Search Results (30)

In a flight test facility twin-aisle cabin demonstrator, a test series was conducted with the objective to investigate cleaning methods for recirculated air. Based on the data, a 3D zonal airflow simulation model of particle spread and cleaning performance was validated with the aim of extrapolating results to arbitrary aircraft cabins. For the tests, particles containing a phi6 bacteriophage, a virus only attacking a specific bacterium and with a similar structure to SARS-CoV-2, was dosed through a breathing head. The particle distribution and infectiveness of the air samples were measured. State-of-the-art HEPA filtering and cleaners based on UV-C and plasma were integrated in the recirculated air path and experimentally investigated. The test results showed the best cleaning performance for the state-of-the-art HEPA filter, while the alternatives showed lower performance levels. It was noted that infectiveness and particle count did not necessarily follow a monotonic function, making the link between these two quantities challenging. Therefore, modeling showed to be able to properly replicate particle distribution in the cabin, while an assumption of infectiveness depending on particle count had to be made. The model could successfully be applied to a single-aisle aircraft cabin geometry. Full article

Heat pump (HP) technology has been widely adopted in electric vehicles (EVs) for cabin and battery heating in cold weather due to its high efficiency. However, when an HP works under low ambient temperatures and high humidity, frost grows on the surface of the outdoor evaporator, deteriorating system efficiency. This study experimentally investigated the performance of an automotive reversible CO₂ HP system under cyclic frosting–defrosting conditions, with different defrost-initiation criteria and orientations of the outdoor heat exchanger. The relationship between the performance degradation of the heat pump system and the feature of frost accumulation on the outdoor heat exchanger is analyzed. The experimental data revealed that the heating capacity of the HP system only mildly degrades (~30%), even with an air-side pressure drop of the outdoor heat exchanger growing 10 times, which enables the system to work in HP mode for a longer time before the defrosting without significantly impacting passengers’ comfort. The horizontally installed outdoor heat exchanger is proven to have better refrigerant distribution, but with approximately a 0.16 bar (11.9%) higher pressure drop, reducing the evaporating temperature by about 0.4 K. Consequently, frost accumulates faster, and the working time in HP mode is shortened by 12 min (18.2%). Moreover, the vertical outdoor heat exchanger drains much more water during the defrosting. As a result, the defrosting time for the vertical outdoor heat exchanger is reduced by 17%. Full article

This study introduces the innovative application of a vapor chamber to mitigate fuel freezing and temperature disparity in power generation cabins operating under extreme cold conditions. A vapor chamber was designed and implemented within a low-temperature power generation platform in Daqing, China, where outdoor temperatures were below −20 °C. The research focused on evaluating the thermal performance of the cabin under natural and forced convection conditions, with and without the vapor chamber. The experimental investigations assessed the effects of the vapor chamber on the thermal dynamics of the power generation cabin, particularly the temperature of the bottom fuel oil and the air temperature distribution. The results indicated that without the vapor chamber significant temperature disparities and potential risks to electrical equipment were present. The vapor chamber effectively utilizes the heat generated by the diesel engine, thus accelerating the heating rate of the fuel at the bottom. It reduces the duration of the decrease in the oil temperature of the upper and lower layers during the initial start-up from 0.44 h and 0.5 h to 0.31 h and 0.35 h, respectively, effectively preventing the risk of fuel freezing in the initial start-up stage. In addition, the installation of the vaporization chamber significantly improves the temperature uniformity of the air inside the cabin. The maximum temperature difference between the upper and lower air in the cabin decreases by 33 °C, effectively improving the overall thermal environment. 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 recent events impacting public health highlight the need for investigating airflow patterns in confined spaces like elevator cabins. It is essential to ensure proper ventilation, prevent the accumulation of contaminants, and ultimately promote a healthy indoor environment for occupants. In this study, an evaluation of the airflow distribution, temperature, and mean age of air control within an occupied elevator cabin is presented. For that, a CFD model that simulated the airflow patterns in an elevator cabin was developed, validated, and used to conduct the study under six air ventilation scenarios, involving mechanical ventilation with air curtains or displacement flows. The proposed ventilation configurations in Cases 2–6 enhanced the airflow circulation within the elevator. Among these configurations, Case 4, a case of displacement flow, exhibited the most favourable conditions, providing an ACH of 27.05, a mean air age of 84.45 s in the breathable plane, an air change effectiveness of 1.478, and a temperature of 25 °C near the doors and around the occupied zone. It is important to highlight Case 3, which had a lower ACH of 21.2 compared to Case 4. Despite this, Case 3 presented a mean average air age of approximately 122.84 s and an air change effectiveness of 1.309. Based on these findings, displacement ventilation (Case 4) is recommended as the most effective configuration, followed by Case 3, which also showed improved air circulation compared to the other scenarios. The results evidence that the ventilation configuration is particularly influential when aiming to promote air ventilation and improve air age conditions in elevator cabins. Full article

