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

More documents

Recommendations

Info

Combined wind-buoyancy flow is more readily found in full-scale buildings, and these twonatural ventilation types can work either together or in opposition. Figure 9 presents the airflowdirection and the relation of pressure versus height in a combined buoyancy-wind naturalventilation case. The total pressures due to each case are added together to determine the totalpressure across an opening: P P P(2.13)TWBUsing the square root law presented in equation 2.8, the total flow rate through an opening iscalculated by:QTP CTDA 2 (2.14)Substituting in the pressure differences for each case into equation 2.12 and then the totalpressure difference into equation 2.13, the total flow rate, Q T , becomes:2UQOT CDA CP gHTBTO2(2.15)1Q 2 2 2Q QT W B (2.16)where Q w is the flow rate component due to wind and Q B is the component due to stack, orbuoyancy flow (Awbi 2003).Figure 9. Combined Wind-Buoyancy Ventilation: Airflow Direction and Pressure versus HeightThere are concerns with the accuracy of this equation (Etheridge 1996) in part due to the relativeeffects of wind and buoyancy. When the buoyancy and wind effects were approximately equal,30
the error in using equation 2.15 was usually 50% (Etheridge 1996). The magnitude of the errorsassociated with equation 2.15 depends on the distribution of both inlet and outlet openings andthe flow characteristics of those openings. However, at present there are not many simplifiedmethods available for calculating the ventilation rate when wind and buoyancy are acting at thesame time.Air change is driven in part by thermal conditions, so it is important to include a ventilationcomponent in an energy balance on a space. Performing an energy balance on a simple room,the total airflow, ρc P Q T ΔT, added to the conduction of heat through the building envelope mustequal the interior heat loads under steady state conditions. The material properties, surface areas,and temperature difference between the interior and exterior environment are used to calculatethe conduction through the walls and windows, Q walls+windows =UAΔT. The internal loads, Q loads ,typically include heat due to occupants, equipment and lights. For steady state conditions, theenergy balance equation is:Qloads Tc TTUA T (2.17)2.3 Design CharacteristicsIOPIOBuilding details, from the macro-scale, such as how to site the building, taking in to account itssurroundings, to the micro-scale, as in the details of a window type and location, can impact theeffectiveness of natural ventilation in an office building. Some of the design characteristicsparticular to naturally ventilated buildings, including the details of those used in the prototypebuilding are presented in this section,.2.3.1 Building LayoutLarge-scale building design decisions, such as orientation and surrounding conditions, canimpact both the thermal and ventilation performance of a naturally ventilated building. From themacroscopic perspective, this influence begins with the choice of a site location itself, and thecharacteristics of the surrounding area. Other building forms can impact the flow of air on thesite, either enhancing or detracting from the airflow relative to the building under consideration.The orientation and geometry of the building is often determined by the lot of land on which thebuilding will be sited, and can impact whether or not cross ventilation or single sided ventilationis an appropriate means to ventilate the building.For natural ventilation to be effective, the depth and layout of the floor space must be consideredalong with the natural ventilation scheme used to ventilate the space. In cellular-type officeplans, single sided ventilation is prevalent due to the configuration of offices, not allowing forcross-ventilation. With this configuration, air enters and leaves the space on the same façade ofthe building. If the window opening is only at one height, then the NPL falls in the mid-point ofthe window; air enters in the lower half and exits out of the upper half of the window. Thisdesign would have a tendency to create a concentration of warmer air at the ceiling and cooler airat the floor. An alternate configuration could use windows at two heights; the lower windowthen becomes the air inlet opening, while the upper window removes the exhaust air, thus havingthe capacity to remove more heat and lower the space temperature better than the single window31
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 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 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
Page 73 and 74: for future design of similar type b
Page 75 and 76: lower and upper openings and natura
Page 77 and 78: the acceptable diffusion rate, or
Page 79 and 80: applications involving full-scale b
Page 81 and 82:
digital camera with both manually o
Page 83 and 84:
Chapter 5.0Dimensional Analysis and
Page 85 and 86:
u oHgHT2uocu Hpo1Re Ar1Re Pr(5.7)(5
Page 87 and 88:
X HM X HP(5.16)5.3.2 Kinematic Sim
Page 89 and 90:
Radiation was found to have an impa
Page 91:
height is used for the full-scale b
Page 94 and 95:
6.3 Model Descriptions6.3.1 Physica
Page 96 and 97:
Figure 30. Floor Plan of the Protot
Page 98 and 99:
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 150 and 151:
The average and exhaust internal bu
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
Page 160 and 161:
160
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
Page 200 and 201:
25 cm / 3 m 24.33 26.62 22.68 22.93
Page 202 and 203:
25 cm / 3 m 24.07 25.26 22.65 22.78
Page 204 and 205:
Two Stacks Open Temperature Stratif
Page 206 and 207:
Stacks Closed Temperature Stratific
Page 208 and 209:
2.3 24.31 24.65 24.781.4 23.35 23.6
Page 210 and 211:
0.6 20.56 20.67 20.94 21.22 21.41 2
show all

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

Create successful ePaper yourself

Delete template?

Save as template?