Analysis of Direct Outdoor Air Cooling Efficency for Combined Variable Air Volume Air-conditioning System in Stores in Cold Climates of China

Direct outdoor air cooling contributes a lot not only to the improvement of the indoor air quality but also to the energy saving. Its full use will reduce the water chiller’s running time especially in some stores where cooling load keeps much higher and longer than that in other buildings. A novel air-conditioning system named Combined Variable Air Volume system (CVAV), combining a normal AHU with a separate outdoor air supply system, was proposed firstly by the authors. The most attractive feature of the system is its full utilization of cooling capacity and freshness of outdoor air in the transition period of the year round. On the basis of the obtain of the dynamic cooling loads of the typical shopping malls in different four cities located in cold climates in China with the aid of DOE-2, the possibility of increasing the amount of outdoor air volume of CVAV system in the transition period instead of operating the water chillers was confirmed. Moreover, a new concept, Direct Outdoor Air Cooling Efficiency (DOACE), was defined as the ratio of cooling capacity of outdoor air to the water chiller, indicating the degree of outdoor air’s utilization. And the DOACE of the CVAV was calculated and compared with that of conventional all-air constant volume air-conditioning systems, the results showed that CVAV bear much more energy saving potential with the 10%~19% higher DOACE and it is a kind of energy efficient systems and can improve the indoor air quality as well.

Computational fluid dynamics modelling of the air movement in an environmental test chamber with a respiring manikin

In recent years, computational fluid dynamics (CFD) has been widely used as a method of simulating airflow and addressing indoor environment problems. The complexity of airflows within the indoor environment would make experimental investigation difficult to undertake and also imposes significant challenges on turbulence modelling for flow prediction. This research examines through CFD visualization how air is distributed within a room. Measurements of air temperature and air velocity have been performed at a number of points in an environmental test chamber with a human occupant. To complement the experimental results, CFD simulations were carried out and the results enabled detailed analysis and visualization of spatial distribution of airflow patterns and the effect of different parameters to be predicted. The results demonstrate the complexity of modelling human exhalation within a ventilated enclosure and shed some light into how to achieve more realistic predictions of the airflow within an occupied enclosure.

Nurturing bilingual learners: challenges and concerns in Singapore

Singapore’s bilingual policy legitimises English not only as the language of governmental administration and interethnic communication, but also as the medium of instruction in all schools on all levels and across all subjects except mother tongues (MTs). As a result of these politics of language recognition, a visible shift has occurred in all ethnic groups away from MTs towards English. To rectify the language shift situation, the government has emphasised that developing bilingualism and raising bilingual children should begin in preschools. In this paper, we examine two top-down official documents: Review of Mother Tongue Languages Report, issued in 2011, and Nurturing Early Learners Framework for Mother Tongue Languages, developed in 2013. Attempting to identify some of the complex factors that influence language shift, we present an intertextual analysis of the Report and the curriculum Framework. In doing so, we compare the consistencies and locate the implicit inconsistencies in the policy position on bilingual education in preschools. We conclude the article by outlining the implications for changing the current bilingual educational models and providing teacher training programmes that maximise the learning opportunities of young bilingual learners.