Problem 3.9: Two cooling towers both read 2000 Scm
From Chapter 3 Problem Set. Level 3: System Integration.
Question
Two cooling towers both read 2,000 µS/cm conductivity. Tower A’s makeup is high in sodium chloride. Tower B’s makeup is high in calcium bicarbonate. Which tower faces a greater scaling risk, and why does identical conductivity not mean identical behavior?
Answer
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Tower B faces far greater scaling risk. Sodium chloride is highly soluble across all normal conditions (manageable lattice cost, sufficient hydration, and favorable dispersion). Calcium bicarbonate, when concentrated and heated, shifts toward calcium carbonate precipitation - a salt with high lattice energy and inverse solubility. Identical conductivity means identical total ionic load, but the identity of the ions determines whether the water scales, corrodes, or behaves benignly.