Thermocompressors are jet pumps which use a high pressure steam gas to entrain and compress low pressure vapor to an intermediate pressure. They usually operate with steam as a motive fluid recovering and reusing energy of exhaust steam, but gas/ gas thermocompressors can also be applied frequently.
Its basic principle and characteristics are identical to the "ejectors". See ejectors item for more information.


Thermocompressors pressure ratios (discharged to suction pressure) between 1,5 to 1,8 hast the best thermodinamic efficiency. For heat recovery units in evaporation , those ratios are correspondent with temperature jumps between 10 to 15° C (saturation outgoing temperature steam to saturation temperature of sucked steam), hence the terms thermocompressor, and with the subsonic and sonic (critical) regimen. 20°C temperature difference (2,2 pressure ratio) require not much high supersonic regimen. It is the maximum advisable temperature jump. That is, from economical point sight, large heat transfer surface of evaporator and little temperature difference are better than little surface and large temperature difference.


Thermocompressors are widely used in the food and dairy industries as heat pumps of multieffect evaporators, chemical and paper industries.They are also used in gas and petroleum industry to recompress low pressure gas with high pressure motive one. Moreover, thermocompressor are fundamental parts of vacuum refrigerator (see these item for more information).