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- 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?

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