# Thermal & Fluids - Sample Exam Problems

### Sample Exam Problems

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### Sample Exam Problem 1 - Distribution Systems

#### The Distribution Systems topic accounts for 9 problems on the PE Exam

A pump pumps 100 GPM through the circuit below. Each valve has an equivalent length of 15 ft. Equipment A has an equivalent length of 25 ft and Equipment B has an equivalent length of 40 ft. What is the amount of GPM through branch A-C and through branch B-C? Assume the same diameter pipe throughout the entire circuit and constant friction factor.

### Sample Exam Problem 2 - Hydraulic and Fluid Equipment

#### The Hydraulic and Fluid Equipment topic accounts for 15 problems on the PE Exam

Two compressors are placed in series, with an intercooler inbetween the two compressors. The intercooler cools the air such that the temperature entering the second compressor is the same as the temperature entering the first compressor. The air enters the 1st compressor at a pressure of 14.7 psia. The required pressure at the exit of the 2nd compressor is 500 psia. What is the pressure of the air exiting the 1st compressor, if both compressors have the same pressure ratio?

See the Sample Exam for the solution.

### Sample Exam Problem 3 - Energy/Power Equipment

#### The Energy/Power Equipment topic accounts for 8 problems on the PE Exam

A steam power plant has a turbine that has a high pressure of 300 psia and a low pressure of 30 psia. If the condenser pressure is reduced to 14.7 psia and the boiler pressure and maximum boiler temperature remain the same, then which of the following statements is true? Assume an ideal Rankine cycle.

(A) The overall power plant efficiency will remain unchanged.

(B) The total amount of useful work produced by the turbine will decrease.

(C) The entropy of the steam entering the condenser will remain unchanged.

(D) Statements A and C are both true.

See the Sample Exam for the solution.

### Sample Exam Problem 4 - Cooling/Heating

#### The Cooling/Heating topic accounts for 6 problems on the PE Exam

A cooling unit cools 4,000 cfm of outside air to 55oF DB, 53oF WB. The outside ambient condition is 87oF DB, 75oF WB. What is the total cooling load required by the air handling unit? Assume that the density of air is 0.075 lbs per cubic foot.

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### Sample Exam Problem 5 - Energy Recovery

#### The Energy Recovery topic accounts for 5 problems on the PE Exam

75 F, 14.7 psia air enters the open Brayton cycle shown below. The air is compressed to a pressure of 100 psia. Air enters the turbine at a temperature of 1200 F and leaves at a pressure of 14.7 psia and a temperature of 550 F. Assume no air leakages, constant heat capacity, isentropic compressor, 80% effective heat exchanger and isentropic turbine. What is the heat added in the combustion process?

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### Sample Exam Problem 6 - Combined Cycles

#### The Combined Cycles topic accounts for 5 problems on the PE Exam

Given the diagram below for a Rankine cycle, determine the value for W_turbine out. Assume the turbine is 75% efficient.

See the Sample Exam for the solution.