HPAC 2023: Our August Quiz

This scorching summer, as so many seek relief from record heat, let’s escape into the subject of cooling and refrigeration. With the assistance of Honolulu-based test prep service Engineering Pro Guides, here are five problems to thaw your talents.
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A cooling tower is used to cool 95° F condenser water down to 85° F. If the design wet bulb is 78° FWB, then what is the range and approach?

Range = 10° F, Approach = 10° F

Range = 7° F, Approach = 10° F

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Range = 17° F, Approach = 7° F

A cooling tower is located such that the fluid level in the basin is 10 ft above the centerline for the suction of the condenser water pump. The water is at an average temperature of 86° F. The friction loss from the cooling tower basin to the suction of the pump is about 15 ft of head. What is the net positive suction head available at the suction side of the pump with a flow rate of 400 GPM?

12.6 ft of head

17.6 ft of head

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30.1 ft of head

A client is considering the purchase of a new high-efficiency pump and motor, with an initial cost of $10,000. The pump has a lifetime of 15 years and is estimated to save approximately $1,000 per year. There is an additional maintenance cost of $300 per year associated with this new pump. It will have a salvage value of $0 at the end of 15 years. Assume the interest rate is 4%. What is the annual value of the pump?

-$499

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$199

$499

A chiller with a refrigerant flow rate of 50 lb/min of R-134a has a suction pressure of 40 PSIA and a discharge pressure of 200 PSIA. The evaporator provides 20° F of super-heating and the condenser provides no sub-cooling. What is the net refrigeration effect?

11 tons

12.25 tons

13 tons

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A counter-flow, heat exchanger has 5,000 CFM of air, entering the coil at 40° F. Water is provided to the heat exchanger with entering conditions of 75° F and leaving conditions of 65° F. What is the LMTD, if the air leaving the coil is at 55° F?

17° F

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30° F

36° F