In cold environments, traditional independent thermal management systems heavily rely on inefficient Positive Temperature Coefficient (PTC) heaters, which exacerbate range anxiety in vehicles. In this study, an energy management-based control strategy for an integrated thermal management system (ITMS) designed for hybrid electric vehicles (HEVs) is proposed. By coupling the four thermal flow circuits of the entire vehicle and integrating driving modes with heating demands, this strategy achieves full vehicle-level integrated control. Through optimizing the distribution and utilization of heat within the vehicle, this enhances the heating performance of the air source heat pump. The simulation results demonstrate that the proposed strategy significantly reduces the power consumption of the heat pump and improves heating efficiency for both the battery and the cabin. By utilizing waste heat from the motor and the engine, the ITMS increases the heating capacity of the heat pump, particularly in low-temperature environments. Compared to traditional thermal management systems, the ITMS control strategy achieves substantial improvements in both heating time and energy efficiency. Specifically, the system reduces battery heating time by 55.94% and enhances the overall heating performance of the vehicle. Furthermore, the strategy reduces fuel consumption by 5.18%, demonstrating its potential to improve the energy efficiency of HEVs in cold climates. Full article

Aircraft cabins have high occupant densities and may introduce the risk of COVID-19 contamination. In this study, a segment of a Boeing 767 aircraft cabin with a mixing type of air distribution system was investigated for COVID-19 deposition. A section of a Boeing 737-300 cabin, featuring four rows with 28 box-shaped mannequins, was used for simulation. Conditioned air entered through ceiling inlets and exited near the floor, simulating a mixed air distribution system. Cough droplets were modeled using the Discrete Phase Model from two locations: the centre seat in the second row and the window seat in the fourth row. These droplets had a mean diameter of 90 µm, an exhalation velocity of 11.5 m/s and a flow rate of 8.5 L/s. A high-quality polyhedral mesh of about 7.5 million elements was created, with a skewness of 0.65 and an orthogonality of 0.3. The SIMPLE algorithm and a second-order upwind finite volume method were used to model airflow and droplet dynamics. It was found that the ceiling accounted for the maximum concentration followed by the seats. The concentration of deposits was almost 50% more when the source was at window as compared to the centre seat. The Covid particles resided for longer duration when the source was at the centre of the cabin than when it was located near the widow. Full article

The civil aircraft cabin is enclosed and highly occupied, making it susceptible to a decline in indoor environmental quality. The environmental quality of civil aircraft cabins not only depends on objective factors such as temperature, relative humidity, and the presence of air pollutants such as carbon dioxide (CO₂), carbon monoxide (CO), ozone (O₃), particle matter (PM), and volatile organic compounds (VOCs) but also the subjective factors pertaining to the perceptions and health symptoms of passengers and crew. However, few studies have thoroughly examined the air quality and thermal comfort parameters that are measured during in-flight testing in airplane cabins, as well as the passengers’ subjective perceptions. In order to evaluate the in-flight thermal comfort and air quality status, this study conducted a review of the recent literature to compile data on primary categories, standard limits, and distribution ranges of in-flight environmental factors within civil aircraft cabins. Following a search procedure outlined in this paper, 54 papers were selected for inclusion. Utilizing the Monte Carlo method, the Predicted Mean Vote (PMV) distributions under different exercise intensities and clothing thermal resistance were measured with the in-cabin temperature and humidity from in-flight tests. Recommendations based on first-hand data were made to maintain the relative humidity in the cabin below 40%, ensure wind speed remains within the range of 0–1 m/s, and regulate the temperature between 25–27 °C (for summer) and 22–27 °C (for winter). The current estimated cabin air supply rate generally complies with the requirements of international standards. Additionally, potential carcinogenic and non-carcinogenic risks associated with formaldehyde, benzene, tetrachloroethylene, and naphthalene were calculated. The sorted data of in-flight tests and the evaluation of the subjective perception of the occupants provide an evaluation of current cabin thermal comfort and air quality status, which can serve as a reference for optimizing indoor environmental quality in future generations of civil aircraft cabins. Full article

