Process fired heater configuration

An apparatus for heating a process fluid, comprising:

• a shell having sides, an upper surface, a lower surface, combustion fluid inlets and a flue gas outlet, wherein the combustion fluid inlets are for admitting a fuel and oxidant mixture and wherein the shell has a height, a width, a top and a bottom;
• at least one process coil disposed within the shell that comprises at least two inlet ports and at least one outlet port less than the number of inlet ports, wherein the at least one outlet port is located between the at least two inlet ports;
• and
• at least two burners disposed on the sides of the shell, and in an opposing configuration;
• wherein the at least two inlet ports and the at least one outlet port of the at least one process coil are disposed on the lower surface of the shell
• wherein the at least one process coil comprises at least three tubes in a parallel orientation and two semicircular tubular sections,
• wherein a first tube and a second tube of the at least three tubes are inlet tubes that each have a first closed end and a second end connected to one of the at least two inlet ports, wherein each of the first tube and the second tube are connected to one of the two semicircular tubular sections between their respective first end and second end,
• wherein a third tube of the at least three tubes is a central outlet tube disposed between the first and second tubes that is connected to both of the two semi-circular tubular sections and has an end connected to the at least one outlet port such that the at least three tubes and the two semi-circular tubular sections form a general configuration of a letter W,
• and wherein the first and second tubes have substantially the same inner diameter.