Finned Tubular Heaters (RHR)

Description

In order to increase the heat transfer of tubular heaters for the heating of air and gases tubular heaters are equipped with a steel strip coiled aro und the heater. Thus enlarging the surface area and increasing turbulences, finned tubular heaters can sustain a higher thermal loading than normal tubular heaters. The surface temperature decreases and the heaters become shorter.

Therefore, T+H finned tubular heaters should be applied where it is required to heat gases or air at temperatures where the differences between the heater and the medium should remain small.

• For air conditioners the deposits of combustible dust is minimized.
• In drying apparatus the drying goods are smoothly treated.
• For varnish dryers you can obtain an even temperature distribution and the maximum surface temperature of the heater can be kept low thus increasing its lifetime.
• Within shrink foil packaging machines these heating elements allow a stable temperature dissipation and prevent the foil from overheating.

Shapes

Assembly

Finned tubular heaters can be supplied straight or bent and with or without threaded nipple M14 x 1.5 ready for the assembly (see illustrations in the Catalogue Air Heaters). Shape A and B are normally equipped with a threaded nipple.

Construction and tolerances

• Due to production reasons the ends of the heaters have to be unfinned for min. 50 mm. The unheated ends need to be at least 5 mm longer than the unfinned portion.
• The length tolerance i.a.w. DIN 44874 is of ±2%, but min. ±5 mm.
• More precise tolerances must be stated on order. For shaped heaters, the dimensional tolerances are negotiable at time of order.
• Finned tubular heaters with an unfinned bend have a reduced surface loading within the bent portion in order to avoid overheating (special type heater).

In case of order or enquiry please indicate the dimensions i.a.w. your requirements.

Bending

T+H finned tubular heaters can be bent within the finned and the unfinned portion. As the bending requires special bending fixtures the heaters can only be bent at our premises.

Other shapes on request.

Connections

T+H finned tubular heaters can be supplied with the following connections:

Heater diameter = 8,5 mm

• Bolt connector Ø 3.5 mm
• Lead connection
• Threaded bolt M4
• Tab connector

Materials

Test

T+H finned tubular heaters comply with the VDE standards. Each heater has to undergo an individual test i.a.w. DIN EN 60335 (VDE 0700).

Materials

The sheath material is CrNi-steel material no. 1.4541 (AISI 321). The fins are made of

• CrNi-steel 1.4541 (C) 6mm oder 10mm fin height, thickness 0,25 mm or
• mild steel material no. 1.0112 (CF) 10 mm fin height, thickness 0,3 mm.

Other materials can be supplied upon request.

Max. permitted temperature on the sheath:

• CrNi-Stahl (C) – material no. 1.4541 – up to 550°C
• Mild steel (CF) – material no. 1.0112 – up to 400°C

Advice on the Immersion Length

The immersion length is the length L1 (acc. ill. 3.6) in cold condition. Heat expansion needs to be considered. At an immersion length of 990 mm and a sheath temperature of 500°C the lengthening of the heater is approximately 10 mm.

Expansion ratio: 1.8 mm per m and 100K

Standard Types and Calculation

Find more information on types available, standard types and all formulas for your calculations in the Catalogue Air Heaters.