Search Results (86)

As global mineral resources at shallow depths continue to deplete, thermal hazards have emerged as a critical challenge in deep mining operations. Conventional localized cooling systems suffer from a fundamental inefficiency where their cooling capacity is rapidly dissipated by the main ventilation airstream. This study introduces the innovative concept of a “microclimatic circulation zone” implemented through a convection–radiation cooling system. The design incorporates a synergistic arrangement of dual fans and flow-guiding baffles that creates a semi-enclosed air circulation field surrounding the modular convection–radiation cooling apparatus, effectively preventing cooling capacity loss to the primary ventilation flow. The research develops comprehensive theoretical models characterizing both internal and external heat transfer mechanisms of the modular convection–radiation cooling system. Using Fluent computational fluid dynamics software, we constructed an integrated heat–moisture–flow coupled numerical model that identified optimal operating parameters: refrigerant velocity of 0.2 m/s, inlet airflow velocity of 0.45 m/s, and outlet aperture height of 70 mm. Performance evaluation conducted at a mining operation in Yunnan Province utilized the Wet Bulb Globe Temperature (WBGT) index as the assessment criterion. Results demonstrate that the enhanced microclimatic circulation system exhibits superior cooling retention capabilities, with a 19.83% increase in refrigeration power and merely 3% cooling capacity dissipation at a 7 m distance, compared to 19.23% in the conventional system. Thermal field analysis confirms that the improved configuration successfully establishes a stable microclimatic circulation zone with significantly more concentrated low-temperature regions. This effectively addresses the principal limitation of conventional systems where conditioned air is readily dispersed by the main ventilation current. The approach presented offers a novel technological pathway for localized thermal environment management in deep mining operations affected by heat stress conditions. Full article

The application of phase change material emulsions (PCMEs) in heating, ventilation, and air conditioning (HVAC) systems is considered to be a potential way of saving energy due to their relatively higher energy storage capacity compared with water. They are now widely used as a heat transfer media, so they are able to reduce the flow rate whilst delivering the same amount of cooling energy. In order to evaluate the energy-saving potential of the integrated PCME air conditioning system, whole-building energy simulation was carried out with the building simulation code TRNSYS. Before simulating the whole system, a mathematical model for a PCME-integrated fan coil unit was first developed and validated. A phase change material emulsion called PCE-10 was used, and the TRNSYS simulation showed that the required volumetric flow rate of phase change material emulsions was 50% less than that of water when providing the same cooling effect, which could contribute to a 7% reduction in total energy consumption. Full article

This study examined the effectiveness of using Internet of Things (IoT) technology to control environmental conditions in open-air pig housing systems in Thailand. This experiment was conducted in three zones: Zone 1, with no environmental controls (natural ventilation); Zone 2, with ventilation fans but no water-spraying system; and Zone 3, equipped with both ventilation fans and a roof-mounted water-spraying system. Key parameters, such as ammonia (NH₃), hydrogen sulfide (H₂S), temperature, and relative humidity, were monitored all year round. Zone 1, with only natural ventilation, exhibited the highest levels of pollutants, with an average ammonia concentration of 7.1 ppm and hydrogen sulfide at 7.6 ppm. The temperature averaged 31.81 °C, and the relative humidity was 53.65%, creating unfavorable conditions for pig farming. Zone 2, featuring ventilation fans, showed improvements, with the average ammonia and hydrogen sulfide levels reduced to 3.75 ppm and 4.12 ppm, respectively, although the temperatures (29.35 °C) were still too high at times, and the relative humidity was 49.50%. Zone 3, incorporating both fans and a water-spraying system, demonstrated the most effective environmental control, achieving lower ammonia (3.0 ppm) and hydrogen sulfide (2.93 ppm) levels, with an average temperature of 28.85 °C and relative humidity of 47.15%. These results suggest that IoT technology, combined with adequate ventilation and cooling systems, significantly enhances environmental conditions, thereby promoting better pig health and growth. Full article

This paper addresses the numerical simulation of unsteady, non-isothermal ventilation in a dead-end mine working of a potash mine excavated using a borer miner. During its operations, airflow can become unsteady due to the variable operating modes of the borer miner, the switching on and off of its motor cooling fans, and the movement of a shuttle car transporting ore. While steady ventilation in a dead-end working with a borer miner has been previously studied, the specific features of air microclimate parameter distribution in more complex and realistic unsteady scenarios remain unexplored. Our experimental studies reveal that over time, air velocity and, particularly, air temperature experience significant fluctuations. In this study, we develop and parameterize a mathematical model and perform a series of numerical simulations of unsteady heat and mass transfer in a dead-end working. These simulations account for the switching on and off of the borer miner’s fans and the movement of the shuttle car. The numerical model is calibrated using data from our experiments conducted in a potash mine. The analysis of the first factor is carried out by examining two extreme scenarios under steady-state ventilation conditions, while the second factor is analyzed within a fully unsteady framework using a dynamic mesh approach in the ANSYS Fluent 2021 R2. The numerical results demonstrate that the borer miner’s operating mode notably impacts the velocity and temperature fields, with a twofold decrease in maximum velocity near the cabin after the shuttle car departed and a temperature difference of about 1–1.5 °C between extreme scenarios in the case of forcing ventilation. The unsteady simulations using the dynamic mesh approach revealed that temperature variations were primarily caused by the borer miner’s cooling system, while the moving shuttle car generated short-term aerodynamic oscillations. Full article

