Ice slurry ingestion for enhanced occupant thermal comfort in warm/hot indoor environments: A comparative study with an energy-efficient desk fan

Ice slurry ingestion has been widely used as an effective pre-exercise cooling strategy for athletes to improve exercise performance while competing in the heat. Nonetheless, its potential to improve thermal comfort for office workers in various indoor environments has received little attention. In this study, two representative external and internal body cooling modalities, ice slurry ingestion (ICE) and desk fan (FAN), were used under free control in three warm/hot environments (30, 32, and 34 °C, RH = 50%). Throughout the heat exposure, the subjects' physiological responses (heart rate and local skin temperatures) were recorded, as well as their overall and local thermal perceptions. The subjects' usage behavior was recorded, including the fanning speed level and ice slurry ingestion rate. The results show that, when compared to the FAN condition, ICE resulted in significantly lower thermal sensation (decreased by 0.93 rating scale, p < 0.01) and sweat rate (38.3 ± 34.6 g/h, p < 0.01), as well as higher thermal comfort (increased by 1.17 rating scales, p < 0.05) at 34 °C. The total amount of ice slurry ingested by the subjects increased significantly with increasing air temperature, from 107.5 ± 64.1 g/h to 249.2 ± 84.1 g/h (p < 0.001). This study demonstrates the pronounced efficacy of ice slurry ingestion to sustain young female occupant thermal comfort at 30–34 °C indoor temperatures. Further research is still necessary to investigate the efficacy of ice slurry ingestion in higher indoor temperatures during extreme heatwaves, however.