Helmets cooling with phase change materials: A systematic review

Helmets are safety tools that are worn by motorcycle drivers, athletes and industrial workers to protect head against impacts. However, the helmets have a big thermal issue as they cause heat discomfort during wearing. An effective solution to enhance helmets cooling is the utilization of phase change materials (PCMs). Generally, the PCMs absorb and store thermal energy generated from the wearer's head, thereby facilitating cooling within the helmet. The current paper systematically reviews the use of PCMs in helmets for cooling purposes, regarding designs, materials, thermal performance, affecting factors, and integrated systems. The review concludes that the PCM has the ability to maintain comfort temperature as long as it is not fully melted. The performance of PCMs is significantly influenced by helmet design, PCM mass, and environmental factors. To further enhance the cooling effect, PCMs can be combined with active systems or nano-particles. Additionally, this paper identifies several opportunities when using helmet-PCM, including raising helmet wearability, improving helmet design standards, and increasing light absorptivity. Furthermore, the review highlights various limitations associated with helmetsPCMs, such as scarcity of eutectic PCMs use, unwanted ventilation in hot climates, non-preferring use of fan at minimal sweating, moisture condensation on the PCM surface, the complexity of predicting PCM cooling effects, and restrictions of numerical studies in simulating physiological behaviors. This paper also discusses potential future directions, including the use of solid-solid PCMs, investigation of optimal PCM quantities, use of phase change humidity control materials, and ergonomic assessment.