Outlet Air Research Articles

Research on Control of Ammonia Fuel Leakage and Explosion Risks in Ship Engine Rooms

Due to the unique physicochemical properties of ammonia fuel, any leakages in the engine room will inevitably endanger ship safety. This study focuses on investigating the diffusion behavior of ammonia fuel within the engine room during ship navigation after leakage, aiming to identify hazardous points and implement measures, such as installing air-blowing and extraction devices, to mitigate the risks. To address potential leakage risks in ammonia-fueled ships, a simplified three-dimensional computational model was developed based on ship design drawings and field investigations. ANSYS Fluent software (2024 R2) was employed to simulate ammonia fuel leakage from pipelines and equipment, analyzing the diffusion patterns of leakage at different locations and evaluating the impact of adding air-blowing and extraction devices on leaked fuel in the engine room. The simulation results demonstrate that leakage at point 3 poses the greatest operational hazard, and ammonia fuel leakage during navigation generates combustible gas mixtures within the explosion limit range around the main engine, severely threatening both vessel safety and crew lives. Installing air-blowing and extraction devices in high-risk areas effectively reduces the explosion limit range of ammonia fuel, with air outlet 3 showing optimal mitigation effectiveness against ammonia fuel leakage during ship transportation.

Performance, Exergy, and Economic Analysis of an Evaporative Cooling System With Air Gap: An Experimental Investigation

ABSTRACTAs global energy demands rise and environmental concerns intensify, evaporative cooling systems emerge as a promising solution to reduce energy consumption and environmental impact. While some studies have demonstrated that air gap spacing between cooling pads improves the energy performance of direct evaporative cooling (DEC) systems, none have explored their exergy and economic performance. This study provides a comprehensive thermal, exergetic, and economic analysis of a DEC system across a broad range of operating circumstances, comparing configurations with and without an air gap between the cooling pads. Tests were carried out using water flow rates of 60 and 35 L/(min·m²) and air velocities ranging from 1 to 3 m/s, under constant inlet conditions of approximately 32°C−33°C dry‐bulb temperature and 28%−30% relative humidity. The results showed that the outlet air temperature decreased by 4%–6%, while heat and mass transfer flux increased by 8.2%–10%, leading to improved cooling efficiency. Performance evaluation criterion and water consumption criterion analyses identified a 200‐mm pad thickness with an air gap at a flow rate of 35 L/(min·m²) as the most thermally efficient configuration, striking a perfect equilibrium between thermal performance, power consumption, and water usage. Moreover, configurations with an air gap proved to be the most cost‐effective, reducing the specific total cost by 6%–9.6%. These findings highlight the potential of air gap configurations to enhance the sustainability and performance of DEC systems, offering an energy‐efficient cooling solution that is particularly suitable for environments with limited water resources.

Exploring a coating design spacing using experimental and simulated coating techniques.

Exploring a coating design spacing using experimental and simulated coating techniques.

Corrosion prediction in medium pressure vent pipes at high sulfur field stations through numerical analysis of internal wall liquid phase distribution

In actual production activities, the venting pipeline systems in high-sulfur natural gas processing plants are often affected by internal corrosion, leading to reduced service life. To determine the optimal corrosion monitoring points within the venting pipelines and provide effective guidance for blowdown operation management, this study conducted a comprehensive predictive analysis of internal corrosion phenomena in the venting pipeline systems of high-sulfur natural gas processing plants. Computational Fluid Dynamics (CFD) is utilized to analyze corrosion at different cross-sections within the medium-pressure venting pipeline, considering the effects of flow field distribution, liquid phase distribution, and hydrogen sulfide distribution. Through comparison of numerical analysis results and measured data from high-sulfur natural gas field stations, the suggested analysis method is validated to be reliable and accurate. The results indicate that the distribution of the liquid phase plays a pivotal role in causing internal corrosion within the venting pipeline of high-sulfur natural gas stations. The areas most severely affected by corrosion are identified as follows: at the blind end of pipeline tees (specifically at 3, 6, and 9 o’clock positions), near the blind end at 6 o’clock, at the air inlet (positions 3, 9, and 12 o’clock), at the air outlet (position 6 o’clock), and at elbows (positions 3, 6, and 9 o’clock). The results of this study effectively contribute to predicting the locations of internal corrosion within the venting pipeline of high-sulfur natural gas field stations and providing corresponding maintenance strategies.

