Final Report

ChE 3423 – 002

Experiment 1: Steam Condensate

By:

Group E

Kingsley EdemidiongZachary Hensley

Kelly WatersVanessa Leary

Performed on Wednesday, February 23rd 2011And

Wednesday, March 2nd 2011

Abstract: Written By Kingsley Edemidiong

This experiment was conducted to study and develop correlations for predicting the heat transfer

coefficient for film condensation on vertical and horizontal Corning glass cylinders, each fixed around

7/8” nominal diameter copper tubes, and comparing the results obtained to the theory of Kern. The

horizontal and vertical tubes were operated with pressurized steam and cooling water. The liquid flow

rate in this experiment ranged from 0 to 11 gallons per minute and the pressure of the steam remained

constant at 3 psig (pounds per square inch). These two components combined, produced condensation

on the horizontal and vertical cylindrical glass shell tubing. The experimental trend that was noticed for

the vertical tube was that the cooling water flow rate increased as the experimental hc values decreased.

The hc experimental correlation values resulted in a range from 88 to 180 BTU/hr-⁰F for cooling water

flow rates of 2 to 6 gallons per minute. For the horizontal tube there was no clear trend, however, the

hc experimental correlation values obtained ranged from 1.00 x 1016 to 8.6 x 1016 BTU/hr-⁰F (Standard

Deviation of ± 1 to 6.0 x 1016 Btu/hr-⁰F) for cooling water flow rates of 2 to 6 gallons per minute. All in

All, the horizontal tube gave higher hc values than the hc values for the vertical tube indicating higher

heat transfer for the horizontal tube.

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Introduction by Vanessa Leary

The vertical and horizontal tubes are used to characterize the heat transfer coefficient for film

condensation. Since heat transfer equipment is utilized in numerous applications within a multitude of

industries among these including condensers therefore having models to predict heat transfer

coefficients for film condensation (the most common and steady type of condensation) allows for more

efficient and optimized operating conditions (Corradini, Earle, Kern 254). The vertical and horizontal

tubes allow for a counter-current flow of hot gas and cooling water to flow which the temperature

difference between the liquid and gas causes the condensation of the hot gas to form on the cooling

water’s pipe demonstrating the film condensation phenomenon.

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Theory by Vanessa Leary

Film condensation is one mechanism of condensation characterized by a continuously wet surface from

the condensation; therefore the site forms a “film” since the water collects indicating an affinity for the

surface (Kern, 252). Whereas drop wise condensation forms water droplets that “drop” off of the site

instead of collecting. This experiment focuses on film condensation in both the vertical and horizontal

tubes. As a result of the mechanism in which the condensate was formed (film vs. drop) the heat

transfer coefficient will be larger in drop wise condensation (up to 8 times as large) since there will be a

resistance to the heat of condensation within the condensate film (253).

The vertical tube apparatus used in this experiment demonstrates Nusselt’s Theory. Nusselt’s theory on

film condensation was based on the assumptions that the heat transfer from the film to the surface

occurred in laminar flow by conduction only, the film thickness was a function of both viscosity and the

amount of condensate forming at that site, only latent heat is involved, a constant temperature change

through film, the film curvature is neglected, the surface temperature is constant, the mean film

temperature determines the properties, and finally the heat transferred is directly related to amount of

condensate (256-7). To determine the heat transfer coefficient of the film condensation equation 1.1

was used for the vertical tube and equation 1.2 for the horizontal tube (refer to equation 1.3 for the

intermediate calculation).

h=0.943[ k3f ρ

2f λg sinα

μ f LΔ tf ]14

Equation 1.1: The heat transfer coefficient equation for the vertical tube where k is the thermal conductivity of the film fluid, ρ is density of film fluid, λ is the latent heat of vaporization, g is gravity, μf is the viscosity of the film fluid, L is the length,

Δt f film temperature difference andα angle from incline (Kern 261).

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h=0.725[ k3f ρ

2f λg

μ f D0 Δt f ]14

Equation 1.2: The heat transfer coefficient equation for the horizontal tube where k is the thermal conductivity of the film fluid, ρ is density of film fluid, λ is the latent heat of vaporization, g is gravity, μf is the viscosity of the film fluid, D0is the

outside diameter of the tube, and Δt f film temperature difference (Kern 263).

