Ceiling-fan-integrated air conditioning: Airflow and temperature characteristics of a sidewall-supply jet interacting with a ceiling fan

Ceiling-Fan-Integrated Air Conditioning (CFIAC) is a proposed system that can greatly increase buildings’ cooling efficiency. In it, terminal supply ducts and diffusers are replaced by vents/nozzles, jetting supply air toward ceiling fans that serve to mix and distribute it within the room. Because of the fans’ air movement, the system provides comfort at higher room temperatures than in conventional commercial/ institutional/retail HVAC. We have experimentally evaluated CFIAC in a test room. This paper covers the distributions of air-speed, temperature, and calculated comfort level throughout the room. Two subsequent papers report tests of human subject comfort and ventilation effectiveness in the same experimental conditions. The room’s supply air emerged from a high-sidewall vent directed toward a ceiling fan on the jet centerline; we also tested this same jet on a fan located off to the side of the jet. Primary variables are: ceiling fan flow volumes in downward and upward directions, supply air volume, and room-vs-supply temperature difference. Velocity, turbulence, and temperature distributions are presented for vertical and horizontal transects of the room. The occupied zone is then evaluated for velocity and temperature non-uniformity, and for comfort as predicted by the ASHRAE Standard 55 elevated air speed method. We show that temperatures are well-mixed and uniform across the room for all of the fan-on configurations, for fans both within or out of the supply jet centerline. The ceiling fan flow dominates the CFIAC airflow, and even though non-uniform is capable of providing comfortable conditions throughout the occupied area of the room

LSST: from Science Drivers to Reference Design and Anticipated Data Products

(Abridged) We describe here the most ambitious survey currently planned in the optical, the Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST will have unique survey capability in the faint time domain. The LSST design is driven by four main science themes: probing dark energy and dark matter, taking an inventory of the Solar System, exploring the transient optical sky, and mapping the Milky Way. LSST will be a wide-field ground-based system sited at Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m effective) primary mirror, a 9.6 deg$^2$ field of view, and a 3.2 Gigapixel camera. The standard observing sequence will consist of pairs of 15-second exposures in a given field, with two such visits in each pointing in a given night. With these repeats, the LSST system is capable of imaging about 10,000 square degrees of sky in a single filter in three nights. The typical 5$\sigma$ point-source depth in a single visit in $r$ will be $\sim 24.5$ (AB). The project is in the construction phase and will begin regular survey operations by 2022. The survey area will be contained within 30,000 deg$^2$ with $\delta<+34.5^\circ$, and will be imaged multiple times in six bands, $ugrizy$, covering the wavelength range 320--1050 nm. About 90\% of the observing time will be devoted to a deep-wide-fast survey mode which will uniformly observe a 18,000 deg$^2$ region about 800 times (summed over all six bands) during the anticipated 10 years of operations, and yield a coadded map to $r\sim27.5$. The remaining 10\% of the observing time will be allocated to projects such as a Very Deep and Fast time domain survey. The goal is to make LSST data products, including a relational database of about 32 trillion observations of 40 billion objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures available from https://www.lsst.org/overvie

Giving Occupants What They Want: Guidelines for Implementing Personal Environmental Control in Your Building

By giving people individual control over the environmental conditions in their workplaces, designers and facility managers can help increase worker satisfaction and productivity. Task/ambient conditioning (TAC) systems allow occupants to control temperature, air flow, and in some cases lighting and sound to meet their individual needs. This technology has recently been gaining a foothold in the U.S. It is often implemented in conjunction with underfloor air distribution, which opens up opportunities for a number of efficiencies in building design and operation. In addition to improving worker satisfaction and productivity, this combined approach has the potential to improve thermal comfort and indoor air quality, reduce energy use and life-cycle building costs, and reduce floor-to-floor height in new construction. Guidelines and recommendations are presented based on recent field and laboratory research results that encourage the intelligent design, installation and operation of TAC systems using underfloor air distribution

Hype Vs. Reality: New Research Findings on Underfloor Air Distribution Systems

this paper is to describe each of these benefits briefly, discuss what is required to take advantage of these potential benefits, and note what is commonly observed in current practic

A Classification Scheme for Radiant Systems based on Thermal TimeConstant

Radiant system design standards and guidebooks classify radiant systems as a function of their structure and geometry. We assume that design approaches, testing methods, and control strategies of radiant systems can be more clearly described and classified based on thermal parameters. We calculated using computational fluid dynamics method the thermal time con-stants for 66 radiant system cases. We found pipe spacing, thickness and material properties of structural layer have a significant impact on time constant, while operative temperature, water temperature and water flow regime do not. We found time constants of radiant ceiling panels vary between 30-91 s; for embedded surface systems between 0.25-3.5 h; for thermally activated building systems with pipes embedded in the massive concrete slabs, between 2.4-7.7 h; and for capillary pipes embedded in a layer at the inner surface, between 0.1-0.6 h. A preliminary radiant system classification scheme based on thermal time constant is proposed

