1

Wat

er s

ide

hea

t tr

ansf

er c

oef

fici

ent,

hi

W/m

2.

C

Velocity of water, v(m/s)

5 psig

Linear (5 psig)

17

Figure 6: Log-log plot of water side head transfer coefficient vs. velocity for 10 psig steam

pressure.

Figure 7: Log-log plot of water side head transfer coefficient vs. velocity for 15 psig steam

pressure.

y = 3894.8x + 480.24

100

1000

10000

0.1 1Velocity of water,v (m/s)

10 psig

Linear (10 psig)

y = 4147x + 412.63

100

1000

10000

0.1 1

Wat

er s

ide

hea

t tr

ansf

er c

oef

fici

ent,

hi

(W/m

2.C)

Velocity of water,v (m/s)

15 psig

Linear (15 psig)

18

Figure 8: (1/U) vs. (1/V)0.8 plot for Wilson plot at 5 psig steam pressure.

Figure 9: (1/U) vs. (1/V)0.8 plot for Wilson plot at 10 psig steam pressure.

0.0005

0.0008

0.0011

0.0014

1.48 2.184 2.888 3.592 4.296 5

1/U

1/v.8

Experimental

Theoretical

Power (Experimental)

Power (Theoretical)

Dirt factor = 0.0006658- 0.000608= 0.0000578

0.0006

0.0009

0.0012

0.0015

1.68 2.344 3.008 3.672 4.336 5

1/U

1/v0.8

Experimental

Theoretical

Power (Experimental)

Power (Theoretical)

Dirt Factor = 0.000747-0.000719= 0.000028

19

Figure 10: (1/U) vs. (1/V)0.8 plot for Wilson plot at 15 psig steam pressure.

0.0006

0.0009

0.0012

0.0015

0.0018

1.92 2.536 3.152 3.768 4.384 5

1/U

1/v0.8

Experimental

Theoretical

Power (Experimental)

Power (Theoretical)

Dirt Factor =0.000848-0.00078= 0.000068

20

Results and Discussions

Range of the Theoretical Overall Heat Transfer Coefficient (UOT), 674.1697 W/m2.oC to

1501.875 W/m2.oC

Range of the Experimental Overall Heat Transfer Coefficient (UOE), 763.644 W/m2.oC to

1644.788 W/m2.oC

Ranges of individual steam side heat transfer coefficient - 7979.871 W/m2.oC to 8377.854

W/m2.oC

Ranges of waterside heat transfer coefficient - 987.6382 W/m2.oC to 1981.433 W/m2.oC

Slope of the straight line Nusselt number Vs. Reynolds number Plots are-

For 5 psig pressure - 0.8569

For 10 psig pressure - 0.8686

For 15 psig pressure - 0.8646

The theoretical value of Nusselt number Vs. Reynolds number Plots are 0.8

When the values of Nusselt no. is plotted against the values of corresponding Reynolds

no. in a logarithmic plot a straight line with a slope of 0.8569 0.8686 is obtained. According

to Dittus-Boelter equation, the slope should be 0.8. This curve also conforms to Dittus-Boelter

equation. Therefore, this finding is highly satisfactory.

The dirt factor from the 1/U vs. 1/v0.8 plot ranges from 0.000028 to 0.000068.

Nusselt no. vs. Reynolds and water side heat transfer coefficient (hi) vs. velocity (v) plots for

different pressure shows straight lines in log-log coordinate. But 1/U vs. 1/v0.8 plots for

different pressure for both theoretical and experimental overall heat transfer coefficients show

straight lines in normal coordinate. As the experimental findings of overall heat transfer

coefficients were generally lower than the theoretical ones, the 1/U curve for theoretical values

was in below the curve for experimental values.

The possible reasons of the discrepancies of theoretical and experimental values are mentioned

bellow

At the times of calculating the theoretical overall heat transfer coefficients the

resistance due to the formation of scale or dirt was not taken into consideration. Hence,

21

Fouling or other factors are left from the calculation. In reality, the performance and

efficiency of any heat exchanger are subject to these factors and this is why industrial

exchangers are dismantled routinely after operating a certain period for cleaning dirts

that are deposited on the wall. The double pipe heat exchanger used in this experiment

is very old and may not undergo overhauling for a long period. The scale deposited in

the meantime is sufficient to deviate the theoretical values from the experimental ones

especially when dirt formation is neglected in calculation.

Malfunctioning of the stream trap is one of the reason for the heat loss becoming

negative.

The steam pressure was considered constant during the experiment. But in practical it

was not constant throughout the experiment.

Heat lost during the experiment due to convection and conduction were not considered.

Could be the unsteady nature of condensate flow caused some error in the determination

of corresponding condensate for a given flow of water.

Some assumptions were made in determination of steam side heat transfer coefficient

determination; such as the vapor pressure was neglected and the condensation was

considered to be laminar and film type. But in practical could not satisfy those

assumptions.

1245678