Heat Exchange“The Alphabet Boys” Group K1

Colin Hannahan, Nerses Haroutunian, Jon Gigas, Adam Haidari

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Table of ContentsCalibration of flow rates with pneumatic valves………………………….……...3

Heat transfer coefficients compared with Reynolds # …………….……….….11

Heat Loss and Fouling Analysis ….………………………………………..……18

Conclusions and recommendations…………………………………..…………22

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Calibrating Flow

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Pneumatic valve setting corresponds to pressure (psig)

Measure flows by measuring mass of water over a given time (lbs/sec)

Calibrating Flowrates: Methods

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Figure 1. A fully closed pneumatic valve. Figure 2. A partially opened pneumatic valve.

Calibrating Flowrates: Methods

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Valves

Calibrating Operation Mode Steam Cooling Water

Process Water

Cooling Water Co-Current Closed Variable Constant

Cooling Water Counter-Current Closed Variable Constant

Process Water Counter-Current Closed Constant Variable

Figure 3. LabView dials for pneumatic valve of process and cooling waters.

Figure 4. View of apparatus outlining direction of flows.

Calibrating Flowrates: Calibration Curves

6Figure 5. Calibration curve for cooling water in co-current operation.

Calibrating Flowrates: Calibration Curves

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Figure 6. Calibration curve for cooling water in counter-current operation.

Calibrating Flowrates: Calibration Curves

8Figure 7. Calibration curve for process water, independent of operation mode.

Flowmeter Error AnalysisFlowmeter readings were compared to values from valve correlation on all data logs.

Figure 8. Flowmeter error of process water at various flowrates. Figure 9. Flowmeter error of cooling water at various flowrates. 9

Calibrating Flowrates: Suggestions1. Cooling water flowrate undetermined under 6 psig.

2. First open each valve fully, then reduce to setpoint.

3. Redundancy moving between different operating method.

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Calculating Heat Transfer Coefficients

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ho and hi

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ho and hi

Figure 10. Cooling-process water heat exchanger

Figure 11. Steam heat exchanger.

hi vs Reynolds Number

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Figure 12. Comparing calculated Reynolds number to heat transfer coefficient for process water

Source: Bergman et al. (2007)

ho vs Reynolds Number

14Figure 13. Comparing calculated Reynolds number to heat transfer coefficient for cooling water in co-current operation mode.

Source: Bergman et al. (2007)

ho vs Reynolds Number

15Figure 14. Comparing calculated Reynolds number to heat transfer coefficient for cooling water in counter-current operation mode.

Source: Bergman et al. (2007)

ho,steam=11.7 kW/(m^2*s)

Reynolds Number Calculation

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Figure 15. Kinematic viscosity of water decreases with increasing temperature.

Calculating hi, ho

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Heat Loss and Fouling Analysis

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Heat Loss: Methodology● Adjusted valve W2 to maintain constant liquid level in the sight glass

● Measured condensate flowrate and performed energy balance on the overall system

Balance:

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Heat Loss: Results● Average total heat loss: 4.3 kW

● Average loss as a percentage of total heat transferred from steam: 9.9%

● Most loss likely due to radiation from steam piping.

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Fouling Analysis● Observed rust in cooling water stream, but not in process water steam

● Significantly higher values of hi vs ho for cooling water at the same

Reynolds number

● Assumed differences due to fouling on outer surface of pipe

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Conclusions● Flowrate valve correlations were developed based on pneumatic valve pressure

○ Flowrate range (0.2 - 1.35 lbs/sec)

● h vs Reynolds number consistent with correlation

● Fouling in cooling water heat exchanger

● Overall heat loss: 4 kW

○ ~ 10 % of total heat transferred

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Recommendations● Valve C7 is very sticky

● Low cooling water valve settings are inaccurate

● Open valves fully (17 psig) to start before adjusting to desired flow

● Ensure that no steam flows out of apparatus

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ReferencesDelta T Heat Exchangers. Fouling in Heat Exchangers. http://deltathx.com/uploadsdocs/foulingfactors.pdf (accessed October 4, 2015).

Engel, Y. A.; Boles, M. A. Thermodynamics: An Engineering Approach; Seventh.; McGraw-Hill: New York, NY, 2011; pp. 868–870.

Kestin, Joseph; Sokolov, Mordechai; Wakeham, William A. Viscosity of Liquid Water in the Range -8 °C to 150 °C. Journal of Physical and Chemical Reference Data. 1978, 7, 941-948.

Pipe and Hose. American National Pipe - NPT/NPS | Pipe and Hose. http://pipeandhouse.com/node/19 (accessed October 4, 2015).

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Process Flow Diagram

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