Problem 11.5: A condenser tube receives tower water at 4
From Chapter 11 Problem Set. Level 2: Applied Thinking.
Question
A condenser tube receives tower water at 4 cycles, pH 8.3, calcium hardness 220 mg/L as CaCO₃ in the makeup, visible suspended solids, and intermittent oxidant feed. Write a free body diagram that includes the following, along with which pillar you would address first.
- System boundary
- Inputs
- Outputs
- Accumulations
- Transformations
- Likely surface conditions not captured by the bulk water tests
Answer
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A strong answer includes:
- System boundary: condenser tube or condenser tube bundle
- Inputs: warm recirculating water, dissolved calcium and alkalinity, suspended solids, intermittent oxidant, heat-transfer load
- Outputs: water leaving at changed temperature, consumed chemistry, any released corrosion products or biological fragments
- Accumulations: scale, solids, biofilm, corrosion products
- Transformations: precipitation, oxidant consumption, biological attachment and growth, corrosion reactions
- Surface conditions not captured by bulk tests: elevated skin temperature, sheltered deposits, localized concentration effects, reduced chemistry penetration beneath deposits
The most defensible first priority is often solids control if visible suspended matter is high, because solids amplify deposition, shelter biology, and promote under-deposit corrosion. A stronger oxidant strategy may also be necessary, but cleaning and solids control often come first.