Heater Catalog - Watlow

DDTubular HeatersFIREBAR Single/Double-Ended HeatersPerformance FeaturesFIREBAR’s flat tubular element geometry producesperformance features and benefits not possible withtraditional round tubular technology. The followingdescribes how and why the FIREBAR is functionallysuperior for many applications—especially thoserequiring large wattage with low watt density.By using the FIREBAR element it will:• Lower the element’s watt density• Reduce element size and keep the same watt density• Increase element life by reducing sheath temperatureFlat Shape Produces Lower Sheath TemperatureThe FIREBAR element operates at a lower sheathtemperature than a round tubular element of equalwatt density because of three factors.1. Flat Surface GeometryFIREBAR’s flat, vertical geometry is streamline. Theliquid’s flow past the heating element’s surface is notimpaired by back eddies inherent in the round tubularshape. The FIREBAR’s streamline shape results in fluidsflowing more freely with more heat carried away fromthe sheath.Comparative WidthsComparate Widths of Flow Resistance0.235 in.0.430 in.Watt Density and Surface Area AdvantagesThe surface area per linear inch of a 1 in. FIREBAR is70 percent greater than the 0.430 in. (11 mm) diameterround tubular element. The 5 /8 in. FIREBAR is nearly10 percent greater.Surface Area PerLinear inch (cm)Element Type in 2 (cm 2 )1 in. FIREBAR 2.30 in 2 (5.84 cm 2 )5 /8 in. FIREBAR 1.52 in 2 (3.86 cm 2 )0.430 in. Round 1.35 in 2 (3.43 cm 2 )2. Normal to the FlowThe element’s width (thickness) of both 1 inch and5 /8 inch FIREBAR elements is just 0.235 in. (5.9 mm).Compared to a 0.430 in. (11 mm) round tubularelement, this relative thinness further reduces dragon liquids or gases flowing past the heater.3. Buoyancy ForceThe FIREBAR element’s boundary layer, or vertical side,is greater than virtually all round tubular elements. Thisis 1.010 and 0.650 in. (25.6 and 16.5 mm) for the oneinch and 5 /8 in. FIREBARs respectively, compared to a0.430 in. (11 mm) diameter on a round tubularelement. The FIREBAR element’s increased height,relative to flow, increases the buoyancy force inviscous liquids. This buoyancy force can be as much as10 times greater depending on the FIREBAR elementand liquid used.WATLOW ®Flat vs. Round Geometry ComparisonsThe unique flat surface geometry of the FIREBARelement offers more versatility in solving heater problemsthan the conventional round tubular element. Thefollowing comparisons show how the FIREBAR elementconsistently outperforms round tubular heaters.FIREBAR elements can:• Reduce coking and fluid degrading• Increase heater power within application spaceparameters• Provide superior heat transfer in clamp-on applicationsresulting from greater surface area contact• Lower watt densityReducing watt density or sheath temperature extends life.The FIREBAR element allows you to do either, withoutsacrificing equipment performance … as is proven by theaccompanying Heater Oil Test, Air Flow and Watt Densityvs. Sheath Temperature graphs.97