Atrium Design Strategies for Daylighting and Natural Ventilation

Transcription

1 GreenBuild: International Conference & Expo Atrium Design Strategies for Daylighting and Natural Ventilation S. Faruq Ahmed, PE Pittsburgh, Pennsylvania November 12 14, 2003 P. Richard Rittelmann, FAIA Jayesh Hariyani Burt Hill Kosar Rittelmann Associates 101 East Diamond Street Butler, PA

2 Introduction The study examines the daylighting and thermal performance of an atrium The atrium is a three-story space The building is located in Troy, New York View from the East

3 Introduction (Cont d) Investigations were conducted to examine the natural cooling/ventilation strategies for the atrium View from the West

4 Building Description The building is a laboratory building, Biotechnology and Interdisciplinary Building, at Rensselaer Polytechnics Institute Total area: 220,000 SF Add building plan Building functions are: Biotechnology and Interdisciplinary Labs Offices Computational Labs

5 Building Description (Cont d) Building massing study (animation)

6 Glass Properties Double Glass assembly Outer Glass ¼ Air gap ½ Inner glass, safety glass ¼ + ¼ Glass Location Light Trans. % Solar Trans. % Summer U Btu/(sq.ft-hr.F) Solar Heat Gain Coeff. SHGC Shading Coeff. Frit. % Top Middle Lower

7 Glass Properties Glass fritting patterns

8 Daylighting Efficient daylighting with little heat gain East Atrium South Atrium

9 Daylighting Daylighting animation, August 1, 7:30 am to 7:30 pm East Atrium South Atrium

10 Atrium Thermal Performance Study Investigate the use of natural cooling Quantify the expected temperature regime in the atrium during the year CFD analysis and TRNSYS were used as complementary methodologies CFD analysis was used for studying temperature profiles and surface temperatures TRNSYS was used to quantify average space temperature throughout the year (hourly simulation)

11 Software Used CFD Analysis Flovent by Flomerics TRNSYS Transient Simulation System from University of Wisconsin Development started in 1975 Modular software No fixed component configuration Flexible modeling approach Single node lumped capacitance model was used

12 Atrium Cooling Strategies The following strategies were investigated Natural ventilation, using CFD analysis Forced ventilation using CFD analysis Hourly simulation on non-vented atrium using TRNSYS Hourly simulation of forced ventilation using TRNSYS Hourly simulation of forced ventilation of atrium, air leakage from conditioned space and night pre-cooling of atrium

13 CFD Analysis - Assumptions In the south atrium, 20% of the air from offices is relieved into the atrium Relief air temperature is 73F Outside heat transfer coefficient, 1.76 Btu/(hr-sq. ft.-f) Solar angles at 2pm solar time were used Number of louvers for air inlet 24 in south atrium 12 in east atrium

14 CFD Analysis Assumptions (Cont d) Five smoke exhaust fans, total 150,000 CFM Max, used at 50% capacity Outlet louvers 27 in South Atrium 18 in East atrium Solar radiation, 900, 600, and 400 Watts/meter sq. CFD analysis done for following times: Natural ventilation: Spring and Fall Forced Ventilation: Summer

15 Results of CFD Analysis CFD-1: Natural ventilation, March, 2 pm Maximum 33,000 CFM flow was observed South Atrium East Atrium

16 Results of CFD Analysis (Cont d) CFD-2: Fall/Spring Forced Ventilation, 2 pm, solar radiation 900 W/m-sq South Atrium East Atrium

17 Results of CFD Analysis (Cont d) CFD-2 (Cont d): Summer Forced Ventilation, 2 pm, solar radiation 900 W/m-sq South Atrium East Atrium

18 Results of CFD Analysis (Cont d) CFD-3: Summer Forced Ventilation, 2 pm, solar radiation 600 W/m-sq South Atrium East Atrium

19 Results of CFD Analysis (Cont d) CFD-3 (Cont d): Temperature profile though stairs, summer Forced Ventilation, 2 pm, solar radiation 600 W/m-sq East Atrium South Atrium

20 Results of CFD Analysis (Cont d) CFD-3 (cont d): Summer Forced Ventilation, 2 pm, solar radiation 400 W/m-sq South Atrium East Atrium

21 Results of CFD Analysis (Cont d) Temperature profile though stairs, summer Forced Ventilation, 2 pm, solar radiation 400 W/m-sq East Atrium South Atrium

22 CFD Analysis - Observations The software assumed no internal reflections from white atrium walls The slopped glazing was modeled as stepped glass Double glass was not modeled, instead single glass was used with corrections to simulate the temperature of glass surfaces Solar modeling capabilities of the software seemed limited, the air flow was accurately modeled

23 Results of TRNSYS Analysis TMY2 weather data for Albany, NY was used. Analysis was performed to quantify the behavior of atrium temperature during the year. Frequency of occurrence of the atrium temperature in various ranges is used to examine various cases (alternatives).

24 Results of TRNSYS Analysis - Cases Studied Case CT-1: Base case, no atrium ventilation Case CT-2: Forced ventilation with smoke exhaust fans. Case CT-3: Forced ventilation (Case CT-2) and lab support relief air. Case CT-4: Same as Case CT-3 and night cooling of the space. Case CT-5: Same as Case CT-4 with uninsulated atrium interior walls and air leakage from door opening

25 Results of TRNSYS Analysis Yearly Performance, SOUTH ATRIUM

26 Results of TRNSYS Analysis Yearly Performance, EAST ATRIUM

27 Result for Selected Strategy Case CT-5 Detailed Performance

28 Observations TRNSYS Analysis The analysis was useful in quantifying the behavior of the space throughout the year The high quality glass allows adequate amount of light transmission but reduces the heat gain to the space Increasing the quantity of forced ventilation does not necessarily help limitation of resource (ambient air temperature)

29 Recommendations Natural ventilation alone is not a very effective strategy Limited amount of of available opening for ventilation Large temperature gradient along the height of the atrium Forced ventilation with smoke control fans using variable frequency drives, provides acceptable comfort conditions

30 Recommendations (Cont d) The air leakage from the computer labs support and the heat conduction through uninsulated interior walls helps The strategy in Case CT-5 allows the elimination of 250 tons of cooling which would have been used for very few hours during the years

31 Recommendations (Cont d) During the study a parametric analysis was performed using various quantities of forced ventilation air quantity. The result shows: Increasing the ventilation beyond 50,000 CFM does not help much At certain times, depending on the outdoor conditions, only 10% of the air flow may be enough

32 Recommendations (Cont d) The building is using the strategies listed in Case CT-5 with fans controlled by an algorithm so that the fan capacity as a function of outdoor air temperature and atrium temperature: Building control system will control the fans and VFD The Building is under construction

33 Overall Observations CFD analysis is an excellent tool for such studies Modeling of solar radiation through the glazing must be evaluated carefully Scattering of solar radiation from inside surfaces must be carefully considered The analyst must have good appreciation of solar systems

34 Overall Observations (Cont d) TRNSYS is an excellent tool which is: Very flexible (configuration is not fixed) Well documented However it is not easy to use Ideally CFD analysis should be used for all hours of the year, however this activity is resource intensive and almost impractical at this time

35 Thank you S. Faruq Ahmed, PE P. Richard Rittelmann, FAIA Jayesh Hariyani