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Air flow, heat transfer and impact study of ventilated and non-ventilated full-face motorcycle helmet

ABSTRACT In tropical countries, there is reluctance to wear motorcycle helmets in summers and monsoon due to the discomfort caused by sweating and high temperature. A computational study is carried out to see if providing vents in the helmet reduce this discomfort. Front impact experiment is then performed to ascertain whether vents affect the safety of the helmets. Results of computational fluid dynamics (CFD) simulations are used to predict the temperature, relative humidity and air velocity in the air gap of helmet. Apparent temperature (AT) heat index is calculated and results are then used to predict the thermal comfort of the riders. Results suggest that 36 °C can be considered as threshold temperature, beyond which if the air inlet temperature is increased, the ventilated helmet becomes less conducive to the rider as compared to non-ventilated helmet. Front Impact absorption test on three ventilated helmets and one non-ventilated helmet were then performed with an initial impact velocity of 7.5 m/s. Maximum head acceleration in the direction of impact is recorded to be 212.3, 205.1 and 198.1 g for three ventilated helmets and 219.2 g for non-ventilated helmet. Head injury criterion (HIC36) is also calculated and it is found to be 1391.2, 1078.9 and 1034.4 for ventilated helmets and 1343.4 for non-ventilated helmet. Results indicate that ventilated helmet satisfies the Bureau of Indian Standard 4151 safety criterion and are safe to wear.