___________________________________________________________________
Iowa Mechanical Engineer Examination
Advanced 100-Question Practice Exam
2026 | Questions & Answers with
Detailed Rationales | Complete Exam
Prep & Study Guide
1. A closed-loop hydronic heating system experiences a significant increase in
pressure when heated from 60°F to 180°F. Which component is primarily
intended to accommodate the resulting fluid expansion?
A. Air separator
B. Expansion tank
C. Check valve
D. Pressure-reducing valve
Answer: B. Expansion tank
Rationale: An expansion tank provides a compressible volume that
accommodates thermal expansion of the system fluid and helps prevent
excessive pressure rise.
, 2. A centrifugal pump operates at 1,750 rpm and produces 600 gpm at a given
head. If the pump speed is increased to 2,100 rpm while the impeller
diameter remains unchanged, approximately what flow rate should be
expected under affinity-law conditions?
A. 500 gpm
B. 600 gpm
C. 720 gpm
D. 840 gpm
Answer: C. 720 gpm
Rationale: For geometrically similar operation, flow varies directly with speed.
Thus, Q₂ = 600(2,100/1,750) = 720 gpm.
3. A steam turbine exhausts to a condenser operating at a vacuum. Which
change would generally increase the turbine's ideal enthalpy drop?
A. Increasing condenser pressure
B. Increasing condenser vacuum
C. Increasing feedwater temperature only
D. Increasing turbine exhaust pressure
Answer: B. Increasing condenser vacuum
Rationale: A lower condenser pressure increases the expansion ratio and
generally increases the available turbine enthalpy drop.
4. A heat exchanger has a hot-fluid inlet temperature of 350°F and outlet
temperature of 250°F. The cold-fluid inlet is 100°F and outlet is 200°F. What
is the log mean temperature difference for counterflow operation?
A. 100°F
B. 125°F
C. 150°F
D. 175°F
Answer: C. 150°F
,Rationale: For counterflow, both terminal differences are 150°F: 350−200 and
250−100. When the terminal differences are equal, LMTD is 150°F.
5. In a vapor-compression refrigeration system, excessive superheat at the
evaporator outlet most directly indicates that the refrigerant is:
A. Too wet entering the compressor
B. Completely vaporized with additional sensible heating
C. Subcooled excessively
D. Condensing prematurely
Answer: B. Completely vaporized with additional sensible heating
Rationale: Superheat is the temperature of vapor above its saturation
temperature at the measured pressure. Excessive superheat means the vapor
has absorbed additional sensible heat after complete evaporation.
6. A boiler produces 50,000 lb/hr of steam while consuming 5,000 lb/hr of
fuel. If the steam generation rate remains constant but fuel consumption
increases to 5,500 lb/hr, boiler efficiency will generally:
A. Increase
B. Remain unchanged
C. Decrease
D. Become exactly 100%
Answer: C. Decrease
Rationale: With the same steam output and greater fuel input, the useful energy
produced per unit of fuel decreases, indicating lower efficiency.
7. Which dimensionless number represents the ratio of inertial forces to
viscous forces in fluid flow?
A. Reynolds number
B. Prandtl number
C. Nusselt number
D. Froude number
, Answer: A. Reynolds number
Rationale: Reynolds number, Re = ρVD/μ, compares inertial forces with viscous
forces and is fundamental in determining laminar or turbulent flow behavior.
8. A pipe carries water at 8 ft/s through a 4-inch inside diameter pipe. If the
diameter is doubled while maintaining the same volumetric flow rate, the
approximate velocity becomes:
A. 1 ft/s
B. 2 ft/s
C. 4 ft/s
D. 16 ft/s
Answer: B. 2 ft/s
Rationale: Area varies with diameter squared. Doubling diameter increases area
by four, so velocity decreases by a factor of four: 8/4 = 2 ft/s.
9. A mechanical system has a rotating shaft subjected simultaneously to
bending and torsion. Which failure criterion is commonly appropriate for
ductile materials when combined stresses must be evaluated?
A. Maximum principal strain only
B. von Mises distortion-energy criterion
C. Bernoulli equation
D. Darcy-Weisbach equation
Answer: B. von Mises distortion-energy criterion
Rationale: The von Mises criterion is widely used for ductile materials under
combined loading because it relates the multiaxial stress state to yielding.
10.A steel beam experiences a bending moment of 60 kip-ft. Its section
modulus is 20 in³. What is the bending stress?
