cooling towers
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Cooling towers
Operation and water management
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Forced Draft Cooling Towers
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Forced Draft Cooling Towers
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Forced Draft Cooling Towers
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Forced Draft Cooling Towers
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Natural Draft Cooling Towers
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Small cooling installations
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Water Distribution Details
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1. Fan 2. Drift eliminator 3. Warm water 4. Water distribution 5. Water sprinkling nozzle 6. Fill packing
7. Air inlet 8. Water pool 9. Cooled water
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Packing Materials
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Cooling Tower Mass Balances
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Water and Salt BalancesA water balance around the entire system is:
M = E + D + W
Since the evaporated water (E) has no salts, a chloride balance around the system is:
M (XM) = D (XC) + W (XC) = XC (D + W)
and, therefore:
XC/XM = Cycles of concentration
= M/(D + W)
= M/(M – E) = 1 + [E ÷ (D + W)]
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Windage Losses
Windage losses (W), in the absence of manufacturer's data, may be assumed to be:
W = 0.3 to 1.0 percent of C for a natural draft cooling tower without windage drift eliminators
W = 0.1 to 0.3 percent of C for an induced draft cooling tower without windage drift eliminators
W = about 0.01 percent of C (or less) if the cooling tower has windage drift eliminators
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Heat Balance
From a simplified heat balance around the cooling tower:
E HV = C · ΔT · cp
Hv = Latent heat of water evaporation = 2260 kJ/kg
Δ T = Temperature difference top to bottom
Cp = Specific heat of water = 4.184 kJkg-1C-1
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Biocides - The Ct Concept
In disinfection, the ability to inactivate microorganisms is a function of both disinfectant concentration and time.
Fractional removal = Cntm
This is generally simplified to Fractional removal = Ct
Ct values have been determined for99.99% virus and 99.9% Giardia removal
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http://www.pnl.gov/fta/6_ozone.htmhttp://www.cti.org/downloads/legion_2000.pdf
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Chlorine Dioxide ProductionClO2 made from Sodium Chlorite: Acidification of Chlorite5 ClO2- + 4 H+ --> 4 ClO2 + 2 H2O + Cl-Oxidation of Chlorite by Chlorine2 NaClO2 + Cl2 --> 2 NaCl + 2 ClO2Oxidation of Chlorite by Persulfate2 NaClO2 + Na2S2O8 --> 2 ClO2 + 2 Na2SO4From Sodium Hypochlorite and Sodium ChloriteNaOCl + 2 NaClO2 + 2 HCl --> 2 ClO2 + 3 NaCl + H2OElectrochemical oxidation of chloriteClO2- --> ClO2 + e-Dry chlorine/chlorite (laboratory method)NaClO2 + 1/2 Cl2 --> ClO2 + NaCl (solid)