Design of a cooling helmet liner

Abstract

Humans wear helmets to protect the head from impact. However, covering part of the body influences the thermal balance due to restricting the heat loss capacity. This is especially the case for the head due of the lack of vasoconstriction response in the head’s skin.
This project focussed on improving thermal comfort and perception when wearing a helmet in warm environments or during physical exercise.
The main problem statement was: accumulation of heat underneath the helmet resulting in a rise in head skin temperature, decreased thermal comfort and exercise performance.

There are five heat loss pathways in order for the human body to lose excess heat: conduction, radiation, and convection complemented with evaporation and respiration. Smith & Havenith (2011) identified the forehead, side of the head and neck as areas of high sweat rate, here evaporative heat loss has high potential for providing cooling. Fanger’s (1970) four conditions state that skin temperature and skin wettedness are the main factors determining a person’s whole body thermal comfort.

The emphasis was placed on convective (airflow) and evaporative heat transfer as main cooling pathways. Also, active cooling was found to be necessary to provide enough cooling for the head according to Strijk’s (2008) model. The new Fantilated helmet features active cooling through ventilation, a pyramid structured padding embedded with micro channels and an absorbing biomaterial.

The Fantilated helmet was prototyped to validate the design and the cooling principle. To test the active cooling system a thermal head manikin with thermal sensors on its surface was covered with a wet cloth to analyse the temperature changes on the head’s surface. The full set-up was placed on a scale to analyse the decrease in weight caused by evaporation.
The active ventilation of the Fantilated helmet rendered positive results in terms of reducing the temperature and an increase in the evaporation rate. Both the decrease in weight and temperature suggest that the active cooling system of the Fantilated helmet will aid in improving thermal comfort.

The Fantilated helmet that was used in this test was not optimal, also, the pyramid structured padding and the absorbing biomaterial were not present in the final prototype (and therefore not tested). Possibly, the final product/design could render even better results than the one used in this test.

In conclusion, the Fantilated helmet is effective in decreasing the surface temperature of the head and improving the evaporation from the head’s surface. However, testing was done on a thermal head manikin and not on actual humans. Further development is recommended and testing on actual users is necessary in order to validate all aspects of the design.