Types of Water Loss in a Cooling Tower
- Evaporation Loss (E)
- The primary loss, caused by a small portion of circulating water evaporating to remove heat.
- Rule of thumb:
E≈0.001×C×ΔTE \approx 0.001 \times C \times \Delta TE≈0.001×C×ΔT
where:
- CCC = Circulating water flow rate (L/min)
- ΔT\Delta TΔT = Cooling range (°C)
- Typically ~1% of circulating water for every 10 °F (≈ 5.5 °C) drop in temperature.
- Drift Loss (D)
- Tiny water droplets carried away with exhaust air.
- Minimized using drift eliminators.
- Usually 0.1 – 0.2% of circulating water flow.
- Blow down (or Bleed-off) Loss (B)
- A portion of circulating water is discharged to control TDS (Total Dissolved Solids) and prevent scaling/fouling.
- Blow down depends on the cycles of concentration (CoC):
B=E(CoC−1)B = \frac{E}{(CoC – 1)}B=(CoC−1)E
- Miscellaneous Losses
- Leaks, overflows, windage (water carried away by wind).
- Normally very small compared to other losses.
Total Water Loss
Total Loss=E+D+B+(Misc. Losses)\text{Total Loss} = E + D + B + \text{(Misc. Losses)}Total Loss=E+D+B+(Misc. Losses)
Summary:
- Evaporation loss (major, ~70–80%)
- Drift loss (minor, reduced by eliminators)
- Blowdown loss (depends on water quality)
Other small leaks/overflows