Methodology to Evaluate the Room ADPI through CFD Simulation

Abstract

Computational fluid dynamics (CFD) is a powerful tool to predict the thermally comfortable environment for occupants living in indoor spaces. There are several parameters like a predicted mean vote (PMV), percentage of people dissatisfied (PPD), air diffusion performance index (ADPI), draft rating (DR) etc. used to predict thermal comfort. This paper focuses on the methodology for evaluating the room ADPI through CFD analysis. ADPI is a single-number rating of the room air diffusion performance of a system of diffusers for a specified supply airflow rate and thermal load. As per ASHRAE standard, ADPI is based only on air speed and effective draft temperature (EDT) at the measuring locations. The experimental procedure for evaluating ADPI is limited to a few measuring locations in the room that may be misleading to evaluate the overall thermal comfort level in the room. Whereas, from the CFD simulation one can get the data at every location in the room, so ADPI can be evaluated based on every location in the room. In the current study, two methodologies are compared to evaluate ADPI of the room. In the first approach, the measuring locations are at selected points as per the experimental procedure and in the second approach, the measuring locations are at every cell point in the occupied zone of the room. The methodology results are correlated with other thermal comfort criteria such as PMV and PPD. Both methodologies are evaluated in the test case of a typical private office room with occupants seated around the table. The results show that evaluating the ADPI by taking all measuring locations in the occupied zone gives a better prediction than the selected few locations as per ASHRAE standard. After performing a detailed comparison study, the limitations and advantages of both methodologies are presented in the paper.