The lack of energy-saving design in national fitness centers has affected low-cost operation and indoor comfort. Existing studies mainly focus on the impact of lighting and heat on energy consumption in sports stadiums, highlighting the need for the comprehensive planning of natural ventilation design to improve energy efficiency. This study uses the national fitness center in Qingdao as a case study, collecting building environmental information through field measurements and questionnaire surveys. Four design elements were selected: the window-to-wall ratio (WWR), proportion of operable window area (OWAR), skylight area ratio (SAR), and floor plan layout. Through the utilization of Ladybug Tools in combination with Radiance and EnergyPlus, an annual energy consumption simulation under natural ventilation conditions was conducted using an airflow network model. This study found that the WWR has a significant impact on lighting, ventilation, and energy consumption. The optimal WWR configuration for the venue was determined to be 0.37 for the north facade, 0.26 for the east, 0.53 for the south, and 0.41 for the west. Compared to no natural ventilation, cooling energy consumption was reduced by 18.02%, and fan energy consumption decreased by 11.03%. The energy-saving effect was optimal when the OWAR was approximately 30%. When the SAR reached 5%, cooling and lighting energy consumption were significantly reduced, resulting in the lowest total energy consumption. The study also compared the energy consumption differences in various floor plan layouts under the influence of natural ventilation. This research evaluates the natural ventilation efficiency of community fitness centers, avoiding the hidden energy consumption transfer typical of traditional single-objective optimization methods, and improves the energy-efficient design approach for national fitness centers. Full article

Windcatchers are effective passive ventilation systems, but their inability to actively reduce and stabilize supply air temperatures reduces indoor cooling performance. This study addresses this limitation by integrating encapsulated phase-change material tubes (E-PCM-Ts) into a solar fan-assisted, multidirectional windcatcher. The novelty lies in the vertical placement of E-PCM-Ts within the windcatcher’s airstreams, enhancing heat transfer and addressing challenges related to temperature stabilization and cooling. Using computational fluid dynamics (CFD) under hot outdoor conditions, the ventilation, cooling, and PCM thermal storage performance are evaluated based on two different E-PCM-T arrangements. Results showed a maximum air temperature drop of 2.28 °C at a wind speed of 1.88 m/s and wind angle of 0°. This offers an optimal temperature reduction that achieved a 6.5% reduction for up to 7 h of air temperature stabilization. Placing E-PCM-Ts in all airstreams improved the thermal storage performance of the windcatcher. A 50% increase in hybrid ventilation efficiency was also achieved when wind angles increased from 0° to 30°. Overall, the proposed system demonstrated superior performance compared to that of traditional windcatchers, delivering improved thermal energy storage and cooling efficiency and adequate hybrid ventilation with supply air velocities of 0.37–0.60 m/s. Full article

Climate change and the need to reduce greenhouse gas emissions have made energy efficiency in modern building operations more critical than ever. This study presents an improved damper control strategy for VAV systems, combined with techniques like DCV and duct static pressure adjustments, to optimize fan energy consumption. Using energy simulations and mathematical models, the research evaluates traditional HVAC operating methods against the proposed novel control approach across diverse climates. Findings show that the refined control integrations effectively adjust ventilation air volumes during low occupancy and achieve up to 47% savings in fan energy, cost, and CO₂ savings annually. While DCV alone had minimal impact on fan energy, it significantly reduced the amount of outdoor air that required conditioning, thereby lowering cooling and heating demands. This research highlights the importance of integrating an advanced control strategy in building mechanical systems to reduce operational costs and environmental impact, contributing to sustainability and carbon reduction goals. Full article

The present study investigates experimental cooling from the ceiling using phase change materials (PCMs) in Yazd, a city characterized by a hot and dry climate. A one-fourth scale model of a real room, measuring 4 m × 3 m × 3 m, was employed for the analysis. To evaluate system performance and the impact of PCM on energy consumption reduction, three configurations were considered: a simple PCM system, a PCM system with a fan (PCM-F), and a PCM system with a mini cooler (PCM-C). Additionally, to assess the influence of window configurations on ventilation, temperature, and comfort conditions within the model, three scenarios were examined: two open windows, one open window, and no windows. The economic analysis compared the two systems with the fan and mini cooler against a full mechanical cooling system without PCMs. Furthermore, CO₂ emissions and environmental impacts associated with the systems were also evaluated. The results indicate that the presence of PCMs in the ceiling, due to heat absorption during phase change, leads to a temperature reduction of 5 to 10 °C in the ceiling and a 3.2 °C reduction in the average room temperature compared to the scenario without PCMs. The findings demonstrate that ceiling cooling with PCMs significantly contributes to energy consumption reduction during peak hours of cooling demand. Specifically, the PCM-F system results in a 92% reduction, and the PCM-C system leads to a 71% reduction in total cost compared to the reference mechanical cooling system. Additionally, the PCM-F system achieves approximately a 36% reduction, and the PCM-C system results in a 34% reduction in environmental impact relative to the reference full mechanical cooling system. Full article

In modern manufacturing environments, pollution management is critical as exposure to harmful substances can cause serious health issues. This study presents a two-stage computational fluid dynamic (CFD) model to estimate the distribution of pollutants in indoor production spaces. In the first stage, the Reynolds-averaged Navier–Stokes (RANS) method was used to simulate airflow and temperature. In the second stage, the Lagrangian method was applied for particle tracing. The model was applied to a theoretical acrylonitrile butadiene styrene (ABS) filament 3D printing process to evaluate the factors affecting the distribution of ultrafine particles (30 nm). Key parameters such as ventilation system effects, the presence of cooling fans and the print bed, and nozzle temperatures were considered. The results show that the highest flow velocities (1.97 × 10⁻⁶ m/s to 3.38 m/s) occur near the ventilation system’s inlet and outlet, accompanied by regions of high turbulent kinetic energy (0.66 m²/s²). These conditions promote dynamic airflow, facilitating particulate removal by reducing stagnant zones prone to pollutant buildup. The effect of cooling fans and thermal sources was investigated, showing limited contribution on particle removal. These findings emphasize the importance of digital twins for better worker safety and air quality in 3D printing environments. Full article

A strategy for effectively utilizing occupants’ adaptive behaviors (OABs) to achieve thermal acceptability while maintaining low energy consumption is necessary. This study aims to clarify the relationship between OABs and thermal acceptability over various climate zones, as well as the change in OABs due to air conditioner (AC) ownership in Indonesian residences. An online questionnaire consisting of perceived OABs’ time intensity, thermal acceptability, and personal attributes from 3000 respondents across Indonesia was analyzed using logistic regression. The results suggested that NV occupants engage in more fan usage and window opening to enhance ventilative cooling, while AC occupants are more likely to adjust clothing and use portable fans to create cooler environments. Moreover, the effects of OABs on NV residences varied depending on the local climate conditions. In hot local climates, averages of 90% fan usage intensity and 92% window opening intensity, complemented with active clothing adjustment, were unable to effectively provide thermal acceptability. These findings imply that there is a range of indoor environmental conditions in which conventional OABs work well. This study highlights the need to promote behavioral adaptations, especially in AC mixed-mode buildings, and to consider behavioral adaptations in NV buildings based on local climates. Full article

This study aims to improve the microclimate conditions in a mechanically ventilated broiler house by proposing and evaluating a ventilation-control algorithm based on heat-energy balance analysis. The new algorithm is designed to optimise the ventilation-rate requirement and thereby improve control of the indoor temperature. The analysis of one year of operational data collected at the experimental farm indicates that the current ventilation-control system successfully maintained optimal indoor temperatures for 74% of the time. In contrast, the proposed algorithm has the potential to improve this number significantly (up to 92%). The new algorithm was implemented and evaluated at two broiler houses (control and experimental) starting from day 20 to day 34 during one rearing period under high-temperature conditions. The results confirm that the new algorithm effectively reduced indoor temperatures by 1.5–2 °C during the day, which reduces heat stress significantly. Even though cooling pad usage increased to about eight times, the reduction in tunnel fan usage (to about 52%) led to significant energy savings. Furthermore, broiler mortality was reduced by 16.5%, which means there is also potential for improved productivity. The proposed ventilation control algorithm can effectively enhance microclimate conditions and energy efficiency in broiler production, though longer-term studies are required to fully assess its impact on growth performance. Full article

