Presentation on theme: "Technical Topics: Steam Condenser. Technical Topics Steam Condenser Facts: The collapsing of the steam forms the vacuum not the ejectors or the vacuum."— Presentation transcript:
Technical Topics Steam Condenser Facts: The collapsing of the steam forms the vacuum not the ejectors or the vacuum pumps The ejectors or vacuum pumps are only required to remove the accumulation of trace non-condensable gases dissolved in the steam and make-up water. Condensate depression is the sub-cooling of the condensed steam below the saturation temperature.
Technical Topics Condensate depression occurs as the condensed steam cascades across the tube bundle and becomes sub-cooled. The sub-cooled condensate will re-absorb the non- condensable gases, primary concern being O 2, at the lower temperature. The steam that bypasses the tube bundle deareates the condensate that is dripping off the bundle. Deareation is: 1. The heating of the dripping condensate and, 2. The heating liberates the reabsorbed dissolved gases due to the solubility of the gases at different temperatures.
Technical Topics Hotwell level is very important: Too high and condensate depression occurs due to the restriction of steam flow for deareation between the hotwell level and the tube bundle. Too low a hotwell level and the hotwell/ condensate pumps do not have sufficient NPSH to pump at the rated conditions. It is not unusual for cavitation in the pump.
Technical Topics The cause for changing vacuum is based upon thermodynamics: Q = ṁ steam x h fg = ṁ cw h c (t out -t in ) Q decreases due to elevated circulating water temperature, therefore, with: Vacuum = 28.5” Hg: h fg =1041.7 Btu/lb Vacuum = 28.0” Hg: h fg =1036.7 Btu/lb The difference in h fg being 0.47%!!