Model validation and parametric study on a personal heating clothing system (PHCS) to help occupants attain thermal comfort in unheated buildings

Personal heating clothing systems (PHCS) incorporated with electrical heating elements have shown its great potential to help occupants attain thermal comfort in cold built environments. Presently there is a lack of a comprehensive study to optimize the PHCS's performance. In this work, a newly developed complete 3D model was used to systematically examine the factors affecting the PHCS's heating performance in various cold unheated built environments. Effects of ambient temperature, clothing insulation, heating power, heating mode and metabolic rate on the PHCS's performance were investigated by performing a numerical parametric study. Validation data have demonstrated that the 3D model could precisely predict human thermophysiological responses while wearing PHCS in the built environment. At 15.0 °C indoor temperature and metabolic rate of 1.6 met, wearing a PHCS with thermal insulation of 1.0 clo and heating power of 20 W could help occupants attain thermal comfort. It was also found that compared with continuous heating, intermittent heating at a high heating frequency could contribute to saving energy without compromise of body temperature reduction. Furthermore, metabolic rate has a significant impact on thermophysiological responses and the mean heaters' temperature. Hence, the selection and operation of a PHCS should be based on the nature of occupant activities. Occupants are advised to adjust the heating power to a lower level when performing more demanding activities because the need for auxiliary heating is not as high as that in the case when occupants are resting or performing seated office activities.