How to calculate the power for a heating element.

02-10-2019

How to calculate the power for a heating element.

This is the most recurring query we face every day.

Many times when we want to calculate the power required for a heating system of our customers we find the false belief that when more power the better. We want to clarify this question because although is true that an electric heater with greater power can heat more and faster, it does not mean that it is the most efficient element or the right choice.

To begin with, it is important to take into account, before total power or watts, the charge density, that is, the W/cm² that we can apply on a heater element. When calculating the watts we need in order to heat a product we will first have to know its specific heat and the dissipation capacity that the resistance will have, especially if it will be in direct contact with a solid body. We must take into account the size of the heating element. The more dissipation surface the resistance has, the better its performance will be and the longer its life will be. Water and oil, although are both liquids, do not dissipate heat for equal, so it is important to know the product that is going to be heated. A resistance to heat water has no the same characteristics as resistance to heat oil, heat fuel, heat paraffin, wine, honey or gasoline.


The surface load or load density that we recommend in different types of heaters is the following:


• Interchangeable ceramic cartridges max. approx. 6 W / cm²
• Non-compacted heating elements with a metal jacket max. approx. 8 W / cm²
• Compact heating elements max. approx. 20 W / cm²
• Large capacity ceramic cartridges max. approx. 100 W / cm²
These maximum surface loads can only be achieved if the proper fluids are used.
The following values ​​have proved useful in practice for the following fluids:
• Water 0 ° dH max. 20 W / cm²
• Circulating water, low oxygen level, VDI 2035 max. 10 - 15 W / cm²
• Drinking water <18 ° dH max. 6 W / cm²
• Drinking water> 18 ° dH max. 3 - 4 W / cm²
• Heat transfer oil max. 4-10 W / cm²
• Fuel oil EL / diesel max. 4 W / cm²
• Rapeseed oil max. 4 W / cm²
• Max. Hydraulic oil 1 - 2 W / cm²
• Heavy oil max. 2 W / cm²
• Max milk 1 W / cm²
• Honey max. 0.5 W / cm²

HERE you will find a simple form where you can find out the watts that are necessary to heat the products that our customers more often need: