Energy and Built Environment最新文献

A well-designed spray system, which is located near the source of high-temperature smoke, can improve the capture efficiency of traditional local exhaust ventilation (LEV). However, there is currently no comprehensive evaluation index that clearly reflects the performance of spray-local exhaust ventilation (SLEV), making it challenging to optimize the spray arrangement. The two-phase flow fields in the SLEV and LEV were compared to evaluate the impact of spray on smoke control. The effects of spray arrangement parameters, such as spray position, spacing, initial droplet size, and angle, on the performance of the SLEV system were further evaluated using current evaluation indicators. Based on this, we developed a comprehensive evaluation model for SLEV using the AHP-entropy combination weighting method. The results revealed that the decrease in smoke control with an increase in rolling speed is primarily caused by a reduction in spray control in the central region of the smoke. When the spray flow rate is 0.0028 kg/s and the velocity is 30 m/s, the primary factor that improves ventilation performance is the downward drag force exerted by the spray on smoke, rather than the cooling effect. The comprehensive model was developed using weights of 0.45, 0.34, and 0.21 for the three evaluation indicators: capture efficiency, high-quality concentration field ratio, and spatial droplet size. The model showed good reliability based on the results of the smoke concentration analysis. The results of this study are expected to guide the design, implementation, and evaluation of SLEV systems.

The energy storage is an effective solution for the current imbalance between energy supply and demand. In particular, the cascaded storage method can enhance the heat exchange temperature difference and heat storage efficiency. Previous research mainly focused on the combination of different phase change materials, while there was rare research on efficient cascaded conversion pathways for electrothermal direct conversion coupled thermal storage devices. This study investigated the influence of sensible and latent heat storage materials on the thermal performance, and identified the optimal volume ratios and materials types. When the volume share of Mg-Al:PW-EG=1:1, the heat storage performance was the optimal with a quantity/efficiency of heat stored as 7328.7 kJ/97.3 %, leading to an increase of 458.5 kJ/6.6 % than the sensible heat storage condition (Mg-Al:PW-EG=1:0) and 630.18 kJ/8.5 % than the latent heat storage condition (Mg-Al:PW-EG=0:1). When the melting point and latent heat of phase change materials increased from 68.9∼79.1 °C and 224.8 kJ/kg to 118.0 °C and 344.9 kJ/kg respectively, the heat storage temperature rose by 162.7 °C, quantity of heat stored rose by 7535.5 kJ. While materials with large subcooling were not recommended for short-term heat storage, as approximately 25.6 % (3309.3 kJ) of stored heat and 22.4 % (2505.2 kJ) of exergy were wasted when the subcooling degree was 70 °C. The findings provided solutions to support the synergistic enhancement of heat storage/release performance of the composite energy storage heat sink.

This article focuses on the thermal bridging issues associated with interface of parkade concrete suspended slab to base of wall. The study aims to determine the optimal length and thickness of insulation at the top and underside of the suspended slab to minimize heat loss. The thermal performance of wall to parkade suspended slab is investigated, for both wood frame and steel stud constructions. Various insulation configurations are proposed and evaluated, including different lengths and thicknesses of extruded polystyrene foam (XPS) and Fiberglass spray insulations. The thermal performance calculations are conducted using steady-state heat transfer analysis. A finite-element based software is utilized for the simulations. The study provides a detailed methodology for analyzing the thermal performance of building envelope details, considering different insulation configurations. The results of the simulations are presented as Thermal Resistance Values (R-Values) and Linear Thermal Resistance Values (PSI-Values), allowing for a comparison of the thermal efficiency of different insulation configurations. The results show that utilizing the optimal insulation configuration can lead to up to 80 % enhancement in the thermal efficiency of the assembly. The findings serve as a guideline and aim to assist building designers in improving the thermal performance of concrete suspended slabs.

