To ensure proper operation of electric radiators and towel warmers they must be filled with an appropriate heating medium (heat conveyor). Such media include: water, oil as well as ethyl or propylene glycol solution.
What criteria should the heating medium meet in order to ensure correct performance of the electric radiator / towel warmer?
- It should not contain any substances that are likely to cause corrosion. This is to protect durability of both – radiator/towel warmer and the heating element.
- Heating solution should be high-temperature resilient. The heating solution will reach its highest temperature near the surface of the heating element. This is where the heating solution may start to disintegrate and as an effect discharge gases or create solid residue. Gas discharge may increase a pressure inside the radiator / towel warmer. If it exceeds critical level it will damage the radiator / towel warmer. Solid residue, on the other hand, will concentrate on the surface of the heating element reducing heat conveyance to the heating solution. Both phenomena will diminish radiator / towel warmer ‘s performance (heating up too slowly or not reaching set temperatures). With time, unsuitable heating solution will permanently damage the heating element.
- Heating solution should have low kinematic viscosity characteristics. Kinematic viscosity – is a physical property which plays a fundamental role in the circulation of heating solution inside the radiator / towel warmer. The lower the viscosity, the better (faster) circulation of the solution and more even heat distribution inside the radiator / towel warmer.
- Heating solution should also have a suitable heat capacity. Heat capacity of the heating solution is responsible for an even heat distribution inside the radiator / towel warmer. Heating solution heats up when in contact with the heating element. As soon as it leaves that area, it starts giving the heat away. Heating solution of a low heat capacity loses its temperature rather quickly and “travels” through the radiator with relatively low temperature. It heats up again on contact with the heating element. This type of behavior can be often observed in big radiators.
- Heating solution should be resistant to freezing (solidification) at the lowest temperatures to which the radiator / towel warmer may possibly be exposed to.
Heating solutions that do not increase their volume when frozen (no water content), may solidify during transport and storage. The user should always check if the heating solution regained its liquidity prior to turning on the radiator / towel warmer (heating element).
Heating solutions that do increase their volume when frozen (water based), should not be exposed to low temperatures in order to prevent them from freezing. Heating solution frozen inside the electric radiator will damage the radiator and heating element capillary.
Heating Solutions
Water
Water is the best heating solution because of its characteristics, however... it can only be used when there is a certainty that surrounding temperature will not drop below „0+”:
- It has a very low viscosity
- It has a high heat capacity
- It is widely available
- It is cheap
- It is environmentally friendly
Examples of oils
Oils used as heat conveyors should meet certain requirements: optimal viscosity up to 5 mm2/s at 40°C, viscosity not exceeding 9 mm2/s at 40°C is also allowed. Solidification temperature should not be higher than the minimum temperature the radiator is likely to be exposed to.
Oil brands
Manufacturer | Product name | Viscosity [mm2/s] at 40°C | Solidification temperature [°C] |
Good viscosity | |||
FUCHS | Renolin Heatingfive | 4,0-5,0 | -30 |
Total | Hydrosel G3H | 4,1 | -19 |
Mobil | Mobiltherm 594 | 4,9 | -57 |
Shell | Flavex 909 | 4,5 | -3 |
Shell | Flavex 709 | 3,9 | -9 |
Satisfying viscosity | |||
Shell | Thermia A | 8,5 | -60 |
BP | Transcal LT | 8,2 | -39 |