IMPROVEMENT OF INDUSTRIAL EXTRUDED PIPE COOLING SYSTEM

MAE 4071: THERMAL SYSTEMS DESIGN

BY:THADDEUS BERGER

MARTIN BONILLACLAUDE BROOKS

CLYDE BROWNALEXANDER EIERLE

JONAS FUGLASELIZABETH HEEKE

JOHN HILKERPAUL KEPINSKI

ANDRE-LOUIS POUNDERAUSTIN SPAGNOLO

NATE VORIS

SUBMITTED: 23 NOV. 2015

INSTRUCTOR:DR. GROVES

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CONTENTS

Figures......................................................................................................................................................................... 3

Tables...........................................................................................................................................................................3

Executive Summary......................................................................................................................................................4

Introduction.................................................................................................................................................................5

Problem Statement..................................................................................................................................................5

Objectives................................................................................................................................................................5

Conceptual Design.......................................................................................................................................................5

Proposed Solution....................................................................................................................................................5

Fluid and Heat Transfer Analysis..............................................................................................................................6

Reliability.................................................................................................................................................................9

Cost Analysis..........................................................................................................................................................11

Modeling................................................................................................................................................................12

Results....................................................................................................................................................................... 16

Conclusion................................................................................................................................................................. 17

Appendix....................................................................................................................................................................18

A: Team Responsibilities*......................................................................................................................................18

B: Budget................................................................................................................................................................19

References.................................................................................................................................................................20

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FIGURES

Figure 1: Original cooling bay in use at industrial plant...............................................................................................5

Figure 2: Proposed cooling bay system schematic.......................................................................................................6

Figure 3: Nozzle..........................................................................................................................................................10

Figure 4: Chiller..........................................................................................................................................................10

Figure 5: Centrifugal pump........................................................................................................................................10

Figure 6: Reservoir tank.............................................................................................................................................10

Figure 7: Full system..................................................................................................................................................11

Figure 8: Original system before modifications..........................................................................................................12

Figure 9: Modified system..........................................................................................................................................13

Figure 10: Close-up view of modified system.............................................................................................................13

Figure 11: Close-up view of tanks and piping.............................................................................................................14

Figure 12: Top view of cooling bay system.................................................................................................................14

Figure 13: Top view system drawing..........................................................................................................................15

TABLES

Table 1: Cast iron pipe data used for system analysis..................................................................................................7

Table 2: Minor loss factors for pipe fittings..................................................................................................................7

Table 3: Failure rates for system components.............................................................................................................9

Table 4: Table of results.............................................................................................................................................16

Table 5: Team responsibilities....................................................................................................................................18

Table 6: Budget for modified system.........................................................................................................................19

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EXECUTIVE SUMMARY

A system to extrude metal pipes coated with thermoplastic for applications in oil rig umbilicals was originally cooled using nozzles which sprayed the pipe with water at 60 F as it moved down a conveyor in an industrial plant. The original system cooled the pipe in 52 feet and was not able to consistently cool the extrusion before the thermoplastic coating began to melt. To address the issue, nozzle flow rate was increased by increasing the water pressure, and temperature difference was increased by adding chillers to the system. For an additional $34,838.05, the solution improved the system by reducing the length of conveyor required to cool the pipe to 24 feet, reduced waste, and opened approximately 560 square feet of additional space on the plant floor. Given the design of the existing manufacturing floor and its preset cooling bay structure the closest reduction was brought to 27ft without drastically altering the system. Without considering the changes in power and wasted materials (among other factors), the additional space alone was determined to be enough to balance the cost of the improvements in less than one quarter.

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INTRODUCTION

PROBLEM STATEMENT

Piping for oil rig umbilical’s consists of extruded metal coated in a protective layer of thermoplastics. The pipe is extruded at about 2,200 F and then quenched with room temperature water, cooling it to 325 F. The pipe then moves to the Steel Cooling Bay where 60F water is sprayed on alternating sides at 100 psi. This is done to bring the steel down to a standard manufacturing room temperature of 80 F. Then the steel pipe proceeds to the thermoplastic extrusion section where a plastic coating is applied to the outside of the steel pipe for protection. If the pipe does not reach its target temperature of 80 F then bubbles or deformities will occur in the plastic extrusion section rendering said product unusable. This ultimately causes a reduction in manufacturing efficiency, profitability and increased fluctuations of waste.