Effective air circulation is crucial for plant growth, requiring adequate airflow and environmental stability. This study utilized Computational Fluid Dynamics (CFD) to analyze airflow patterns in a controlled testing chamber, focusing on how miniature fan placement affects airflow direction and temperature distribution. Ten case studies were conducted, with the CFD model validated against experimental data collected from six monitoring locations on the plant growth table. Model validation was performed using statistical analyses including coefficient of determination (R²), root mean square error (RMSE), and mean absolute error (MAE). The validation results showed strong agreement between simulated and experimental data, with R² values of 0.92 for temperature and 0.89 for airflow velocity. Statistical analysis showed significant differences in both airflow and temperature models at the 0.05 level, with the CFD model validation yielding an RMSE of 2.02 and an average absolute error of 1.17. Among the tested configurations, case M1 achieved the highest air velocity (0.317 m/s) and lowest temperature (27.03 °C), compared to M2 (0.255 m/s, 27.17 °C) and M3 (0.164 m/s, 27.18 °C). The temperature variations between cases significantly impacted cold storage efficiency, with case M1’s superior airflow distribution providing more uniform cooling. These findings offer practical guidelines for optimizing ventilation system design in medicinal plant cultivation facilities, particularly in maintaining ideal storage conditions through strategic fan placement and airflow management. Full article

Historical building reuse is aimed at preservation, where buildings are recovered for new uses connected to cultural activities. This paper presents the analysis of the impact of thermo-fluid dynamics due to a 500 kW electrical power transformer installed inside a historical building. The analysis is performed using computational fluid dynamics simulations validated through measurement campaigns carried out during the summer period. High temperatures and wide humidity variations can damage building plasters and cause malfunctions in power equipment. To avoid these situations, two different installation layouts were studied. One consists of the power transformer directly installed in the environment and cooled by an inlet fan, and the other consists of the power transformer being insulated from the external environment by an enclosure connected to a forced ventilation system. The second layout showed better results both inside and outside the transformer enclosure. The maximum indoor condition was about 4.3 °C, with a −7.2% RH and an airflow rate of 1100 m³/h, and the maximum outdoor air condition was 3.3 °C, with a −1.39% RH and a flow rate of 2200 m³/h. However, the temperatures and humidity inside the building and outside the transformer enclosure were almost the same. Full article

Pressure differences in the envelope of a building result in leakage airflow (i.e., the unintended flow of air). This can lead to increased building heating and cooling energy, decreased thermal comfort for occupants, and the spread of moisture. To address this problem, it is necessary to know the leakage airflow in a building. Generally, the leakage airflow in a building is calculated by determining the leakage function through fan pressurization methods, such as the blower door test, and substituting the pressure difference measured by the pressure sensor. However, it is difficult to install continuous pressure sensors in an operating building. Therefore, this study proposes a method to utilize the supply and return airflow of an air conditioning system to predict the variation in the leakage airflow with changing indoor and outdoor airflow, and the efficacy of this approach was verified through experiments. The experiment measured the indoor and outdoor pressure difference of the building with a change in the speed of the supply and return fans and the opening rate of the variable air volume (VAV) damper. As a result of the experiment, the indoor–outdoor pressure difference is proportional to the difference between the indoor supply airflow and the ventilation airflow. In addition, the relationship between the pressure difference and the leakage airflow was derived through the pressurization/decompression method using an air handler, and the leakage airflow from the pressure difference generated by the operation of the air conditioning system was calculated. Lastly, the relationship between the supply and return airflow difference and the leakage airflow was derived based on the experimental results, and the leakage airflow was predicted based on the relationship. Full article

This paper aims to investigate the indoor environmental conditions and energy use behaviours of older individuals in rural cold climates of China, with a specific focus on cooling practices during the summer months in the Shandong region. This study employs a mixed-method approach, combining quantitative indoor environmental monitoring with qualitative interviews and observations, to explore the relationship between environmental factors, household living conditions, and energy use patterns across five types of elderly households: three generations living together, older people living with grandchildren, older people living with children, older couples living together, and older people living alone. Data collection was conducted over five weeks during the summer of 2023 using HOBO UX100-003 data loggers, while external weather conditions were monitored by the China Meteorological Administration. Face-to-face interviews were conducted to gain deeper insights into daily cooling behaviours and energy use. The results reveal that cooling practices and indoor environmental conditions vary significantly among the different household types. Multigenerational households showed more complex energy use dynamics, with younger family members frequently operating high-energy appliances like air conditioners, while older individuals tended to rely on natural ventilation and electric fans to reduce energy costs. In contrast, older couples and solitary older individuals demonstrated more conservative cooling behaviours, often enduring higher indoor temperatures due to limited financial resources and a desire to minimize energy expenditures. Despite the high energy use intensity in some households, many homes failed to achieve comfortable indoor environments, particularly in dwellings with minimal insulation and older building materials. This study concludes that economic status, household structure, and building characteristics play crucial roles in shaping cooling behaviours and indoor comfort during the summer. Full article