windscreen effect on performance and structure, before and...

Cosimo BianchiniGary Mirsky Mitch Frumkin

Windscreen effect on performance and structure, before and after,

and comparison with CFD

- ACC UG 2018 - Colorado Springs, Gary Mirsky -

Objectives

• Find A Recent Installation

• Verify Reduction in Thermal Deficiency Predicted by CFD Analysis After Wind Screen Installation

• Detail Causes of Deficiency

• Present the Steps of the Structural Analysis

• Changes Required Due to Structural Analysis

• Aerial Photo of APEX 6 x 5

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Our candidate for case study

• APEX Power Plant Owned by SCPPA

• LADWP is 100% Participant

• 2 GAS Turbines – Rated at 172 MW Each Gross

• 1 Steam Turbine – Rated at 230 MW Gross

• 531 Net MW

• In Service 2003• Photo Shows Obstructions Caused

by Cable Trays

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ACC data• Forced draft A-frame type

– 6 streets per 5 rows

• Design point– Turbine exhaust steam flow 1450∙103 lbm/h– Turbine exhaust steam pressure 10 inHgA– Condensing heat load 1426 Mbtu/h

• 30 Howden fans– 34’ diameter– 5 fiberglass reinforced epoxy blades– 200 ft/s tip speed – 162 BHP power

• Balcke-Durr finned tube bundles– 10 bundles per module– 140 single pass oval finned tubes per bundle

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Why were screens installed?

• Best ROI option• Photo Shows

Completed Windscreen Installation. Perimeter Screens Behind Cable Trays

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Timeline

• Structural Analysis – Fall 2017

• ACC Cleaned – December 2017

• Screen Installation – Completed Feb. 22, 2018

• Rotor Upgrade – April 19 to June 10, 2018

• Very Narrow Window for Data Comparison

• Perimeter and Cruciform Screens

6


Presenters

• CFD Analysis– Dr. Cosimo Bianchini

Ergon Research

• Structural Analysis– Mitch Frumkin

P.E./PresidentKipcon Engineering

• Photo of Cruciform Screens

7

Ergon ResearchVia Campani 50 Firenze

Air Cooled Condenser Users Group 2018Colorado Springs

Presenter:

Cosimo Bianchini

Wind screen effects on performance

- ACC UG 2018 - Colorado Springs, Cosimo Bianchini -

Highlights• Analysis of PI Data: overall improvement in plant production of nearly 10%

– Difficult to discern single contributions

• The aerothermal field around the ACC was computed by means of CFD with and without the windscreens– Numerical analysis confirms that windscreens are beneficial

• Thermodynamic benefits– Low wind scenario: overall gain 5.45%

Reduced thermal recirculation (-4.71%)– High wind scenario: overall gain 12.06%

Fan flow rate and recirculation significantly improved• Mechanical benefits

– Computed pressure field permitted to estimate the fluctuating load on the fan blades– The oscillating mechanical load can be reduced up to 75% of its initial value

9


Analysis of PI Data• Power data:

– Hourly acquisition of plant gross power and fuel consumption Estimate of plant heat rate

– Data made dimensionless respect to a reference average value after plant revamping

• Comparison of homogeneous time serie before and after revamping– Early summer 2017 and 2018

• Time serie analysis and average daily peak show– Improvement of nearly 10% gross

power– Reduction in the heat rate of 7%

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Average daily peak


Analysis of PI Data• Weather data:

– Hourly registrations for more than 2 years– Wind direction is mainly aligned with S direction

More than 20% of events at 180° Including neighbor directions nearly 40% of events fall within 45 deg from principal wind

direction– Secondary main direction is ENE with 13% of events

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Wind speeds in mph


• Wind: – Principal wind direction S 180° from geographical N

Angle between geographical north and plant north is β=-10.84° Actual wind direction respect to ACC is α=169.16°

Analysis of PI Data

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E

S

W

N

Wind direction

β

Geographical north

Plant north

α

Wind direction


Analysis of PI Data• Weather data:

