The document summarizes the design of a heat rejection system for a power plant consisting of a shell-and-tube condenser and a natural draft cooling tower. Steam enters the condenser at 46°C and exits as saturated liquid at 10kPa. Cooled water from the tower at 31°C enters the condenser and exits at 41°C. The condenser is designed as two parallel counter-flow heat exchangers based on effectiveness calculations. The cooling tower design is based on energy and mass balances to reject heat from the condenser outlet water to the ambient air. The total cost of the heat rejection system is estimated to be 1.04 billion USD.

1. HEAT REJECTION
Thomas Assaid http://benkay.net/blog/wp-content/uploads/2008/08/nuclear-
power_5810.jpg
po er 5810 jpg
Grant Welch
Jean P. Cortes
David Sobhi

2. Heat Rejection - Design
Qout
Natural draft
cooling tower
Shell-and-
Qin
tube
condenser
Schematic representation of our heat rejection system.

3. Heat Rejection – Condenser Principles
1) Cooled water from the cooling tower at T1= 31oC.
2) Hot water to the cooling tower at T2= 41oC.
3) Steam in two-phase region (x = 0.88, P = 10kPa, 46oC) from
turbine.
turbine
4) Saturated liquid toward the nuclear reactor (x = 0, P = 10kPa)
∞ heat capacity due to phase change T and P do not change.
3)
2)
1)
4)
Condenser single-pass counter-flow shell-and-tube HX.
*higher effectiveness then the parallel-flow of similar type*
Note:
Shell-and-tube heat exchanger, Ref. [1]
HX = heat exchanger

4. Heat Rejection – Condenser Analysis
Calculate the h for the steam side and the water side.
Re, Pr,
Re Pr and Nu number of the two flows.
flows
internal flow.
Water side
external flow across tube bundles.
Steam side
These numbers change with respect to geometric variables of HX itself
• Diameter of the tubes
• Number of tubes
• Number of condensers
NTU method:
Note:
h = convective heat transfer coefficient
HX = heat exchanger

5. Condenser- MathCAD calculations
The final design for the condenser is two single-
single
pass counter-flow shell-and-tube HX in parallel.
The dimensions for each:
• 15,000 1.5” schedule 40 tubes.
• 24 7 meter long tubes with one diameter between tubes in the
24.7
staggered arrangement.
• 8.1 meter diameter shell.
• 48 000 k / of cooling water.
48,000 kg/s f li t
• Less than 10oC temperature rise.
Staggered alignment of the tube bundle, Ref. [4]

6. Heat Rejection - Cooling Tower (CT)
• Evaporative cooling tower Natural draft
draft.
• Direct counter-flow contact and mass transfer
between moist air and hot water
water.
Water will transfer heat/energy to the surrounding air
(evaporation of small portion of water due to latent heat )
then water will cool down.
Air will be heated and humidified by the sprayed-hot water
coming from the condenser.
g
• This cooled water will work as coolant for our
condenser.

7. Heat Rejection – CT Principles
Qrejected (heated air out)
Drift
eliminators
Splash-type
fill packing
Hot
Spray water
distribution
Air in
Air in
Film-type
fill packing
Cold
water
Schematic representation of a counter flow cooling
tower depicted from ASHRAE. Systems and
Equipment 1996, pp. 36.2,36.3

8. Heat Rejection – CT Analysis
Detailed Analysis iteration solution, trial and error
solution
procedure, or graphical solution.
Schematic diagram of
1) From the energy balance between air counterflow cooling tower
g
and water at dV element,
2) Water energy balance in terms of the
heat- and mass-transfer coefficients,
heat mass transfer
hc and hD; and substituting
Le = hc/hD*cpa
3) Air-side water-vapor mass balance
Note:
W = humidity ratio.
h = enthalpy
hs,w enthalpy of saturated moist air evaluated at tw
ma = mA= mass of the moist air.
AV= area of the splash-type packing

9. Heat Rejection – CT Analysis
W
Conclusion: the minimum Twater leaving the
cooling tower would be the Twet-bulb_air_in
t b lb i i
T
NTU method Graphical solution on the psychrometric chart.
CT effectiveness (ε) = ratio of actual energy transferred to the maximum possible
energy transfer units for the fluid with minimum capacity rate. Assuming minimum
t f it f th fl id ith i i it tA i ii
evaporation and Le = 1
The error can be reduced by using two or more increments rather than one. As
more increments are considered, the assumption of a linear relationship
between saturated moist air enthalpy and temperature becomes more exact.

10. Cooling Tower- Final Design
The final design for the cooling tower is the natural draft
type.
The dimensions are:
• 9971 m3 volume of splash type packing.
• 1.9 m of the packing height .
• 80 m diameter of packing fill.
• 18,750 kg/s of moist air.
• ΔT = 10oC of water
water.
• Approximately 120 m tall hyperbolic design.

11. Pumping and piping calculations
The final design for pumping system :
• 2 Pumps to the condenser,
Power: 18 MW
Head loss: 32 m
Mass flow rate: 48000 kg/s
• 2 Pumps to the makeup water:
Power: < 100 KW
Head loss:3 m
Mass flow rate: 2400 kg/s
g
The final design for piping network:
• Diameter: 2.5 m
• Transport pipe total length: 800 m
Total length from the pump to the condenser: 200 m
Total length from the condenser to the cooling tower: 200 m
Note:
Pumps are Vertical Wet Pit from Goulds Pumps
Pipes: mild steel.

12. Discussion of Results

13. Environmental Impact
Environmental Impact:
Environmental impact can be briefly described in two categories:
• Harmful usage effects on the environment such as natural resource p
g pollution.
• Performance efficiency reduction due to the surroundings such as fouling,
corrosion and drift.
Design and operating considerations related to the environmental impact:
g g
•In air conditioning installations with the experience of Legionella, it is now
mandatory to keep a working log as well as a record of hygiene testing to
determine non existence of bacteria.
•Cooling tower water treatment by chlorine dosing is recommended by certain
local authorities.
•Close checks should be kept on the overall system and extra cleaning of the
tower pack and distribution system should be taken under such circumstance
p y
where gusty conditions by windage or blow-out from the air inlets or by outside
influences

14. Economic and Budget
Cost Estimate:
•The estimated purchase cost value of the cooling tower
was determined to be 13.4 million USD using the volumetric
flow rate (GPM) of the cooled water, and assuming liner
interpolation of the cost estimate curve.
•The estimated purchase cost value of all the equipments in
p qp
the heat rejection system was determined to be 136 million
USD.
• The operational cost was determined to be 462.35 million
USD.
•Including direct costs, indirect costs, and 43% overhead
Including costs costs
costs, the total cost of the entire systems was determined
to be 1.04 billion USD

15. Heat Rejection - Conclusion and Recommendations
Component Strength Weakness
Condenser High effectiveness and NTU. Larger overall volume than a
cross flow fin and tube heat
Two condensers, so if needed
exchanger
the plant can still operate
while one is worked on.
Cooling tower Most reliable compared to To build it is expensive
other t
th types of cooling t
f li towers.
Low operating costs
Pumps Small amount of head loss due Large pump power due to the
to parallel system high mass flow rate of the
system
Condenser:
• Split it up for iterative solution solving for the h as the xsteam changes
• Parametric analysis should include:
• Type of material used for the tubes .
• Tube spacing and thickness.
Cooling tower:
• Develop a detailed analysis and compare the NTU method.
• Set up an iterative solution that will calculate for the variable
diameter.
• Develop a means of calculating the packing mass transfer coefficient
instead of assuming one.

16. THANK YOU FOR YOUR ATTENTION
QUESTIONS?