Wind Screen effect on performance, before and after, and comparison … · 2020-05-05 ·...

Cosimo BianchiniGary Mirsky Mitch Frumkin

Wind Screen effect on performance, 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

3


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

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Presenters

• CFD Analysis– Dr. Cosimo Bianchini

Ergon Research

• Structural Analysis– Mitch Frumkin

P.E./PresidentKipcon Engineering

• Photo of Cruciform Screens

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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%

Ò Reduced thermal recirculation (-4.71%)

– High wind scenario: overall gain 12.06%

Ò 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

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Analysis of PI Data• Power data:

– Hourly acquisition of plant gross power and fuel consumptionÒ 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

Ò More than 20% of events at 180°Ò 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

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

Analysis of PI Data

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E

S

W

N

Wind direction

E

SW

N

β

Geographical north

Plant north

α

Wind direction


Analysis of PI Data• Weather data:

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

– Far field boundary layer uses a power law profile

Ò V y = $%&'× )*+,-

./$%&'0%&'1

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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 ! = #$

%.'()*

– 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 lossÒ Lateral windÒ Neighbour fansÒ Recirculation losses


Wind screen position• Combined wind screen protection

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

– Simplified anchoring– Reduced wind load on structure

– Screens are made of 60% solid fabric with known aerodynamic resistanceÒ 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• ($̇%&&'())*+, -.+/ 01**/ − $̇%&&34_+67')**+)/$̇%&&34_+67')**+ : 100

• Relative Gain:• Percentage improvement of ACC air mass flow rate• ($̇%&&4.+/ 7')**+0 − $̇%&&+67')**+0)/$̇%&&+67')**+0 : 100


Results

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• Thermal performance parameters:• Recirculation:

• Percentage increase in temperature at the fan due to recirculation

• R= !"#$% &%'#( )$%*!$"+&#%(!+,%-'#*!$"+&#%(

. 100

• Combined performance parameters:• Bundle thermal power:

• Thermal power extracted at condenser• 3̇ = 5̇677 . 89,;<= . 1 − ? . @=AB − @CDEFGA

+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

Dmax = 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

Dmax = -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

Dmax = 12.06 %

S

EW

N


Results• Oscillating load on blade:

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

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

– Chosen as representative examplesÒ Fan 4_2: severe flow disuniformity Ò 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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DPmax = 104 Pa DPmax = 53 Pa


DPmax = 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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DPmax = 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 loadingÒ At low wind thermal recirculation effects are mitigatedÒ At high wind fan flow rate and recirculation are improvedÒ The oscillating fan blade load is largely reduced

– A significant interference with a neighbour heat exchanger is registered when wind is blowing from NorthÒ 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

Ò Overall improvement in plant production of nearly 10%

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Ergon ResearchVia Campani 50 Firenze

Air Cooled Condenser Users Group 2018Colorado Springs

Presenter:

Cosimo Bianchini

Questions?

Wind screen effects on performance

Wind Screen effect on performance, before and after, and comparison … · 2020-05-05 ·...

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