5.3.2 Computer assisted design evaluation
The second and more recent design evaluation method uses computer techniques to assess the performance of steam condensers. The computer program simulates the fluid flow, heat transfer and air concentration processes locally through the condenser.
Since the interaction of these processes is very complex, the program begins by representing the condenser as a series of parallel slices perpendicular to the CW flow. Each slice is divided into a number of control volumes so as to represent both the tubenest and the steam access lanes. The program first finds the steam flow pattern, and calculates the local condensation rates starting at the CW inlet. The laws of conservation of mass, momentum and energy are applied to each control volume to produce a large number of simultaneous equations for each slice. The program also calculates whether air pockets exist in the tubenest, and identifies where they will form. The sizes of the air pockets are determined by the pressure at the air vent points — the higher the vent pressure, the larger the air pockets. From the solution the condenser vacuum can be predicted for given rates of steam flow, air leakage, condenser surface configuration, and cooling water flow, together with the CW inlet temperature.
For a more detailed understanding of the computer techniques currently being researched, the reader should refer to a paper presented at the International Symposium on Condensers: Theory and Practice .