Engineering Certification Engineering Certification Thermodynamics & Fluid Mechanics 2

Question 1

In a heat exchanger, what does the term 'LMTD' stand for?

Accepted Answer

Log Mean Temperature Difference

Answer

LMTD (Log Mean Temperature Difference) is the logarithmic average of the temperature differences between hot and cold fluids at each end of a heat exchanger.

Question 2

What is the thermal efficiency of a Carnot heat engine operating between temperatures T_H and T_C?

Accepted Answer

η = 1 - (T_C / T_H)

Answer

The Carnot efficiency η = 1 - T_C/T_H (using absolute temperatures in Kelvin) represents the maximum possible efficiency for any heat engine operating between those temperatures.

Question 3

What is the gauge pressure of a fluid if its absolute pressure is 200 kPa and atmospheric pressure is 101.3 kPa?

Accepted Answer

98.7 kPa

Answer

Gauge pressure = Absolute pressure − Atmospheric pressure = 200 − 101.3 = 98.7 kPa.

Question 4

Which dimensionless number characterizes the ratio of inertial forces to viscous forces in a fluid?

Accepted Answer

Reynolds number

Answer

The Reynolds number Re = ρvL/μ is the ratio of inertial forces to viscous forces and determines the flow regime in fluid systems.

Question 5

In thermodynamics, what is enthalpy (H) defined as?

Accepted Answer

H = U + PV

Answer

Enthalpy is defined as H = U + PV, where U is internal energy, P is pressure, and V is volume; it accounts for flow work in open systems.

Engineering Certification Practice Test

Engineering Certification Practice Test

Engineering Certification Engineering Certification Thermodynamics & Fluid Mechanics 2