High population density, dense high-rise buildings, and impervious pavements increase the vulnerability of cities, which aggravate the urban climate environment characterized by the urban heat island (UHI) effect. Cities in China provide unique information on the UHI phenomenon because they have experienced rapid urbanization and dramatic economic development, which have had a great influence on the climate in recent decades. This paper provides a review of recent research on the methods and impacts of UHI on building energy consumption, and the practical techniques that can be used to mitigate the adverse effects of UHI in China. The impact of UHI on building energy consumption depends largely on the local microclimate, the urban area features where the building is located, and the type and characteristics of the building. In the urban areas dominated by air conditioning, UHI could result in an approximately 10–16% increase in cooling energy consumption. Besides, the potential negative effects of UHI can be prevented from China in many ways, such as urban greening, cool material, water bodies, urban ventilation, etc. These strategies could have a substantial impact on the overall urban thermal environment if they can be used in the project design stage of urban planning and implemented on a large scale. Therefore, this study is useful to deepen the understanding of the physical mechanisms of UHI and provide practical approaches to fight the UHI for the urban planners, public health officials, and city decision-makers in China.

Numerical simulation is vital for evaluating urban ventilation. However, accurate urban-scale ventilation modeling requires extensive building surface simulation for computational demand. The distributed drag force approach simplifies the urban canopy by modeling buildings as a porous volume that accounts for momentum and turbulence. This method is a practical solution for simulating urban airflow. The drag force coefficient (C_d) is a crucial aerodynamic parameter in this approach. This study examines how C_d varies with urban design parameters such as plan area density (λ_p), average building height (H), frontal area density (λ_f), floor aspect ratio (AR), and sky view factor (SVF). Employing extensive numerical simulations conducted under neutral atmospheric conditions, we explore ranges of λ_p = 0.04–0.07 and λ_f = 0.1–1.2. The numerical model has been validated against existing wind tunnel data. The results show that C_d is insensitive to the model scale and background wind speed. We discover a nonlinear relationship between C_d and the parameters λ_p, λ_f, and SVF. For urban layouts with cubic-shaped buildings, C_d peaks at different λ_p within the range of 0.2~0.8. When λ_p and H are constant, C_d has a linear relationship with AR and λ_f. It is recommended to use λ_p, SVF, and AR as predictors for C_d across various urban configurations.

Thermal storage capacity and airflow rate of a solar chimney combined with different PCMs are numerically studied during nighttime. PCMs with phase change temperatures of 38°C, 44°C, 50°C, and 63°C are selected in this numerical study. Results show that the maximum average ventilation rate of 610 kg/m² and maximum thermal storage of 4750 kJ/m² are achieved at the phase change temperature of 38°C. However, for phase change temperature of 63°C, night ventilation does not occur under the identical conditions. The findings reveal that a lower phase change temperature can increase the chargeability (and therefore the dischargeability) of a solar chimney, since a higher phase change temperature demands higher solar radiation intensity and longer charging time for a solar chimney. For PCM with a phase change temperature of 44°C, most of the heat stored in PCM is lost to ambient through glass cover by radiation and only a small portion is used for heating the air within air channel.

Buoyancy-driven natural ventilation has the potential to improve the indoor thermal environment without any energy consumption. In this study, the applicability of the dimensionless area design method was studied, and the airflow rate and excess temperature deviation of rooms on different floors were verified. The results demonstrate that the airflow rates on the first, second and third floors are 887.68, 861.84 and 820.93 m3/h, respectively, and the corresponding airflow rates per capita are 88.77, 86.18 and 82.09 m3/h, respectively. In addition, the average indoor temperatures on the first, second and third floors are 298.78, 299.05 and 299.58 K, respectively, with corresponding excess temperatures of 5.72, 5.99 and 6.52 K. The deviation of airflow rate in the room is within the range of 0.59%-4.2%, indicating that the dimensionless area design method is suitable for designing naturally ventilated buildings.