Analysis of influential factors on temperature field in the construction of concrete warm shed method for pile cap

In order to enhance the curing efficiency of the heating shed method, this study employs field testing and numerical simulation techniques. A heater is utilized as the heat source within the shed, investigating the impacts of exhaust temperature, exhaust velocity, initial heater temperature, shed wall material, and heater placement on temperature variations in both concrete and the shed. The findings demonstrate that elevating the heater outlet air temperature, reducing air outlet velocity, decreasing initial concrete temperature, lowering thermal conductivity of shed wall materials, and arranging heaters more uniformly can effectively mitigate surface-to-interior temperature differentials in concrete. Moreover, through grey relation analysis, it is determined that the initial concrete temperature significantly influences curing quality. Based on these relations among factors degrees of association with each other, recommendations for implementing warm shed construction are proposed. The research outcomes provide theoretical support for controlling temperatures during winter construction using warm sheds.

Presence of SARS-CoV-2 on Hospital Surfaces Before and After Disinfection: A Case Study of Two Large Hospitals in Urmia, Iran

Background and objectives Although inhalation of contaminated air and contact with contaminated surfaces were known as main routes of SARS-CoV-2 transmission, the degree of surface contamination in actual hospital environments and the effectiveness of regular disinfection remained crucial questions. The aim of the present study was to investigate the presence of SARS-CoV-2 on various hospital surfaces before and after disinfection in two large hospitals of Urmia megacity, Iran. Methods In this cross-sectional study, a total of 144 samples were collected from high-touch surfaces inside and outside of patient rooms, both before and after disinfection. Samples were taken using sterile swabs and SARS-CoV-2 was identified via real-time reverse-transcriptase polymerase-chain-reaction (rRT-PCR). Results SARS-CoV-2 was found on 38% (8/21) of surfaces within patient rooms in Hospital A and 20% (3/15) in Hospital B before disinfection. Rates of contamination outside patient rooms were 7/21 in Hospital A and 7% (1/15) in Hospital B. Especially, SARS-CoV-2 was positive in 81.8% of ventilation duct dampers (air outlet covers of mechanical ventilation) from Hospital A and 66.7% from Hospital B. Most importantly, no SARS-CoV-2 was found in any samples collected following disinfection (using benzalkonium chloride and 70% ethanol with a 15-minute contact time). Conclusion The results revealed a high likelihood of SARS-CoV-2 being present on surfaces near patients. Many samples from ventilation duct dampers also tested positive, which pointed to the role of airborne transmission. Importantly, after cleaning, no SARS-CoV-2 was detected on any surfaces, showing that standard hospital cleaning practices effectively lower surface contamination.

Design and Development of Solar Assisted Tray Drying System for Khoa Powder Preparation

A solar parabolic trough concentrator (PTC) air heater was designed, fabricated and coupled with an electrically operated tray dryer for drying Khoa, which was then converted to Khoa powder. The designed solar PTC air heater had collector aperture width of 1.016 m, collector length of 1.970 m, focal length of 0.226 m and rim angle of 96.6° with collector aperture area of 2.0 m2. Two receivers made up of galvanized iron and aluminum coated with black paint on the surface were tested. Parameters like direct normal irradiance (DNI) and temperatures were recorded along with atmospheric air, receiver output air and receiver surface temperature from 9:00 h to 16:00 h. The average maximum outlet air temperature, receiver surface temperature and thermal efficiency were observed to be 62.8°C, 159.4°C and 21.71%, respectively for the galvanized iron receiver and 67.8°C, 170.4°C and 23.69% for aluminum receiver coated with black paint, respectively. The Khoa was made from full cream milk and dried in an electrical tray dryer coupled with solar PTC air heater at 55°C, 60°C and 65°C. The average thermal efficiency of the tray dryer at 55°C, 60°C and 65°C was 20.44%, 23.33% and 27.46%, respectively. The average requirement of energy per kg moisture evaporation at 55°C, 60°C and 65°C was obtained at 3.25, 2.84 and 2.41 kWh, respectively. A comparative investigation on energy consumption for Khoa drying in a tray dryer without a PTC solar heater (2.65 kWh) was about 2.5 times compared to electrically heated tray dryer coupled with PTC solar heater (1.04 kWh).

