Abstract: A flameless nitrogen vaporizing unit includes a first internal combustion engine driving a nitrogen pump through a transmission. A second internal combustion engine drives three coolant circulation pumps against a variable back pressure so that a variable load may be imposed upon the second engine. Liquid nitrogen is pumped from the nitrogen pump driven by the first engine into a first heat exchanger where heat is transferred from exhaust gases from the first and second internal combustion engines to the liquid nitrogen to cause the nitrogen to be transformed into a gaseous state. The gaseous nitrogen then flows into a second heat exchanger where it is superheated by an engine coolant fluid to heat the gaseous nitrogen to essentially an ambient temperature. The superheated nitrogen is then injected into the well. The engine coolant fluid is circulated in a coolant circulation system by the coolant circulation pumps. Methods of vaporizing nitrogen are also disclosed.