Comparing the improvement of occupant thermal comfort with local heating devices in cold environments

Local heating can improve the thermal comfort of occupants and save energy in buildings in cold environments; however, few studies have investigated the effects of heat-transfer modes. Here, we aimed to evaluate different local heating measurements including five-sided enclosed radiant panel, heating plate, and fan heater using climate chamber experiments with 20 participants in cold environments (14 degrees C). Skin temperature and thermal perception votes under two radiation types with low and high power, one condition of conduction, and one condition of convection were collected and analyzed (RL, RH, CD, and CV). Under conditions RH, CD, and CV, the investigated parameters significantly improved by three local heating devices, with foot skin temperature rising by 0.46 degrees C, foot thermal sensation rising by 1.25 scores, and overall thermal comfort increasing by 0.36 score; however, their energy consumption varied greatly. In contrast, no significant improvement was observed in the RL group. Additionally, direct application of heat at sites of palpable cold discomfort was not always the optimal approach, and heating other parts of the body may provide significant alleviation. We recommend that the surface temperature of local heaters based on conduction and radiation for heat transfer should not be lower than 40.38 degrees C and 52.15 degrees C, respectively. To maintain thermal comfort, air outlet temperature should not be lower than 34.56 degrees C for convection type heaters. Our results provide technical and experimental basis for designing energy-saving buildings.