Evaluating the Thermohydraulic Performance of Microchannel Gas Coolers: A Machine Learning Approach

In this study, a numerical model of a microchannel gas cooler was developed using a segment-by-segment approach for thermohydraulic performance evaluation. State-of-the-art heat transfer and pressure drop correlations were used to determine the air and refrigerant side heat transfer coefficients and friction factors. The developed model was validated against a wide range of experimental data and was found to accurately predict the gas cooler capacity (Q) and pressure drop (ΔP) within an acceptable margin of error. Furthermore, advanced machine learning algorithms such as extreme gradient boosting (XGB), random forest (RF), support vector regression (SVR), k-nearest neighbors (KNNs), and artificial neural networks (ANNs) were employed to analyze their predictive capability. Over 11,000 data points from the numerical model were used, with 80% of the data for training and 20% for testing. The evaluation metrics, such as the coefficient of determination (R2, 0.99841–0.99836) and mean squared error values (0.09918–0.10639), demonstrated high predictive efficacy and accuracy, with only slight variations among the models. All models accurately predict the Q, with the XGB and ANN models showing superior performance in ΔP prediction. Notably, the ANN model emerges as the most accurate method for refrigerant and air outlet temperatures predictions. These findings highlight the potential of machine learning as a robust tool for optimizing thermal system performance and guiding the design of energy-efficient heat exchange technologies.

Effects of Particle Diameter and Permeability on Air Cooling Performance of a Porous Bed

This study investigates varying particle diameters and porosity to improve the cooling performance of a porous bed. It also considers actual and scaled-down clinker bed sizes. The result from the study was validated with existing data from actual-size clinker beds. For the actual size, predicted air outlet temperature, when compared to the experimental and numerical simulation results produced deviation of –5.46% and +1.65% respectively. For the scaled down-sizes, the air outlet temperature when compared with the actual size of experimental result, yielded deviations of 3.96% and 4.9% because the scaled sizes have 3 and 9 scale factors, respectively. The initial increase in air outlet temperature was minimal, but as the diameter increased, the temperature reduction became significant. The rate of air outlet temperature decrease was slightly consistent from 0.1 to 0.5, but widens as porosity increases. However, as porosity increases, the rate widens. Furthermore, it was discovered that, the heat transfer rate between air and clinker decreases less significantly between diameters of 0.01 to 0.02 m, but increases as porosity increases to 0.6, 0.7, and 0.8, resulting in a significant reduction. The study concluded that as clinker particle diameter increases, outlet temperature also increases, pressure drop decreases, with a significant decrease observed between 0.01 and 0.02 m and porous bed with scale factor 9 had high pressure drop values as the other three bed sizes showed similar results.

Enhancing freshwater production and cost-effectiveness in humidification-dehumidification (HDH) technology: Novel wheat straw packing and configuration optimization

ABSTRACT The sustainable utilization of water resources is a critical global concern. Humidification-Dehumidification (HDH) technology has emerged as a promising solution to meet increasing freshwater demands. This study examines the performance of HDH systems by introducing wheat straw as novel packing material and evaluating its effectiveness across multiple system configurations. The research explores the influence of different humidifier arrangements, such as parallel and counterflow setups, in both open-air and closed-air cycles. Additionally, the study investigates the role of heat recovery mechanisms in enhancing system efficiency. Results indicate that a five-stage HDH unit with wheat straw packing material demonstrates high effectiveness. In the parallel flow, open-air configuration, the humidifier achieved an impressive effectiveness of 0.8564, and the outlet air humidity reached 99.9%. Moreover, the maximum Gain Output Ratio (GOR) of 1.206 was observed in the counterflow, closed-air cycle with heat recovery configuration, resulting in a productivity rate of 0.975 L/h. The cost of freshwater production was estimated to be 2.45 EGP/L (approximately 0.07 USD/L) under counterflow and closed-air cycle conditions. These findings provide valuable insights into the efficiency and economic viability of freshwater production using HDH technology, underscoring its potential as a sustainable solution to address water scarcity challenges.

