Junjing Yang

Computational fluid dynamics study and evaluation of different personalized exhaust devices

This article investigates the performance of three different types of personalized exhaust devices. A top-personalized exhaust, which is a round device just above the human head; a shoulder-personalized exhaust, which consists of two local exhaust devices installed at the chair just above shoulder level; and a chair-personalized exhaust, which is at the upper part of a chair just behind the human head, were simulated, evaluated, and compared numerically using the computational fluid dynamics method. Two seated occupants representing healthy and infected manikins equipped with two types of personalized ventilation devices in a simulated consulting room in a healthcare center were modeled. Two indices—personalized exposure effectiveness and inhaled fraction—were introduced to evaluate the improvement of general inhaled air quality after adding different types of personalized exhaust devices and to compare the performance of different kinds of personalized exhaust devices with respect to the healthy manikins exposure to exhaled contaminated air. The computational fluid dynamics models were validated with a set of experiments conducted in an environmental chamber. The results indicate that all the three personalized exhaust devices might be able to reduce the transmission of exhaled air between occupants. The lowest inhaled fraction was achieved by the combination of a vertical desk grill and a top-personalized exhaust. However, only the shoulder-personalized exhaust device has the potential to improve the amount of personalized ventilation air in the inhaled air.

Retrofitting solutions for two different occupancy levels of educational buildings in tropics

ABSTRACT Within the multi-functionality of educational buildings, the energy conservation potential can be very different. In addition, among different retrofitting solutions investigated involving interventions on the building envelope, ventilation strategies, artificial lighting systems as well as equipment upgrading, different saving potential would come from different aspects. The opportunities for energy saving potential from the overall point of view and from the detailed aspect view of different retrofitting solutions would be very useful and important for building renovation decision making. This study presents a detailed retrofitting study of two different educational buildings. One represents a building with average occupancy variation and containing mainly offices and labs. The other one represents a building with high occupancy variation and containing mainly lecture rooms and studios. This comparison of the results gives an idea of the different energy saving potential for different types of educational buildings. Principal component analysis is also adopted to investigate the detailed performance of one of the buildings which is influenced stronger by these retrofitting solutions.

Energy utilizability concept as a retrofitting solution selection criterion for buildings

AbstractRetrofitting is widely explored as one of the energy conserving opportunities for existing buildings, in which both passive and active solutions are carefully evaluated. However, when different retrofitting solutions are combined and applied to a building, the total energy savings potential, which is less than the sum of the savings from applying the various individual retrofitting solutions, is considerably reduced and the synergies among the various technologies need to be understood and evaluated. In this study, the concept of utilizability is employed for the analysis of multiple energy retrofitting solutions in buildings and is defined as the ratio of energy savings derived from applying combined solutions to a building over the sum of individual energy savings from applying individual solutions. It is aimed at providing a better understanding of the combined retrofitting solutions. The sensitivity analysis on the utilizability value further provides a selection criterion for retrofitting sol...

A time-based analysis of the personalized exhaust system for airborne infection control in healthcare settings

In healthcare centers, healthcare workers would not know if patients are infected or not until the infected person is diagnosed and moved to an isolation room; therefore, the effectiveness of ventilation systems in removing the exhaled infectious air in the consultation room becomes important. To prevent the transmission of exhaled air, two types of personalized exhaust devices were explored: top-personalized exhaust and shoulder-personalized exhaust. Three different arrangements with 30 cases between 2 manikins were studied experimentally using tracer gas. The intake fraction was compared with and without the personalized exhaust at the end of three different exposure durations: 10, 20, and 30 min. The results show that after applying either top-personalized exhaust or shoulder-personalized exhaust, the intake fraction is significantly decreased. With the higher flow rate of 20 L/s of personalized exhaust, the intake fractions at 30 min are found to be even lower than the intake fractions at 10 min without personalized exhaust. This implies that despite a longer exposure time, if the exposure amount is reduced, the infection risk is observed to be lower.

5.20 Energy Management in University Campuses

University campuses which can be viewed as small cities due to their size, users, and mixed complex activities. The energy and environmental impact caused by institutional buildings via activities and operations in teaching and research, as well as provision of support services could be considerably reduced by an effective choice of energy technologies and management. The aim of the present chapter is to outline the recent technological developments in the energy management for University Campuses. The energy technologies that are suitable for University Campus buildings, as well as the role of users, are analyzed and discussed. Two case studies are analyzed in order to present the role of energy management in the energy consumption and indoor environmental quality of campus buildings ‘users.