Methodology for the Evaluation of Natural Ventilation in ... - Cham

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calculation of the airflow rate in naturally ventilated spaces configurations. The BREEZEsoftware program estimates ventilation and airflows in multi-zone buildings, and calculatesairflow rates based on user defined openings and leakage paths (Orme and Leksmono 2002).COMIS and CONTAMW are two software programs that are multi-zone modeling tools withoccupancy and opening schedules, but have underlying assumptions that make them less thanideal for the prediction of detailed information on a specific space within a building (Orme andLeksmono 2002). One of the major assumptions in both modeling systems is that of a wellmixedspace, which does not necessarily occur in naturally ventilated buildings. Furthermorethese software programs are meant to model the ventilation portion of the system based only onmass flow balances, not to consider any thermal loads which often overshadow mass floweffects. Ventilation models and thermal models are then ‗coupled‘ together in an attempt toovercome this deficiency.More complex software packages such as DOE-2 and EnergyPlus have some ability to modelnatural ventilation, but again assume a well-mixed environment. DOE-2 relies on a user-input forthe ventilation rate, while EnergyPlus is integrated with the COMIS multi-zone airflow model todetermine flow rates. These programs are considered whole building simulation programs, andaccount for conduction through the building envelope, occupancy, lighting and equipmentschedules in addition to ventilation modeling issues.Numerical software packages such as PHOENICS model airflow and thermal conditions for arange of applications, but do not account for conduction through the building envelope. They areunique in their ability to predict airflow patterns and temperature distributions throughout asingle space or simple building, rather than bulk airflow rates (Orme 1999). Still, when inputtingthe boundary conditions and parameters describing the space, the user must take care to provideenough detail. The numerical solutions from these computational fluid dynamic models must bevalidated and results verified, as this limitation in their modeling structure can cause erroneousresults.1.3 Examples of Naturally Ventilated BuildingsThere is a trend for more buildings to incorporate natural ventilation as a scheme for cooling andventilating part of or a whole building. Some of these buildings emphasize design characteristicsmaking them stand out in a typical streetscape, while others lean toward a more traditionalbuilding façade. Both strategies work and examples of each are presented here for comparison.Office buildings selected for comparison include each of three types of natural ventilation:buoyancy or stack driven flow, cross ventilation, and cross ventilation with an atrium. Theseexamples demonstrate the application of natural ventilation to buildings that have schedules andheat loads typical of commercial office buildings, and show the effectiveness of naturalventilation in building design. Most naturally ventilated buildings are located in Europe, and theexamples here are from the United Kingdom and the Netherlands.Of the examples, one in particular accentuates the design characteristics on the façade of thebuilding, the home of the British Research Establishment (BRE). This building incorporatesstack vents into the ventilation scheme, and makes them pronounced in the architecture of thebuilding. The BRE, designed by Fielden Clegg and built in 1997, is well known for its low18
energy usage and efficient design. It combines the use of thermal mass, cross ventilation andstacks to passively cool the building. The building‘s stacks not only are a prominent feature inits façade, but also assist in driving buoyancy and stack driven air flow. They are constructed ofglass block, shown in Figure 1, creating a greenhouse effect that warms up air within the shaftwhich as it rises, draws in cooler air through other openings on the façade. The occupants havecontrol over the lights and window openings as shown in Figure 2.The European Patent Office (EPO) is a naturally ventilated office building in The Hague thatuses cross ventilation to passively cool and ventilate the tower portion of the building. Thestructure was built in 1972 by architect R.D. Bleeker, with a limited number of designrequirements for the building. The design includes large amounts of thermal mass and exteriorshading to temper the interior environment and shade it from large solar heat gains, as shown inFigure 3. Each perimeter office is equipped with manually controlled windows, two upperwindows and two lower windows, shown in Figure 4.The Pearson Education Building (Figure 5), otherwise known as the Edinburgh Gate building,combines an open office floor plan with operable windows and louvers to promote naturalventilation and airflow through the building. This building primarily relies on cross-ventilationto meet ventilation and summer cooling requirements. There are three atria located throughoutthe building to assist in ventilating the surrounding offices, and which supply warmer air in thewinter and exhaust warm air in the summer. Built in 1995, the Pearson building incorporatessolar shading, thermal mass, and uses awning type windows (Figure 6).These examples are of buildings that have been in operation a minimum of 5 years and use avariety of natural ventilation strategies. Their performance has been monitored by organizationssuch as NatVent, which is a Pan-European project encouraging the use of natural ventilation inoffice-type buildings. The post-occupancy monitoring of these passively ventilated buildingsprovides critical insight into the functioning and performance of specific buildings thatincorporate various design strategies. These buildings were assessed primarily based on remotemonitoring, which only provides part of the overall performance.19
Page 2 and 3: Thesis Committee:Leon R. Glicksman,
Page 4 and 5: Table of ContentsTable of Contents
Page 6 and 7: 7.1.3 Full Model Case .............
