K.W. Mui

Adaptive comfort temperature model of air-conditioned building in Hong Kong

The indoor thermal climate is an important issue affecting the health and productivity of users in buildings. In designing of air-conditioning systems, it is believed that the conventional fixed temperature setpoint concept is not appropriates, the indoor comfort temperature depends on the outdoor air temperature and the business culture, such as the nature of activities, dress of occupants, etc. Researchers have been interested in investigating adaptive temperature control for a realistic in situ temperature control for comfort. Unfortunately, these studies put great emphasis on the energy saving opportunity, rather than providing an integrated solution. In this paper, we report the findings of a large-scale survey that was performed to develop new notions about adaptive comfort temperature (ACT) in buildings in humid sub-tropical Hong Kong, and determine the adaptive interface relationship of indoor comfort temperature with outdoor air temperature in order to preset the indoor air temperature as a function of outdoor air temperature. This ACT algorithm is intended to optimise the energy used for cooling that air, but achieve the acceptance of thermal comfort, as determined by physical measurements and subjective surveys. With the integration of the ACT model, the total percentage of energy saving is about 7%.

Numerical modeling of exhaled droplet nuclei dispersion and mixing in indoor environments

n Abstractn n The increasing incidence of indoor airborne infections has prompted attention upon the investigation of expiratory droplet dispersion and transport in built environments. In this study, a source (i.e. a patient who generates droplets) and a receiver (i.e. a susceptible object other than the source) are modeled in a mechanically ventilated room. The receivers exposure to the droplet nuclei is analyzed under two orientations relative to the source. Two droplet nuclei, 0.1 and 10μm, with different emission velocities, are selected to represent large expiratory droplets which can still be inhaled into the human respiratory tracts. The droplet dispersion and mixing characteristics under well-mixed and displacement ventilation schemes are evaluated and compared numerically. Results show that the droplet dispersion and mixing under displacement ventilation is consistently poorer. Very low concentration regions are also observed in the displacement scheme. For both ventilation schemes, the intake dose will be reduced substantially if the droplets are emitted under the face-to-wall orientation rather than the face-to-face orientation. Implications of using engineering strategies for reducing exposure are briefly discussed.n n

An Experimental and Numerical Study on Deposition of Bioaerosols in a Scaled Chamber

This work presents an experimental facility designed and built with the objective of understanding the deposition of bioaerosols in indoor environments. Multiple depositions of two microorganisms Staphylococcus and Micrococcus inside a test chamber were investigated under two air mixing conditions. Airflow rate was demonstrated to have an influence on the concentration homogeneity. An increased proportion of particle deposition was found in the floor section near the chamber wall opposite to the air inlet when air mixing was not enhanced by the mixing fans. Both the experimental results and Eulerian-Lagrangian computations revealed that a small mixing fan inside the chamber prompted very effective mixing while non-homogeneity was observed even at a very high ventilation rate. The results showed that both ventilation rate and mixing conditions in the ventilated chamber have influence on the bioaerosol dispersion and deposition.

Air quality influence on chronic obstructive pulmonary disease (COPD) patients’ quality of life

UNLABELLEDnChronic obstructive pulmonary disease (COPD) is one of the leading causes of death. The relationship between urban air pollution and its short-term health effects on patients suffering from COPD is confirmed. However, information about the impact of air pollutants upon the quality of life (QOL) in patients with COPD is lacking. Through a cross-sectional survey, this study investigates such impact in terms of the scores of the (Chinese) chronic respiratory questionnaire (CCRQ) and the measurements of indoor air quality (IAQ), lung function and Mosers activities of daily living (ADL). Using Yules Q statistic with a cutoff |Q|>0.7 to identify the strong relationships between environmental parameters and CRQ sub-scores, this study reveals that patient emotion is strongly associated with indoor environmental quality although the evidence of a causal relationship between them needs further research.nnnPRACTICAL IMPLICATIONSnAs QOL in patients with COPD and indoor environmental parameters are strongly associated, indoor air pollutants must be monitored for related studies in the future.

