Time length of adaptation phase for subjective thermal environment evaluation based on thermal stability time

Abstract

The adaptation phase is the primary process of subjective thermal comfort evaluations. The time length of the adaptation phase in existing studies disperses largely, which either risks low evaluation reliability or high time and economic costs. This study proposes to determine the time length of the adaptation phase for reliable subjective thermal environment evaluation and to avoid unnecessarily large time and economic costs. First, the variation and distribution of the initial thermal status of the adaptation phase are inferred from a steady bioheat model with ASHRAE (American Society of Heating, Refrigerating and Air-conditioning Engineers) Thermal Comfort Database II. Second, with the initial thermal status, the variation and distribution of the thermal stability time are inferred from the dynamic bioheat model. Third, the time length of the adaptation phase is quantified from the distribution of the thermal stability time according to the targeted reliability level. Results show that under the summer scenario, the time length of the adaptation phase increases from 16.9 – 31.2 min to 25.2 – 38.9 min when the reliability level increases from 90.0 % to 97.5 %. The time length of the adaptation phase of the winter scenario increases by 5.3 – 9.7 min relative to that of the summer scenario. A strategy of shifting the adaptation phase from thermal neutrality to slight warmth is proposed to effectively shorten the time length of the adaptation phase by 5.6 % – 19.4 % and 7.8 % – 23.9 % in the summer and winter scenarios respectively. These results are tabulated for practical convenience.