Medium Flow Rate Research Articles

Investigating the impact of gaspers on airborne disease transmission in an economy-class aircraft cabin with personalized displacement ventilation

Overhead gaspers provide directional fresh airflow, and thus affect the local airflow pattern and contaminant distribution. To investigate the impact of gaspers on airborne disease transmission in an aircraft cabin with a personalized displacement ventilation system, numerical calculations were conducted in a seven-row, single-aisle, fully occupied, economy-class aircraft cabin with the computational fluid dynamics (CFD) simulation method. We first investigated the impact of source gasper direction and flow rate on the airborne transmission near the contaminant source. We then investigated the protective effect of the receptor's gasper. For a source passenger's gasper, the direction and flow rate of the gasper flow either increased or decreased the air contaminant transmission to other passengers. Directing the source gasper to the abdomen with a medium flow rate performed best by reducing the receptors' mean exposure index by at least 45%, as this approach minimized the contaminant circulation in the cabin. Turning on a receptor passenger's gasper could be an effective strategy to protect the receptor, and the working mechanism was revealed. The gasper-induced jet flow entrained the surrounding air into the jet region, and the protective effect was related to the contaminant concentration at ceiling level. With a suitable gasper direction and flow rate, the gasper jet formed a virtual barrier between the source passenger and the receptor. When the contaminants were transported upwards to a receptor's breathing zone, turning on the receptor's gasper reduced the contaminant concentration, since the downward gasper jet altered the airflow pattern in front of the receptor.

Direct pore-scale simulation of the effect of capillary number and gas compressibility on cyclic underground hydrogen storage & production in heterogeneous aquifers

Understanding the flow dynamics of hydrogen-water in aquifers is critical to maximizing hydrogen storage and recovery. By using direct computational fluid dynamics at elevated pressure, this paper aims at detailed pore-scale investigation of the effect of flow regime, compressibility, and hysteresis on flow pattern, trapping mechanisms and the efficiency of hydrogen storage and recovery. The results reveal that the favorable rates during hydrogen injection and production differ and a medium flow rate corresponding to drainage capillary number of ∼10−7 and imbibition capillary number of ∼10−5 can minimize both capillary and viscous fingering mechanisms, leading to more storability and recovery factor. We show that neglecting the local compression and expansion of hydrogen and a low working pressure, typical in modeling and experimental studies, result in misinterpretation of flow regimes and hydrogen storability. Finally, we report that during the cyclic process, the trapped hydrogen bubbles produce a “self-cushion gas" effect, improving hydrogen storage.

Virus spreading in cruiser cabin

This paper concerns virus droplet simulations in a typical cruiser's cabin. Effects of ventilation rates and positions of the coughing person were investigated. The study also emphasizes the importance of including evaporation models to simulate the process accurately. A higher ventilation rate is not always the best strategy to avoid the spread of airborne diseases, as saliva droplets can spread further at high ventilation rates. Regardless of the ventilation strategy, they evaporate faster than the room's air renewal. One should aim for minimum droplet spreading inside the cabin and different ventilation strategies for occupied cabins. The authors propose using ventilation systems at medium flow rates of around 120 m3/h or three air changes per hour when a cabin is occupied. This value is also close to the recommended value of 108 m3/h from the latest standard by the American Society of Heating, Refrigerating and Air-Conditioning Engineers. The suggested value minimizes droplet spreading while maintaining good ventilation, comfort, and energy consumption.

Simple Empirical Relation for an Evacuated-Tube Solar Collector Performance Prediction from Solar Intensity

In this paper, the effect of solar intensity on the heat pipe tip temperature in a heat pipe type—evacuated-tube solar collector (HP-ETSC) was investigated. A simple relation was proposed, relating the solar intensity to the heat pipe tip temperature generated from the experimental data. This simple empirical relation was applied in a set of heat transfer equations derived to predict the heating medium temperature at the manifold outlet of the evacuated-tube solar collector. The calculated results corresponding to two types of heating medium, i.e., palm oil and water, were compared with experimental results from the literature. The results show that the average error was 6.41% for the case of palm oil and 4.66% for the case of water. Based on the case of water as a heating medium fluid, it was found that the flow rate of the heating medium fluid affected the accuracy of prediction, as the percentage error increased with the heating medium flow rate. The maximum percentage error increased from only 1.83% for a water inlet flowing at a Reynolds number of about 2.4 × 103 to 15.23% for a water flow rate at a Reynolds number of about 2.6 × 104. The correction factor was added into the correlation to predict the heat transfer coefficients of heating medium fluids. With this correction factor, the maximum error could be reduced from 11.78% to 7.29% for the palm oil case and from 15.23% to 5.57% for the water case. The average errors corresponding to palm oil and water cases could be reduced to 0.74% and 1.26%, respectively.