Research on thermal comfort has revealed various adaptive behaviours in a hostel room, such as changing clothing, use of windows, doors, and ceiling fans. Hostel rooms are used for various activities and are typically furnished with a wardrobe, bed, study table, and chair. Recent studies indicate that ceiling fan fixed at the centre of the room may not provide adequate air velocity for different activities occurring in different parts of a room. Although students generally arrange furniture based on their preferences and room geometry, the influence of fan-induced air on furniture layout to improve thermal comfort is yet to be established. In this context, this study investigates spatial adaptation and identifies the factors affecting furniture layout preferences in hostel rooms. In a yearlong study, patterns of furniture layout were observed in twenty-one naturally ventilated hostel buildings to find their relationship with environmental and non-environmental factors. A total of 1665 observation data was collected from single, double, and triple occupancy rooms. Influence of various factors on arranging the furniture was identified through a questionnaire survey. Throughout the survey, outdoor temperature varied between 23 and 41 °C and outdoor relative humidity varied between 32.3 % and 97.5 %. The spatial arrangement of furniture was evaluated against fan location. Results indicate that fan location and indoor temperature significantly influence the furniture arrangement. A logistic regression equation was developed to evaluate the trigger temperature when students began moving furniture towards ceiling fan. In a single occupancy room, above 34.2 °C, the probability of moving the bed towards the fan was found to be maximum. In single and double occupancy rooms, students move the bed near the ceiling fan predominantly during night-time to get sufficient air movement. A cautious design of furniture layout and adding a personalised fan for various activities may improve the thermal comfort in hostel rooms.

Climate crisis mitigation roadmaps, policies and directives have increasingly declared that a key element for the facilitation of sustainable urban development is on-site decentralized renewable energy generation. A technology with enhanced capabilities, able of promoting the integration of renewable energy into buildings, for energy independent and resilient communities, is Photovoltaic Thermal (PVT) systems. Ongoing research has potential yet displays a lack in unified methodology. This limits its influence on future decision-making in building and city planning levels. In this investigation, the often overlooked air-based PVT technology is put on the spotlight and their suitability for integration with energy systems of buildings is assessed. The aim of this study is to highlight vital performance and integration roadblocks in PVT research and offer suggestions for overcoming them. The methodology of reviewed literature is examined in detail with the goal of contributing to a unified approach for more impactful research.

The electricity consumption of the urban metro system can be mainly divided into the following two categories: the electricity consumption for train traction (E_t) and the electricity consumption for station operation (E_s). Although understanding the hourly fluctuation characteristics of E_t and E_s contributes to renewable energy integration and achieving carbon emission reduction of the metro system, the hourly fluctuation characteristics have been poorly reported in the literature. Thus, a typical underground non-transfer metro station of a city's metro system in the North China Plain is selected in this study, and E_t and E_s were monitored to portray their hourly fluctuation characteristics. Results reveal that the hourly E_t shows a significant intraday “U” shape on weekdays, indicating two symmetric peaks in morning and evening rush hours. While the hourly E_s shows an intraday “flat” shape, indicating it is nearly free from the effect of rush hour. Moreover, it is statistically proved that the train frequency is the core influencing factor resulting in the intraday fluctuation of hourly E_t. In the case study, when the train frequency increases from the mean (20 trains per hour) to maximum (32 trains per hour), the hourly E_t will increase by 53.4%.

In order to solve the problems of low thermal conductivity and easy liquid leakage of a stearic acid (SA), the composite phase change material(PCM) was prepared by adding boron nitride (BN) and expanded graphite (EG) to melted SA, and its thermal conductivity, crystal structure, chemical stability, thermal stability, cycle stability, leakage characteristics, heat storage/release characteristics, and temperature response characteristics were characterized. The results showed that the addition of BN and EG significantly improved the thermal conductivity of the material, and they efficiently adsorbed melted SA. The maximum load of SA was 76 wt. % and there was almost no liquid leakage. Moreover, the melting enthalpy and temperature were 154.20 J • g ^{− 1} and 67.85°C, respectively. Compared with pure SA, the SA/BN/EG composite showed a lower melting temperature and a higher freezing temperature. In addition, when the mass fraction of BN and EG was 12 wt. %, the thermal conductivity of the composite was 6.349 W • m⁻¹ • K⁻¹, which was 18.619 times that of SA. More importantly, the composite showed good stability for 50 cycles of heating and cooling, and the SA / BN / EG-12 hardly decomposes below 200°C, which implies that the working performance of the composite PCM is relatively stable within the temperature range of 100°C. Therefore, the composite can exhibit excellent thermal stability in the field of building heating.