Increasing operational safety of auxiliary heaters

Doctorate at OWI

For the tests to produce deposits on porous media evaporators, fuel mixtures were stored for several months at 8°C and 40°C to simulate ageing. Photo: OWI

27 June 2018 – M.Sc. Winfried Koch successfully defended his dissertation at RWTH Aachen University in April 2018. His work deals with the influence of the thermal stability of liquid fuels and combustibles on the formation and degradation of residues in porous media evaporators. It was written at the OWI Oel-Waerme-Institut as part of the research project “Influence of evaporation behaviour on the coking tendency of liquid fuels on wetted surfaces”.

The evaporation of liquid fuels and combustibles in porous media evaporators enables an alternative combustion technology. This technology is state-of-the-art for engine-independent stationary and auxiliary heaters in vehicles and can also be used for heating buildings. With these evaporation concepts, a comparatively high thermal load of the fuels and combustibles occurs in their liquid phase during evaporation. The reason for this is the high temperatures of the components wetted with the fuel. This can lead to the formation and accumulation of residues during the evaporation of long-term stored and thus aged liquid fuels and combustibles. The formation of such residues can lead to malfunctions.

With the help of the idealized basic test bench for porous media evaporation developed in the work, an assessment was made of the surface temperature of the fleece evaporator and the running time of the system at which residue-free evaporation of liquid fuels and combustibles is possible. Furthermore, the temperature was investigated at which regeneration by combustion of formed residues after evaporation is possible.

The findings of the idealised basic investigations on the build-up and decomposition of residues during the evaporation of liquid fuels or combustibles in isothermal energy (temporal or spatial constancy of temperature) must be tested in subsequent work in combustion engineering investigations using application-specific test cycles, whereby the flame serves as heat source.

The dissertation Winfried Koch – Influence of the thermal stability of liquid fuels and combustibles on the composition and degradation of residues in nonwoven evaporators (ISBN: 978-3-8440-5966-3) can be obtained as a print and e-book edition under the mentioned link.


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