Cooling towers are a very important part of many chemical plants. They represent a relatively inexpensive and dependable means of removing low grade heat from cooling water.

In many cases it's convenient to have simple equations for estimation of heat transfer coefficients. Below is a collection of recommended correlations for single-phase convective flow in different geometries as well as a few equations for heat transfer processes with change of phase. Note that all equations are for mean Nusselt numbers and mean heat transfer coefficients.

A boiler is a closed vessel where water is heated, steam is generated, or steam is superheated with heat from combustion fuels, electricity, or nuclear energy.  Boilers consist of two main parts:  the furnace and the convection sections.  The furnace section is where the heat is generated (we'll assume the more common combustion heat source).  This section is designed to accommodate the three "T's" of combustion: time, temperature, and turbulence.