In this study, a numerical model of the cable cabin of a comprehensive pipe gallery was established to study the smoke flow diffusion behaviour of a comprehensive pipe gallery fire under a rectangular cross-section. The effects of fire source power (Q = 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 MW) and fire source location (D = 10, 20, 40, 50, 60, 80, 100 m) on the smoke flow characteristics—such as smoke layer height and thickness, longitudinal airflow velocity, and ceiling temperature distribution—were analysed, and the corresponding prediction model was fitted. The results show the following: (1) The height of the smoke layer decreases with increasing fire power, and the predictive model of the smoke layer thickness obtained from the fitting is proportional to the smoke mass flow rate and inversely proportional to the aspect ratio of the pipe gallery. (2) Longitudinal air velocity prediction models of D < 50 m and D ≥ 50 m are fitted, and the average error between them and the numerical simulation values is 9.611%. (3) The temperature decay gradient of the smoke decreases gradually with increasing distance from the fire source, while there is a significant temperature difference between the two sides of the fire source. The average relative errors of the dimensionless temperature rise models fitted upstream and downstream of the fire source in the form of $\frac{\Delta T}{T_0}=A{e}^{B\left(\frac{D-X}{H}\right)+C}$ exponentials with respect to the numerical simulations were 11.688% and 7.296%, respectively. The results of the study can provide a reference for smoke flow and fire prevention and control in comprehensive pipe galleries. Full article

This study investigates the airflow and thermal management of a compact electric energy storage system by using computational fluid dynamic (CFD) simulation. A porous medium model for predicting the flow resistance performance of the battery modules in a battery cabinet is developed. By studying the influence of rack shapes, the effects of heat exchanger arrangements and other parameters on the airflow and battery thermal distribution are analyzed. When applying a larger bottom air channel, the inlet flow uniformity of each battery cabin in the cabinet increases by 5%. Meanwhile, temperature standard deviation decreases by 0.18 while raising the flow rate from 3 m/s to 8 m/s, indicating better temperature uniformity in the battery cabin. When the charge–discharge ratio reaches 0.5 C, the temperature deviation of the entire cabinet significantly increases, reaching 8 K. Furthermore, a rack-level thermal management scheme is proposed to effectively reduce the thermal deviation of the container electric energy storage system and improve the overall temperature uniformity. Results reveal that the rack-level thermal management of the wavy cabinet in the electric storage container can effectively improve the thermal uniformity of the distributed battery cabin, and the overall thermal deviation is controlled within 1.0 K. Full article

Highway buses are used in a wide range of commuting services and in the tourist industry. The demand for highway bus transportation has dramatically increased in the recent post-pandemic world, and airborne transmission risks may increase alongside the demand for highway buses, owing to a higher passenger density in bus cabins. We developed a numerical prediction method for the spatial distribution of airborne transmission risks inside bus cabins. For a computational fluid dynamics analyses, targeting two types of bus cabins, sophisticated geometries of bus cabins with realistic heating, ventilation, and air-conditioning were reproduced. The passengers in bus cabins were reproduced using computer-simulated persons. Airflow, heat, and moisture transfer analysis were conducted based on computational fluid dynamics, to predict the microclimate around passengers and the interaction between the cabin climate and passengers. Finally, droplet dispersion analysis using the Eulerian–Lagrangian method and an investigation of the spatial distribution of infection/spread risks, assuming SARS-CoV-2 infection, were performed. Through parametric analyses of passive and individual countermeasures to reduce airborne infection risks, the effectiveness of countermeasures for airborne infection was discussed. Partition installation as a passive countermeasure had an impact on the human microclimate, which decreased infection risks. The individual countermeasure, mask-wearing, almost completely prevented airborne infection. Full article

The vehicle in-cabin is subject to several types of pollutants infiltrating from the outdoors or emitted directly inside it, such as Volatile Organic Compounds (VOCs). The concentration of TVOC (total volatile organic compounds) is the result of the emission from different equipment surfaces that compose the car cabin. In the present study, the experimental characterization of TVOC emission from the interior surfaces of a car cabin is discussed by considering the influence of two parameters: the temperature and ventilation modes. A measurement location grid was used to measure TVOC’s emissions from 267 points on all surfaces of the car’s interior equipment. Three different temperatures and two ventilation modes (recirculation and outdoor air) were investigated. The results indicate that the concentration of TVOC increases with the temperature inside the cabin with a contribution that varies with the type of cabin equipment including the dashboard, center console, seats, and carpets. On the other hand, the concentration distributions of TVOC showed relative differences of 10–13% and 2–5% for surface and volumetric measurements, respectively. This implies no preferential positioning of the in-cabin probe for TVOC volumetric concentration measurements. In addition, the recirculation ventilation mode results in a higher accumulation of TVOC; therefore, higher concentrations are measured. Full article

