Closed-Loop Wet Cooling Towers

Closed-loop wet cooling recirculates water through a tower, cutting withdrawal versus once-through but raising consumption because cooling is by evaporation.

Recirculating design

In a closed-loop (recirculating) system the same water cycles between the condenser and a cooling tower. Only makeup water enters, replacing what evaporates and what is discharged as blowdown. This became the standard as once-through cooling fell out of regulatory favor.

The withdrawal-consumption swap

Closed-loop cooling withdraws far less water than once-through, because it reuses its inventory, but it consumes more, because the cooling itself is evaporation. For a data center concerned with net water consumed in a stressed basin, the closed-loop tower is often the larger footprint.

Operating burdens

• Continuous makeup water supply must be secured and permitted
• Water chemistry must be managed to limit scale, corrosion, and biofouling
• Blowdown must be treated or discharged under permit
• Plume and drift must be controlled

Why the burner is different

The burner's closed coolant loops carry only residual heat, and they can reject it to air rather than to an evaporative tower. There is no large evaporative inventory to make up, no blowdown stream from evaporative concentration, and no plume. The closed-loop tower's central trade, less withdrawal for more consumption, does not arise.