Electrical Heating in Vacuum Applications

摘要

APPLYING ELECTRICAL HEAT to materials under vacuum can be an important manufacturing process to ensure product quality when drying, high-purity processing or when other vacuum-type heating is required. The use of vacuum promotes off-gassing and reduces the boiling point of trapped liquids. Unfortunately, vacuum alone may cause liquid to evacuate from the material or the part to freeze. What remains are ice particles that are not easily evacuated from the system. Using heat and vacuum in tandem provides improved results compared to either process used separately. Applying heat with vacuum prevents ice formation and decreases the heat needed to sufficiently remove moisture and volatile compounds from parts. Three common applications utilizing the heat/vacuum combinatior include: vacuum drying, vacuum bakeout and vacuum heating for metal processing. To regulate heat applied in any vacuum application, a PID (proportional-integral-derivative) temperature controller is required to more accurately control the heating process.