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Characterization of an immersion heater


A company specializing in the production of Teflon immersion heaters and temperature probes asked us to calculate the energy efficiency of a 6 kW immersion heater, in fact it must justify its efficiency to a laboratory at the request of 'a customer. 

The immersion heater in its use at the customer is placed flat at the bottom of a tank filled with a fluid in the liquid state. It is supplied in three-phase by a 6m long cable, part of the energy of which is potentially lost.

Measurement bench


We have designed and produced a test device based on an experimental approach of heat balance coupled with an electrical balance.

The calculation of the efficiency of the immersion heater is done for the following two conditions:

  • 4m submerged and 2m non-submerged power cable 
  • 30cm submerged and 5.7m non-submerged power cable 


This will allow by comparison to highlight the impact of the latter on the heat balance. 

This efficiency will be the ratio between the electrical power absorbed and the thermal power returned. 


The electrical power supply to the immersion heater is measured from the three resistors and the supply voltages.

The restored thermal power is measured using previously calibrated PT100 type temperature sensors. Three temperature probes are positioned above the immersion heater and another probe in a corner.

The bath tank is insulated to limit heat losses as much as possible. A dimensioning is carried out beforehand to make the choice of the type and thickness of this insulation.