Scoping indoor airborne fungi in an excellent indoor air quality office building in Hong Kong

This study aims to investigate the differences in indoor airborne fungal exposure between a selective subset of air-conditioned offices within a building classified with excellent indoor air quality (IAQ) in Hong Kong and typical offices in Hong Kong and other countries. Assessments of the indoor and outdoor fungal exposure levels and compositions, and indoor-to-outdoor (I/O) fungi count ratios were conducted in 82 offices of a building with excellent IAQ. The indoor airborne fungi were detected in 97.6% air samples with airborne fungi count (AFC) ranged from 2 to 92CFUm , and with a mean I/O ratio of 0.5. It was reported that the indoor AFC was significantly lower than other typical offices in Hong Kong and other countries. Aspergillus, Cladosporium, Penicillium and yeast were dominant indoors but an outdoor dominant fungi Alternaria was not detected in the offices. This study reveals that better control of thermal conditions and proper maintenance of the air-conditioning system would lower the AFC. In addition, a significantly higher relative abundance (RA) of Aspergillus and lower RA of Cladosporium were also reported. It presents a useful reference for IAQ assessment regarding the quantification of airborne fungal exposure in air-conditioned offices in a building with excellent IAQ. Practical application: An assessment of exposure levels to common indoor airborne fungi, such as Aspergillus, Cladosporium, Penicillium and yeast in Hong Kong air-conditioned offices reveals that an excellent office environment with good thermal and IAQ control would associate with a significantly lower airborne fungi count. A significant different pattern of indoor airborne fungi were observed that a significantly higher relative abundance of Aspergillus and lower relative abundance of Cladosporium were reported.This study aims to investigate the differences in indoor airborne fungal exposure between a selective subset of air-conditioned offices within a building classified with excellent indoor air quality (IAQ) in Hong Kong and typical offices in Hong Kong and other countries. Assessments of the indoor and outdoor fungal exposure levels and compositions, and indoor-to-outdoor (I/O) fungi count ratios were conducted in 82 offices of a building with excellent IAQ. The indoor airborne fungi were detected in 97.6% air samples with airborne fungi count (AFC) ranged from 2 to 92 CFU m—3, and with a mean I/O ratio of 0.5. It was reported that the indoor AFC was significantly lower than other typical offices in Hong Kong and other countries. Aspergillus, Cladosporium, Penicillium and yeast were dominant indoors but an outdoor dominant fungi Alternaria was not detected in the offices. This study reveals that better control of thermal conditions and proper maintenance of the air-conditioning system would lower the AFC. I...

Mathematical models for accurate prediction of atmospheric visibility with particular reference to the seasonal and environmental patterns in Hong Kong

Atmospheric visibility impairment has gained increasing concern as it is associated with the existence of a number of aerosols as well as common air pollutants and produces unfavorable conditions for observation, dispersion, and transportation. This study analyzed the atmospheric visibility data measured in urban and suburban Hong Kong (two selected stations) with respect to time-matched mass concentrations of common air pollutants including nitrogen dioxide (NO2), nitrogen monoxide (NO), respirable suspended particulates (PM10), sulfur dioxide (SO2), carbon monoxide (CO), and meteorological parameters including air temperature, relative humidity, and wind speed. No significant difference in atmospheric visibility was reported between the two measurement locations (pu2009≥u20090.6, t test); and good atmospheric visibility was observed more frequently in summer and autumn than in winter and spring (pu2009<u20090.01, t test). It was also found that atmospheric visibility increased with temperature but decreased with the concentrations of SO2, CO, PM10, NO, and NO2. The results showed that atmospheric visibility was season dependent and would have significant correlations with temperature, the mass concentrations of PM10 and NO2, and the air pollution index API (correlation coefficients ∣u2009Ru2009∣u2009≥u20090.7, pu2009≤u20090.0001, t test). Mathematical expressions catering to the seasonal variations of atmospheric visibility were thus proposed. By comparison, the proposed visibility prediction models were more accurate than some existing regional models. In addition to improving visibility prediction accuracy, this study would be useful for understanding the context of low atmospheric visibility, exploring possible remedial measures, and evaluating the impact of air pollution and atmospheric visibility impairment in this region.

Science for Healthy and Sustainable Living Environments

This service learning project focuses on organizing learning activities for school students in which schools and teachers can ensure that education for sustainable development is integrated into the other learning activity (OLE) in the school curriculum. The objectives can be achieved by (i) exposing school students to situations of poor families, they will be encouraged to look at the ways how the sustainability can be integrated into everyday living; (ii) introducing them to interesting ways of learning scientific topics and exposing them to activities related to higher education, and spending extended periods of time with university students, they may be better motivated to spend more time pursuing their studies, and (iii) working in teams to complete a project; they will build up their communication skills, teamwork and self-confidence.