Evaluation of Phase Change Materials for Personal Cooling Applications

Eleven phase change materials (PCMs) for cooling humans in heat-stressed conditions were evaluated for their cooling characteristics. Effects of packaging material and segmentation were also investigated. Sample packs with a different type PCM (water- and oil-based PCMs, cooling gels, inorganic salts) or different packaging (aluminum, TPU, TPU + neoprene) were investigated on a hotplate. Cooling capacity, duration, and power were determined. Secondly, a PCM pack with hexagon compartments was compared to an unsegmented version with similar content. Cooling power decreased whereas cooling duration increased with increasing melting temperature. The water-based PCMs showed a >2x higher cooling power than other PCMs, but were relatively short-lived. The flexible gels and salts did not demonstrate a phase change plateau in cooling power, compromising their cooling potential. Using a TPU or aluminum packaging was indifferent. Adding neoprene considerably extended cooling duration, while decreasing power. Segmentation has practical benefits, but substantially lowered contact area and therefore cooling power.

A novel personal ventilation strategy to circumvent aerosol transmission

In the pandemic of COVID-19, a rigorous lockdown or social distancing will mitigate transmission, but some alternative strategy is needed especially for mass-gathering events. Given that the main path of transmission is through droplets or aerosols, a swift removal of them immediately after exhalation, which may attain “personal air zoning”, would be more effective and feasible than whole room ventilations. In the present study, an artificial fog was employed as a model aerosol to be exhaled and readily visualized on movies and quantified on dust indicators. The temporal and spatial distribution of this model microdroplet amounts corresponded reasonably well with previously published data, where talking air flow was quantified as a negative staining, in that it predominates below the mouth height rather than horizontal, and that it travels forward over 1.5 m in 30 sec. Under this model condition, nearly 99% of exhaled microdroplets could be efficiently blown up beyond the bystanders’ head heights, when a minimal air flow (2.5 m/s) was applied, using a typical personal cooling fan just below the chin. This swift upward removal of microdroplets would prevent bystanders’ immediate inhalation and provide sufficient probation periods for safe exhaustion from indoor spaces.

Cooling Interventions Among Agricultural Workers: Qualitative Field-Based Study

Introduction: Agricultural workers perform intense labor outside in direct sunlight and in humid environmental conditions exposing them to a high risk of heat-related illness (HRI). To implement effective cooling interventions in occupational settings, it is important to consider workers’ perceptions. To date, an analysis of agricultural workers’ experience and perception of cooling devices used in the field while working has not been published. Methods: Qualitatively data from 61 agricultural workers provided details of their perceptions and experiences with cooling interventions. Results: The participants in the bandana group reported the bandana was practical to use at work and did not interfere with their work routine. Cooling vest group participants agreed that the vest was effective at cooling them, but the practicality of using the vest at work was met with mixed reviews. Conclusion: The findings of this qualitative study support and extend existing research regarding personal cooling and heat prevention research interventions with vulnerable occupational groups. Personal cooling gear was well received and utilized by the agricultural workers. Sustainable heat prevention studies and governmental protection strategies for occupational heat stress are urgently needed to reduce the risk of heat-related morbidity, mortality, and projected climate change health impacts on outdoor workers.

Methods for personal cooling in hot environment used in clothing and wearables

The use of an efficient personal cooling system in hot environments is becoming increasingly popular, as the increased air temperature provokes thermophysiological discomfort, heat stress, reduced productivity and could lead to several health issues. Different methods and devices for personal and local cooling have been developed over the years. The paper summarises the cooling methods applied in clothing and wearable items: phase-change materials, Peltier elements, evaporative cooling, water cooling and hybrid cooling. The local vs total (of the whole body) cooling is examined. The passive and active colling are analysed in terms of advantages, disadvantages and application.