TABLE OF CONTENTS To determine cooling water system flows, use a heat and material balance and a chloride balance (concentration ratio is usually calculated from chloride concentrations).
| (1) |  |
| (2) |  |
| (3) |  |
so
| (4) |  |
| (5) |  |
| (6) |  |
so
| (7) |  |
| (8) |  |
Use Equation 2 to get E, then Equation 7 to get B, and finally Equation 5 or 8 to get M. where
| D = | Cooling system duty, Btu/hr |
| C = | System circulation rate, GPM |
| ?T = | Cooling system temperature difference (hot return water minus cold supply water), F |
| E = | Cooling system evaporation rate, GPM |
| CR = | Cooling system concentration ratio |
| Cl - = | Chloride concentration in the makeup or blowdown |
| M = | Cooling system makeup rate, GPM |
| B = | Cooling system total blowdown, GPM. This includes both planned blowdown plus cooling system windage (or drift) losses (of course any system leakage counts as part of "planned" blowdown) |
To determine the required amount of planned blow-down, subtract windage losses from B. Use Table 1 for windage losses in liew of manufacturer's or other test data.
| Type of Cooling Device | Windage Loss as Percentage of System Circulating Rate |
|---|---|
| Spray pond | 3 |
| Atmospheric cooling tower | 0.7 |
| Mechanical draft cooling tower (Drift eliminators may do better than 0.2) | 0.2 |
When cooling systems are treated, chemicals are sometimes added in shots rather than continuously. Equation 9 gives a chemical's half life in a cooling system:
| (9) |  |
where
| T | = Half life, min. |
| S | = System capacity, gal |
Branan, C. R.,