OBJECTIVES

The objective of this project is an optimized system which can consistently and efficiently cool the extruded pipe within the desired time range so that the thermoplastic being extruded onto the pipe coating will not melt. Ideally, to further optimize the system, the length of the cooling process could be reduced by increasing the cooling rate of the steel pipe after the clenching phase. This will shorten the length of the overall cooling bays and dramatically open plant floor space, which provides the availability for new manufacturing process and space availability. This would improve the overall efficiency and profitability of the plant.

CONCEPTUAL DESIGN

PROPOSED SOLUTION

The proposed solution consisted of chillers in parallel cooling water to be pumped from a reservoir through a high-flow rate circulation pump. The pump chosen used 1.5 hp and had a flow rate of 40 gpm, which resulted in a 0.3918 gpm flow rate from each of the 32 nozzles. The chillers (5 hp) could operate up to 15 gpm and each had a 36 gallon capacity. A 60 gallon reservoir was used between the chillers and the pump. A schematic of the solution is shown in Figure 1, and a more detailed breakdown of the components and their respective costs can be found in Appendix B.

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Figure 1: Original cooling bay in use at industrial plant.

Figure 2: Proposed cooling bay system schematic.

From the reservoir, the water will be flowing at 40 gpm due to the centrifugal pump. The cooling water entering the chillers is assumed to be at a room temperature of 72.

For the control volume of a chiller, the volumetric flow rate would be a third of the total flowrate. Then, applying an energy balance to the control volume:

q=(mass flow ) ¿c p (T out−T ¿ )

It is found that the outlet temperature from each chiller will be 64; therefore, the cooling water will enter the nozzles at the temperature. This is a decent temperature change for a total flowrate of 40 gpm.

FLUID AND HEAT TRANSFER ANALYSIS

The following assumptions were made in the analysis of the problem:

1. The nozzles are arrayed around the circumference of the pipe so that they completely cover a section of pipe 7.14 inches long with water at 40 F.

2. Water flows with constant velocity.3. Neglect heat loss due to convection of air.4. Constant cooling rate.5. The pipe exits the quencher at 325 F.6. The pipe’s desired ending temperature is 80 F.

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Piping assumptions

Pipe Type Inner Diameter Friction Factor

Cast Iron Fittings 0.824 in 0.025

Table 1: Cast iron pipe data used for system analysis.

Fitting Minor Loss

Threaded Tee 0.9

90 Degree Threaded 1.5

Union Threaded 0.08

Table 2: Minor loss factors for pipe fittings.

The constants used for analysis were:

● ρ = 0.2834 lbm/in3

● cp = 0.12● Tinfinity = 40F● Ts, final = 80F● Ts, initial = 325F● Thickness = 0.25 in● k = 7.743 x 10-6 in2/s● v = 239.616 x 10-5 BTU/s in F● Pr = 10.518● Nozzle Spray Swath: 7.14 in● Nozzle Exit Velocity: 91.11 in/s● Tube Extrusion Speed: 0.75 in/s● Nozzle Array Distribution: 1 array every 3 ft of cooler length● z1 = 0 in, centrifugal pump is on floor● z2 = 36 in, system is 36 in off the floor● P1 = 25 psi, pump pressure output● P2 = 100 psi, specification pressure of nozzles● hL = 0, due to no major losses● a1 = 1, base alpha● a2 = (1+ζL /D+Σk )

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Using the modified Bernoulli equation shown below, we wanted to find the flow rate for all 32 nozzles.

¿¿

The area of analysis is from the pump to the nozzle head,

α 2=(1+0.025∗(30.5/0.824)+4.22)=6.145

The pump chosen has a flow rate of 40 GPM thus,

V 1=40gpm=9240i n3/min≫υ1=(3240 in3/min)(1/0.53 in2)(1min/60 s )=288∈¿s❑

Now plugging into the Bernoulli equation gives,

¿

υ2=91.11∈¿ s≫V 2=48.3 i n3/s∨12.54GPM

From our analysis we determined the resulting flow rate to 12.54 GPM the combine nozzle flow rate, thus each individual nozzle experiences a flowrate of 0.3918 GPM.

