Numerical Analysis of a Natural Convection Air Cooled Condenser

Air cooled condensers (ACC's) are finned tube arrays that use air to condense steam in power plants, when large amounts of water are not available. ACC's are environmentally more sustainable and therefore require fewer permits for installation, however, they are expensive to install and operate, needing large structures to be effective and require significant power to run cooling fans. This study investigates the feasibility of a natural convection induced ACC which would reduce the requirement of external fans.;The proposed design places the entrance to the condenser tube assembly at 12.5 m along a vertical steam supply pipe. The minimum boundary layer thickness at the entrance of the condenser assembly is approximately 1 m perpendicularly from the vertical supply pipe. The condenser tube assembly consists of 212 condenser tubes evenly spaced radially around the vertical supply pipe. Spanning the tubes are thin fins that create small ducts through which air flows. The tubes are patterned in a conical helical spiral that decreases in height with circumferential progression. The air currents produced by the horizontal and vertical supply pipe pass through these ducts and cools the working fluid. The new design also significantly reduces construction and operating costs associated with current ACC designs.;The proposed design involves shifting the horizontal orientation of the steam supply line to a vertical one while having the main steam supply line feeding it from beneath. It was found that the air currents produced by the horizontal and vertical supply pipes, due to natural convection, create a maximum velocity of 1.35 m/s. The amount of heat transfer per unit length of condenser tube is 1.29 kW/m which is less than the required value of 2.5 kW/m.;In order to reach the required heat transfer per unit length of 2.5 kW/m, a fan must be used to induce a velocity. However, the current spiral pattern of the condenser tube assembly would allow for a higher structure density leading to smaller total footprint. The additional benefit would be the use of smaller fan blades with the spiraled condenser assembly; 4.5 m fan blades could be used rather than the current 6 m fan blades. Less power would be required for operation and higher cooling flow velocities could be obtained by the smaller fans. A dual level condenser assembly was investigated for a forced convection condition to determine if the assembly could be a viable alternative. The stacked condenser assembly would decrease the total area by 45%, provide a heat transfer per unit length of 2.85 kW/m, and a total heat transfer of approximately 12 MW. These findings show a spiraled condenser could be viable alternative and is worth investigating further in the future.