Problem 10.5: A cooling tower has a system volume of 3000

From Chapter 10 Problem Set. Level 2: Applied Thinking.

Question

A cooling tower has a system volume of 3,000 gallons and a recirculation rate of 800 GPM. (a) What sidestream flow rate is needed to turn over the system volume every 4 hours? (b) What percentage of the recirculation rate is this? (c) If the tower is near an active construction site, would you recommend increasing this target?

Answer

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(a) Required throughput = 3,000 gal ÷ 4 hr = 750 gal/hr = 12.5 GPM. (b) 12.5 GPM ÷ 800 GPM = 1.56% of the recirculation rate. (c) Yes. Near an active construction site, solids loading will be significantly higher than normal. Increasing the sidestream flow rate to turn over the system volume every 2–3 hours (18.75–25 GPM, or roughly 2.3–3.1% of the recirc rate) would be prudent. Additionally, check the filter type - construction dust may include fine particles that require a sand or multimedia filter rather than a screen or disk filter.