– Principal wind direction (S) data Discrete contributions of wind speed ranges shows negligible events (< 1%) above 15 mph Typical high wind speed condition: 12 mph (5% of events – 90th percentile) Typical low wind speed condition: 3 mph (6% of events – 10th percentile)

– Far field boundary layer uses a power law profile

V y = 𝑉𝑉𝑟𝑟𝑟𝑟𝑟𝑟 × 𝑦𝑦𝐻𝐻𝑟𝑟𝑟𝑟𝑟𝑟

𝑎𝑎

�𝑉𝑉𝑟𝑟𝑟𝑟𝑟𝑟𝐻𝐻𝑟𝑟𝑟𝑟𝑟𝑟𝑎𝑎

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High wind dayLow wind day


Modelling details• Fan model

– Digitized from manufacturer data– Pressure rise is a quadratic function of fan velocity

• Bundle model– Pressure drop modelled by means of a pressure drop coefficient 𝐾𝐾 = 𝑑𝑑𝑑𝑑

0.5𝜌𝜌𝑈𝑈2

– Actual value calculated to respect provided resistance curve– Temperature rise across the bundle is assumed at 8K

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• Duty point– Set at 758.434 m3/s and 101.5 Pa– It does not consider any

additional type of loss Lateral wind Neighbour fans Recirculation losses


Wind screen position• Combined wind screen protection

– Suspended perimeter plus ground installed cruciform Cruciform is split on two consecutive axis

– Simplified anchoring– Reduced wind load on structure

– Screens are made of 60% solid fabric with known aerodynamic resistance Recent experiments conducted at Stellenbosch University

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Perimeter

Lower cruciform

Upper cruciform

Principal wind direction


Results

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• Aerodynamic performance parameters:• Actual mass flow wind loss:

• Change in ACC air mass flow rate respect to low wind speed LW without screens• (�̇�𝑚𝐴𝐴𝐴𝐴𝐴𝐴𝑐𝑐𝑐𝑐𝑟𝑟𝑟𝑟𝑟𝑟𝑐𝑐𝑐𝑐𝑤𝑤𝑤𝑤𝑐𝑐𝑤𝑤 𝑠𝑠𝑠𝑠𝑟𝑟𝑟𝑟𝑤𝑤 − �̇�𝑚𝐴𝐴𝐴𝐴𝐴𝐴𝐿𝐿𝐿𝐿_𝑐𝑐𝑛𝑛𝑛𝑛𝑐𝑐𝑟𝑟𝑟𝑟𝑟𝑟𝑐𝑐)/�̇�𝑚𝐴𝐴𝐴𝐴𝐴𝐴𝐿𝐿𝐿𝐿_𝑐𝑐𝑛𝑛𝑛𝑛𝑐𝑐𝑟𝑟𝑟𝑟𝑟𝑟𝑐𝑐 � 100

• Relative Gain:• Percentage improvement of ACC air mass flow rate• (�̇�𝑚𝐴𝐴𝐴𝐴𝐴𝐴𝐿𝐿𝑤𝑤𝑐𝑐𝑤𝑤 𝑛𝑛𝑐𝑐𝑟𝑟𝑟𝑟𝑟𝑟𝑐𝑐𝑠𝑠 − �̇�𝑚𝐴𝐴𝐴𝐴𝐴𝐴𝑐𝑐𝑛𝑛𝑛𝑛𝑐𝑐𝑟𝑟𝑟𝑟𝑟𝑟𝑐𝑐𝑠𝑠)/�̇�𝑚𝐴𝐴𝐴𝐴𝐴𝐴𝑐𝑐𝑛𝑛𝑛𝑛𝑐𝑐𝑟𝑟𝑟𝑟𝑟𝑟𝑐𝑐𝑠𝑠 � 100


Results

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• Thermal performance parameters:• Recirculation:

• Percentage increase in temperature at the fan due to recirculation

• R= 𝑇𝑇𝑚𝑚𝑟𝑟𝑚𝑚𝑐𝑐 𝑤𝑤𝑐𝑐𝑖𝑖𝑟𝑟𝑐𝑐 𝑟𝑟𝑚𝑚𝑐𝑐−𝑇𝑇𝑚𝑚𝑚𝑚𝑎𝑎𝑤𝑤𝑟𝑟𝑐𝑐𝑐𝑐

𝑇𝑇𝑎𝑎𝑐𝑐𝑐𝑐𝑤𝑤𝑖𝑖𝑟𝑟−𝑇𝑇𝑚𝑚𝑚𝑚𝑎𝑎𝑤𝑤𝑟𝑟𝑐𝑐𝑐𝑐� 100

• Combined performance parameters:• Bundle thermal power:

• Thermal power extracted at condenser• �̇�𝑄 = �̇�𝑚𝐴𝐴𝐴𝐴𝐴𝐴 � 𝐶𝐶𝑑𝑑,𝑎𝑎𝑎𝑎𝑟𝑟 � 1 − 𝑅𝑅 � 𝑇𝑇𝑟𝑟𝑟𝑟𝑟𝑟 − 𝑇𝑇𝑏𝑏𝑏𝑏𝑏𝑏𝑑𝑑𝑏𝑏𝑟𝑟

+5.45%

+12.1%


Results• WS 3 mph:

– Temperature

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No wind screens

Wind direction

E

W

S N

With wind screens

E

W

S N



– Temperature

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Wind direction

E

W

S N

E

W

S N

No wind screens With wind screens



– Vertical velocity w

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No wind screens

Wind direction

E

W

S N

With wind screens

E

W

S N




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Wind direction

E

W

S N

E

W

S N




– Temperature with velocity vectors on plane parallel to wind

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Wind direction

S N S N



– Temperature with velocity vectors on plane parallel to wind

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Wind direction

S N S N



– Velocity vectors on plane parallel to wind

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Wind direction

S N S N



– Velocity vectors on plane parallel to wind

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Wind direction

S N S N



– Backward streamlines with temperature

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Wind directionS

N

S

N



– Backward streamlines with temperature

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S

N

S

N

Wind direction


Results @12 mph

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• Wind direction effects:

WORST BEST

∆max = 6.79 %

S

EW

N


Results @12 mph• Wind direction = North-East:


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Wind direction

E

W

S N

E

W

S N



Results @12 mph

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WORST BEST

∆max = -5.23 %

S

EW

N


Results @12 mph• Wind direction = North:

– Forward streamlines with temperature from fin fan outlet

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S

N

Wind direction

S

N


Results @12 mph

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WORST BEST

∆max = 12.06 %

S

EW

N


Results• Oscillating load on blade:

– The blade load was computed examining the pressure values on the fan surface Gauge pressure is plotted

– The high wind condition was studied since it is the most critical Wind blows from S at 12 mph

– Chosen as representative examples Fan 4_2: severe flow disuniformity Fan 4_5: mild flow disuniformity

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4_5

4_2Wind direction


Effect of fan positioning• Fan 4_2: severe flow disuniformity

– Windscreens are able to avoid backflow on the upstream fans

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∆Pmax = 104 Pa ∆Pmax = 53 Pa


∆Pmax = 132 Pa

Effect of fan positioning• Fan 4_2: mild flow disuniformity

– Windscreens are able to further promote flow uniformity on the downstream fans

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∆Pmax = 27 Pa


Highlights• A CFD campaign was completed to compute the aerothermal field around the ACC

with and without the windscreens– The numerical analysis predicts that windscreens are beneficial both for thermodynamic

and fan blade loading At low wind thermal recirculation effects are mitigated At high wind fan flow rate and recirculation are improved The oscillating fan blade load is largely reduced

– A significant interference with a neighbour heat exchanger is registered when wind is blowing from North Worst scenario considered

– Wind screens are optimized for the prevailing wind direction obtaining a 12.06% overall gain

• Analysis of PI Data confirms these benefits– Quantitative improvements due to wind screens only could not be computed

Overall improvement in plant production of nearly 10%

36

Ergon ResearchVia Campani 50 Firenze

Air Cooled Condenser Users Group 2018Colorado Springs

Presenter:

Cosimo Bianchini

Questions?

Wind screen effects on performance

windscreen effect on performance and structure, before and...

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