Jingchao Xie

A Review of the Piston Effect in Subway Stations

In recent years the piston effect in subways has become a topic of interest for researchers and engineers. Many publications have appeared on this topic, but reliable information is scattered and poorly organized. This review paper covers the latest publications on the piston effect in subways. We compile information about the mechanism of the piston effect, evaluate its influence, and describe how it can be effectively utilized.

Investigation of indoor environmental quality in urban dwellings with schoolchildren in Beijing, China

This study attempts to collect more comprehensive data about the indoor environmental quality in urban dwellings with schoolchildren in Beijing, China. For this purpose, indoor air temperature, relative humidity and the levels of indoor chemical and biological pollutants in 14 households were measured in 2013. Results show that, in cold winter, indoor relative humidity was often lower than the comfort limit of 30%, while indoor CO2 concentration was often higher than the acceptable level of 1000 ppm in poorly ventilated homes with high occupant load. Indoor PM2.5 pollution was very severe with the highest level of 523 µg/m3 in living room and 345 µg/m3 in children’s bedroom in winter. Compared with the recommended thresholds, the levels of indoor volatile organic compounds and carbonyl compounds in most homes were low. Cigarette smoke is an important indoor source of PM2.5, formaldehyde, acetaldehyde, acetone and benzene. Also, there are significant correlations between the concentration of total volatile organic compounds and other compounds (acetaldehyde, acetone, benzene and toluene). Furthermore, two phthalates: di (2-ethylhexyl) phthalate and di-n-butyl phthalate were frequently detected in house dust. Penicillium, Cladosporium, and Aspergillus were predominant fungi in indoor air. The fungal pollution levels in different seasons and rooms were also compared.

A review on phase change material application in building

In the past several decades, many literatures have emerged on the topic of phase change material and latent heat storage techniques used in building. Accordingly, it is essential to review previous work to know about phase change material application in building better. This article presents a review on phase change material application situations in building, and several aspects are discussed: phase change material major applications in building, phase change material application areas, phase change material application types, phase change material thermal–physical properties, and phase change material application effects. The results of this research show that phase change material application areas are mainly concentrated into four parts of north latitude from 25° to 60° and south latitude from 25° to 40°. No matter in which region, the use of paraffin is the broadest (the maximum use frequency is up to 87.5%). For organic phase change material, the melting temperature and the heat of fusion vary from 19°C to 29°C and from 120 kJ/kg to 280 kJ/kg, respectively. The best phase change material application effect found is a reduction of 4.2°C for air temperature in room. This study has important and directive significance for the practical application of phase change material in building.

Comments on Thermal Physical Properties Testing Methods of Phase Change Materials

There is no standard testing method of the thermal physical properties of phase change materials (PCM). This paper has shown advancements in this field. Developments and achievements in thermal physical properties testing methods of PCM were commented, including differential scanning calorimetry, T-history measurement, the water bath method, and differential thermal analysis. Testing principles, advantages and disadvantages, and important points for attention of each method were discussed. A foundation for standardized testing methods for PCM was made.

Generalized design principle and method for a non-balanced thermal insulation system in building envelope

In regions with abundant solar energy, building walls facing different directions absorb very different amounts of solar energy. These differences should be considered in thermal insulation design, unlike the current design standard in China, which does not take directionality into account when calculating the limit value of the heat transfer coefficient of building envelope. To address this short-coming, this article proposes a generalized non-balanced thermal insulation system for the building envelope: walls receiving greater amounts of solar energy should have less insulation, while walls receiving less amounts of solar energy should have more insulation. By analysis of outdoor synthetic temperatures for different orientations, non-balanced heat transfer coefficients are calculated under a constant heat flux condition. Considering the Lhasa region as a case study, the testing of an indoor thermal environment in winter was conducted, and a novel non-balanced thermal insulation system was built. The internal surface temperature of the external walls under two types of heat transfer coefficient limit values and the frequency responses of the two types of thermal insulation wall constructions are analyzed using the wall thermal theoretical method. The results show that this new thermal insulation design can make better use of solar energy, thus reducing conventional heating. This article provides a theoretical reference for the future design of non-balanced thermal insulation systems for building envelope and also provides a theoretical calculation method for the part of building envelope thermal design in the national standard of the People’s Republic China (Thermal Design Code for Civil Building-GB50176).

Investigation on Indoor Air Pollution and Childhood Allergies in Households in Six Chinese Cities by Subjective Survey and Field Measurements

Greater attention is currently being paid to the relationship between indoor environment and childhood allergies, however, the lack of reliable data and the disparity among different areas hinders reliable assessment of the relationship. This study focuses on the effect of indoor pollution on Chinese schoolchildren and the relationship between specific household and health problems suffered. The epidemiological questionnaire survey and the field measurement of the indoor thermal environment and primary air pollutants including CO2, fine particulate matter (PM2.5), chemical pollutants and fungi were performed in six Chinese cities. A total of 912 questionnaires were eligible for statistical analyses and sixty houses with schoolchildren aged 9–12 were selected for field investigation. Compared with Chinese national standards, inappropriate indoor relative humidity (<30% or >70%), CO2 concentration exceeding 1000 ppm and high PM2.5 levels were found in some monitored houses. Di(2-ethylhexyl) phthalate (DEHP) and dibutyl phthalate (DBP) were the most frequently detected semi-volatile organic compounds (SVOCs) in house dust. Cladosporium, Aspergillus and Penicillium were detected in both indoor air and house dust. This study indicates that a thermal environment with CO2 exceeding 1000 ppm, DEHP and DBP exceeding 1000 μg/g, and high level of PM2.5, Cladosporium, Aspergillus and Penicillium increases the risk of children’s allergies.