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Dry Cooling Business Unit CD
Comparison of Dry Cooling Systems 1.
Air-Cooled Condenser - ACC 2. HELLER Type
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General System Layout
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General Design Features of HELLER System

• Natural Draft Cooling Tower
• vertical fin tube bundles at tower circumference
• air pre-heaters ("peak" coolers)
• louvers to control air flow (cooling capacity)
• considerable distance to turbine house required
  for better air flow
• no concrete tower shell for earthquake
  conditions steel structure more expensive
• Cooling Water Cycle
• jet condenser with recovery turbine (note water
  jet pump for boiling condensate requires extra
  NPSH)
• mixing of boiler feed water with cooling water
  (mass ratio 1 50)
• chemical treatment for appropriate pH value in
  boiler feed water and cooling water cycle
• Jet Condenser
• "Zero" terminal temperature difference cannot be
  reached - practical gt 1 K
• evacuation system

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General Design Features of ACC

• ACC Platform
• bundles arranged in "A" frames and several
  "streets" on rectangular platform
• identical modules with one steam side flow path
• condenser modules (co-current steam condensate
  flow)
• dephlegmator modules (counter-current steam
  condensate flow)
• forced fan arrangement
• wind wall at circumference
• near distance to turbine house
• low height of overall structure
• steel support structure suitable for earthquake
  conditions
• Steam Duct
• large diameter to reduce steam velocity
  pressure drop
• steam bypass line (to control condensate
  sub-cooling)
• evacuation system
• full dephlegmator operation may be provided

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General Design Features of Heller Type Fin Tubes

• Core Tube
• circular shape manufacturing tube length 5 m
• material pure aluminium pH-value of 7 required
  in cooling water cycle
• Finning
• pure aluminium fins with turbulators
• protective coating to prevent atmospheric
  corrosion (must be 100 failure free)
• low structural stiffness
• Fin Tube
• fin tube connected by mechanical expansion
• tube to tube sheet connection by O-Rings
• 15 - 20 m tube bundle assembled from 5 m fin tube
  pieces

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General Design Features of ACC Fin Tubes

• Core Tube
• elliptical shape
• steel (same material as in power
• station steam cycle)
• Fin Tube
• wound-on fins (without turbulators or spacers)
• steel fin, hot-dip galvanized
• high structural stiffness
• Multi-Row System with Fin Pitch Adjustment
• suppression of steam side maldistribution
• flexibility to operation requirements (flow area
  pressure drop)
• Proven Technology

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Comparison Thermohydraulics
Air-Cooled Condenser
Heller Type

• Indirect system
• reduced MTD
• enlargement of surface
• Aluminium fin tube material
• heat conductivity high
• Circular core tubes
• large wake region
• poor fin (surface) efficiency
• high air side pressure drop
• erosion corrosion at water inlet into tube
• Fin extremely distant corners
• reduced fin (surface) efficiency
• heat transfer (contact) resistance at fin foot

Direct system optimum MTD reduced
surface Hot dip galvanization Zinc layer
contributing to fin tube efficiency no contact
resistance at fin foot due to metallic
bond Elliptical core tubes small wake
region ideal fin (surface) efficiency low air
side pressure drop Fin low height i.e. high
fin efficiency high proportion of core tube
surface
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Thermohydraulics Heller Type Fin Tube System

• High finning with extreme corners
• - reduced fin efficiency
• - enlarged air side pressure drop

• Large wake region
• - reduced active fin surface

• Strong variation of stream wise flow
  direction
• - enlarged pressure drop

Circular Core Tube

• Contact gap between core tube and fin
• - additional heat transfer resistance
• - reduction of overall heat transfer

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Thermohydraulics Optimised ACC Fin Tube

• Fully active fin surface
• - even fin height around core tube
• - no distant fin area no turbulators

• No close packing
• - superior cleanability

• Elliptical shape of core tube
• - enhancement of heat transfer
• - reduction of air side pressure drop