Pressure drop characterization on cryogenic multiphase flow in spiral wounded heat exchanger under high mass flow conditions

In order to clarify the influence of dryness, working medium and mass flow rate on pressure drop characteristics in shell side of spiral wound heat exchanger, a simplified test section has been analyzed in this study. The model is with a coiled section under compact design: 1 mm layer spacing of and 2 mm tube spacing in the main structure. The mixed alkane composed of methane, ethane, propane and others are used as working fluid. The current study is focused on the pressure drop behaviors and the effects of multiphase flow in different stages of cooling process in the cryogenic heat exchanger. Systematic numerical model has been established in this study to investigate the pressure behaviors, which are also verified against newly constructed experimental system. Operating conditions range from vapor quality of 0.1–0.9, mass flux of 60–120 kg·(m2·s)−1, under the operation pressure of 0.25 MPa and temperature from −27 °C to −170.6 °C. The absolute error of pressure measurement is less than 1.5 kPa and the absolute error of pressure drop measurement is less than 25 Pa, and the relative error is 0.25 % for the current test. The experimental results show that the friction pressure drop increases with the increase of vapor quality from 0.1 to 0.9 and mass flux from 60 to 120 kg·(m2·s)−1, and the growth gradient of friction pressure drop decreases with the increase of vapor quality. A set of pressure drop correlation has been established to reflect the influence of factors such as vapor quality and mass flow rate, and the deviation between predicted pressure drop and experimental data was within ±20 %.

Sodium alginate based artificial biofilms polymerized by electrophoretic deposition for microbial hydrogen generation

This study developed an artificial biofilm of Rhodospirillum rubrum bacteria immobilized within an alginate matrix using electrophoretic deposition (EPD) on an electrode. The resulting biofilm immobilized bacteria effectively and maintained a high survival rate, facilitating stable and high-efficiency hydrogen generation for longer periods compared to biofilms produced using free bacteria. Hydrogen production efficiency remained constant when the substrate was periodically replaced, indicating that the bacteria could survive within the biofilm for long-term hydrogen production. EPD produced mechanically stable large-scale biofilms economically and rapidly, which effectively overcame operational limitations such as culture medium temperature, pH, and flow rate. Therefore, this proposed method has the potential to accelerate the commercialization of biohydrogen production systems through large-scale biofilm production to facilitate continuous hydrogen generation. The technique can be utilized in various hydrogel-based applications, providing a cost-effective and efficient manufacturing process with customized biological and mechanical properties. The developed biofilms have implications beyond biohydrogen production and could be applied to hydrogel-based medical, cosmetic, and food applications. This study highlights the importance of immobilizing bacteria for stable and efficient hydrogen generation and demonstrates the potential of EPD in fabricating mechanically stable biofilms for large-scale production.

Greenwall Filtration System for Lakewater Treatment: A Case Study on Cocopeat/Perlite Filter Media

Anthropogenic activities often result in varying degrees of lakewater contamination. Conventional lakewater treatment processes require expansive space allocation which could be challenging under certain topographical situations. A greenwall filtration system is a vertical wall that consists of plants or greenery. In this system, greenery is planted in a growing medium made up of a combination of soil, stone, or water. A robust greenwall filtration system could serve as a potential solution for lakewater treatment. However, the efficacy of various filtering media in eliminating contaminants and various water quality indicators such as Chemical Oxygen Demand (COD) from lakewater remains unknown. Previous research has demonstrated that coir and perlite are suitable filter media for a greenwall system. In this study, the effects of various height ratios of the filter media and different lakewater flowrates were investigated. The treatment performance was assessed using various lakewater flowrates: low flowrate (13.10 L/h), medium flowrate (26.57 L/h) and high flowrate (45.18 L/h). The mixed media ratio of 3:1 cocopeat-to-perlite during low flowrate (13.10 L/h) attained the highest removal of COD with an overall removal of 71.00%. It was further discovered that the Langmuir isotherm model could better explain the adsorption process than the Freundlich isotherm model as it possesses an overall high coefficient of determination, R2 where the value of R2 for cocopeat to perlite ratio at 1:1, 1:3, and 3:1; are 0.9397, 0.9823, and 0.5348, respectively.