A. 18 ksi
B. 24 ksi
Iowa Mechanical Engineer Examination
Advanced 100-Question Practice Exam
2026 | Questions & Answers with
Detailed Rationales | Complete Exam
Prep & Study Guide
1. A closed-loop hydronic heating system experiences a significant increase in
pressure when heated from 60°F to 180°F. Which component is primarily
intended to accommodate the resulting fluid expansion?
A. Air separator
B. Expansion tank
C. Check valve
D. Pressure-reducing valve
Answer: B. Expansion tank
Rationale: An expansion tank provides a compressible volume that
accommodates thermal expansion of the system fluid and helps prevent
excessive pressure rise.
, 2. A centrifugal pump operates at 1,750 rpm and produces 600 gpm at a given
head. If the pump speed is increased to 2,100 rpm while the impeller
diameter remains unchanged, approximately what flow rate should be
expected under affinity-law conditions?
A. 500 gpm
B. 600 gpm
C. 720 gpm
D. 840 gpm
Answer: C. 720 gpm
Rationale: For geometrically similar operation, flow varies directly with speed.
Thus, Q₂ = 600(2,100/1,750) = 720 gpm.
3. A steam turbine exhausts to a condenser operating at a vacuum. Which
change would generally increase the turbine's ideal enthalpy drop?
A. Increasing condenser pressure
B. Increasing condenser vacuum
C. Increasing feedwater temperature only
D. Increasing turbine exhaust pressure
Answer: B. Increasing condenser vacuum
Rationale: A lower condenser pressure increases the expansion ratio and
generally increases the available turbine enthalpy drop.
4. A heat exchanger has a hot-fluid inlet temperature of 350°F and outlet
temperature of 250°F. The cold-fluid inlet is 100°F and outlet is 200°F. What
is the log mean temperature difference for counterflow operation?
A. 100°F
B. 125°F
C. 150°F
D. 175°F
Answer: C. 150°F
,Rationale: For counterflow, both terminal differences are 150°F: 350−200 and
250−100. When the terminal differences are equal, LMTD is 150°F.
5. In a vapor-compression refrigeration system, excessive superheat at the
evaporator outlet most directly indicates that the refrigerant is:
A. Too wet entering the compressor
B. Completely vaporized with additional sensible heating
C. Subcooled excessively
D. Condensing prematurely
Answer: B. Completely vaporized with additional sensible heating
Rationale: Superheat is the temperature of vapor above its saturation
temperature at the measured pressure. Excessive superheat means the vapor
has absorbed additional sensible heat after complete evaporation.
6. A boiler produces 50,000 lb/hr of steam while consuming 5,000 lb/hr of
fuel. If the steam generation rate remains constant but fuel consumption
increases to 5,500 lb/hr, boiler efficiency will generally:
A. Increase
B. Remain unchanged
C. Decrease
D. Become exactly 100%
Answer: C. Decrease
Rationale: With the same steam output and greater fuel input, the useful energy
produced per unit of fuel decreases, indicating lower efficiency.
7. Which dimensionless number represents the ratio of inertial forces to
viscous forces in fluid flow?
A. Reynolds number
B. Prandtl number
C. Nusselt number
D. Froude number
, Answer: A. Reynolds number
Rationale: Reynolds number, Re = ρVD/μ, compares inertial forces with viscous
forces and is fundamental in determining laminar or turbulent flow behavior.
8. A pipe carries water at 8 ft/s through a 4-inch inside diameter pipe. If the
diameter is doubled while maintaining the same volumetric flow rate, the
approximate velocity becomes:
A. 1 ft/s
B. 2 ft/s
C. 4 ft/s
D. 16 ft/s
Answer: B. 2 ft/s
Rationale: Area varies with diameter squared. Doubling diameter increases area
by four, so velocity decreases by a factor of four: 8/4 = 2 ft/s.
9. A mechanical system has a rotating shaft subjected simultaneously to
bending and torsion. Which failure criterion is commonly appropriate for
ductile materials when combined stresses must be evaluated?
A. Maximum principal strain only
B. von Mises distortion-energy criterion
C. Bernoulli equation
D. Darcy-Weisbach equation
Answer: B. von Mises distortion-energy criterion
Rationale: The von Mises criterion is widely used for ductile materials under
combined loading because it relates the multiaxial stress state to yielding.
10.A steel beam experiences a bending moment of 60 kip-ft. Its section
modulus is 20 in³. What is the bending stress?
A. 18 ksi
B. 24 ksi
