TABLE OF CONTENTS The converging-diverging steam jet is a startlingly complex device. Not only is the theory of operation rather weird, but the jets are subject to a wide range of odd, poorly understood, and never reported malfunctions. For all these reasons, I dearly love to retrofit and troubleshoot steam jet systems.
Steam jets have been around for a long time. They have just as ancient an origin as do steam-driven reciprocating pumps. They were used on early steam engines to pull a vacuum on the now-archaic barometric condenser. More recently, they were used to develop vacuums in such services as
Surface condensers that condense the exhaust steam from steam turbines
Petroleum refinery crude-residue vacuum towers
Flash evaporators used to produce concentrated orange juice
Steam jets are also employed to recompress low-pressure steam to a higher-pressure steam. Jets are sometimes used to compress low-pressure hydrocarbon vapors with higher-pressure hydrocarbon gas (instead of steam). They are really wonderful and versatile machines.
The converging-diverging steam jet is rather like a two-stage compressor, but with no moving parts. A simplified drawing of such a steam jet is shown in Fig. 19.1. High-pressure motive steam enters through a steam nozzle. As the steam flows through this nozzle, its velocity greatly increases. But why? Where is the steam going to in such a hurry? Well, it is going to a condenser. The condenser will condense the steam at a low temperature and low pressure. It will condense the steam quickly. The steam accelerates...
