A double tank heat roller which utilizes vaporization and condensation of ethylene glycol has been designed and manufactured for uniform surface temperature distribution and fast temperature response in reheating. PID controller is employed to heat up heat roller fast in start-up and to maintain it accurately to the set temperature. IR probes and a thermal image system are employed for measuring the temperature of the heat roller surface.
A uniform surface temperature distribution over the double tank heat roller (±2~3℃) is obtained, compared with a conventional heat roller (±20~30℃). Fast temperature response in reheating decreases the reheating time to 305sec compared with 2700sec of reheating time from cold state in a black-coated heat roller. Large heat loss occurs in the heat roller by radiation for a black-coated surface and also by conduction to the driving mechanism. Therefore, non-black coating and employment of non-conducting materials and/or structure are highly recommended not only for energy savings but also for fast reheating.