Rate of Temperature Loss

Reynolds Number (Length)

Nusselt Number (Length)

Convection Heat Transfer Coefficient (Length)

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Final Cooler Length

hx=0.000115063∗√(91.11−0.75)/ x

We assume that the rate of temperature loss is constant, thus we set dT/dt equal to itself and found:

dT /dt=[−0.00230126√91.11−0.75 /x (T−40)] /(0.2834∗0.25∗0.12)

Thus, we determined the required total spray swath to be 50.77 inches:

285/ 40=√ x1/x2→x1/ x2=81225/1600→x1=50.77 x2

With that we were able to calculate the Reynolds number, Nusselt number and the convection heat transfer at start of the process 0.0011 BTU/s-F-in2 and the heat transfer at end of the process. That and our constants we were able to calculate the final cooler length.

Re2=0.75∗50.77/239.616∗10−5=15891.1

N u2=0.332 ¿

h2=(7.743∗10−6/50.77)∗91.7=0.00015 BTU /sFin2

Final Length=36∈¿¿

This measurement is strictly required by the nozzle array set-up, so taking to account the needed empty space, the actual cooler length comes out to be 24ft.

RELIABILITY

Reliability in Series:

R s=e−∑

❑

❑

❑ λt

Reliability in Parallel:

R¿∨¿=e−λ1t+e−λ 2t−e−( λ1+λ 2)t ¿

t = 2000 hours

Part Reliability (rate/hour)

90 Degree Elbow 0.2x10-6

Splitting T 0.5x10-6

Nozzle 10.0x10-6

Pump 60.0x10-6

Chiller 85.0x10-6

Tank 5.0x10-6

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Table 3: Failure rates for system components.

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Figure 3: Nozzle.

R s1=e−(0.2 x10−6+10 x 10−6)(2000)=0.97

R s2=e−(0.2 x10−6+0.5 x10−6 )(2000)=0.99

R s3=e−(10 x 10−6)(2000)=0.98

R s1∨¿ s2=(0.97+0.98)−(0.97)(0.98)=0.99

RT=(0.99)(0.99)=0.98

R s17 Nozzles=0.9817=0.70

R s17∨¿ s17=(0.7+0.7)−0.72=0.91

Figure 4: Chiller.

Rchiller 1∨¿chiller 2=2e−(85 x 10−6)(2000)−e−(2∗85 x 10−6)(2000)=0.9755

Rchiller 3=e−(85 x10−6)(2000)=0.84

Rchiller 1∨¿chiller 2∨¿chiller3=(0.9755+0.84)−(0.84)(0.9755)=0.996

Figure 5: Centrifugal pump.

Rpump=2e−(60 x 10−6)(2000)−e−(2∗60 x 10−6)(2000)=0.9872

Rpump3=e−(60 x10−6 )(2000)=0.8869 Rpump1∨¿ pump2∨¿ pump3=(0.9872+0.8869)−(0.8869)(0.9872)=0.998

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Figure 6: Reservoir tank.

Rtank=e−(5 x10−6 )(2000)=0.99

Figure 7: Full system.

R system=(0.998)(0.996)(0.91)(0.99)=0.8955

Reliability of System: 89.55%

COST ANALYSIS

By reducing the total length of the cooling bay by almost half, we have freed up space in the manufacturing facility. The facility is rented at $20 per square foot per month. Using the renting price over the opened area, we found the time to balance the cost of the changes and improvements of the cooling bay is only 2 months and 23 days.

L = length of cooling block

W = width of cooling block area

p = price per square foot

OriginalCost perMonth=L∗W∗price=52∗48∗$ 20.00=$49,920.00 permonth

NewCost per Month=27∗20∗$ 20.00=$25,920.00 per month

Cost of changes = $34,838.05

Time¿ RecuperateChange∈Cost=Cost of changes ÷Change∈cost=34,838÷(49,920−25,920)