Thermal and Thermo-Hydraulic Performance of a Semi-Circular Solar Air Collector Utilizing an Innovative Configuration of Metal Foams

The enhancement of the thermal and thermo-hydraulic performance of a semi-circular solar air collector (SCSAC) is numerically investigated using porous semi-circular obstacles made of metal foam with and without longitudinal porous Y-shaped fins. Two 10 and 40 PPI porous material samples are examined. Three-dimensional models are built to simulate the performance of SCSAC: model (I) with clear air passage; model (II) with only metal foam obstacles, and model (III) with metal foam obstacles as well as porous Y-fins. COMSOL Multiphysics software version 6.2 based on finite element methodology is employed. A conjugate heat transfer with a (k-ε) turbulence model is selected to simulate both heat transfer and fluid flow across the entire computational domain. However, only the local thermal non-equilibrium (LTNE) model of heat transfer is applied in the porous regions. The findings demonstrated that adding metal foam as the novel proposed configuration particularity of model (III) may enhance the thermal efficiency by about 30%, and the outlet air temperature may rise to 7% compared to other models. Also, the performance evaluation factor of this model is greater than one in all cases. Additionally, the thermal enhancement is accomplished by occupying only 5% of the air passage volume, thereby including an associated pressure drop of minimal magnitude.

A new ventilation method for rapidly diluting coal mine gas: Experimental and simulation of airflow field with bladeless fan

ABSTRACT Mechanized comprehensive approach has accelerated coal mining operations, and the local areas such as the upper corner of working face and the Y-shaped ventilation triangle area are prone to gas exceeding limits, posing a serious threat to coal mining process safety. The high-speed gap jet bladeless fan, characterized by large air volume and intrinsic safety, holds promising potential for rapidly diluting methane in the flammable and explosive environments of coal mines. This study analyzed the flow field of the bladeless fan through experiments and simulations, exploring the effects of air pressure and size on the fan’s performance. The results show that an increase in the outlet gap width reduces the air amplification effect, with the outlet air volume being 13.9 times the intake volume at a gap width of 1.5 mm. As the duct length increases, the outlet pressure, wind speed, and air volume ratio initially rise and then decrease, with the optimal length being 2.0 meters. With an increase in inlet pressure, the air volume ratio reaches its maximum at 0.4 MPa. This study provides a theoretical foundation for the application of bladeless fans in localized methane management in coal mines.

Recurrent Neuronal Networks for the Prediction of the Temperature of a Synchronous Machine During Its Operation

This work presents the development of an adaptive thermal protection system for synchronous machines (SMs), taking into consideration the final cooling temperature and the operation point of the machine. This system aims to improve current thermal protections, which consist of a fixed alarm and trip thresholds regardless of the generator’s operating point or ambient temperature. A recurrent neural network (RNN)-based approach has been employed to predict SM temperatures during operation. Multiple tests have been conducted on a specially designed test bench. Inside the windings and iron core of the 5.5 kVA generator, multiple Pt100 sensors have been installed to train the neural network with real temperature values, enabling accurate predictions. The selected RNN model is Long Short-Term Memory (LSTM). Its inputs include electrical variables and the inlet and outlet air temperatures of the SM’s cooling system. The results show that the model accurately defines warning and trip thresholds, significantly improving thermal protection, as these thresholds are no longer fixed values. Additionally, the study suggests validating the model under cooling system failures and exploring its application in water-cooled systems. This research is supported by a patent on real-time thermal diagnostics for synchronous machines, highlighting its potential contribution to predictive maintenance and the monitoring of power generation systems.

