Improvements of stratified micro-environments on the satisfaction of individual thermal preferences and energy-efficiency

Abstract

Stratified micro-environments (SME) aim to simultaneously provide various thermal comfort levels in a shared space to satisfy individual needs at different positions. The first objective of this study is to find out the quantitative improvements made by applying the SME against stratum ventilation (SV), mixing ventilation (MV), and displacement ventilation (DV). Thermal comfort indices, including predicted mean vote (PMV) and draft rate (DR), are used to quantify individual preferences. The PMV1 and PMV2 represent overall thermal sensation levels at Positions 1 and 2, set in a simulated small office, respectively. The DRs are named in the same rule. Results show that the |PMV1- PMV2| value under SV, MV, and DV only reaches 24.7%, 4.4%, and 4.6% of that under the SME on average, and the |DR1-DR2| value reaches 24.9%, 10.6%, and 7.0%. Later, the PMV prediction model for non-free-jet conditions is developed by multiple linear regression method. With practical constraints attached, the scope for the SME operation is identified. The maximum |PMV1- PMV2| value is 1.8; for DR, it is 24.9%. Only 9.9% of the PMV combinations and 3.8% of the DR combinations under the SME can be satisfied by total volume ventilation (TVV). Lastly, a normal distribution of PMV preference of [-0.5, 0.5] consisting of 40 individuals is utilized as a case study. Over 85% preferences are better satisfied by the SME than TVV, accompanied by an energy-saving rate of 55%-95% than MV.