Page 8 and 9: Figure 41. Wind Direction Data for
Page 10 and 11: List of TablesTable 1. Energy End U
Page 12 and 13: Table 64. Comparison of Dimensionle
Page 15 and 16: Chapter 1.0IntroductionEnergy consu
Page 17: insulated building envelopes with t
Page 21 and 22: Figure 3. European Patent Office Bu
Page 23: selecting boundary conditions) to e
Page 26 and 27: 2.2.1 Buoyancy-Driven VentilationVe
Page 28 and 29: Figure 7. Neutral Pressure Level fo
Page 30 and 31: Combined wind-buoyancy flow is more
Page 32 and 33: design. The depth of natural ventil
Page 34 and 35: of cooling required by 30 percent o
Page 36 and 37: considered when determining how the
Page 38 and 39: environmental conditions are examin
Page 40 and 41: As natural ventilation is prevalent
Page 43 and 44: Chapter 3.0Evaluation of Prototype
Page 45 and 46: Figure 12. Interior Atrium ViewFigu
Page 47 and 48: Table 8. Prototype Building Window
Page 49 and 50: Figure 15. HOBO® H8 Series Tempera
Page 51 and 52: Finally, airflow visualization was
Page 53 and 54: only is the airflow almost never at
Page 55 and 56: Table 10. Window Bag Device Measure
Page 57 and 58: Mon 7-21Tue 7-22Wed 7-23Thu 7-24Fri
Page 59 and 60: 12:00 AM1:00 AM2:00 AM3:00 AM4:00 A
Page 61 and 62: 27-Jul27-Jul28-Jul28-Jul29-Jul30-Ju
Page 63 and 64: A range of air exchange rates was f
Page 65 and 66: the windows on the second floor, or
Page 67 and 68: Total Electric (kWh/m2)Total Gas (k
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movement, Houghton Hall has much le
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Chapter 4.0Modeling and Visualizati
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for future design of similar type b
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lower and upper openings and natura
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the acceptable diffusion rate, or
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applications involving full-scale b
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digital camera with both manually o
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Chapter 5.0Dimensional Analysis and
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u oHgHT2uocu Hpo1Re Ar1Re Pr(5.7)(5
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X HM X HP(5.16)5.3.2 Kinematic Sim
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Radiation was found to have an impa
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height is used for the full-scale b
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6.3 Model Descriptions6.3.1 Physica
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Figure 30. Floor Plan of the Protot
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Figure 31. North Facade of Model wi
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Monitoring data collected from the
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By default, there was no accounting
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40-location card inserted into the
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6.5 ExperimentsTo evaluate the mode
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modified to determine the impact of
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Figure 39. Two Heated Zone ModelWit
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minute interval, the model was assu
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Figure 42. Cross-Section of Wind-Ge
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Table 25. Wind-Assisted Ventilation
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Figure 44. Heaters and Zones for a)
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Height from Floor (m)Height from Fl
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Where V is the outlet velocity, A o
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Table 32. Conduction Heat Loss for
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a) Air Modelb) Water ModelFigure 50
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Height from Floor (m)The temperatur
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Height from Floor (m)In the atrium
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First NorthUpper Window 0.17 m/s -0
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Height from Floor (m)the column at
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Height from Floor (m)Height from Fl
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Height from Floor (m)3.53.02.52.01.
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was less than 12 percent. These val
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Table 39. Variation of Outlet Wind
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temperature of the air was the same
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3.532.521.55m/s4m/s3m/s2m/s1m/s1.5m
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3.532.521.55m/s4m/s3m/s2m/s1m/s1.5m
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The average and exhaust internal bu
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Table 43. Calculated Wind and Buoya
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In the last two lines, for both the
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Figure 80. CFD Simulation of the Te
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uoyancy case the air from the groun
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160
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windows of naturally ventilated bui
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difficult to select the boundary co
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simulations are able to do would al
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Bordass, W.T., A.K.R. Bromley and A
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Linddament, M. 1996. Why CO2? Air I
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172
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MODEL: K20-8SERIAL: 10047RECORDER_I
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2 Boiler-3 50.00 C1 N1 1.0 ON ON OF
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|PW|DESCRIP |KW |KWH|KVA|KVH|------
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2:5 ;day_ofYr17:P30 ;EOT = 0.000075
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2:3136:P30 ;DUM2 = -0.040891:-4.089
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;7:21 ;input location;8:0 ;mulptipl
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;79:P22 ;EXC w/DELAY (only for dela
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1:45 ;port5 (homeSense)2:31 ;exit l
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13:P95 ;ENDIF14:P95 ;ENDIF15:P3 ;pu
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2:20 ;RH30:P70 ;sample1:12:20 ;RH31
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194
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Five Windows Open: Upper versus Low
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One Window Open: Upper versus Lower
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25 cm / 3 m 24.33 26.62 22.68 22.93
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25 cm / 3 m 24.07 25.26 22.65 22.78
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Two Stacks Open Temperature Stratif
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Stacks Closed Temperature Stratific
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2.3 24.31 24.65 24.781.4 23.35 23.6
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0.6 20.56 20.67 20.94 21.22 21.41 2
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