Δt f=2 (T f−T b )

Equation 1.3:Where, the bulk temperature (T b )is the average of the vapor and condensate temperatures and the film

temperature is the average of the vapor and the bulk temperature (T f ) (Welty, 283,299).

These equations illustrate the strong difference that position of the condenser can have on the heat

transfer. Horizontal tube heat transfer coefficients are found to be approximately 3 times as large as

those from vertical tubes since vertical films can become turbulent therefore the assumption within the

above equation (1.1) will no longer be valid. As a result, most industrial applications install condensers in

the horizontal position maximizing their heat transfer capabilities. However, for distillation column

applications involving sub cooling of the condensate vertical condensers are employed illustrating the

cost effective use of both equipment types (269).

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Equipment Description by Kingsley Edemidiong:

To perform the steam condensation experiment, two tubes in shell units were used. One tube

was made up of a cylindrical Corning glass that was placed in the vertical position. Within the vertical

tube was a 16 BWG (Birmingham Wire Gauge) copper tube that had a 7/8” nominal diameter and was

48 inches in length. A second cylindrical Corning glass shell tube with a 3.5 inside diameter was placed

horizontally. The horizontal tube had a 16 BWG copper tube that was placed in the middle of the

Corning glass shell. The horizontal copper tube had a 7/8” nominal diameter and measured 36 inches in

length. Figures 1 and 2 provide a description of how the horizontal and vertical cylindrical glass tubes

were positioned.

A blue steam valve, manufactured by NIBCO, controlled the flow of steam to the condenser. To measure

the pressure of steam that flowed to the condenser, a Foxboro pressure gauge was used. A red drain

valve, manufactured by B and K, drains any residual steam trapped in the condensate line. This red

drain valve was positioned below a red steam valve. Another red valve controlled the flow of cold water

to the condenser. The water rotameter, manufactured by F and P Company, measured the flow of cold

water, from 0 to 11 gallons per minute, through the copper tubes. A set of thermocouples

manufactured by Omega, measured the inlet and outlet water temperatures as well as the exhaust

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Figure 1: Vertical Condenser. Figure 2: Horizontal Condenser.

steam. Two blue valves were used to direct the flow of water to the desired copper tubing. A set of red

valves positioned below the apparatus controlled and directed the flow of condensate to be measured.

Operating Procedure by Kelly Waters:

Before any system operation began, the apparatus used for this experiment was carefully studied to

determine all possible flow paths. The steam condensate trap was opened and allowed drainage of any

residual steam condensate that may have been trapped in the line from previous apparatus operation.

The thermocouple reading unit was turned on before experimentation to allow it to warm up for 5

minutes prior to taking any readings. It was decided that experimentation and data collection on the

vertical steam condenser would be accomplished to its entirety before the operation of the horizontal

steam condenser was analyzed and data for that unit were taken.

Once flow paths were determined for cool water and steam flow to the vertical pipe, the appropriate

valves were opened and closed to allow the cold water to enter from the bottom of the tube, flowing

upwards with an exit stream out of the top of the vertical unit. To prevent damage to the flexible seals

between the corning glass shell and copper tube, a minimum cooling water flow rate was always kept

circulating through the apparatus. For the vertical tube unit, there were two steam condensate streams

flowing from the bottom, each equipped with two red valves. One of the valves from each stream was

turned to the off position to allow the flow of condensate directed only to one stream (this was

desirable, since the closed valve directed condensate flow directly to the drain where it could not be

collected). A steady flow rate of steam at, or slightly less, than 3 psig reading was directed through the

apparatus. After the system had reached steady state, and a noticeable amount of steam was flowing

through the unit, the red residual condensate steam drain valve/knob was closed. Beginning at a cool

water flow rate of 2 gpm, all temperature readings from all 7 thermocouples were recorded. The

temperatures collected, corresponded with a number on the thermocouple reading unit taking

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temperature of (1) inlet cooling water, (2) exhaust cooling water, (3) wall condensate, (4) tuber

condensate, (5 )condenser tube glass, and (6) inlet steam. Condensate was collected from both

condensate streams for a total of a minute each, and then the volumetric amount of water was taken

using a graduated cylinder. This allowed for volumetric flow rate of the condensate to be measured.

