Techniques and calculation tools which are useful in plant hydraulic designs or operations involving process or utility lines are presented in this volume of vapor-liquid equilibrium flash vaporization (EFV) and fluid flow. The EFV and flow equations are first presented via consistent principles of thermodynamic laws. Physical laws governing conservations of mass, force/momentum and heat with an equation of state are interwoven with the thermodynamic treatment in presenting of analytical equations. Reversible and irreversible analyses of a process lay the basis for understanding Bernoulli's law, Hagen-Poiseuille law, Darcy's velocity head equation, Fanning or Darcy friction factors, flow coefficients, plus incompressible and compressible fluid in piping or internal restrictions. Sizing of orifices, nozzles, pressure relief valves and control valves, net expansion factors, sonic gas flow, hydro-static pressure test, etc. are also presented.