Chen Zhang

Bio: Chen Zhang is an academic researcher from Aalborg University. The author has contributed to research in topics: Ceiling (cloud) & Welding. The author has an hindex of 19, co-authored 72 publications receiving 956 citations. Previous affiliations of Chen Zhang include Shanghai Jiao Tong University & Huazhong University of Science and Technology.

Effect of drop size on the impact thermodynamics for supercooled large droplet in aircraft icing

Abstract: Supercooled large droplet (SLD), which can cause abnormal icing, is a well-known issue in aerospace engineering. Although efforts have been exerted to understand large droplet impact dynamics and the supercooled feature in the film/substrate interface, respectively, the thermodynamic effect during the SLD impact process has not received sufficient attention. This work conducts experimental studies to determine the effects of drop size on the thermodynamics for supercooled large droplet impingement. Through phenomenological reproduction, the rapid-freezing characteristics are observed in diameters of 400, 800, and 1300 μm. The experimental analysis provides information on the maximum spreading rate and the shrinkage rate of the drop, the supercooled diffusive rate, and the freezing time. A physical explanation of this unsteady heat transfer process is proposed theoretically, which indicates that the drop size is a critical factor influencing the supercooled heat exchange and effective heat transfer duration between the film/substrate interface. On the basis of the present experimental data and theoretical analysis, an impinging heating model is developed and applied to typical SLD cases. The model behaves as anticipated, which underlines the wide applicability to SLD icing problems in related fields.

韧性（Resilience）的概念分析

Abstract: 韧性（resilience）是指个人面对生活逆境、创伤、悲剧、威胁及其他生活重大压力的良好适应，也是个人应激（stress）和应对（coping）的正面结果。在过去的数十年，护理学等健康相关领域的学者们一直在关注为什么一些人在逆境、压力、疾病等高危（high risk）经历下也能较好地维持健康，而一些人则被逆境打败，身心健康也随之处于不良状态。近年来，应激心理学、健康心理学、精神医学、教育学、护理学等各学科对韧性概念越来越重视，尤其是临床领域的研究，从过去强调人的缺点和脆弱性的病理模式转变为关注个人的优势和强韧性的健康模式。

The fluid mechanics of natural ventilation

Abstract: Natural ventilation of buildings is the flow generated by temperature differences and by the wind. The governing feature of this flow is the exchange between an interior space and the external ambient. Although the wind may often appear to be the dominant driving mechanism, in many circumstances temperature variations play a controlling feature on the ventilation since the directional buoyancy force has a large influence on the flow patterns within the space and on the nature of the exchange with the outside. Two forms of ventilation are discussed: mixing ventilation, in which the interior is at an approximately uniform temperature, and displacement ventilation, where there is strong internal stratification. The dynamics of these buoyancy-driven flows are considered, and the effects of wind on them are examined. The aim behind this work is to give designers rules and intuition on how air moves within a building; the research reveals a fascinating branch of fluid mechanics.

Towards sustainable, energy-efficient and healthy ventilation strategies in buildings: A review

Abstract: Energy demand has been increasing worldwide and the building sector represents a large percentage of global energy consumption. Therefore, promoting energy efficiency in buildings is essential. Among all building services, Heating, Ventilation and Air Conditioning (HVAC) systems are significantly responsible for building energy use. In HVAC, ventilation is the key issue for providing suitable Indoor Air Quality (IAQ), while it is also responsible for energy consumption in buildings. Thus, improving ventilation systems plays an important role not only in fostering energy efficiency in buildings, but also in providing better indoor climate for the occupants and decreasing the possibility of health issues in consequence. In the last decades, many energy-efficient ventilation methods are developed by researchers to mitigate energy consumption in buildings. This paper reviews scientific research and reports, as well as building regulations and standards, which evaluated, investigated and reported the development of energy-efficient methods for ventilation in buildings. Besides energy-efficient methods such as natural and hybrid ventilation strategies, occupants’ behaviours regarding ventilation, can also affect the energy demand in buildings. Therefore, the influence of occupants’ behaviour on the energy use and the correlation between ventilation and the occupants’ health and productivity were also considered. The review showed that ventilation is interrelated with many factors such as indoor and outdoor conditions, building characteristics, building application as well as users’ behaviour. Thus, it is concluded that many factors must be taken into account for designing energy-efficient and healthy ventilation systems. Moreover, it should be mentioned that utilizing hybrid ventilation in buildings integrated with suitable control strategies, to adjust between mechanical and natural ventilation, leads to considerable energy savings while an appropriate IAQ is maintained.