| 摘要 |
To prevent damage to an electrical resistance heater (13-16) which, when energized by electrical energy, for example in the order of 100 A at 12-24 V, a heat reservoir substance is included in the filter, positioned in heat transfer relation to the electrical resistance heater (13-16) and located, with respect to the flow direction of the gas stream through the filter, upstream of the filter material (15). Preferably, the electrical resistance heater is a perforated, tubular sheet-metal structure, axial ends of which are electrically connectable by connecting bolts (21, 25) to an electrical energy supply. The heat reservoir substance (14) is either wrapped at the outside over the tubular resistance heater (13-16), applied as a layer (14a) at the inside of the tubular resistance heater, or filled into the hollow interior thereof in form of a wire wool (14b). This substantially increases the heat transfer or heat exchange surface between the resistance heater and gases flowing therethrough, thus decreasing required electrical heating energy and protecting the resistance heater (13-16) against overheating upon variations in gas flow when the heater is energized. A typical heater temperature is 1300 DEG C., and it is, for example, made of sheet metal of 22% chromium, 4.8% aluminum, the remainder iron; the filter material preferably includes mineral fibers and metal wire; the heat reservoir substance (14) can be Inconel (Reg. TM) wire, preferably knitted.
|
