# Sheath temperature

## Sheath temperature

##### CALCULATION OF THE SHEATH TEMPERATURE OF THE HEATING CABLE

Determining sheath temperatures in application against the pipes

If the cable is free in air, the heat transfer will be poor, but if the cable is fixed with aluminium tape the heat transfer will increase considerably.

This gives us the following formula:

 Ts = Q uA + Tp
 Q = W/m The output of the heating cable per meter A = m²/m The surface of the heating cable/m cable u = W/m²°C u = u = Heat transfer coefficient Loose cable against pipe 17 – 28 W/m²°C With aluminium tape 57 W/m²°C Ts = °C Sheath temperature Tp = °C Prozess temperature A stated according to following: A(m²) = p x D (m) D = The diameter of the heating cable (m)

The determination of parallel resistive and series resistive heating cables sheath temperature is easy, since the output is constant which is is not for self-limiting heating cables.

To be able to determine the sheath temperature for a self-limiting heating cable you should go to the data sheet and in the output diagram read the emitted output at the required process temperature, i.e. the temperature that the thermostat/regulator of the heating cable is set on.

## Example

Example

Series resistive cable TCT

 Ts = 20 0,009 x 57 + 50°C = 87°C

Heating cable 20W/m mounted with aluminium tape, process temperature 50°C

Series resistive cable TCTR

 Ts = 20 0,016 x 57 + 50°C = 72°C

Heating cable 20W/m mounted with aluminium tape, process temperature 50°C

Parallel resistive cable EST/CWM

 Ts = 20 0,024 x 57 + 50°C = 65°C

Heating cable 20W/m mounted with aluminium tape, process temperature 50°C

Self-limiting cable RSL

 Ts = 15 (SRL-10) 0,032 x 57 + 50°C = 59°C

The heating cable gives approx. 15 W/m at process temperature 50°C mounted with aluminium tape

Self-limiting cableRSM

 Ts = 20 (SRM-8) 0,032 x 57 + 50°C = 61°C

The heating cable gives approx. 20 W/m at process temperature 50°C mounted with aluminium tape