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

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1.4 Goals of this ResearchMonitoring alone provides insight into the operation of a particular building over a determinedamount of time, but monitoring alone does not enable that insight to be extended and use topredict the performance of other buildings. The focus of this research is to develop amethodology that can be used to evaluate and then predict the performance of natural ventilationin other buildings. The development starts with the monitoring of an existing naturallyventilated building with certain design characteristics. Through modeling and supported by datafrom monitoring, the operation of the building under certain environmental conditions can beunderstood. The natural ventilation strategies modeled are pure buoyancy-driven flow, winddrivenflow, and combined wind-buoyancy driven flow. By using data from a monitoredbuilding to calibrate the results of a reduced-scale air model through dimensional analysis andsimilitude, the configuration of the model then can be altered to determine what impact changesin certain design characteristics would have under the three natural ventilation strategies. Inaddition, the reduced-scale air model can provide a validation of models using computationalfluid dynamic simulations. Once developed this new methodology will provide the frameworkfor furthering the understanding of the performance of natural ventilation in buildings andimproving current simulation methods to better predict temperatures and flow patterns withinnaturally ventilated buildings. First, the underlying driving forces of natural ventilation must beunderstood and applied to airflow in buildings. Then key design characteristics will be moreeasily identified so that their affect on the indoor environment can be enhanced. This increasedpredictive ability in turn will help in the development of better simulation tools for designers andengineers to assess the benefits of incorporating passive cooling in new or rehabilitatedcommercial buildings.While this research has three parts (monitoring, modeling, and simulation), each part is used forcomparing and evaluating a modeling procedure. Data from the monitoring of a naturallyventilated building is used in the development and construction of a reduced-scale air model thatcan then be utilized to evaluate design characteristics of the original building. The numericalsimulations of the reduced-scale model provide verification of results from the experimentalwork, and identify issues in numerical modeling tools. The experimental work is nondimensionalizedto compare it to the original data from the full-scale building and numericalsimulation of the full-scale building, and then applied to determine the influence of the threetypes of natural ventilation on temperature distribution and airflow patterns within the building.1.5 Scope of documentThis thesis presents the foundation of the methodology for modeling natural ventilation airflowin buildings. The focus is on the three natural ventilation cases: buoyancy-driven, wind-driven,and combined buoyancy-wind driven ventilation. A methodology is developed and used toevaluate natural ventilation in a commercial office building, using a reduced-scale air model. Anumerical model using computational fluid dynamics was created to check the experimentalresults and better understand some of the heat transfer phenomena, not readily obtained throughexperimental work. With the validation of this methodology, other configurations of naturallyventilated buildings can be evaluated using reduced-scale air models (or CFD with care in22
selecting boundary conditions) to enhance the performance of naturally ventilated buildings andimprove simulation methods.The organization of this thesis is as follows:Chapter 2 presents the three types of natural ventilation and building characteristics thatare often considered in the design of naturally ventilated buildings. Also presented are themethods used to assessing the performance of a naturally ventilated commercial officebuilding used as reference point for the development of the methodology.Chapter 3 describes the process and measurements taken in evaluating the reference, orprototype building, Houghton Hall. A description of the building and presentation of thedata resulting from 16 months of monitoring are presented and will be used in part tovalidate the methodology in a later chapter.Chapter 4 explains the modeling and flow visualization techniques that are currently inuse for models at a variety of scales and working fluids. An overview of the three mainmodeling techniques is presented, along with the impact of scale, fluid, and naturalventilation type under investigation. The principles of flow visualization and itsapplication to buildings is discussed, along with the selection of the technique used in thereduced-scale modeling experiments.Chapter 5 provides dimensional analysis and similitude requirements for the use of scalemodeling in simulating full-scale phenomena. The governing equations for the analysis offlow are presented and then non-dimensionalized to obtain the dimensionless parameters.The selection of which dimensionless parameters to match is discussed, along with othersimilarity requirements for reduced-scale modeling.Chapter 6 outlines the experiments conducted using the reduced-scale air model in thetest chamber. Buoyancy, wind and combined natural ventilation experiments aredescribed for several different configurations using both the physical model and thecomplimentary numerical model,. The equipment and model materials used in theconstruction and measurement of the reduced-scale air model are presented.Chapter 7 presents the data gathered from the experimental and computational models.Included in this chapter are the analyses and comparisons of the modeling techniquesused, and issues that arose while conducting the experimental and simulation work. Theresults are presented in non-dimensionalized form for comparison.Chapter 8 provides guidelines for modeling airflow in naturally ventilated buildings. Acomparison of the current techniques including the methodology developed for thisresearch, how to apply those techniques in modeling, and the limitations of eachtechnique are discussed.Chapter 9 concludes the thesis and provides suggestions for future research. A summaryand evaluation of the method developed for evaluating natural ventilation in buildingsusing a reduced-scale air model are presented. References and appendices follow Chapter 923
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 and 18: insulated building envelopes with t
Page 19 and 20: energy usage and efficient design.
Page 21: Figure 3. European Patent Office Bu
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
Page 69 and 70: movement, Houghton Hall has much le
Page 71 and 72: 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
Page 87 and 88:
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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