Numerical Simulation of the Protective Effect of Air Walls on Liquid Hydrogen Leakage

Abstract Liquid hydrogen storage stands out among various storage and transportation methods for its high efficiency. However, accidental leaks of liquid hydrogen pose safety hazards due to the formation of hydrogen clouds. Therefore, a research project developed a three-dimensional numerical model using the open-source computational fluid dynamics (CFD) code OpenFOAM. The accuracy of the numerical simulations was validated by comparing the results with experiments conducted by NASA. An innovative approach called the “air wall” has been proposed as an enhanced safety measure alternative to traditional fencing systems. The air wall consists of a series of upward air outlets designed to intercept the lateral diffusion of low-temperature, high-density hydrogen. The air wall alters the trajectory of hydrogen, increasing convection and diffusion rates and effectively reducing the hazardous range of hydrogen dispersion. The protective efficacy of the air wall was verified through numerical simulations. The geometric model was based on modifications to fencing designs from NASA experiments. Comparative analysis between the traditional cofferdam and the innovative air wall revealed significant differences in hydrogen dispersion trajectories. The research findings demonstrate that the air wall provides a safer option for mitigating the consequences of liquid hydrogen leaks.

Numerical Simulation on the Effect of Different Airflow Schemes in a Large Space

Abstract The underground plant of a pumped storage power station was taken as the object for studying the airflow in a large space. Computational Fluid Dynamics (CFD) is utilized to analyze the characteristics and patterns of airflow organization under summer operating conditions. Three airflow organization schemes including variable inlet dimension, number and air supply velocity are set. The airflow effects are compared according to the air velocity and air temperature distribution. The longitudinal profile of the air supply as well as the horizontal height of the work area are selected. Results demonstrate that a reasonably designed air outlet layout can fulfill the wind speed and temperature requirements for the working area. Moreover, homogeneity and stability of the airflow field in the working zone can be realized.

Research on Cooling and Dust Removal Technology of Circulating Airflow in Metal Mine Working Face

To address ventilation challenges in the working face of metal mine excavation, an equal-scale physical model was established with a mine section as the test site, combined with field-measured data and relevant parameters of spent air reuse equipment. Numerical simulations were carried out using Fluent 2020 R2 software to analyse the characteristics of the airflow field, temperature field, and dust distribution in the excavation roadway. The results show that when the cold air outlet temperature (T0) is 22 °C, the temperature within the cooling zone does not exceed 26.3 °C, thereby demonstrating effective cooling. The equipment parameters significantly impacted cooling and dust removal. When the distance from the cold air outlet to the heading face was set to Zm = 8 m, the air outlet temperature was T0 = 22 °C, and the ventilation circulation rate was F = 40%, the working area achieved better cooling and dust removal effects. On-site application showed that within 15 m of the working face, temperatures dropped by 3–3.5 °C, reaching a low of 25.1 °C. The relative humidity at a point 1 m away from the working face decreased from 90.6% to 70.2%, and the average dust removal efficiency was 44.9%, which significantly improved the comfort and safety of the working environment at the heading face.

Design and Optimization of Shell and Tube Heat Exchanger (STHE) in Continuous Flow Multigrain Dryer Fueled by Biomass Using CFD

Efficiency is a crucial factor in grain drying because it determines the quality and shelf life of the dried grains produced. Dryer technology in industrial scale that is widely used is continuous flow multigrain dryer. The use of biomass as the main fuel source can reduce dependence on fossil energy while utilizing agricultural waste, especially in remote areas. This research focuses on the design and optimization of Shell and Tube Heat Exchanger (STHE) because it is one of the main components in controlling the drying water temperature. Optimization is done using Computational Fluid Dynamics (CFD) by considering thermal efficiency, economy and ease of manufacturing. The process parameters analysed were drying air outlet temperature, heat transfer coefficient and pressure drop. The most optimal design was obtained for the STHE with a length of 3.2 m, heat transfer rate of 419.76 kW, drying air outlet temperature of 80.90 °C, pressure drop of 43.79 kPa and percent thermal coefficient of 89.43%. The design can meet the drying water needs of a continuous flow multigrain dryer system with a capacity of 20 tons with biomass fuel.

Study on the influence of return position on the combustion performance of CFB

In this study, the effect of the return position on the biomass-coal coupled combustion process was studied by numerical simulation of a 15 kg/h small circulating fluidized bed experimental device. The results show that the furnace center temperature in the dilute phase zone shows a trend of rising first, decreasing subsequently and then stabilizing with the increasing the height of the return position, and when the relative return position (the ratio of the distance between the return port and the feeding port to the distance between the upper secondary air outlet and feed port) reaches 0.4, the furnace temperature distribution is the most uniform. Combined with the comparison results of nitrogen oxide concentrations at the outlet of the separator, optimal range of relative return position is 0.12-0.6 (the return port position is from the upper part of the dense phase zone to the lower part of the transition zone). When the range of relative return position is 0.12-0.6, the exothermic response rate is 3.4 kW/s∼3.8 kW/s, and the dynamic stability of varying conditions would be obtained.

