NCEES TFS 120- Compressor Problem

Professional Engineer & PE Exam Forum

Help Support Professional Engineer & PE Exam Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

nirvick

Active member
Joined
Jul 15, 2016
Messages
33
Reaction score
0
Can anyone please explain the equation they used to solve the problem? Why not (m2-m1)x(T2-T1)+m1(T3-T1) ?

Screenshot_3.jpg

Screenshot_2.jpg

 
This is an energy balance. All change in energy is due to work done by compressor.

Note: all Work,  enthalpy and mass terms are "dot" (differential with time).

Work =  delta h3    +   delta h2

Work = m3 * cp * delta T3    +   m2 * cp * delta T2

Work = (m1 - m2) * cp * (T3 - T1)  +   m2 * cp * (T2 - T1)

P&C

 
Back
Top