Each condensate from both streams was collected and measured twice (2 runs). Therefore, for each

flow rate there were 4 condensate volumetric flow rate data taken (2 for the condensate collected from

the copper tube, and 2 samples from the condensate collected from the outer glass shell). A total of ten

different flow rates ranging between 2 gpm to 7 gpm were collected, and 4 different readings were

taken for this particular cooling water flow rate. Between each water flow rate change, the steam

pressure was monitored, and the system was allowed time to reach steady state.

A similar procedure was used for the data collection on the horizontal tube unit. However, with the

horizontal tube there was the option for cool water flow rate both co-current with the steam, and

countercurrent flow to the steam. It was decided that countercurrent data collections would be taken

on the horizontal tube. Appropriate valves were opened or closed to direct cool water flow from one

end of the tube, and steam flow from the other end. With the horizontal tube, condensate from both

the tube and the outer glass shell were combined to one condensate exit stream, which was separated

into two with two valves. Again, the drainage valve was closed, and all steam condensate was directed

to one single stream for collection. The same procedure for measuring the condensate flow rate from

the vertical tube, was used for the horizontal tube, as well as all temperature readings taken for each

flow rate. The thermocouples (labeled 7-13) on the horizontal tube measured the; (7) inlet cooling

water, (8) exhaust cooling water, (9) total condensate, (10) condenser tube glass, (11) inlet steam, (12)

upper condensate tube, (13) lower condensate tube. Cool water flow rate ranged from 2 gpm to 6 gpm,

with a constant steam pressure at 3 psig. Nine different flow rates were taken, and two samples of

condensate and temperature readings were taken for each flow rate as well.

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Shut down procedures included turning off steam pressure. Water flow was slowly decreased to 0 gpm.

Thermocouple unit was turned off. All condensate stream valves below the unit were opened, and. all

cool water exit draining valves were left opened to allow the system to drain.

Safety Precautions:

The unit does include work with steam, meaning water and unit will be subject to high temperatures

above water’s boiling point of 212 degrees Fahrenheit, most data collected had a steam temperature of

216-219 degrees Fahrenheit. Thus the corning glass shell will be hot and the exit steam condensate

streams will be hot to the touch, as a result of conduction through the surface mediums. Care will be

taken to avoid direct skin contact with hot surfaces, and hot liquid from the steam. Also, glasses are

worn to protect the eyes from any debris of water that may exit the apparatus unintentionally.

Experimental Plan Day 2: (operating procedure day 2) by Kelly Waters

Data for horizontal tube concurrent water and stream flow rate will be collected. This includes

appropriate temperature readings for inlet, outlet flow of both steam and water. Also,

condensate volumetric flow rate.

o Appropriate valves opened and closed to direct flow rates of both cooling water and

steam to the unit.

o Jobs divided for this section: one person changes cooling water flow rate, which also

taking the temperature readings. One person collects condensate sample after system

has reached steady state for each cooling water flow rate. One person measures flow

rate sample. One person inputs data and appropriate graphs are made.

Rerun data collection for vertical tube to collect the right temperature readings from the corning

glass, so that correct calculations of hc and appropriate graphs will be made possible. This

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would be helpful in making sure that there is temperature change within the data greater than

15 degrees.

If time permits, all graphs/plots will be completed so as to ensure proper execution of

experiment.

Take picture of apparatus to include in final report.

Check all manufacturers and equipment specifications for final report.

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First Day Results by Zachary Hensley

Due to taking the wrong vapor temperature readings our graphs reflect a small change in film

temperature. This greatly hampers the accuracy of the results obtained from day 1. By having the

incorrect vapor temperature the film and average film temperatures are wrong. It is for this reason we

will have to repeat the day 1 portion of temperature data collection. It is important that we gather the

right data to properly calculate the day 1 values of h so that when compared with the data of day 2 we

can make the correct correlations.

1401

10

100

f(x) = 0.0664715626383572 x + 65.2077344033729

Vertical Tube

Vertical TubeLinear (Vertical Tube)Linear (Vertical Tube)

ΔTf(°F)

h(Bt

u/h

ft^2

°F)

Figure 1- log-log plot of the calculated h value vs. the average film temperature for the vertical tube. The

Linear line fit correlates to the equation hC=

a

L1/4(Δt f )

b

(Kern). Where the slope on the graph is equal to the exponent b and the intercept is equal to the a value of the equation.

