A low cost, maintenance-free way to compress and mix gases or Vapors

JET-VAC Thermocompressors use a jet of high-pressure media to entrain a low-pressure gas or vapor, mix the two and discharge the mix at an intermediate pressure. The fluids can be steam, air, propane or any other vapor phase material. When both vapors are steam, the compressor is referred to as a thermocompressor.


  • Simple construction with no moving parts
  • Low cost and upkeep
  • Intrinsically safe for potentially explosive environments (excluding instrument transmitters)
  • Low maintenance requirements allow use in remote locations
  • Available in a variety of materials – cast iron, Hastelloy™ and others

How Thermocompressors work

Motive steam, under pressure, enters the thermocompressor and flows through its nozzle. The nozzle converts the high-pressure vapor into a high-velocity stream, creating suction and causing entrainment of the low-pressure steam. The two vaporsmix in the thermocompressor body. The diffuser then converts the velocity head of the mixture into a static head to obtain the proper discharge pressure.

Thermocompressors are used in the process, paper, petroleum, power and gas industries to circulate steam, boost low-pressure steam and to mix, transfer and compress other gases and vapors.

Thermocompressor types (based on performance requirements)

Thermocompressor designs are classified based on the fluid velocity in the throat diffuser. When the velocity is supersonic, the design is identified as critical.

Non-critical thermocompressors
These have an absolute discharge pressure of less than 1.8 times the absolute suction pressure for steam as the motive fluid. Constant suction pressure is maintained at varying capacities by controlling the motive flow.

Critical thermocompressors
These have an absolute discharge pressure equal or greater than 1.8 times absolute suction pressure. The motive fluid cannot control the suction pressure. It is necessary to add a secondary suction fluid or vary the suction pressure by introducing an artificial pressure drop in the suction lines.