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A chilled beam is a type of convection HVAC system designed to heat or cool large buildings.〔Oughton, Hodkinson, and Faber, 2008, p. 222-224.〕 Pipes of water are passed through a "beam" (a heat exchanger) either integrated into standard suspended ceiling systems〔Price, 2011, ''Engineer's HVAC Handbook'', p. 1067, ISBN 978-0-9868802-0-9〕〔''2012 ASHRAE Handbook HVAC Systems and Equipment'', ASHRAE, 2012, p. 20.9, ISBN 978-1-936504-25-1〕 or suspended a short distance from the ceiling of a room.〔Beggs, 2009, p. 271.〕 As the beam chills the air around it, the air becomes denser and falls to the floor. It is replaced by warmer air moving up from below, causing a constant flow of convection and cooling the room.〔Hamilton and Watkins, 2009, p. 158.〕〔Levermore, 2000, p. 407.〕 Heating works in much the same fashion, similar to a steam radiator. There are two types of chilled beams. Some passive types rely solely on convection whilst there is a "Radiant"/convective passive type which cools through a combination of radiant exchange (40%) and convection (60%) which can provide higher thermal comfort levels,〔http://www.cibsejournal.com/cpd/2014-06/〕 while the active type (also called an "induction diffuser")〔 uses the momentum of ventilation air entering at relatively high velocity to "induce" circulation of room air through the unit (thus increasing its heating and cooling capacity).〔 The chilled beam is distinguishable from the chilled ceiling.〔〔Roth, Kurt; Dieckmann, John; Zogg, Robert; and Brodrick, James. "Chilled Beam Cooling." ''ASHRAE Journal.'' September 2007.〕 The chilled ceiling uses water flowing through pipes like a chilled beam does; however, the pipes in a chilled ceiling lie behind metal ceiling plates, and the heated or cooled plates are the cause of convection and not the pipe unit itself.〔 Chilled beams are about 85 percent more effective at convection than chilled ceilings.〔 The chilled ceiling must cover a relatively large ceiling area because it provides heating and cooling mainly by radiant, rather than convective, heat transfer. ==Physics== Water can carry significantly more energy than air. Although of air has a capacity to hold heat of 37 joules per kelvin (JK−1), the same volume of water has a heat capacity of 20,050 JK−1.〔(Geary, 2010, p. 9. )〕 A metal pipe of water just in diameter can carry as much energy as an metal duct of air.〔 This means that chilled beam HVAC systems require much less energy to provide the same heating and cooling effect as a traditional air HVAC system. Chilled beam cooling systems require water to be treated by heating and cooling systems. Generally, water in a passive chilled beam system is cooled to about .〔Hare and Fisher, 2000, p. 246.〕〔Sisle, Leonard, and Weiss, 2010, p. 152.〕 In active chilled beam heating systems, water temperature is usually .〔Oughton, Hodkinson, and Faber, 2008, p. 223.〕 (Chilled beam heating systems usually cannot rely solely on convection, however, and often require a fan-driven primary air circulation system to force the warmer air to the ground where most people sit and work.)〔 There are effectiveness and cost differences between the two systems. Passive chilled beam systems can supply about 5.6 to 6.5 watts per foot (60 to 70 watts per metre) of cooling capacity.〔 Active chilled beam systems are about twice as effective.〔 In both cases, convection is so efficient that the ratio of incoming air to heated/cooled air can be as high as 6:1.〔Alexander, Darren and O'Rourke, Mike. "Design Considerations For Active Chilled Beams." ''ASHRAE Journal.'' September 1, 2008.〕 However, studies of the energy cost-savings of active versus passive chilled beam systems remained inconclusive as of 2007, and appear to be highly dependent on the specific building.〔 The active chilled beam system employs fins to help heat and cool.〔 Active chilled beam systems are effective to the point where outdoor air can be mixed with the indoor air without any traditional air conditioning (such as heating, cooling, humidifying, or dehumidifying), thus enabling a building to meet its "minimum outdoor air" air quality requirement.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Chilled beam」の詳細全文を読む スポンサード リンク
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