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Personal comfort devices (PCDs) are widely used in air conditioning rooms to improve occupants’ thermal comfort and save energy. However, when used in practical applications, the current PCD has many flaws; for example, it is often based on a single heat transfer mode and covers a small stimulation area, as well as can only be used in a single season. To solve the aforementioned issues, a novel personal comfort device was proposed. Sixteen college students were recruited to investigate the effect of the novel PCD on occupants' perceptual responses at three different room temperatures (26°C, 28°C and 30°C), as well as the temperatures and velocities around the face and abdomen areas. Results showed that using the novel device could provide airflow to the face and abdomen areas at a temperature 2°C cooler than room temperature. At 26°C, 28°C and 30°C, subjects’ overall thermal sensation was reduced by 0.5, 0.75 and 0.8, respectively. Meanwhile, subjects’ overall thermal comfort was significantly improved while allowing them to freely adjust the device’s airflow rate. Eighty-eight percent of subjects accepted a room temperature of 28°C, and almost no dry eye discomfort was reported. At 28°C, the novel device could provide energy-efficient thermal comfort.

Noise is recognized as one of the major indoor environmental issues in dental settings. This study presents the noise measurements and questionnaire surveys conducted in the clinics for pediatric dentistry and laboratories in the Prince Philip Dental Hospital in Hong Kong. Noise level and octave noise spectrum were measured at 60 locations distributed around the working areas. Totally, 60 valid questionnaires were collected, of which 30 were completed by dental surgery assistants and 30 by laboratory technicians. Data were coded and analyzed statistically using SPSS 19.0. The average noise levels in the dental clinics and laboratories were 62.6 dB(A) and 67.7 dB(A), respectively, which are well below the limit of 85 dB(A) for causing hearing loss. Statistical analysis shows that there is a significant difference in hearing status (condition of hearing ability) between different gender, age and occupation groups. Among others, noise generated by the equipment operated by others presents a principal influence on dental professionals. Importantly, suddenness and frequency of noise occurrence, rather than noise level, produce a significant influence on dental works. Most dental professionals work routinely and do not take any precautions or actions against noise at work. Practical application: The findings of this study should first increase the understanding of acoustical environment in dental settings for clinicians and its influence on dental professionals and second help designers and engineers improve the acoustical environment in dental settings.

Single-sided ventilation rate is difficult to accurately predict because it has a complex relationship with many factors, including the direction of the approaching wind and building envelope features. In addition, the incursion of outdoor pollutants into the interior through a ventilation opening has been recognized as a serious threat to indoor air quality (IAQ). This article presents on-site measurements of the ventilation performance and IAQ in four high-rise residential rooms in Hong Kong. Key parameters including the air changes per hour, respirable suspended particulate matters (PM: PM10 and PM2.5), and total volatile organic compounds were continuously recorded over a specified period. A comparison of cases with floor-extended and window-like openings is made. The results indicate that single-sided ventilation performs well regardless of the orientation of the apartment room and the configuration of the opening. Previous empirical models based on single-room buildings are not reliable in determining the ventilation rate of high-rise buildings. The measurements reported here also identify an important route for the incursion of outdoor pollutants, namely the downward re-entry of aerosol particles from an upper unit to a lower unit in the same building. A combination of gravitational and wind effects means this downward transport route significantly increases the PM10 and PM2.5 concentrations in the lower room.

This article presents a study of airflow pattern inside a five-story wind-driven naturally ventilated atrium building. Firstly, field measurement conducted in the atrium building reveals the existence of reversed flows from the atrium to windows, which could cause air cross-contamination between floors during the period of an infectious disease outbreak. The computational fluid dynamics technique was then employed to further investigate the airflow pattern inside the building, under different wind directions and opening ratios. It is found that the airflow pattern inside a wind-driven naturally ventilated atrium building is very sensitive to the oncoming wind direction. Under parallel and perpendicular incident wind directions, the existence of adversely reversed flows in a certain floor and the re-entry of used air from an upper floor into its adjacent lower floors through the atrium results in the decrease of indoor air quality and the effective air exchange through windows. Nevertheless, the building has good natural ventilation performance under oblique incident wind direction, although the expected role of the atrium is still not fully achieved. In addition, the improvement of airflow pattern inside wind-driven naturally ventilated buildings cannot be achieved by simply modifying the opening ratios. Practical application: Considering the indoor airflow pattern could substantially influence the elimination efficiency of pollutants and overheated air, this study is expected to help designers and engineers who are considering the use of an atrium at the design stage to have a better understanding of the airflow pattern inside a wind-driven naturally ventilated atrium building.

