Ceiling fan air speeds around desks and office partitions

Abstract

Ceiling fans may cool room occupants very efficiently, but the air speeds experienced in the occupied zone are inherently non-uniform. Designers should be aware of several generic flow patterns when positioning ceiling fans in a room. Key to these are the fan jet itself and lateral spreading near the floor. Adding workstation furniture redirects the jet's airflow laterally in a deeper spreading zone, making room air flows more complex but potentially increasing the cooling experienced by the occupants. This paper presents the first evaluation of the effects of tables and workstation partitions on a room's generic air flow and comfort profiles. In a test room with a ceiling fan, we moved five anemometers mounted in a "tree" at heights of 0.1, 0.6, 0.75, 1.1, and 1.7 m to sample a dense measurement grid of 7 rows and 6 columns. We tested five different table and partition configurations and compared them to the empty room base case. From the results we propose a simplified model of room airflow under ceiling fans, useful for positioning fans and workstation furniture. We also present comfort contours measured in two ways that have comfort standards implications. The measured data are publicly available on the internet. Keywords: Ceiling fan; air speed; furniture; comfort cooling; corrective power Highlights 1. We performed high resolution measurements of ceiling-fan-induced air flow in an empty room; 2. We compare this reference case to air flow profiles measured in the room with five different table and partition configurations. The data are included as publicly available supplementary material; 4. The initial ceiling fan flow in the room could be modeled as a free jet; 5. The subsequent room circulation, with and without tables and partitions, may be represented by an intuitive model for designers who are placing fans and furniture; 6. The extent of comfort cooling provided by the fan air flow can be represented by the metric 'corrective power'. Corrective power equates the cooling effect of the fan as an ambient temperature reduction, ºC. We present the corrective power distribution in the room in two ways--with and without the air speed at ankle level--to evaluate air speed cooling effect. This evaluation is significant for thermal comfort standards.

Ceiling fans: Predicting indoor air speeds based on full scale laboratory measurements

“…al. [27] showed that when the fan jet impinges directly on furniture, it widens the higher air speed region beyond the fan diameter, however, the majority of the room still has lower air speeds. This difference between higher air speeds in one location than in others may be problematic where there are multiple occupants who cannot freely or easily move about the room, with some too cool and some too warm depending on where they happen to be located.…”

“…We reviewed previous investigations on air speed distribution induced by a ceiling fan, focusing on the factors which affect that distribution. These factors include fan rotational speed [8,[30][31][32][33], blade shape and number [31,32,34,35], direction (upward or downward) [30,[36][37][38], mount distance [32,36], ceiling height [32], multiple fans [26,33], and furniture [26,27].…”

“…Further experiments could validate this and develop regressions to adjust the models if needed. Finally, it is important to note that [27] shows that furniture strongly affects the air speed distribution. Furniture layout isn't typically known at design stage and in any case changes often within the building lifetime.…”

Experimental and numerical investigations of indoor air movement distribution with an office ceiling fan

“…First, detailed laboratory measurements of occupied zone air speeds, with and without furniture, have been taken under a single ceiling fan. The detailed measurements profiles are described [13].…”

“…Simulations in this study are based on a previous experimental study of an office room conducted at the Center for the Built Environment (CBE) at University of California, Berkeley [13]. The room had geometries of 5.5 (X) × 5.5 (Z) × 2.5 (Y) m, as shown in Fig.…”