Cooling tower make-up water – sources of loss to be replaced In industrial cooling towers, make-up water must be added to compensate for which combined losses from the circulating water system?

Introduction / Context:
Cooling towers reject heat by evaporating a small portion of circulating water into the atmosphere. Water balance and chemistry control require adding make-up water to offset specific losses and maintain cycles of concentration within limits that prevent scaling, corrosion, and biofouling.

Given Data / Assumptions:

• Open recirculating cooling system with tower.
• Water quality management via blowdown is practiced.
• Minor leaks and drift are present within typical design allowances.

Concept / Approach:
Three principal loss mechanisms exist: (1) evaporation (latent heat removal), (2) drift (entrained droplets carried out with exhaust air), and (3) blowdown (intentional purge to control dissolved solids), plus incidental leakage. Make-up water must replace the sum of these to sustain circulation rate and chemistry. Evaporation is the largest component; drift is minimized by eliminators; blowdown is set by cycles of concentration.

Step-by-Step Solution:

Verification / Alternative check:
Cooling tower manuals and CTI guidelines present the same mass balance and define drift and blowdown targets to size make-up supply lines.

Why Other Options Are Wrong:
Choosing only one or two loss types understates true make-up requirements and leads to rising TDS, scaling, or pump cavitation due to low basin levels.

Common Pitfalls:
Ignoring blowdown in calculations; although smaller than evaporation, it is vital for controlling concentration and preventing operational problems.

Final Answer:
all (a), (b) and (c)