Study on Flow Resistance Characteristics of Cold Plate in Pump-driven Two-phase Cooling System

This paper summaries and analyzes the study on the two-phase flow pattern in cold plate in pump-driven two-phase cooling system. Based on the experimental system, the inlet and outlet flow resistance of the cold plate under different conditions is tested and analyzed. Through the experiment to get the cold plate in different heat flux, different inlet flow rate state of inlet and outlet pressure value, the relationship between the flow resistance and the flow rate, the flow resistance and heat flux of cold plate are analyzed and summarized. The experiment results show that the outlet pressure of cold plate is basically unchanged under different heat flux of cold plate, while the inlet pressure of the cold plate rises with the increase of the inlet flow rate of the phase change medium. The inlet pressure will accelerate after exceeding a certain critical flow, and the different heat flux has no effect on the flow resistance of the cold plate.

Расчетно-теоретическое и экспериментальное исследования кавитационных характеристик шиберных запорно-регулирующих устройств с внутренним байпасом

Hydraulic systems include control devices that create local resistance. Decreasing and increasing the working medium pressure and flow rate in the control devices cause cavitation, vibration, noise, material destruction, increase in the energy losses and decrease in the efficiency, which adverse effects could be reduced by using a bypass. One of the important tasks in designing the control devices is establishment of the cavitation characteristics. Introduction of an internal bypass in such devices makes it possible to reduce forces on the control elements displacement and the specific pressures in opening and closing, as well as to locate the cavitation bubbles collapse point in the flow behind the control gates. The paper presents results of a computational theoretical study using a modern complex of engineering analysis and experimental determination of the cavitation characteristics of the gate wellhead device with an internal bypass.

Расчет удельных давлений в задвижках при давлениях газа до 105 МПа

In power calculation of the valves, maximum specific pressures at the gate valves are determined only in the closed position, not taking into account decrease at the sealing fields contact area between the slide valve (wedge) and the valve seats in opening, throughput characteristic of the slide valve and working medium flow rate and density. Results are provided of calculating specific pressures at the gate of the slide valve DN 150 PN 25 MPa LLC “Scientific and Production Company “MKT-ASDM” at the gas pressure drop of up to 105 MPa depending on the slide walk stroke and taking into account the gas flow rate and density using the valve actual throughput characteristics. Specific pressures of maximum values were achieved in the slide valve relative stroke range of 0.1…0.2. It is recommended to determine the specific pressure maximum value taking into account reduction in the sealing fields contact area when the wedge is raised, throughput characteristic of the sliding gate valve and the working media flow rate and density. This should be done after calculating the specific pressure with gate valve closed according to the well-known method used in the valves’ power calculation

Thermal Performance of the Evaporator in the two Phase Mechanically Pumped Cooling Loop

In the two-phase mechanically pumped cooling loop, the performance of the evaporator is very important as it directly contacts with the electronic equipment to absorb the waste heat. The evaporator with the micro channels which can enhance heat exchange is designed and it can be used to dissipate the heat generated by the electronic equipment with discrete heat sources. The effects of working medium flow rate and heating power on the performance of the evaporator were analyzed through numerical simulation. Meanwhile, the changes of evaporator performance were also investigated while the heating power changed periodically and suddenly. In addition, the flow and heat transfer process in the evaporator at the initial stage were analyzed by transient calculation. The results showed that the evaporator with micro channels can reduce the maximum temperature by 47.66% and the maximum temperature difference by 83.39% compared with the evaporator without micro channels. In addition, the evaporator showed good stability under variable power condition.

Bio-decarbonization by microalgae: a comprehensive analysis of CO2 transport in photo-bioreactor

Microalgae biofilm is a typical porous structure where CO2 is converted by microalgae into organic matter. Therefore, CO2 transport and its distribution in porous biofilm are crucial for microalgae decarbonization and its energy utilization. In order to get detailed process information of CO2 transport and its bioconversion, a mathematical model considering the microalgae growth and its material consumptions was established for substances' flow and transport processes in an immersed microalgae biofilm reactor. Modeling results showed that CO2 concentration on the surface of biofilm reduced about 26.57% along the flow direction. Increased inlet CO2 concentration (0.2–5.2 ​mM) significantly promoted the average specific growth rate of biofilm, which was more dramatical at a low flow rate with an enhancement about 7.38 times. Essential reason for it is a synchronous increase on total transfer flux of CO2 (8.25 times by ϕ_CO2) and average CO2 consumption rate (7.48 times by ACR_CO2) in biofilm. However, such promotion gradually waned with a growing initial carbon supply concentration. Enhanced CO2 transport in biofilm caused by increasing culture medium's flow rate (1–6 ​mL ​min−1) doesn't always result in synchronous improvements on biofilm growth. At sufficient carbon supply, increased flow rate doesn't further effectively improve biofilm growth but greatly reduced CO2 removal. Whether increasing carbon supply concentration or flow rate, biofilm growth can't be significantly promoted unless the ϕ_CO2 and ACR_CO2 in biofilm were increased by almost the same level. This work provides a new and deeper mechanistic insight into macroscopic growth characteristics of biofilms from the perspective of CO2 transport in it, as well as providing some theoretical guidance towards the cultivation of immersed microalgae biofilm for bio-decarbonization.

