Operator’s Manual: ThermoJet
Chapter 6: Base Unit Controls
© SP Industries, Inc.
200-31974-999 Rev. 009
53
The ThermoJet air delivery assembly is a "single path" system. The air flows through the same
path regardless of exit temperature. Even when operating at maximum temperature, the air
enters the air delivery assembly below -80°C and the refrigeration system is fully on. Exit air
temperatures are controlled by “bucking” the cold flow with a 2.5 kW resistive heater located
inside the black aluminum shell at the end of the air delivery assembly.
The air delivery assembly’s small size, lightweight, and flexibility are the result of the single air
path and the absence of refrigeration lines. This, in turn, facilitates moving and positioning the
ThermoJet head/shroud to interface with test fixtures.
A Type-K thermocouple located in the exit nozzle supplies a control signal to the System
Controller. This temperature is the main process variable when operating in Nozzle Air Control
mode and inner loop process variable when operating in DUT (cascade) Control mode.
On certain models, the air delivery assembly is supported by a heavy-duty mechanical arm, and
raised/lowered by means of a pneumatic actuator.
Refrigeration Assembly
The cooling capability of the THJ80 ThermoJet is provided by a robust, efficient, cascade
mechanical refrigeration system. Two hermetically sealed compressors are located inside the
base unit cabinet. Working together in series, these compressors cool the air stream by means of
a refrigerant-to-air heat exchanger. The entire refrigeration system is resides within the base unit.
No cooling occurs in the air delivery assembly.
