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

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The average and exhaust internal building temperatures were known for both the prototypebuilding and the reduced-scale air model. The ambient temperature was known for each case aswell. The height in the buoyancy force calculation used was the overall building/model height,15m for the building and 1.2 meters for the model.In the prototype building field measurements, the air velocity for the surrounding environmentwas known from recorded data at the weather station. The entering air velocity at the awningtypewindow was known for several site visits, and was measured in the horizontal plane of thewindow (neglecting the side/vertical pieces and their contribution). For the reduced-scale airmodel, the entering air velocity was known at the window face, which was a vertical, rectangularopening in the façade. Since the velocities were at different locations and for different windowconfigurations, the pressures due to wind and buoyancy were used rather than the buoyant andreference velocities. The Archimedes number then could be calculated as:PBAr (7.7)PWFrom Chapter 2, the pressure due to buoyancy, or the stack effect, was given as: TI TOP BOgH(7.8) TIThe pressure due to wind was given as:2U POw CPO(7.9)2with C p equal to the (C p upwind -C p downwind ) The pressure due to wind could also be calculated usingthe power law equation:PQ cdA 2 (7.10)The pressure difference could be calculated based on the flow rate through the model. After this,re-arranging, equation 7.10 becomes:2 Q 1 PW A2 (7.11)Cd Where Q is the flow rate, A is the area of the inlet opening, and C d is the discharge coefficient,normally estimated as 0.6 for windows.7.3 Measurements and Results for the Prototype BuildingThe goal of the reduced-scale air model is to predict the ventilation performance of a full-scalebuilding, using temperature distributions and airflow patterns. Data from the reduced-scale airmodel, reduced-scale CFD model, and full-scale CFD model were compared to the prototypebuilding. The models predicted steady-state conditions for a given ambient temperature andinternal load, while the prototype building was operating under transient conditions. Thereduced-scale model was created based on a typical temperature differential between interior andexterior temperature of 5-8°C.150
Data from four building-occupied days during a site visit to the prototype building were applied,using temperature measurements from the mid-day period, when the temperature differencebetween the interior and exterior fall within the above range. The building internal temperatureused in calculating the temperature difference was determined by taking the average temperatureover all three floors. The temperature differences for the four days are presented in Table 40.The variables used in calculating the pressure differences due to stack and wind are listed inTable 41.Table 40. Measured Temperature Difference for Prototype BuildingTemperatureDifferenceOutsideVelocity (m/s)Site-1 3.50 6.7Site-2 3.69 3.7Site-3 1.06 4.3Site-4 1.69 4.1Site-5 0.75 3.4Table 41. Variables Used in Calculating Pressure Differencesvariable valueρ 1.2g 9.8H 15.0C p 0.6C d 0.6Using the above equations, the pressure difference due to wind and buoyancy each werecalculated for the prototype building on the days of the site visits. Calculations were made usingboth data sets available, the ambient wind conditions with the pressure coefficient, and thewindow velocity measurements with the coefficient of discharge. The method that used thewindow velocity measurements were adjusted for the total airflow through the window, ratherthan just the flow through the horizontal section of the window opening. It was estimated that anadditional 70 percent of airflow would be present when the sidepieces were accounted for. Thiswas based on the bag device measurements for determining the volume of air entering a windowand the relative areas of the horizontal and vertical pieces. The resulting wind and buoyancypressure differences for each method are presented in Table 42 and Table 43.Table 42. Calculated Wind and Buoyancy Pressure Differences and Resulting ArchimedesNumber Using Ambient Wind Conditions and Equation 7.8Pw Pb ArSite-1 16.2 27.4 1.7Site-2 4.9 26.6 5.4Site-3 6.7 7.4 1.1Site-4 6.1 12.4 2.0Site-5 4.2 5.2 1.2151
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Thesis Committee:Leon R. Glicksman,
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Table of ContentsTable of Contents
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7.1.3 Full Model Case .............
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Figure 41. Wind Direction Data for
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List of TablesTable 1. Energy End U
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Table 64. Comparison of Dimensionle
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Chapter 1.0IntroductionEnergy consu
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insulated building envelopes with t
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energy usage and efficient design.
