ASHRAE Journal - December 2009 - 35

The design team performed cooling and heating load calcula- 65°F (15.6°C to 18.3°C). As in the case of any chilled surface in tions for the proposed facility. All of the relevant building and an occupied space, the design must ensure that the surface temoccupant characteristics were collected, and a standard computer perature exposed to occupied conditions not be allowed to drop modeling program was used to determine loads. When this de- below the space dew-point temperature to avoid condensation. This appears simple when studying the design point on a sign was executed in early 2006, there was no proven computer model for UFAD system load calculations, and certainly none psychrometric chart. The design point for occupied spaces at the that would have accommodated chilled beams. Using sound en- facilities is 72°F db [22°C db] and 50% RH, which corresponds to gineering judgment, the team used a methodology that attributed a dew-point temperature of 52.4°F (11.3°C). However, the actual heat gains to occupied zones (occupants, computers, and exterior dew-point temperature in an occupied space with an appreciable wall/window transmission/solar gain from the floor to a height ventilation (or infiltration) air load may drift well above the deof 6 ft [2 m] above the floor) and unoccupied zones (lights and sign value unless active measures are used to maintain relative exterior wall/window transmission/solar gain above 6 ft [2 m] to humidity within a tolerance value of the design point. the typical ceiling height of 11 ft [3 m]). UFAD UFAD With Radiant UFAD With Passive This data was then used to size central Alone Cooled Ceilings Chilled Beams plant chillers and boilers. The plant design Supply Air Quantity (cfm) 560,000 240,000 240,000 included N+1 redundancy chilled water Supply Fan Power (hp) 600 280 280 and heating hot water capacity. Return Fan Power (hp) 280 5,600 120 2,400 120 2,400 Increasing Efficiency, Maximizing Space After building loads and central utility 1.6 0.7 0.7 Weighted Airflow (cfm/ft2) plant loads were determined, the design Qualitative Flexibility Good Fair Good team addressed the selection and sizFirst Cost ($) Reference +4,250,000 +100,000 ing of air-handling equipment. Space requirements and overall facility design Operating Cost Payback N/A >50 years <2 years dictated that the air-handling units *Swirl diffusers are floor-mounted air devices for supply air delivery into the occupied space. would be located in penthouses on the Table 1: Comparison of UFAD with and without supplemental cooling systems. roof, requiring vertical utility chases for supply and return ductwork and service piping. As the team Among the factors in favor of radiant cooled ceilings were brainstormed potential systems solutions, they considered the noninvasive supplemental cooling (meaning the cooling was ways to minimize floor requirements necessary for vertical accomplished without any ductwork, devices, or duct chases air chases, maximizing usable floor area. obtruding into the occupied space) and the effectiveness of the The solution was to use a UFAD system combined with some system. The low cooling capacity, typically around 30 Btu/h·ft2 form of passive cooling within the occupied space (cooling that (95 W/m2), would have required most of the ceiling to be radiwould not require central system airflow). To determine the ant. Initial cost and aesthetic considerations were the primary best form of passive cooling, the team investigated a number of factors against radiant cooled ceilings. technologies, with particular attention given to innovative and Passive chilled beams use chilled water piping circuited energy-efficient applications. The search produced a list including through coil-like structures at or above the space’s suspended ceilUFAD in conjunction with radiant cooled ceilings (also known as ing or, in spaces without a suspended ceiling, near the underside chilled ceilings) and UFAD in conjunction with chilled beams. of the deck. The units function similarly to finned-tube convectors, For the chilled beams option, active and passive chilled except that the chilled beams operate based on the greater denbeams were a consideration. However, active chilled beams sity of cooled air relative to the air within the space, as opposed were quickly rejected because they would require air-handling to the finned-tube convectors’ reliance on the lesser density of systems and ductwork that the supplemental cooling system was the heated air relative to the air within the space. Ambient air is intended to eliminate. Further, active chilled beam systems have cooled by the chilled beams and “falls” due to its greater density, mixing characteristics that eliminate the benefits of supplying displacing warmer room air and creating convective currents.2 fresh air directly to the occupied zone. The condensation concerns governing the installation of radiant cooled ceilings, and the associated chilled water temperatures, Radiant Cooled Ceilings Versus Passive Chilled Beams apply to chilled beams as well. But the comparative simplicity of Radiant cooled ceiling systems use cooling panels mounted components, greater cooling output (beams for this project were within the ceiling to provide sensible cooling of the occupied selected to provide 180 Btu/h per lineal foot [173 W per lineal mespace. The panels typically have a face panel compatible with the installed ceiling, which is combined with chilled water tubing About the Authors circuited throughout the back surface of the face.1 The chilled Steve Weidner, P.E., and Jerome Doerger, P.E., are vice presidents and water piping is situated above the ceiling, and the exposed face Michael Walsh, P.E., is a senior electrical engineer and project manager at of each radiant panel is maintained at approximately 60°F to PEDCO E & A Services in Cincinnati. December 2009 ASHRAE Journal 35 Total Swirl Diffusers* Required

