NCEES TFS Problem 114 in the
NCEES Mechanical Practice Exam for Thermal and Fluid Systems is a classic mixing chamber problem, however the first equation given in the NCEES solution makes it look like you get the answer by “averaging” the enthalpies, but could have used any of the other intensive properties like specific volume, specific internal energy, or specific entropy. But you cannot. What is missing in the NCEES solution is the application of both Conservation of Mass and Conservation of Energy, meaning the 1st Law for Open Systems. In this video Dr. Tom shows those missing steps, an how the magnitudes of the mass flow rates given and that only enthalpy can be used determines the answer. He also provides you with a general equation that would apply to similar problems with any given mass flow rates. This is a perfect example of the application of the Dr. Tom Method and its effectiveness in solving classes of problems.
Dr. Tom's Solution to NCEES TFS Problem 114
DTC recommends that anyone taking the PE Exam purchase the NCEES
Practice Exam for the exam they are taking. It is an essential exam
review resource.
https://account.ncees.org/exam-prep/
Begin your review for the October PE Exam today!
Hop on the Fast Track with a $25 Off Coupon: fast25B
Taking the April 2018 Exam?
Targeted Mechanical and Civil PE Exam Reviews that work!