The purpose of this study was to investigate the effect of a new building which can impose on its immediate ambient environment, on air movement and thermal comfort of people using the area. The effect of eight prevailing wind directions around the building was simulated using computational fluid dynamics (CFD). The CFD simulation was validated by two wind tunnel experiments. The CFD results were used to conduct an air ventilation assessment using velocity ratio (VR) indicator and to assess thermal comfort by an extended predicted mean vote (PMV) evaluation. An analysis of the relationship of VR and PMV with the to-be-built building (the front area index λf and plan area density λp) was also conducted. The result indicates that the PMV trend was generally opposite to the VR trend. The λp would increase due to the new building and the λf would increase in all wind directions except East-South-East and South-East. There could be a significant change in thermal comfort when the λf became smaller than 12% and a significant change in ventilation efficiency if the λf was smaller or larger than 12%. It means that λf can be used as an urban planning parameter for the thermal comfort study in the natural ventilated urban environment.

This article presents a numerical study of ventilation performance of balconies using computational fluid dynamics. The pressure coefficients distributed on the opposite walls of a five-storey building model, both with and without balconies, were studied under variation of the wind direction, balcony dimensions and building height. The effect of balconies on the capacity for wind-induced natural ventilation is discussed. The numerical results show good agreement with the experiments of Chand et al. They also indicate that a balcony enhances the cross-ventilation of intermediate floors but weakens that of the ground and top floors, by significantly changing the pressure distribution on the windward wall. Finally, the ventilation performance of a balcony is not greatly affected by variations in its size but is slightly weakened as the height of the building increases. Practical application: This study provides information and guidance in how best to incorporate the use of a balcony in building development at the design stage.

Chand et al. conducted experiments in a low speed wind tunnel to study the effect of balconies on the ventilative force on low-rise buildings without openings. Using their model, this study intends to investigate indoor ventilation performance by examining mass flow rate and average velocity on the working plane using computational fluid dynamics. Simulations were validated against their experiments. The numerical results indicate that, for single-sided ventilation, the provision of balconies increases mass flow rate and reduces average velocity on the working plane in most rooms, but for cross ventilation, this provision has no significant effect under normally or obliquely incident wind conditions. After the addition of balconies, the worst ventilation circumstances on the windward side under single-sided ventilation conditions were found on the intermediate floor. The simulation results also showed that, in many cases, wind flows into and out of the rooms through the left or right side of the opening rather than through the bottom and top of the opening, especially in the case of buildings that are obliquely oriented to the air stream. This phenomenon demonstrates that predictions of single-sided ventilative force using data relating to the bottom and top parts of the opening are not accurate enough.

The presence of the parapet and floor of a balcony is expected to have a range of effects on a building’s environmental behaviour, in terms of aspects, such as natural ventilation, thermal comfort, pollutant transportation and shading and daylighting. The authors have previously reported that the presence of a balcony can significantly increase the air flow rate of most rooms in a naturally ventilated building. In this study, the CFD technique and Fanger and Toftum’s extended PMV—PPD model are combined to investigate numerically the effect of a balcony on thermal comfort for naturally ventilated buildings in tropical-humid regions. The results show that although a balcony reduces the indoor average velocity for most rooms, and in turn increases the PMVnv value in both the seated and standing positions, it does not change the indoor thermal comfort level. However, the presence of a balcony improves comfort by increasing the uniformity of indoor air distribution. PMVnv is also shown to be less sensitive to velocity than PMV, allowing for a wider thermal comfort range for naturally ventilated buildings. Practical application: This study will help designers and engineers who are considering the use of a balcony at the design stage to have a better understanding of its effect on thermal comfort in naturally ventilated buildings.