ASHRAE Journal - December 2009

Table of Contents for the Digital Edition of ASHRAE Journal - December 2009

ASHRAE Journal - December 2009
Contents
Commentary
Industry News
Letters
Meetings and Shows
ASHRAE Building EQ Program
Feature Articles
A Closer Look at Chiller Ratings
Cooling With Less Air: Using Underfloor Air Distribution and Chilled Beams
Cooling Concrete: Containerized Water Chilling Plant
Geothermal for Community Center
Anniversary Feature: Air-Recovery System Versus Conventional Air Conditioning
Technical Topics
New Product Preview
Products
Emerging Technologies
Washington Report
People
Special Products
2009 Feature Articles Indices
Classified Advertising
Advertisers Index
ASHRAE Journal - December 2009 - ASHRAE Journal - December 2009
ASHRAE Journal - December 2009 - Cover2
ASHRAE Journal - December 2009 - 1
ASHRAE Journal - December 2009 - 2
ASHRAE Journal - December 2009 - Contents
ASHRAE Journal - December 2009 - 4
ASHRAE Journal - December 2009 - Commentary
ASHRAE Journal - December 2009 - Industry News
ASHRAE Journal - December 2009 - 7
ASHRAE Journal - December 2009 - 8
ASHRAE Journal - December 2009 - 9
ASHRAE Journal - December 2009 - 10
ASHRAE Journal - December 2009 - Letters
ASHRAE Journal - December 2009 - 12
ASHRAE Journal - December 2009 - 13
ASHRAE Journal - December 2009 - 14
ASHRAE Journal - December 2009 - 15
ASHRAE Journal - December 2009 - Meetings and Shows
ASHRAE Journal - December 2009 - 17
ASHRAE Journal - December 2009 - Feature Articles
ASHRAE Journal - December 2009 - 19
ASHRAE Journal - December 2009 - 20
ASHRAE Journal - December 2009 - 21
ASHRAE Journal - December 2009 - A Closer Look at Chiller Ratings
ASHRAE Journal - December 2009 - 23
ASHRAE Journal - December 2009 - 24
ASHRAE Journal - December 2009 - 25
ASHRAE Journal - December 2009 - 26
ASHRAE Journal - December 2009 - 27
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ASHRAE Journal - December 2009 - 29
ASHRAE Journal - December 2009 - 30
ASHRAE Journal - December 2009 - 31
ASHRAE Journal - December 2009 - 32
ASHRAE Journal - December 2009 - 33
ASHRAE Journal - December 2009 - Cooling With Less Air: Using Underfloor Air Distribution and Chilled Beams
ASHRAE Journal - December 2009 - 35
ASHRAE Journal - December 2009 - 36
ASHRAE Journal - December 2009 - 37
ASHRAE Journal - December 2009 - 38
ASHRAE Journal - December 2009 - 39
ASHRAE Journal - December 2009 - 40
ASHRAE Journal - December 2009 - 41
ASHRAE Journal - December 2009 - Cooling Concrete: Containerized Water Chilling Plant
ASHRAE Journal - December 2009 - 43
ASHRAE Journal - December 2009 - 44
ASHRAE Journal - December 2009 - 45
ASHRAE Journal - December 2009 - 46
ASHRAE Journal - December 2009 - 47
ASHRAE Journal - December 2009 - Geothermal for Community Center
ASHRAE Journal - December 2009 - 49
ASHRAE Journal - December 2009 - 50
ASHRAE Journal - December 2009 - 51
ASHRAE Journal - December 2009 - Anniversary Feature: Air-Recovery System Versus Conventional Air Conditioning
ASHRAE Journal - December 2009 - 53
ASHRAE Journal - December 2009 - 54
ASHRAE Journal - December 2009 - 55
ASHRAE Journal - December 2009 - 56
ASHRAE Journal - December 2009 - 57
ASHRAE Journal - December 2009 - 58
ASHRAE Journal - December 2009 - 59
ASHRAE Journal - December 2009 - 60
ASHRAE Journal - December 2009 - 61
ASHRAE Journal - December 2009 - Technical Topics
ASHRAE Journal - December 2009 - 63
ASHRAE Journal - December 2009 - 64
ASHRAE Journal - December 2009 - New Product Preview
ASHRAE Journal - December 2009 - 66
ASHRAE Journal - December 2009 - 67
ASHRAE Journal - December 2009 - 68
ASHRAE Journal - December 2009 - 69
ASHRAE Journal - December 2009 - 70
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ASHRAE Journal - December 2009 - 112
ASHRAE Journal - December 2009 - 113
ASHRAE Journal - December 2009 - Products
ASHRAE Journal - December 2009 - 115
ASHRAE Journal - December 2009 - 116
ASHRAE Journal - December 2009 - Emerging Technologies
ASHRAE Journal - December 2009 - Washington Report
ASHRAE Journal - December 2009 - 119
ASHRAE Journal - December 2009 - People
ASHRAE Journal - December 2009 - Special Products
ASHRAE Journal - December 2009 - 2009 Feature Articles Indices
ASHRAE Journal - December 2009 - 123
ASHRAE Journal - December 2009 - 124
ASHRAE Journal - December 2009 - 125
ASHRAE Journal - December 2009 - Classified Advertising
ASHRAE Journal - December 2009 - 127
ASHRAE Journal - December 2009 - Advertisers Index
ASHRAE Journal - December 2009 - Cover3
ASHRAE Journal - December 2009 - Cover4
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