The exploitation of natural resources is associated with many natural hazards. Currently, the copper ore deposits exploited in Polish mines are located at a depth of about 1200 m below the surface. The primary temperature of the rocks in the exploited areas reaches 48 ${}^{\circ }$C, which constitutes a major source of heat flux to the mine air. However, another important source of heat is the machine plant, which mainly consists of machines powered by diesel engines. Following the results of in situ measurements, boundary conditions for a simulation were determined and a geometric model of the cabin was created. Furthermore, an average human model was created, whose radiative heat transfer was included in the analysis. Three cases were studied: the first covering the current state of thermal conditions, based on the measurement results, and two cases of forecast conditions. In the second case, the temperature of the conditioned air was determined, and in the third, the flow velocity required to ensure thermal comfort was found. The results of the simulation indicated that for the microclimatic conditions established based on the measurements (ambient air temperature in the excavation 35.0 ${}^{\circ }$C, air-conditioned airflow 2.4 × 10${}^{-2}$ m${}^3$/s, and temperature 10.0 ${}^{\circ }$C), the temperature of the air inside the air-conditioned operator’s cabin would be 20.4 ${}^{\circ }$C. Based on the personal mean vote (PMV) index, it was concluded that the thermal sensation would range from neutral to slightly cool, which confirmed the legitimacy of the actions taken to reduce the adverse impact of the microclimatic conditions on workers in the workplace. However, for the case of predicted conditions of enhanced heat flux from strata and machinery, resulting in an average ambient temperature increased to 38.0 ${}^{\circ }$C, it would be necessary to lower the temperature of air from the air conditioner to 8.00 ${}^{\circ }$C or increase the flow rate to 3.14 × 10${}^{-2}$ m${}^3$/s to maintain thermal comfort at the same level of PMV index. Full article

The distribution and evolution of air in airliner cabins is an important basis for the study of cabin thermal environment and pollutant propagation. Due to the complex heat and mass transfer problems caused by forced and natural convection in a large-scale space, the accurate prediction of air distribution in airliner cabins still faces huge challenges. This study takes the cabin of the Airbus A320 as the research object. The accurate numerical simulation of the flow and heat transfer process in an airliner cabin under mixing ventilation mode was carried out using the Hybrid Thermal Lattice Boltzmann Method (HTLBM) combined with GPU (Graphics Processing Unit) acceleration technology, and the influence of human thermal plumes on air distribution and evolution characteristics in an airliner cabin was analyzed. The research shows that the human thermal plume changes the air distribution in the passenger cabin. The thermal plume slows down the jet attenuation, increases the energy exchange in the area near the passengers, and offsets the jet trajectory. The airflow self-locking effect is easier to form in the passenger breathing area, which increases the time for the flow field to develop into the steady state. The influence of human thermal plumes on the airflow distribution in the passenger cabin cannot be ignored. Full article

The city of Seoul will limit the maximum particulate matter (PM₁₀) concentration to ≤35 μg/m³ (from 2024). Herein, a numerical parametric study was conducted on the PM removal efficiency of the heating, ventilation, and air conditioning (HVAC) filters installed in the ceiling of subway cabins. The PM₁₀ concentration distribution was explored according to the flow rate and flow rate ratio of the air introduced into the cabin. Under the current ventilation conditions of the subway train HVAC system, the PM₁₀ concentration was highest in the cabin central area where exhaust outlets are located and decreased toward both ends of the cabin. The indoor airflow was improved and the PM₁₀ concentration was reduced by increasing the flow rate of the supplied air at both ends of the cabin while decreasing it in the central area. It was found that the strengthened PM₁₀ concentration criterion of Seoul can be met by increasing the ventilation flow rate to 700 CMH (currently, 500 CMH) and the filter efficiency to 85% (currently, 70%) while maintaining the current flow rate ratio. These results are expected to be used as important reference data for reducing the PM concentration in subway cabins and thereby improving indoor air quality. Full article