Design and optimization of cooling system for aerospace bearing temperature measurement device based on orthogonal design

Abstract As a core component of an aero-engine, monitoring the temperature of an aerospace bearing is essential for assessing the bearing’s lifespan and performance. While existing research has primarily focused on temperature rise in bearings, there has been limited study on temperature measurement of aerospace bearings operating at high rotational speeds and the cooling and heat dissipation systems of the measurement devices. To address the issue of heat generation in the inner ring of aerospace bearings, this paper develops an effective passive wireless temperature monitoring device. The study targets the device’s internal circuit board and nickel-metal hydride battery pack, proposing a cooling and heat dissipation method that primarily utilizes air cooling, supplemented by aerospace-grade thermal insulation cotton to enhance heat transfer. To verify the accuracy and effectiveness of the proposed method, both experiments and simulations were conducted. First, various air-cooled heat dissipation modes were investigated to identify the optimal configuration. Additionally, an orthogonal analysis was employed to examine the effects of the number of air inlets, the number of air outlets, and the spacing between air inlets and outlets along the x-axis on the air cooling performance. The influence of each factor on the cooling effectiveness was also analyzed quantitatively. Experimental results demonstrate that the cooling system effectively dissipates heat from the measurement device. When the inner ring temperature of the aerospace bearing reaches 70 °C, the average temperature of the internal circuit board decreases by 18.76%, and the average temperature of the battery pack decreases by 16.57%. These findings provide a scientific basis and reference for the design of devices and thermal management systems in the field of aerospace bearing temperature monitoring.

Potensi Air Outlet IPAL Sebagai POC Untuk Pertumbuhan Tanaman Cabai Rawit (Capsicum frustescens L.) Di PT. Jamu Air Mancur Karanganyar

Semakin pesatnya era industrialisasi saat ini, menyebabkan penurunan kualitas lingkungan, salah satunya yaitu kualitas air. Salah satu industri yang berkontribusi memberikan limbah cair paling banyak adalah industri makanan dan minuman. Limbah yang dihasilkan ini dapat berpotensi untuk diolah menjadi pupuk organik cair bagi pertumbuhan tanaman. Tujuan penelitian ini adalah untuk menganalisis kandungan POC pada unsur N, P, K, dan pH dari air outlet IPAL PT. Jamu Air Mancur dan untuk mengetahui potensi POC dari air outlet IPAL PT. Jamu Air Mancur terhadap pertumbuhan tanaman cabai rawit (<em>Capsicum frutescens L.</em>). Penelitian ini menggunakan metode Rancangan Acak Lengkap (RAL), dengan 6 variansi konsentrasi perlakuan sebagai berikut: A (0% POC Air Outlet IPAL), B (20% POC), C (40% POC), D (60% POC), E (80% POC), dan F (100% POC). Masing-masing perlakuan diulang sebanyak 4 kali sehingga didapatkan 24 tanaman uji. Variabel pengamatan penelitian meliputi, tinggi batang tanaman, jumlah helai daun, dan panjang akar tanaman. Analisis data menggunakan SPSS dengan uji oneway ANOVA kemudian dilanjutkan uji DMRT (<em>Duncan Multiple Range Test</em>). Uji kandungan POC meliputi unsur Nitrogen, Fosfat, Kalium dan pH. Hasil uji kandungan Nitrogen 0,196%, Fosfat 1,367%, Kalium 0,81% dan pH 5,42. Nilai total NPK ini sudah memenuhi standar POC berdasarkan Keputusan Menteri Pertanian No. 261 Tahun 2019. Hasil pengamatan pengaplikasian POC terhadap tanaman menunjukkan pengaruh yang signifikan terhadap pertumbuhan tanaman cabai rawit (<em>Capsicum frustescens</em> L.) dengan konsentrasi optimal yaitu pada konsentrasi 40% POC