Natural and Hybrid Ventilation Assignment

Added on - 21 Apr 2020

  • 23

    pages

  • 4584

    words

  • 13

    views

  • 0

    downloads

Showing pages 1 to 6 of 23 pages
Running Head: NATURAL AND HYBRID VENTILATIONNATURAL AND HYBRID VENTILATIONStudent’s Name:Institutional Affiliation:
NATURAL AND HYBRID VENTILATION2Executive summaryMost people disregard the importance of ventilation in the comfort of a building. The ventilationand air circulation in a building is equally as important as all the other building elements such asthe columns and slabs. Therefore, this branch of building physics should be greatly appreciated.In the report below, an analysis is provided of a potential building site for an office building. Thecomfort and analysis of the various elements that make air circulation all the more useful areanalyzed. The building has two proposed sites for its construction the first is an urban centerwhile the second is a green field outskirt 15km south west of London. In the design, the proposedhybrid ventilation system is to make use of the environment and the building structure and to putin place measures that ensure that the air and energy distribution is at the least possible cost.Furthermore, considering that it is an office building, the design has to ensure that there is anefficient balance between the energy obtained from the environment and the mechanicaltechnology, which in turn will ensure that the occupants have full control and knowledge of thebuilding.Winter and summer pose significant challenge in the design of any ventilation system. As amatter of fact, summer poses a significant challenge compared to winter. All these have beenaddressed in the report below where there is need for optimal equilibrium between indoor airquality needs and energy use.To begin with is the stack pressure. Stack pressure is the pressure caused by the difference indensity between the inside and outside air and as such, considering that this difference isrelatively higher in winter, the stack pressure is proportionally higher. More to this is the fact thatthe temperature difference is higher during winter than in summer. However, it does not pose asignificant threat to the building since the effects of stack pressure are felt in buildings that are
NATURAL AND HYBRID VENTILATION3higher than three floors. An increase in the stack pressure means that there is an increase in thetotal building pressure. The building pressure depends on the wind, stack effect and the pressuredue to ventilation. As a matter of fact, the North West side is bound to expect more pressure thanany other part of the building and therefore special consideration should be put in place.The wind pressure depends on a lot of variables such as the angle of incidence, the terrain andobstacles and more to this is the fact that it is relatively higher above the ground and therefore,the terrain chosen and all the named variables will determine the pressure and the ventilationrequirements.Another important consideration taken in the design of the proposed building is the heat loss andrequirements for the buildings. The thermal resistance of the elements that are used in the designof the building determines the heat lost to the surrounding.Therefore,the building should bemodified in such a way that there is sufficient heat loss during summer and proper heat resistanceduring winter.
NATURAL AND HYBRID VENTILATION4ContentsExecutive summary...................................................................................................................................2Calculation of pressure and opening areas..............................................................................................7Stack pressure between the offices and the outside.................................................................................7Wind induced pressure at each external opening...................................................................................8Flow networks describing the flow during the two seasons....................................................................9Orifice type opening area........................................................................................................................10Ventilation flow rate calculation............................................................................................................10Ventilation Heat loss for a 24 hr. period of summer.............................................................................12Cooling ventilation energy required.......................................................................................................13Additional restrictions imposed for ventilation if the urban site (option 2 site) is chosen for thebuilding.....................................................................................................................................................14Strategies using hybrid ventilation to optimize indoor air quality in urban buildings......................15Wind speed at the facade up the third floor of the proposed building................................................15Bibliography..............................................................................................................................................16
NATURAL AND HYBRID VENTILATION5The diagram of the building is as shown belowThe following parameters are known for the building:1. Total floor area 1500m2, distributed in three floors.2. Total occupancy 120 occupants, engaged in sedentary (office) activities.3. Winter design conditions: 21oC in office areas, 19oC in circulation/auxiliary areas, externaltemperature 0oC, wind velocity 3m/s.4. Summer design conditions: 25oC not be exceeded for 5% of the working hours in the officesareas (higher temperatures might be accepted in circulation/auxiliary areas). Externaltemperature 23oC, wind velocity 4.5m/s.
NATURAL AND HYBRID VENTILATION6Calculation of pressure and opening areasStack pressure at each external openingiiostackdcog T TpChgTWhereρi =the average density of the air present in a typical building and is equal to 0.075 lbm/ft3(=1.20 kg/m3)∆h = refers to the difference in elevation from a predetermined and neutral ground with positiveindicating an upward direction while negative a fall in the vertical distance .The units formeasurement taken as ft (m)g = 32.17 ft. /s2 (9.80 m/s2) This is the acceleration caused by gravitational pull [gc= 32.17(lbm· ft)/(lbf· s2)]Ti and To = the temperatures measured on an absolute scale (the indoor and outdoor temperaturerespectively), °R (K)Cd = This is a variable that takes into account the resistance to the flow of air between twoconsecutive floors and is known as the draft coefficientThere are 5 direct openings between the building and the environment (3 openings between00021CCandand 2 openings between00190Cand C)Assuming a standard building height (between floors) of about 4 meters:
desklib-logo
You’re reading a preview
card-image

To View Complete Document

Become a Desklib Library Member.
Subscribe to our plans

Download This Document