Experimental study of thermal comfort in a field environment chamber with stratum ventilation system in winter

Stratum ventilation has potentials to be used for winter heating. Both local and overall thermal perceptions are essential for ensuring indoor satisfactory thermal environments. This study aimed to comprehensively investigate the subjective perceptions in a field environment chamber heated by stratum ventilation. The chamber was configured as a two-row classroom. Eleven cases were conducted with supply air velocities of 0.8-1.4 m/s and supply air temperatures of 23-30 degrees C. With room air temperatures of approximately 20-24 degrees C, thirty-six subjects were recruited to evaluate the thermal environments. The questionnaires concerned overall thermal sensation and comfort (OTS and OTC), local thermal sensation and comfort (LTS and LTC), draft sensation, and humidity sensation. The results showed that the OTS conformed to Category C in ISO 7730. The overall discomfort was related to the OTS cooler than thermal neutrality. The LTSs of body segments fluctuated within the range of -0.7 - 0.7. Among the body segments, the head had the most significant influence on OTC, and followed by the feet. The percentage of dissatisfied due to discomfort of warm head and/or cold feet (PD) might exceed 10%, which was mainly resulted from the discomfort risk of cold feet. The relationship between PD and LTS of the feet indicated that with LTS of the feet higher than -0.5, the PD could be below 10%. With stratum ventilation for winter heating, the air movement was acceptable with draft rate less than 20%. However, the humidity environment remained to be improved by additional measures.