place of medical school training. Neither will engineering software packages
replace the traditional engineering education. They will simply cause a shift
in emphasis in the courses from mathematics to physics. That is, more time
will be spent in the classroom discussing the physical aspects of the prob-
lems in greater detail, and less time on the mechanics of solution procedures.
All these marvelous and powerful tools available today put an extra bur-
den on today’s engineers. They must still have a thorough understanding of
the fundamentals, develop a “feel” of the physical phenomena, be able to
put the data into proper perspective, and make sound engineering judg-
ments, just like their predecessors. However, they must do it much better,
and much faster, using more realistic models because of the powerful tools
available today. The engineers in the past had to rely on hand calculations,
slide rules, and later hand calculators and computers. Today they rely on
software packages. The easy access to such power and the possibility of a
simple misunderstanding or misinterpretation causing great damage make it
more important today than ever to have solid training in the fundamentals of
engineering. In this text we make an extra effort to put the emphasis on
developing an intuitive and physical understanding of natural phenomena
instead of on the mathematical details of solution procedures.Engineering Equation Solver (EES)
EES is a program that solves systems of linear or nonlinear algebraic or dif-
ferential equations numerically. It has a large library of built-in thermody-
namic property functions as well as mathematical functions, and allows the
user to supply additional property data. Unlike some software packages,
EES does not solve engineering problems; it only solves the equations sup-
plied by the user. Therefore, the user must understand the problem and for-
mulate it by applying any relevant physical laws and relations. EES saves
the user considerable time and effort by simply solving the resulting mathe-
matical equations. This makes it possible to attempt significant engineering
problems not suitable for hand calculations, and to conduct parametric stud-
ies quickly and conveniently. EES is a very powerful yet intuitive program
that is very easy to use, as shown in Examples 1–11 and 1–12. The use and
capabilities of EES are explained in Appendix 3 on the enclosed DVD.36 | Thermodynamics
EXAMPLE 1–11 Solving a System of Equations with EESThe difference of two numbers is 4, and the sum of the squares of these two
numbers is equal to the sum of the numbers plus 20. Determine these two
numbers.Solution Relations are given for the difference and the sum of the squares
of two numbers. They are to be determined.
Analysis We start the EES program by double-clicking on its icon, open a
new file, and type the following on the blank screen that appears:x^2y^2xy 20xy 4