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1.00E+05 1.00E+061

10

100

f(x) = 2.97829131651024E-08 x + 37.528473465493

Vertical Tube

Vertical TubeLinear (Vertical Tube)

4G'/μ

h/k(

ν^2/

g)^1

/3

Figure 2- log-log plot of h/k(ν^2/g)^1/3 vs. 4G’/μ for the vertical tube. A line of best fit should create a line

which the slope and intercept should be determined.

1301.00E-02

1.00E-01

1.00E+00

f(x) = − 5.76511134459473E-05 x + 0.0623213887222625

Horizontal Counter Current Flow

Run 1

Linear (Run 1 )

ΔTf(°F)

h(Bt

u/h

ft^2

°F)

Figure 3- log-log plot of the calculated h value vs. the average film temperature for the horizontal tube

with counter current flow. The Linear line fit correlates to the equation hC=

a

L1/4(Δt f )

b

(Kern). Where the slope on the graph is equal to the exponent b and the intercept is equal to the a value of the equation.

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1.00E+04 1.00E+050.0001

0.001

f(x) = − 4.99754781691487E-09 x + 0.000436198344355292

Horizontal Countercurrent Flow

Horizontal Countercurrent FlowLinear (Horizontal Coun-tercurrent Flow)

4G"/μ

h/k(

ν^2/

g)^1

/3

Figure 4- log-log plot of h/k(ν^2/g)^1/3 vs. 4G”/μ for the vertical tube. A line of best fit should create a

line which the slope and intercept should be determined.

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Sample Calculations by Kelly Waters

Calculations for Vertical Tube, steam pressure at 3 psig, cool water flow rate at 2.6 gpm RUN 1.

Calculation of G’:

G'= condensate flow ratewetted perimeter of the tube

(condensate flow rate per linear foot)

5.583/ (π*(.0729))=24.37 mL /sft

Calculation of tw:

tw=(inlet temperature+outlet temperature)

2 (temperatures from experimental data)

(54.8+85.8)/2=70.3 ⁰F

Calculation of average film temperature tf:

t f=(T v+ tw)

2 (Tv temp of saturated vapor, tw temperature of outside tube wall based on bulk average water

temp)

(216.1+70.3)/2=143.2 ⁰F

Calculation of Δtf:

∆ t f=2(t f−tw) (T in ⁰F from experimental values)

2*(143.2-70.3)=145.8 ⁰F

Calculation of heat transfer coefficient hc :

hc=a

L14

(∆ t f )b

using equation from Kern (12.19) hc=0.943( k3 ρ2 λgμf L∆ t f )

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0.923*[(.3833*61.32*972.43*32.2)/ (2.9E-04*4*143.2)]1/4= 74.89

Calculations for horizontal unit, steam pressure 3 psig, cool water flow rate 2.6 gpm, RUN 1

Calculation of G”:

G= {condensate flow rate} over {tube length (condensate flow rate per linear foot)

6.3/4 = 1.575 mL /sft

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*same calculation for vertical for tw, tf and Δtf*

Calculation of heat transfer coefficient hc:

hc=1.51¿¿ (from Kern (12.40))

1.51*(4*1.575/2.9E-04)-0.33 = 5.39E-02

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References

Corradini, Michael, L. "Condensation." Basic Processes of Condensation. University of Wisconsin-

Madison, 03 11 1997. Web. 28 Feb 2011.

<http://wins.engr.wisc.edu/teaching/mpfBook/chapter9/node1.html>.

Earle, R, L. "Heat Transfer Applications." Unit Operations in Food Processing . University of

Wisconsin-Madison, 1983. Web. 28 Feb 2011.

<http://www.nzifst.org.nz/unitoperations/httrapps.htm>.

Kern, Donald. Process Heat Transfer. New York, NY: McGraw-Hill, 1950. 252-311. Print.

Welty, Wicks, Wilson, and Rorrer. Fundamentals of Momentum, Heat, and Mass Transfer. 5th . John

Wiley & Sons, 2008. 551-636. Print.

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