Wednesday, October 17, 2012
High Temperature Blower at Work
Highly reflective insulation is not an ideal material to photograph but it is easier to blow clean, reflective surfaces do reflect heat, and it effectively contains the ceramic insulation.
The testing has showed that the highest gains in efficiency were made with recirculation of the heated air. Of course that does create some challenges especially if high pressures are required. High pressures require positive displacement or high speeds. Design solutions involve benefit tradeoffs. A really good design makes use of the component's strengths without being penalized for its shortcomings.
Improving the insulation involves preserving the heated area, facilitating the application of the insulation, and reusing the heat that does escape i.e. air that is used to cool the high speed belt. To effectively utilize that cooling air there has to be a sufficient temperature differential between it and the item to be heated. It does work well in preheating a batch because the 70°C flowing air can impart energy to ambient temperature batches.
The air is used to preheat diverse products in order to reduce the load on the main system. The temperature is too low to create a moisture problem therefore condensation requirements are reserved to the main circuit. Another efficiency gain would be to use the processed batch to raise the temperature of incoming batch. Direct contact risks contaminating both batches but heat exchangers have become very efficient providing the throughput is sufficiently high.
Apart from the coffee roasting application we are involved in fluidized bed drying. A high pressure and high temperature convection oven that can also distribute super heated steam is only in the testing stage.
NOTE: Regarding the comments that this is an old Blower; the Blower is new but the Belt Cover has been repurposed. The original cover was made from sheet metal only, while this one, had some vibration dampening bars inside. Further testing showed that noise dampening material was lighter and more effective. We just kept the old cover for testing prototypes. Time for a coffee.