Biogenic material design by stone waste treatment with biologically induced mineralization

One of the most widely studied branches of biologically induced mineralization (BIM) processes, microbially induced calcium carbonate precipitation, also known as microbially induced calcite precipitation, can be used as a method for the reinterpretation of waste natural stone particles into a sustainable material. By overcoming the need for synthetic adhesives or energy-consuming firing or sintering procedures for regaining such wastes, a natural and sustainable solution is proposed through certain biological treatment processes. The aim of this study was to determine the main processing variables affecting microbially induced biocement production using waste stone as a scaffold material. Bacillus pasteurii bacteria were used for biological induction of calcite precipitation. A custom-made reactor was designed for controlled incubation and medium injection into the waste stone scaffold. The parameters examined were the particle size of the waste stones, the effect of the stone type on cementation, the urease activity of the bacterial culture, temperature, the pH and flow rate of media, the mechanical strength of cemented scaffolds and water absorption capacity. This research demonstrated a potential solution to the waste generation problem of the global natural stone industry through the treatment of such wastes with BIM for creating a sustainable and biogenic material.

АНАЛИЗ ВЛИЯНИЯ ОТНОСИТЕЛЬНОЙ ШЕРОХОВАТОСТИ ТРУБОПРОВОДОВ НА ПОТЕРИ НАПОРА

The dependence of the relative roughness of pipelines on pressure losses at different flow rates of the liquid medium is studied

Study on Microfluidic Chip Flow Rate Uniformity for Cell Activity Detection.

During the cell viability detection process inside a microfluidic chip, the more uniform the distribution of medium flow rates, the higher the accuracy of detection results. In order to achieve this goal, a multichannel microfluidic chip with uniform distribution of medium flow rates has been successfully designed. The multichannel microfluidic chip is designed with cell injection channels, vascular network-shaped medium injection channels, buffer zones, and a culture chamber. The medium flow rates inside culture chambers of the multichannel microfluidic chip and the common single-channel microfluidic chip are compared by COMSOL Multiphysics software and particle velocimetry experiment. The simulation and experimental results show that the medium flow rate distribution inside the culture chamber of the multichannel microfluidic chip is more uniform and changes more smoothly. When the medium perfusion flow rate is 0.5 μL/min, the maximum flow rate difference inside the culture chamber of the single-channel microfluidic chip is more than 13 times that of the multichannel microfluidic chip. Therefore, the multichannel microfluidic chip can ensure a uniform supply of medium inside the culture chamber, which is beneficial to improve the accuracy of cell viability detection.

District Heating System Optimisation: A Three-Phase Thermo-Hydraulic Linear Model

Investments in the development of the district heating system require a thorough analysis of the technical, economic, and legal aspects. Regarding the technical and economic context, a mathematical model of the district heating system has been proposed. It optimizes both the technical and economic aspects of the function and development of a district heating system. To deal with non-linearities, the developed linear programming model is divided into three phases: flow, thermal, and pressure. Therein, non-linear dependencies are calculated between the linear optimization phases. This paper presents the main assumptions and equations that were used to calculate the parameters of the heating system, along with the optimal level of heat production, the flow rate of the heating medium in the heat nodes and edges of the network graph, the heat, power, and temperature losses at each edge, and the purchase costs of heat and its transmission. The operation of the model was tested on a real-world district heating system. The case study results confirm that the model is effective and can be used in decision support. The economic results of the model, before the calibration process, were 3.6% different from historical values. After the calibration process, they were very similar to the real data—all percentage deviations were within 1%.

