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.
Highlights1. Design and control of a radiant system depend on its thermal response time 2. State space and thermal resistance models are used to calculate response time 3. Response time can vary between a few minutes (RCP) up to 20 hours (TABS) 4. Concrete thickness, pipe spacing, and concrete properties impact response time 5. A classification scheme for radiant systems based on response time is proposed
AbstractRadiant system design and control standards and guidebooks currently classify radiant systems as a function of their structure and geometry. We assume that design solutions, testing methods, and control strategies of radiant systems can be more clearly described and classified based on their thermal parameters. In this study, we use the thermal response time to evaluate the dynamic thermal performance of radiant systems. We defined the response time (τ95) as the time it takes for the surface temperature of a radiant system to reach 95% of the difference between final and initial values when a step change in control of the system is applied as input. The state space and thermal resistance models are used to calculate the response time for different radiant system types with a variety of configurations and boundary conditions. We performed 56,874 simulations. Concrete thickness, pipe spacing, and concrete properties have significant impact on the response time of thermally activated building systems, while pipe diameter, room operative temperature, water temperature and water flow regime do not. We find τ95 < 10 min for radiant ceiling panels; 1 < τ95 < 9 h for embedded surface systems; 9 < τ95 < 19 h for thermally activated building systems. A preliminary radiant system classification scheme based on thermal response time is proposed.
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