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

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energy consumption and reduced first cost with ventilation equipment, but also in terms of theoccupant environment. Occupant comfort, though difficult to quantitatively measure, has beenevaluated through occupant surveys such as the PROBE studies (Bordass 2001). It has beenfound that the indoor temperature associated with thermal comfort of occupants has a largerrange in naturally ventilated buildings (Braeger and de Dear 2000), extending the range ofexterior temperatures at which natural ventilation is usable. The interior temperature is only oneaspect of the indoor environment, which includes air velocities and surface temperatures as well.In the design of naturally ventilated buildings, concern over the disturbing of papers due to highair velocities is a factor, but slightly higher velocities can also help in maintaining comfort withhigher internal temperatures. With slight increases in velocities, from 0.1 m/s to 0.25 m/s,occupants can tolerate a temperature increase of 3.6°C without any additional discomfort(Chandra et al 1986). For air velocities within the occupied space up to 0.4m/s occupants cantolerate interior temperatures of 28°C or 30°C as long as there are cooler surface temperatures onsurrounding walls, floors or ceilings (Allard 2002). Cooler surface temperatures can be achievedthrough proper use of thermal mass in the building design. Passively cooled and ventilatedenvironments have increased occupant satisfaction when occupants have the ability, or perceivedability, to control their own environment through the use of operable windows (Jones and West2001).The location of the building affects its performance as well. Climate influences the feasibilityand usage period of natural ventilation as a means to cool a building. Buildings in temperateclimates can use natural ventilation for most of the cooling season, May through October. Inclimates with a wider temperature range, including hot summers, passive cooling is stillapplicable, but greater attention to detail and design characteristics must be made. Lechner(1991) divided the United States into 17 different climate regions, based on maximum, minimumand average monthly temperatures, humidity, wind, sunshine and degree-days. Of the 17climates identified, 12 regions could benefit from natural ventilation, at least for a portion of thecooling period (Jones and West 2001).1.1 Building Energy UseIn temperate climates, the energy consumption required to cool and ventilate a building can bereduced by incorporating natural ventilation in the building design, though it is not often done. Inthe United Kingdom (UK), which has a climate suitable for naturally ventilated buildings, only ahandful of naturally ventilated commercial office buildings exist. The number is even less in theUnited States (US). Thirteen percent of the UK total energy consumption is used in the servicesector, which includes retail buildings. Of the 13 percent, 61 percent is consumed by the privatecommercial sector (DTI 2004), or commercial office buildings. Thus, commercial buildingsconsumed 7.9 percent of total energy used in the UK, as compared to 17 percent of the totalenergy usage consumed by commercial buildings in the US (EIA 2004). Though heating makesup most of the energy usage both in the US and UK, cooling energy is also a significant portion,representing almost 10 percent of all energy usage for commercial buildings (DTI 2004). In theUS, only 3 percent of commercial office buildings do not have air-conditioning. The breakdownof energy usage by sub-system for commercial office buildings in both the US and the UK ispresented in Table 1. The majority of the energy is used for heating, cooling, and ventilatingoccupied spaces. The US tends to have better envelope systems, but not necessarily highefficiency lighting or lighting controls. The UK, on the other hand, is known for its under-16
insulated building envelopes with their substantially higher heating energy requirements. Theadoption of passive cooling and ventilation methods in the United States could impact energyuse, particularly for cooling and ventilation, which together make up almost 15 percent ofcommercial office building energy consumption.Table 1. Energy End Use for Commercial Office Buildings, Percent of TotalSpace Cooling and Water Lighting Cooking Office OtherHeating Ventilation HeatingEquipmentUnited 25.0 14.6 8.9 28.9 1.0 15.6 5.9StatesUnitedKingdom59.2 9.0 6.6 13.6 2.7 6.3 2.6The use of passive cooling techniques could be a potential design strategy component even in theUnited States. By incorporating energy efficient technologies, control schemes, and improvedbuilding envelope design required heating and cooling loads could be decreased. More energyefficientlighting fixtures, combined with control systems that allow lighting to be turned offwhen not in use or dimmed when sufficient light levels exist, would address lighting-relatedenergy efficiency issues and are commonly used in commercial office buildings. Designers andengineers continue to improve the building envelope and façade treatments to reduce heat lossthrough the envelope and solar gains through the windows, thereby decreasing heating andcooling requirements and minimizing the difference between indoor air and surface temperaturesthat may cause occupants discomfort. The increased use of thermal mass to temper the indoor airtemperature has become more widely used in commercial building design.1.2 Difficulties in Predicting Natural VentilationAlthough natural ventilation has the potential to significantly reduce energy consumption relatedto cooling buildings, several factors impede the application of this ventilation strategy incommercial office buildings. There is concern over building performance and occupant comfort,particularly in which occupants will not be subject to warm temperatures outside of their comfortarea or uncomfortable interior environments during their workday. There is a lack ofunderstanding of natural ventilation and the resulting temperatures and airflows for specificclimates, a lack of comprehensive tools to analyze design strategies effectively, quickly and indetail, and a preconceived notion that appearance of a naturally ventilated building will be odd.Currently there are limited tools to predict or assess the performance of natural ventilation inbuildings, pre or post occupancy. Tools for use in the design stage, such as MIT‘s DesignAdvisor (http://designadvisor.mit.edu), provide preliminary data on the performance of a singlespace when building characteristics, such as orientation, materials, and location, are enteredthrough the user interface. However, modeling programs do not adequately model naturalventilation effects. Some commercially available programs, such as AIDA and AIM-2 onlymodel single zones and do not have the ability to set occupancy schedules. Other programs, suchas AIOLOS and BREEZE are able to model multiple zones but still do not take into accountoccupancy schedules or conductive heat transfer into or out of the building (Emmerich et al2001). These last two programs do allow the user to define opening schedules for windows aspart of a simulation. The AIOLOS software, based on network modeling, is used for the17
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: Chapter 1.0IntroductionEnergy consu
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 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
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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
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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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