Elliptical Core Tube

• Open spaces in adjacent tube rows
• - turbulent mixing of cooling air
• - heat transfer enhancement
• - reduction of pressure drop

Elliptical Fin

• Small wake region
• - enlarged active fin surface

• Wide fin pitch in leading tube row
• - reduced air side pressure drop
• - enhanced heat transfer (bare tube)

Cooling Air
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Rated Lifetime Cost Comparison
Standard 350 MW CCPP
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Comparison Stability - Cleaning
Heller Type
Air-Cooled Condenser
Material Aluminium (99,7) poor stability fins
do not withstand external loads protective
coating must remain failure free may be damaged
by fin side fouling or cleaning jet Cleaning by
water-air mixture (10 bar) not suitable for
regions with high cleaning requirement (dust,
dirt, biological fouling, etc.) Connection tube
to tube sheet O-Rings susceptible to thermal
stress and embrittlement leaks cause freezing
problems in winter
Material Steel high structural stability long
service lifetime Cleaning possible with high
pressurized water (up to 250 bar) effective
cleaning in all tube rows due to elliptical core
tube shape Connection tube to tube sheet weld
connection permanent leak proof connection no
deterioration of condensate quality
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Comparison Water Chemistry
Heller Type
Air-Cooled Condenser

• pH Value
• pH7 in cooling water cycle
• pHgt9 in steam cycle
• pH Value control
• permanent pH control required because of mixing
  of boiler-feed water cycle and cooling water
  cycle
• chemical treatment to maintain
• pH gt9 (boiler-feed water cycle)
• 7 (cooling water cycle)
• Filter
• cooling water flow rate 30-50 times higher than
  boiler-feed water flow rate
• mixed-bed-filter required for full water flow
  rate

pH Value same as boiler-feed water cycle gt
9 Filter not required for ACC operation
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Comparison Operation
Heller Type
Air-Cooled Condenser
Louvers required to control air flow rate louvers
enlarge air side pressure drop and reduce cooling
capacity Winter conditions air pre-heaters
required isolated tanks fast draining of bundles
required to prevent freezing Wind vertical
cooling bundles at cooling tower circumference
extremely susceptible to wind reduced cooling
capacity
Louvers no louvers required air flow rate
controlled by fan speed Winter conditions full
dephlegmator operation prevents freezing process
flow steam must be turned into condensate before
possible freezing Wind tube bundles protected by
wind wall at circumference negative effect of
wind is reduced
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Comparison Maintenance
Heller Type
Air-Cooled Condenser
Condensate pump Cooling water pump Recovery
turbine Jet condenser Water polishing Tube to
tube sheet connections regular maintenance
because of extreme number of seals freezing if
leaks occur in winter Cleaning of tube
bundles depending on site conditions performance
drop Louvers
Condensate pump Fan motors maintenance low
(proven equipment) Gearboxes / V belt
drives regular change of lubrication oil V belts
proven equipment Tube to tube sheet
connections failure free (welded) Cleaning of
tube bundles depending on site conditions full
performance recovered
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Comparison Availability
Heller Type
Air-Cooled Condenser
Availability high - because of high stability and
corrosion resistance of hot-dip galvanized fin
tubes, welded tube to tube sheet
connections Freezing no freezing Fouling effective
cleaning by high pressure water jet keeping full
performance Service lifetime 30 - 40
years long-term proven equipment
O-Ring seals susceptible to thermal
stress embrittlement approx. 250 000 O-Ring
seals required for 200 MW Freezing regular
replacement of damaged tube bundles required
(e.g. 5 annual replacement in China) Control
valves big number of control valves in water
cycle are susceptible to failure Fouling tubes
extremely susceptible to fouling degradation of
tube performance Service lifetime 10 - 15
years
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Conclusion

• SPX Cooling Technologies ( former Balcke-Dürr)
• elliptical multi-row systems comprise all
  features required for up-to-date power station
  technology
• Flexibility to operation needs
• Low power consumption
• High stability of fin tube system
• High corrosion protection
• Long service lifetime
• Proven technology at competitive cost