ISSUES ARISING FROM THE USE OF CHILLED BEAMS IN ENERGY MODELS
Fred Betz, James McNeill, Bill Talbert, Harshana Thimmanna, Norbert Repka
Chilled beam technology has seen increasing deployment throughout the United States during the past few years as designers seek the means to address larger sensible cooling demands without increasing duct sizes. While passive and active chilled beams work by basic principles well understood by engineers, their deployment in energy modeling software is often problematic or even erroneous. Active chilled beams have been the most commonly discussed type in the modeling community and our design experience has found these to be the most commonly applied as well. Active chilled beam model workarounds exist for the most commonly used simulation tools for the active chilled beams and tend to be based around induction units. Our experience has been that the magnitude of the simulated energy use results can seem reasonable, so many modelers stop there, though detailed review of hourly reports suggests that the various system components often aren’t acting as the system is intended to operate. The perception of appropriate savings is just that, a perception, albeit misguided. This paper focuses on the differences of the design of actual chilled beam systems versus how they are modeled in eQuest, EnergyPlus, IES-VE, Trane TRACE, and TRNSYS rather than on the results of each software.
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