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Fouling mitigation
Test No . |
Cooling Water Flowrate ( gpm ) |
Differential Temperature ( O F ) |
Improvement in Overall Heat Transfer Coefficient ( U . ) of Neotiss Tubes Over Control Tube
Pre-Cleaning
Post-Cleaning
|
1 |
55 |
10 |
28 % |
30 % |
2 |
55 |
5 |
13 % |
17 % |
3 |
55 |
3 |
9 % |
9 % |
4 |
25 |
15 |
20 % |
22 % |
5 |
30 |
10 |
16 % |
20 % |
6 |
30 |
5 |
8 % |
10 % |
Table 2 . Performance comparison at different cooling water flowrates and temperature rise . |
averages , and each case must be evaluated separately on their unique process conditions . How to take advantage of these enhancements depends on the customer goals . In a debottlenecking or retrofit case , there is the possibility to increase heat duty and throughput without having to build a new or larger shell , piping , and foundation . In a new equipment case , it can lead to a smaller heat exchanger , or the ability to use the available pressure drop more effectively . If it can be shown that the increased turbulation inside the tube also reduces the fouling rate , then this would be another long-term benefit . However , even more important is to make sure that there is not an increase in the cooling water fouling rate with the enhanced surface that offsets the performance gains over time .
Southern Company test results A set of Helix tubes was tested in a pilot-scale steam surface condenser at Southern Company ’ s Water Research and Conservation Center near Atlanta , GA to determine the heat transfer performance of the Helix tubes compared to the performance of a smooth condenser tube . A test program was conducted monitoring biological fouling development over time and its impact on heat transfer . Three titanium Helix tubes were installed alongside one titanium smooth condenser tube as a control in the pilot condenser . For the initial fouling test , standard operating conditions of the cooling water were set to a flow rate of 25gpm , a temperature rise of 15 ° F , and a conductivity of 400 µ S / cm . Table 1 shows a significant degradation in overall heat transfer for all four tubes over the duration of the testing with the formation of fouling . The Helix tubes maintained high performance over the control tube for the first half of the test program , with a 16-21 % higher average overall heat transfer coefficient . The test on July 10 showed a drop in heat transfer for all four tubes , indicating the onset of significant fouling . The results indicate that the Helix tubes can provide an improvement in overall heat transfer > 15 % when condenser cleanliness is maintained . In conditions where fouling is present on the tubes , both overall performance and performance relative to the control tube decrease due to the added heat transfer resistance of the fouling . However , even under fouled conditions , the performance of the Helix Tubes was higher than the control tube in all tests .
Taprogge balls were used to clean the tubes ( one-time cleaning , not continuously ) and proved effective in removing biofouling on all tubes to restore performance . These tests were conducted at a range of operating conditions to evaluate performance at different cooling water flowrates and temperature rise . The overall heat transfer coefficients for all four tubes were lower under fouled conditions , but the fouled Helix Tubes consistently maintained a higher average overall heat transfer coefficient than the fouled condenser tubes . The comparative performance of the tubes at a heat input and flow rate that most closely represent real power plant conditions at full load showed the average heat transfer coefficient of the Helix tubes was 28 % and 30 % higher than the control tube in the pre- and post-cleaning tests , respectively . The test results indicate that the Helix tubes did not foul at a higher rate than smooth tubes and that higher performance can be maintained even when fouling is present .
Potential impact to full-scale power plant The results of the tests conducted in the HTL can be used to estimate the potential impact of the NEOTISS™ Helix Tubes on overall power plant heat rate , fuel costs and CO2 emissions intensity . A curve fit equation was determined for the ratio of the helix tube heat transfer coefficient to the control tube heat transfer coefficient . The equation was applied to typical heat transfer rates Q . and heat transfer coefficients U . of a baseload 2-on-1
Condenser Performance Improvement
Heat Rate Change ( BTU / kWh )
Winter
Table 3 . Summary of seasonal heat rate impact .
Summer Full Pressure 2-on-1 Min Load Full Pressure 2-on-1 Min Load
15 % 12 % 16 % 13 %
-11.8 -5.6 -22.6 -11.9
Condenser Performance Improvement 14 % Annualized Average Heat Rate ( BTU / kWh ) 6,987 Heat Rate Improvement 0.19 % Annual Fuel Cost Savings * $ 233,960 Table 4 . Summary of annualized estimated heat rate improvement and fuel cost savings . www . heat-exchanger-world . com Heat Exchanger World September 2024
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