Abstract
A large number of models for transfer processes that contain equations are
based on laws of conservation of momentum, mass and energy. Some of the
models that were developed initially are based on simple laws and were
inspired by experimental observations. The laws, though limited in scope,
are still used not only as sub-models of various rigorous models but also in
various engineering calculations. However, it is essential to understand the
simplicity as well as limitations of these models. The simple laws provide us
with initial guess values required while using rigorous models. These laws
can be used as sub-models or as assumptions if a given process is not very
sensitive to a particular parameter. The use of numerical methods is helpful
in easily solving some of the problems based on these simple laws. A few
commonly used simple laws will be presented in this chapter. They include
the ideal gas law, which is used for estimation of thermodynamic properties; the cubic equation of state (EOS), particularly the Peng-Robinson EOS;
Newton’s law of viscosity and its application in flow problems; Fourier’s law
for conduction; Fick’s first and second laws for diffusion; kinetic rate expressions; the Arrhenius equation and isotherms for adsorption. Definitions
of the heat and mass transfer coefficients and resistances to heat and mass
transfer are presented. A few applications of the simple laws are presented
to demonstrate the importance of these problems.