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Figure 3. European Patent Office Bu
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selecting boundary conditions) to e
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2.2.1 Buoyancy-Driven VentilationVe
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Figure 7. Neutral Pressure Level fo
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Combined wind-buoyancy flow is more
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design. The depth of natural ventil
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of cooling required by 30 percent o
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considered when determining how the
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environmental conditions are examin
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As natural ventilation is prevalent
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Chapter 3.0Evaluation of Prototype
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Figure 12. Interior Atrium ViewFigu
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Table 8. Prototype Building Window
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Figure 15. HOBO® H8 Series Tempera
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Finally, airflow visualization was
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only is the airflow almost never at
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Table 10. Window Bag Device Measure
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Mon 7-21Tue 7-22Wed 7-23Thu 7-24Fri
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12:00 AM1:00 AM2:00 AM3:00 AM4:00 A
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27-Jul27-Jul28-Jul28-Jul29-Jul30-Ju
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A range of air exchange rates was f
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the windows on the second floor, or
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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
Page 100 and 101: Monitoring data collected from the
Page 102 and 103: By default, there was no accounting
Page 104 and 105: 40-location card inserted into the
Page 106 and 107: 6.5 ExperimentsTo evaluate the mode
Page 108 and 109: modified to determine the impact of
Page 110 and 111: Figure 39. Two Heated Zone ModelWit
Page 112 and 113: minute interval, the model was assu
Page 114 and 115: Figure 42. Cross-Section of Wind-Ge
Page 116 and 117: Table 25. Wind-Assisted Ventilation
Page 118 and 119: Figure 44. Heaters and Zones for a)
Page 120 and 121: Height from Floor (m)Height from Fl
Page 122 and 123: Where V is the outlet velocity, A o
Page 124 and 125: Table 32. Conduction Heat Loss for
Page 126 and 127: a) Air Modelb) Water ModelFigure 50
Page 128 and 129: Height from Floor (m)The temperatur
Page 130 and 131: Height from Floor (m)In the atrium
Page 132 and 133: First NorthUpper Window 0.17 m/s -0
Page 134 and 135: Height from Floor (m)the column at
Page 136 and 137: Height from Floor (m)Height from Fl
Page 138 and 139: Height from Floor (m)3.53.02.52.01.
Page 140 and 141: was less than 12 percent. These val
Page 142 and 143: Table 39. Variation of Outlet Wind
Page 144 and 145: temperature of the air was the same
Page 146 and 147: 3.532.521.55m/s4m/s3m/s2m/s1m/s1.5m
Page 148 and 149: 3.532.521.55m/s4m/s3m/s2m/s1m/s1.5m
Page 152 and 153: Table 43. Calculated Wind and Buoya
Page 154 and 155: In the last two lines, for both the
Page 156 and 157: Figure 80. CFD Simulation of the Te
Page 158 and 159: uoyancy case the air from the groun
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Page 162 and 163: windows of naturally ventilated bui
Page 164 and 165: difficult to select the boundary co
Page 166 and 167: simulations are able to do would al
Page 168 and 169: Bordass, W.T., A.K.R. Bromley and A
Page 170 and 171: Linddament, M. 1996. Why CO2? Air I
Page 172 and 173: 172
Page 174 and 175: MODEL: K20-8SERIAL: 10047RECORDER_I
Page 176 and 177: 2 Boiler-3 50.00 C1 N1 1.0 ON ON OF
Page 178 and 179: |PW|DESCRIP |KW |KWH|KVA|KVH|------
Page 180 and 181: 2:5 ;day_ofYr17:P30 ;EOT = 0.000075
Page 182 and 183: 2:3136:P30 ;DUM2 = -0.040891:-4.089
Page 184 and 185: ;7:21 ;input location;8:0 ;mulptipl
Page 186 and 187: ;79:P22 ;EXC w/DELAY (only for dela
Page 188 and 189: 1:45 ;port5 (homeSense)2:31 ;exit l
Page 190 and 191: 13:P95 ;ENDIF14:P95 ;ENDIF15:P3 ;pu
Page 192 and 193: 2:20 ;RH30:P70 ;sample1:12:20 ;RH31
Page 194 and 195: 194
Page 196 and 197: Five Windows Open: Upper versus Low
Page 198 and 199: 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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