How to design Air Cooled Condenser and specification guideline:

 How to design ACC and specification guideline:

1.    Fundamental design consideration:

·       Heat Load and Performance: Size the ACC at maximum steam flow and heat rejection duty at peak ambient temperature ( often summer ambient dry bulb temperature consider). The process margin and extreme conditions are also considered.

·       Low IDT means larger size ( size of the ACC inversely proportional to ITD), ITD is maintained 15-16deg.C

·       ITD = TCond – Tamb, ITD= Initial temperature difference

·       Heat Load/ ITD = Constant

·       Q rejected = U.A. LMTD where U is heat transfer coefficient, A is surface area of the      condenser

·       Thermal duty= Q(required)= Ms x(h steam at turbine exhaust – h condensate), Ms is steam flow at turbine exhaust.

·       It is important to verify the heat to be rejected is matched or exceeded to the supplier’s offer.

2.    Heat surface area:

·       For SRC the ratio of the air side surface area and the total “face” area is approximately 120.

·       Large ACC is maintained modular, direct forced air cooling system ( A- frame, SRC- single row flat tube having 209mmwidth x 19mm th made of CS with aluminum brazed fins,

·       No. of modules consist of condensing and dephlegmator bundles.

3.    Out air temperature:

·       Outlet air temperature is less than the steam temperature can be calculated in the following equation:   

·       Q required = Ms x Cp air x ( Tair out – T air,in )

4.    Face velocity of the Air:

                 The face velocity of the air, while not typically provided by the supplier, can be calculated from the mass of airflow rate, the air density, and the total face area of the ACC. Typical values will run from about 3 ft/sec (~1 m/s) to as much as 8–10 ft/sec (~3 m/s), with the average being about midway between those limits. Engineers who have performed velocity measurements at the ACC exit plane know that, while the average velocity may be in those limits, variations of a factor of five can occur at the outlet.

5.    Fan static pressure:

               Fan static pressures will vary depending on whether the fan is a low noise or more standard design. Fan static pressure, which in essence is the force required to overcome the system resistance (with the required design airflow rate), will typically run from 0.3–0.5 inches of water (~100 Pa +/- 20%) for a standard fan and system design.

6.    Fan Power :

              Total fan power can be calculated using the aforementioned information and assuming nominal gearbox efficiencies of approximately 97% and motor efficiencies of approximately 92–94%.

7.    Pricing:

Typical ACC Component Cost Breakdown Component % Cost Est. $

 Heat Exchanger Bundles 32.0% $ 192,000

Structural Steel 16.0% $ 96,000

Casing 0.5% $ 3,000

Fan Inlet Bell 0.9% $ 5,400

 Ducting 6.0% $ 36,000

Expansion Joints/Bellows 1.3% $ 7,800

 Piping 1.5% $ 9,000

Mechanical Equipment 5.4% $ 32,400

 Air Removal Pumps 1.4% $ 8,400

Valves and Instrumentation 0.5% $ 3,000

Drain Pumps & Rupture Disc 0.1% $ 600

 Condensate Tank / “Decorator Dome” 0.2% $ 1,440

Shipping (U.S. Destination) 11.0% $ 66,000

Engineering/Project Mgmt. 5.0% $ 30,000

Subtotal 81.8% $ 491,040

 Overhead, Contingency, Profit 18.2% $ 108,960 Total 100.0% $ 600,000