Showing papers in "Ashrae Journal in 2010"

Radiant Slab Cooling for Retail

Abstract: Most large retail spaces are ventilated, cooled, and heated by all-air systems via constant air volume (CAV) packaged rooftop units (RTUs). CAV RTUs are low first cost, easy to install, and straightforward to maintain. However, designers have begun to decouple ventilation from occupant comfort conditioning. One strategy pairs a dedicated outdoor air system (DOAS) for ventilation and dehumidification with a radiant floor system for sensible cooling.

Cooling load design tool for UFAD

Abstract: Almost all energy and load calculation methods in widespread use by the industry today are not able to represent (without the use of workarounds) two distinguishing aspects of the thermal performance of UFAD systems under cooling operation: • Room air stratification: cool supply air delivered by floor diffusers interacts with space heat loads to produce higher temperatures at ceiling level and cooler temperatures near the floor. Most models assume a well-mixed uniform space temperature. • Underfloor air supply plenums: as the cool supply air from the air handler flows through the plenum, heat is transferred from both the concrete slab (in a multistory building) and the raised floor panels to the plenum air, resulting in most cases in temperature gain (thermal decay). Most models simply ignore heat gain to supply air in both plenums and ducts. Recently, the situation has been improved with the release in April 2009 of version 3.1 and all subsequent versions of EnergyPlus,1 a publicly available whole building energy simulation program capable of modeling the more complex heat transfer processes, like those found in UFAD systems. While EnergyPlus is certainly capable of being used to make load calculations, from a practical point of view it is important to develop a simplified load calculation procedure for designers. Previously a spreadsheet-based cooling airflow design tool for interior zones was described by Bauman, et al.2 In this article, we present an updated and more complete version of the simplified tool. The design tool and detailed user notes are available at: www.cbe.berkeley.edu/research/ ufad_designtool-download.htm.

HVAC for prisons

Abstract: Various considerations towards the design, construction, and operation of correctional facilities such as jails and prisons in the US, are presented. Security level of the facility or the area of the facility that vary as per minimum, medium, and maximum security, include suicide-resistant grilles and barrier grilles/bars specified in all ductwork penetrating the secure perimeter walls. For life safety, the air-handling unit serving the dayrooms and cells should provide makeup air to the area in a smoke purge event by ramping up via a variable frequency drive (VFD). Selection of a good security system is based on considerations such as costs and an efficient operators for system maintenance long after the project's completion. Water conservation in these correctional facilities is made possible through cogeneration, massive solar arrays, and photovoltaics.

Cleanroom Energy Efficiency: Metrics and Benchmarks

Abstract: Cleanrooms are among the most energy-intensive types of facilities. This is primarily due to the cleanliness requirements that result in high airflow rates and system static pressures, as well as process requirements that result in high cooling loads. Various studies have shown that there is a wide range of cleanroom energy efficiencies and that facility managers may not be aware of how energy efficient their cleanroom facility can be relative to other cleanroom facilities with the same cleanliness requirements. Metrics and benchmarks are an effective way to compare one facility to another and to track the performance of a given facility over time. This article presents the key metrics and benchmarks that facility managers can use to assess, track, and manage their cleanroom energy efficiency or to set energy efficiency targets for new construction. These include system-level metrics such as air change rates, air handling W/cfm, and filter pressure drops. Operational data are presented from over 20 different cleanrooms that were benchmarked with these metrics and that are part of the cleanroom benchmark dataset maintained by Lawrence Berkeley National Laboratory (LBNL). Overall production efficiency metrics for cleanrooms in 28 semiconductor manufacturing facilities in the United States and recorded in themore » Fabs21 database are also presented.« less