The potential risk of spreading a virus during bus transportation motivates us to understand the aerosol transmission of SARS-CoV-2 and seek effective ways to protect passengers in a bus. In this paper, a typical scenario in which the virus spreads in a bus under a windless environment is numerically studied for further understanding of the spreading characteristics of aerosol transmission in an enclosed space. The air flow in the bus and the spreading processes of droplets with different open windows configurations are obtained and analyzed. The variations of droplet concentration in the air with time are examined and analyzed. In addition, the transient droplet concentration deposited on the passengers is also counted to analyze the potential contact transmission. The results indicate that opening a window next to an infected person shows an unsatisfactory performance in limiting droplet spreading range and reducing droplet concentration, eventually leading to a high risk of infection by aerosol transmission following contact transmission. In addition, opening multiple windows also shows an unsatisfactory result for removing droplets in a bus since the turbulence flow accelerates the spreading speed and expands the spreading range. In contrast, the droplets are removed from the indoor space of the bus quickly if a window is opened in the row in front of the infected person, which is beneficial for reducing aerosol and contact transmission in the bus. Furthermore, it is strongly recommended to avoid sitting in the row in front of the infected person where the highest droplet concentration can be observed.

Thermal Fatigue of flip chip component solder joints is widely existing in thermal energy systems, which imposes a great challenge to operational safety. In order to investigate the influential factors, this paper develops a model to analyze thermal fatigue, based on the Darveaux energy method. Under cyclic thermal loading, a theoretical heat transfer and thermal stress model is developed for the flip chip components and the thermal fatigue lives of flip chip component solder joints are analyzed. The model based simulation results show the effects of environmental and power parameters on thermal fatigue life. It is indicated that under cyclic thermal loading, the solder joint with the shortest life in a package of flip chip components is located at the outer corner point of the array. Increment in either power density or ambient temperature or the decrease in either power conversion time or ambient pressure will result in short thermal fatigue lives of the key solder joints in the flip chip components. In addition, thermal fatigue life is more sensitive to power density and ambient temperature than to power conversion time and ambient air pressure.

Facility agriculture, which involves agricultural production in controlled environments such as greenhouses, indoor farms, and vertical farms, aims to maximize efficiency, yield, and quality while minimizing resource consumption and environmental impact. Energy-saving technologies are essential to the green and low-carbon development of facility agriculture. Recently, phase change heat storage (PCHS) systems using phase change materials (PCMs) have gained significant attention due to their high thermal storage density and excellent thermal regulation performance. These systems are particularly promising for applications in facility agriculture and related buildings, such as solar thermal utilization, greenhouse walls, and soil insulation. However, the low thermal conductivity of PCMs presents a challenge for applications requiring rapid heat transfer. This study aims to provide a comprehensive review of the types, thermophysical properties, and various forms of PCMs, including macro-encapsulated PCMs, shape-stabilized PCMs, and phase change capsules (PCCs), as well as their preparation methods. The research methodology involves an in-depth analysis of these PCMs and their applications in active and passive PCHS systems within facility agriculture and related buildings. The major conclusion of this study highlights the critical role of PCMs in advancing energy-saving technologies in facility agriculture. By enhancing PCM performance, optimizing latent heat storage systems, and integrating intelligent environmental control, this work provides essential guidelines for designing more efficient and sustainable agricultural structures. The article will serve as the fundamental guideline to design more robust structures for facility agriculture and related buildings.

A vapor chamber can meet the cooling requirements of high heat flux electronic equipment. In this paper, based on a proposed vapor chamber with a side window, a vapor chamber experimental system was designed to visually study its evaporation and condensation heat transfer performance. Using infrared thermal imaging technology, the temperature distribution and the vapor–liquid two-phase interface evolution inside the cavity were experimentally observed. Furthermore, the evaporation and condensation heat transfer coefficients were obtained according to the measured temperature of the liquid near the evaporator surface and the vapor near the condenser surface. The effects of heat load and filling rate on the thermal resistance and the evaporation and condensation heat transfer coefficients are analyzed and discussed. The results indicate that the liquid filling rate that maximized the evaporation heat transfer coefficient was different from the liquid filling rate that maximized the condensation heat transfer coefficient. The vapor chamber showed good heat transfer performance with a liquid filling rate of 33%. According to the infrared thermal images, it was observed that the evaporation/boiling heat transfer could be strengthened by the interference of easily broken bubbles and boiling liquid. When the heat input increased, the uniformity of temperature distribution was improved due to the intensified heat transfer on the evaporator surface.

Vapor-liquid phase change is regarded as an efficient cooling method for high-heat-flux electronic components. The copper-water bent heat pipes are particularly suited to the circumstances of confined space or misplaced heat and cold sources for high-heat-flux electronic components. In this paper, the steady and transient thermal performance of a bent copper-water heat pipe is studied based on a performance test system. The effects of cooling temperature, working conditions on the critical heat flux, and equivalent thermal conductivity have been examined and analyzed. Moreover, the influences of heat input and working conditions on the thermal response of a bent heat pipe have also been discussed. The results indicate that the critical heat flux is enhanced due to the increases in cooling temperature and the lengths of the evaporator and condenser. In addition, the critical heat flux is improved by extending the cooling length only when the operating temperature is higher than 50°C. The improvement on the equivalent thermal by increasing the heating length is more evident than that by increasing cooling length. It is also demonstrated by the experiment that the bent copper-water heat pipe can respond quickly to the variation of heat input and possesses superior transient heat transfer performance.

The dynamic formation characteristics of droplets in a cross-junction can be captured via a high-speed image setup. The experimental results show four flow regimes: slug, dripping, jetting (threading and tubing), and viscous displacement. When Ca_d and Ca_c are small, the slug regime occurs. The dripping regime occurs when Ca_c is relatively high. The jetting regime appears when Ca_d increases to a considerable value. When Ca_c is much smaller than Ca_d, the viscous displacement regime occurs. In the slug and dripping regimes, the dispersed phase will experience growing, squeezing, and pinching off stages in the formation of droplets. These four flow regimes are strongly affected by Ca_c and Ca_d. In addition, the flow rates of the two phases can be changed to adjust the sizes of the generated droplet in the cross-junction under the slug regime and dripping regime. The dimensionless droplet length l* can be predicted via l* = (0.248 + 0.55Q)Ca_c^−0.203.