¿1.45months

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MODELING

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The CAD modeling of the solution was done in SolidWorks. The assembly can be seen on the following pages. Figure 7 illustrates the plant if the assembly were to stay at its given length of 52 ft long. The current setup utilizes 4 recycling tanks which collect all of the drained water after it has come in with the hot steel pipe. There are 3 low grade heat exchangers which then cool the water and feed them back into the nozzles. Figure 8 illustrates the system after the heat transfer process has been overhauled to be more efficient. This system incorporates two recycling tanks, 3 pumps and 3 heat exchangers of high quality. The water first is collected through the drains in the steel cooling bays and funneled into the recycling tanks (Figure 10). From there the recycled water is then sucked out of the tanks and into the (chiller) heat exchanger so that the 80F water can be cooled down to 40F (Figures 9 and 11). After the water has been chilled it is the sucked out of the heat exchanger by use of the pump at roughly 15 gpm per pump and into the nozzle spray apparatuses (Figures 9 and 11). Then through the use of pipe reducers, the water is funneled from ¾ in pipe to ⅛ in nozzles where the psi is drastically increased (Figure 9). From there the nozzles then spray the steel pipes in a manner at which 50% of one side is sprayed and then 50% of the other side is then sprayed at a 100 psi and 40F. The water is then once again drained from the cooling bays and repeated over and over again in an open-loop heat transfer process. The drawing (Figure 12, pg. 16) of the assembly demonstrates the dimensional analysis of the final reduced system. The overhaul of the system reduced the steel cooling bay from 52 ft long to 27 ft long. This left the system with 3 total heat exchangers, 3 15 Gpm pumps, and two tanks being used.

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Figure 8: Original system before modifications.

Figure 9: Modified system.

Figure 10: Close-up view of modified system.

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Figure 11: Close-up view of tanks and piping.

Figure 12: Top view of cooling bay system.

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Figure 13: Top view system drawing.

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RESULTS

The final results of the modified system are shown below:

Required Total Spray Swath 50.77 Inches

Final Cooler Length 24 Feet

Rate of Temperature Loss 10.35 F/s

Initial Convection Heat Transfer Coefficient 0.00015 BTU/s-in2-F

Final Convection Heat Transfer Coefficient 0.0011 BTU/s-in2-F

Total Flow Rate 12.54 GPM

Individual Nozzle Flow rate 0.3918 GPM

System Reliability 79.58%

Cost $34,838.05

Time to Recover Cost 3.11 months

Table 4: Table of results.

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CONCLUSION

By increasing the pressure and adding chillers to the system, the length of the cooling bay was reduced by 52%, while consistently cooling the extruded pipe to 80 F before adding the thermoplastic coating. The new system will improve plant profitability by reducing waste and opening additional space on the plant floor. The reliability of the system was found to be about 89%. The improved design will cost an additional $34,838.05, which is more than balanced by the improved ability of the system to cool the extruded pipe consistently to an acceptable temperature and the additional floor space that becomes available as a result of shortening the cooling bay. In fact, the extra space alone can balance out the cost of the improvements in its first quarter of use.

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APPENDIX

A: TEAM RESPONSIBILITIES*

*Everyone helped with the presentations.

Name Position Responsibility

Thaddeus Berger Technical Writing Lead Writing

Martin Bonilla CAD Analyst CAD

Claude Brooks Technical Writer Writing

Clyde Brown Team Lead CAD

Alexander Eierle Reliability Calculations Calculations

Jonas Fuglas CAD Analyst CAD

Elizabeth Heeke Technical Writer Writing

John Hilker Cost Calculations Calculations

Paul Kepinski Fluids Calculations Calculations

Andre-Louis Pounder Heat Calculations Calculations

Austin Spagnolo Calculations CAD

Nate Voris Heat Calculations Calculations

Table 5: Team responsibilities.

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B: BUDGET

Part Unit Price Quantity Total Price

Circulation Pump for water, 1.5 hp 208-240/460 V AC, 40 gpm flow rate

$661.95 3 $1985.85

High-Flow, Circulating Process Chiller, 60 kBTU/hr, 460 V/3 PH, 5 hp, 15 gpm flow rate, 36 gal tank

$10,619.44 3 $31,858.32

Horizontal Polyethylene Tank w/ Legs, 60 gal w/ drain, 38.5” length

$496.94 2 $993.88

Total $34,838.05

Table 6: Budget for modified system.

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REFERENCES

Incropera, F.P., DeWitt, D.P., Bergman T., and Lavine A., Fundamentals of Heat and Mass Transfer, 6 th Edition, Wiley (2006).

Cengel, Y.A., and J.M. Cimbala, Fluid Mechanics – Fundamentals and Applications, 3rd Ed., McGraw-Hill (2014).

Parts:"Circulation Pumps." McMaster-Carr. N.p., n.d. Web."Easy-Drain Cylindrical Tanks." McMaster-Carr. N.p., n.d. Web."Polyethylene Tanks." McMaster-Carr. N.p., n.d. Web.

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