Window ventilation efficiency in the case of buoyancy ventilation

Zhang

et al. 2017

Energy and Buildings

a b s t r a c tNatural ventilation is an effective strategy to control thermal comfort in buildings, and can be enhanced depending on the window style. The combination of natural ventilation and window can also facilitate the removal or dilution of gaseous pollutants from indoor sources in newly decorated buildings. However, the windows on the same facade may cause gaseous pollutant cross-transmission during single-sided natural ventilation between households on different floors close to the source. Although some research has focused on the pollutant cross-transmission in buildings, the simplification of windows into rectangular openings often affects accurate knowledge of pollutant transmission characteristics. Therefore, this investigation explored gaseous pollutant cross-transmission through real windows during singlesided, buoyancy-driven ventilation in a multistory building. Six types of windows were modeled for the indoor pollutant of gaseous formaldehyde (HCHO). Computational fluid dynamics (CFD) was utilized to solve characteristics of pollutant transmission inside and outside the multistory building. The results indicated that the ventilation rates, thermal profiles and pollutant transmission inside and outside the building varied for each window type, although the open window areas were identical. The re-entry ratio of exhausted air entering upper floors and the infection risk of epidemic viruses caused by airborne cross-transmission was sensitive to ventilation rates and window configurations, while the sensitivities for window configurations varied case by case. The comparisons also revealed that the specification of ambient temperature and pollutant release rate ultimately did not affect the evaluation of pollutant cross-transmission using CFD.

Section: Cfd Model Validationmentioning

confidence: 99%

“…In the study by Grabe et al [42], the experiment consists of a test chamber and an environmental chamber, as shown in Fig. 4(a).…”

Section: Cfd Model Validationmentioning

confidence: 99%

Section: Cfd Model Validationmentioning

confidence: 99%

See 1 more Smart Citation

Gaseous pollutant transmission through windows between vertical floors in a multistory building with natural ventilation

Zhang

et al. 2017

Energy and Buildings

International Journal of Ventilation

“…Caciolo et al (Caciolo et al 2011) used a value of 0.6 to describe the flow characteristic when calculating ℎ for various open window geometries while a of 1.0 is used in (Dascalaki et al 1996). The work by Grabe is outlined in section 3.2 (Grabe 2013;von Grabe et al 2014). Both Pinnock (Pinnock 2000) and Sharples et al (Sharples and Chilengwe 2006) have carried out experimental work considering the use of alternative exponent values in the power law equation when dealing with the buoyancy alone case and slot louvres respectively.…”

Section: Definition Of Asymptote For Ventilation Componentsmentioning

confidence: 99%

Non Dimensional Analysis and Characterisation of Driving Forces for a Single Sided Slot Louvre Ventilation System

O’Sullivan

Kolokotroni

2016

Adopting natural ventilation as a low impact retrofit strategy for space cooling is attractive due to the cooling potential of untreated outdoor air for large periods of the extended cooling season, particularly in northern climates. Furthermore, it is important to characterise the performance of natural ventilation components in successfully transferring the cooling potential of outdoor air to the occupied zone. This paper presents an analysis of the results from 25 individual ventilation rate tests of a single sided slot louver ventilation system installed in a low energy retrofit application and 13 tests from a pre-retrofit window opening, taken as a control space. Parameters permitting characterisation of different permutations for combined momentum and buoyancy driving forces during each test were also recorded allowing an investigation of the existence of any underlying patterns as well as the relative effect of the different opening configurations. Analysis shows that different patterns emerge for the dominant driving forces depending on opening configuration in the slot louver system. Owing to the primary airflow exchange mechanisms normally present, the transient evolution of the normalised tracer gas concentration during tests is analysed using the concentration fluctuation amplitude. The slot louver ventilation system has led to steadier ventilation rates. Opening height and geometry is shown to have a significant effect on the net contribution from momentum driving forces and the fluctuation amplitude of the ventilation rate and this effect is wind direction dependant. Ventilation rates are shown to correlate well with fluctuation amplitude. The nature of the ventilation rate during tests for different wind directions is shown to vary depending on wind patterns at the building envelope.

“…Documented evidence exists on building ventilation performance diagnosis for thermal comfort and indoor air quality [1, 7:Ai, 2014 #617], hygrothermal performance and ventilation energy efficiency [8][9][10]. They are equally focused on design optimisation [11][12][13] and performance assessment of new building component design [14,15].…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Ventilation Efficiency in a Dentistry Surgical Room

et al. 2016

Abstract.As a response to the need to provide an acceptable thermal comfort and air quality in indoor environments, various ventilation performance indicators were developed over the years. These metrics are mainly geared towards air distribution, heat and pollutant removals. Evidence exists of influencing factors on these indicators as centered on ventilation design and operations. Unlike other indoor environments, health care environment requires better performance of ventilation system to prevent an incidence of nosocomial and other hospital acquired illnesses. This study investigates, using in-situ experiments, the ventilation efficiency in a dentistry surgical room. Thermal and hygric parameters were monitored on the air terminal devices and occupied zone over a period of one week covering both occupied and unoccupied hours. The resulting time-series parameters were used to evaluate the room's ventilation effectiveness. Also, the obtained parameters were benchmarked against ASHRAE 170 (2013) and MS1525 (2014) requirements for ventilation in health care environment and building energy efficiency respectively. The results show that the mean daily operative conditions failed to satisfy the provisions of both standards. Regarding effectiveness, the findings reveal that the surgical room ventilation is ineffective with ventilation efficiency values ranging between 0 and 0.5 indicating air distribution short-circuiting. These results suggest further investigations, through numerical simulation, on the effect of this short-circuiting on thermal comfort, infection risk assessments and possible design improvements, an endeavour that forms our next line of research inquiries.