Analysis and Research of Compound Refrigeration based on Logic Control Battery

In order to ensure the safety and stability of the power battery, the design of refrigeration system is very important. Firstly, a battery model based on logic control and lumped heat parameters was established to determine the real-time and accurate state of battery heat generation, heat transfer, radiation heat dissipation and battery temperature. The feasibility of the simulation model is verified by the experimental results. Secondly, the refrigeration system of battery air cooling and liquid cooling is established, and a new composite cooling system is proposed and built. By changing the wind speed and flow rate, the variation of the cooling effect of air cooling and liquid cooling with the medium flow rate was analyzed. The results show that, in a certain range, the larger the flow rate, the more obvious the cooling effect of the cooling method, and the flow rate is positively correlated with the cooling effect. In order to compare the cooling effect of the new composite cooling system, the temperature rise curves, temperature difference curves and energy consumption of different cooling methods were analyzed under the discharge rates of 4C and 8C.he results show that when the system tends to be stable, the total energy consumption of liquid cooling and mixed cooling is almost the same, and the energy consumption of air cooling is the largest. According to the analysis of the maximum equilibrium temperature difference inside the battery unit when the temperature is stable, the temperature difference of the composite cooling method is the smallest, about 1℃. Moreover, by analyzing the fluctuation range of battery pack temperature when it is stable, the fluctuation of composite refrigeration is the smallest, only 2℃. In conclusion, the hybrid refrigeration system based on logic control has good cooling performance.

Corrosion Cause Analysis of a Surface Pipeline Flange

Corrosion was found on the inner wall and sealing groove end face of a surface pipeline flange in an oilfield in western China after one year’s service. Corrosion causes were investigated by physical and chemical property tests, metallographic examination, scanning electron microscope, scanning electron microscopy(SEM) inspection, energy disperse spectroscopy(EDS) analysis and X-ray diffraction(XRD) analysis. The results showed that the chemical composition and mechanical properties of the flange were all in accordance with the corresponding parameter requirements, and the corrosion phenomenon was mainly attributed to CO2 corrosion. High temperature and high medium flow rate also had a big influence on the acceleration of the corrosion process. Corrosion of the sealing groove end face was attributed to galvanic corrosion, the corrosion potential difference between the flange and gasket was the main reason for the galvanic corrosion.

Performance of TiO2 nanofluids on the efficiency of a parabolic trough collector using a corrugated tube absorber with conical strip inserts

The paper discusses how to improve the performance of a parabolic trough collector with a corrugated tube absorber and conical strip inserts by using (Titanium Oxide) TiO2/DI water nanofluids. To evaluate the performance of the proposed system, three different concentrations (0.1%, 0.2%, and 0.3%) of TiO2 nanofluid were used on a volume basis, and experiments were conducted using different mass flow rates (0.011, 0.012, 0.013, 0.014, and 0.015 kg/s) of the working medium. Using a 0.3% volume concentration of TiO2 nanofluid with the combination of a corrugated tube (pc = 8 mm and hc = 2 mm) and the conical strip insert (pi = 20 mm), the maximum collector efficiency of 61% was observed. Compared to the corrugated tube, the improved collector efficiency of the conical strip inserts of 20, 30, and 50 mm pitches were 10.9%, 7.8%, and 4.3% higher, respectively.

Research of gas dynamics of highly efficient turbo-impact compressed gas separator for gas turbine installation

The gas dynamics of multiphase mixtures of high-pressure fuels in turboimpat separators with coagulation structural elements at a flow rate of the working medium G = 500-2200 kg/h were investigated. The geometry of the turboimpat separator with a radial guide jet element consists of a first stage and a separator, consists of a plate with a diameter of 250 mm, on a diameter of 97 mm of which there is a corrugated separation element, the dimensions of which vary from 10 to 40 mm, depending on the working geometry. At the bottom of the first stage of the separator are grooves of rectangular shape 3x2 mm at a distance of 27 mm. In the second stage of the separator at a diameter of 270, 240 and 180 mm respectively there are through rectangular grooves 5x10 mm. In a turboimpact separator with a radial coagulation element, a uniform velocity distribution was observed, the maximum of which is 43.7 m / s, which indicates a uniform turboimpact particle transfer. The turboimpact separator with a radial guide jet element is characterized by the close location of the corrugated mesh element to the jet cleaning zone. Preversal of flow, in the channel nered grid element forms a vortex zones, which will further lead to the displacement of undeposited particles to the lower wall of the channel. In the first stage of purification turboimpact separator with radial coagulation element after passing through the working medium of the jet cleaning zone, the flow was evenly distributed throughout the entire section of the channel, which contributes to the uniform distribution of the polydisperse phase in the working medium in front of the mesh element. It was established that the optimal pressure drop of 1 KPA is observed in a turboimpact separator with a radial arrangement of a coagulation element, which allows using this design for cleaning multiphase mixtures of high-pressure fuels.