Problem 12.5: Using the evaporation rate from Problem 4

From Chapter 12 Problem Set. Level 2: Applied Thinking.

Question

Using the evaporation rate from Problem 4, calculate the total annual makeup water (in gallons) at 3 cycles and at 6 cycles, assuming 4,380 hours of operation per year. What is the annual water savings from increasing cycles?

Answer

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At 3 cycles: B = 19.1 ÷ (3 − 1) = 9.55 GPM. M = 19.1 + 9.55 = 28.65 GPM. Annual = 28.65 × 60 × 4,380 = 7,529,220 gal/yr ≈ 7.53 Mgal. At 6 cycles: B = 19.1 ÷ (6 − 1) = 3.82 GPM. M = 19.1 + 3.82 = 22.92 GPM. Annual = 22.92 × 60 × 4,380 = 6,023,376 gal/yr ≈ 6.02 Mgal. Savings = 7.53 − 6.02 = 1.51 Mgal/yr. Over 1.5 million gallons saved on a single tower by increasing from 3 to 6 cycles.