A novel classification scheme for design and control of radiant system based on thermal response time

Radiant 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 (τ 95) 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&nbsp;τ 95&nbsp;&lt;&nbsp;10&nbsp;min for radiant ceiling panels; 1&nbsp;&lt;&nbsp;τ 95&nbsp;&lt;&nbsp;9&nbsp;h for embedded surface systems; 9&nbsp;&lt;&nbsp;τ 95&nbsp;&lt;&nbsp;19&nbsp;h for thermally activated building systems. A preliminary radiant system classification scheme based on thermal response time is proposed

A novel classification scheme for design and control of radiant system based on thermal response time

Radiant 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 (τ 95) 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&nbsp;τ 95&nbsp;&lt;&nbsp;10&nbsp;min for radiant ceiling panels; 1&nbsp;&lt;&nbsp;τ 95&nbsp;&lt;&nbsp;9&nbsp;h for embedded surface systems; 9&nbsp;&lt;&nbsp;τ 95&nbsp;&lt;&nbsp;19&nbsp;h for thermally activated building systems. A preliminary radiant system classification scheme based on thermal response time is proposed

Design guidelines for stratification in underfloor air distribution (UFAD) systems

The control of room-air stratification is critical to the design and operation of successful underfloor-air-distribution (UFAD) systems, representing an oftentimes complex balancing act: Increasing stratification by reducing airflow or mixing for a given space heat load saves energy, while decreasing stratification by boosting airflow or mixing for a given space heat load improves occupant comfort.The Center for the Built Environment (CBE) has conducted full-scale laboratory experiments to study the impact of stratification in interior and perimeter office spaces. Because the findings cover topics that are of considerable interest to the industry at this time, the following interim guidelines are offered. Each of the topics outlined in this article require more research for specific guidelines to be offered. For a more complete overview of UFAD design requirements, see “Underfloor Air Distribution (UFAD) Design Guide” and the Underfloor Air Technology Web site (www.cbe.berkeley.edu/underfloorair)

A Classification Scheme for Radiant Systems based on Thermal TimeConstant

Radiant system design standards and guidebooks classify radiant systems as a function of their structure and geometry. We assume that design approaches, testing methods, and control strategies of radiant systems can be more clearly described and classified based on thermal parameters. We calculated using computational fluid dynamics method the thermal time con-stants for 66 radiant system cases. We found pipe spacing, thickness and material properties of structural layer have a significant impact on time constant, while operative temperature, water temperature and water flow regime do not. We found time constants of radiant ceiling panels vary between 30-91 s; for embedded surface systems between 0.25-3.5 h; for thermally activated building systems with pipes embedded in the massive concrete slabs, between 2.4-7.7 h; and for capillary pipes embedded in a layer at the inner surface, between 0.1-0.6 h. A preliminary radiant system classification scheme based on thermal time constant is proposed

Task/ambient conditioning systems: Engineering and application guidelines

During recent years an increasing amount of attention has been paid to air distribution systems that individually condition the immediate environments of office workers within their workstations. As with task/ambient lighting systems, the controls for the “task” components of these systems are partially or entirely decentralized and under the control of the occupants. Typically, the occupant has control over the speed and direction, and in some cases the temperature, of the incoming air supply. Variously called “task/ambient conditioning,” “localized thermal distribution,” and “personalized air conditioning” systems, these systems have been most commonly installed in open-plan office buildings in which they provide supply air and (in some cases) radiant heating directly into workstations. A large majority of these systems have included a raised access floor system through which underfloor air distribution is used to deliver conditioned air to the space through floor grills, or in conjunction with the workstation furniture and partitions.The purpose of this document is to present and discuss engineering and application guidelines and recommendations that encourage the intelligent design, installation, and operation of task/ambient conditioning (TAC) systems in commercial buildings. A well designed TAC system should take maximum advantage of the potential improvements in thermal comfort, ventilation performance, indoor air quality, and occupant satisfaction and productivity, while minimizing energy use and costs. The development of these guidelines is based on a compilation of available information, including (1) TAC system design experience described in the literature, (2) laboratory experiments on several TAC systems, (3) field studies of TAC systems installed and operated in buildings, (4) computer simulations of whole-building energy use with and without TAC systems, (5) a survey of heating, ventilating, and air-conditioning (HVAC) engineers and manufacturers about TAC systems, and (6) the results of the Workshop on Task/Ambient Conditioning Systems in Commercial Buildings, May 4-5, 1995, held in San Francisco, California [Bauman 1995]. Since experience with TAC systems is still rather limited, the recommendations and guidelines contained in this guide represent our best estimates at this time of sound engineering judgment. As more information and experience becomes available, we expect to periodically revise and improve this document. The guide is intended for use by design engineers, architects, building owners, facility managers, equipment manufacturers and installers, utility engineers, researchers, and other users of TAC technology