Demand and efficiency evaluations of local convective heating to human feet and low body parts in cold environments

Abstract

A good practice of the personal comfort system is to extend acceptable comfort zones and achieve energy savings in buildings; while quite few studies look into the use of local heating in winter. This study was designed to understand the demands of the local heating and the appropriate devices in the Hot Summer and Cold Winter (HSCW) region of China. This was achieved by combining online survey and two series of experiments in a climate chamber. Results from survey revealed that various heating devices were employed by occupants in buildings; the feet and lower body parts were the most preferred parts to be heated in winter. A local heating device was designed to supply warm air to subjects' feet and calves directly. In Experiment I with ambient temperatures of 16 °C and 18 °C, no remarkable improvements were found by local heating, due to higher clothing insulation (1.3clo) and a neutral thermal sensation of subjects. When decreasing to 14 °C and 12 °C in Experiment II, subjects’ thermal sensation for both feet and overall were increased significantly when local heating was supplied. The high heating efficiency was suggested with decreasing ambient temperature under 16 °C and increasing supply air temperature to 30 °C-40 °C. The findings provide a support to design local heating devices and manage personal comfort for occupants. The outcomes are expected to relieve demands on winter heating in the HSCW region and trade off the building energy quota target for China.