Increasing Air Flow Rate Research Articles

Model construction and photothermal conversion performance of a miniature non-imaging concentrator for capturing solar radiation in full sunlight

Non-imaging concentrators have been widely applied in the field of solar concentration. However, there are also unfavorable factors such as short effective working time, high production cost of curved reflector, which restrict its wider application in industry and agriculture. Therefore, this paper proposes a miniature non-imaging concentrator (FC-CPC) that can capture solar radiation in full sunlight based on the principle of edge ray. The geometric structure of the FC-CPC was optimized using the VC++ program, resulting in the development of an all-equal multi-section non-imaging concentrator (FM-CPC). On this basis, the optical performance and photothermal conversion performance of FM -CPC during operation were investigated. The results indicate that the average optical efficiency of FM-CPC direct radiation is 50.9 %, and the energy density distribution on the absorber surface is relatively uniform with a low energy density peak. The photothermal conversion system integrated with the FM-CPC shows an increase in collection efficiency as air flow rate increases, reaching a highest average efficiency of 54.1 %.

Techno-economic feasibility study of ammonia recovery from sewage sludge digestate in wastewater treatment plants

Wastewater treatment plants play a vital role in resource recovery, particularly through biogas production, a key renewable energy source. Beyond biogas, the digestate from anaerobic digestion is rich in nutrients like ammonia. This study explored the feasibility of recovering ammonia from sewage sludge digestate using air stripping. The process was modeled using Aspen Plus® software, utilizing real data from As-Samra WWTP in Jordan. Various operational parameters, such as digestate feed flow, air flow rate, temperature, and pressure, were analyzed to optimize ammonia recovery. The results showed that with a feed flow rate between 10,000 and 30,000 kg/hr, ammonia recovery reached 85%, with production exceeding 100 kg/hr, where the effect of the flow rate appears mostly at elevated feeding temperatures. Increased air flow rates significantly boosted recovery, achieving 90% efficiency at 60 °C with 50,000 kg/h as air flow. Flashing pressure peaked at 1.5 bar, with 85% efficiency at 95 °C, while higher pressures yielded diminishing returns, stabilizing production around 106 kg/hr. The NaOH feed rate also influenced output, rising from 100 kg/hr at a 50 kg/hr feed rate to 107 kg/hr at 750 kg/hr, with recovery efficiency exceeding 85%. The economic analysis showed that the project had a payback period of 6.07 years, reflecting a reasonable recovery of the initial investment. The net present value was 122,924 USD over 15 years, with 8% amortization rate, indicating that the project created value beyond the initial cost. The internal rate of return was 14.23%, surpassing the discount rate and highlighting the project's financial attractiveness.

Effect of surface air cooling on the high frequent cyclic ablation of C/C-SiC-AlSi composite prepared by slurry injection technique

C/C-SiC-AlSi composites with uniform distribution of SiC ceramic phase were prepared by ultrasound-assisted slurry injection combined with the PIP+PI process. Ablation tests were performed by alternant plasma and surface cooling airflow for 0.2 s×200 cycles under the flame temperature of 2600 K. Results showed that the mass and linear ablation rates continued to decrease with the increasing of airflow rate from 0 to 3 m3/h, the minimum ablation rates were 0.1525 mg/s and 3.1725 μm/s, respectively. Micro-morphologies and surface temperature analysis suggested that ablation behavior of the composites was affected by the cooling effect of airflow and mechanical erosion. On the one hand, surface temperature of composites reduced and local physical and chemical reactions of the composites alleviated; on the other hand, the increase of airflow rate caused surface cracks and fragments of the composites. According to the ablation results, the former should play a leading role more than the latter.

Performance analysis of a conventional two-stage indirect evaporative cooler

With the aim of saving a portion of the high-quality energy consumed in mechanical vapor compression systems for air conditioning applications, the present work focuses on utilization of low-quality energy conversion processes due to fluid evaporation. The conventional indirect evaporative cooler is selected based on its preference for further modification compared to a regenerative indirect evaporative cooler. It is configured to be operated with two identical stages in series. This task is achieved by developing a thermodynamic model to analyze the performance of the cooling unit and to indicate the extent of its development compared to the cooler in one stage. Preliminary results show that the best operating condition is when the ratio of primary air to secondary air is 1. The cooling unit produces fairly comfortable air within limited climatic conditions. It delivers air at 26 °C and lower even at climatic temperatures as high as 48 °C, but within a very low relative humidity range. The relative humidity range extends to less than 58% as the outdoor air temperature decreases. At high humidity levels (64 to 80% depending on climate temperature), cool air cannot be obtained at 26 °C, and the cooling unit performance is limited only by what the first stage produces. The average performance of the cooling unit exceeds that of the first stage by 42.6%. Increasing air flow rate leads to an increase in cooling capacity, but it also has a negative impact on supply temperature and effectiveness.

Quality control of functioning of the structure “object-thermoelectric cooler-heat sink” of the system of providing thermal modes

The analysis of the mathematical model of the system of providing thermal modes with the use of thermoelectric cooling to assess the influence of the conditions of heat exchange of the heat sink with the medium on the main parameters, reliability indicators and dynamic characteristics of a single-cascade thermoelectric cooler at a given temperature level of cooling, medium temperature, geometry of branches of thermoelements for different current operating modes is considered. The results of calculations of the main significant parameters, reliability indicators, dynamic and energy characteristics of a single-cascade cooler and heat sink of the selected design at a given temperature level of cooling, medium temperature, thermal load, geometry of branches of thermoelements for various characteristic current operating modes are given, when the conditions of heat exchange on the heat sink of the given design under variation of the heat transfer coefficient. It is shown that with the increase of air flow velocity on the heat sink the heat transfer coefficient increases and thus the temperature drop on the heat sink of the thermoelectric cooler with the medium decreases, which allows to significantly reduce the relative failure rate of the cooler and thus increase the probability of failure-free operation of the whole device. When operating a system for providing thermal modes comprising a cooling device, a heat sink, and an electric fan used for dissipating heat output to the environment, different modes of operation of the electric fan (air flow rate) can be used. With the increase in air flow rate of the electric fan increases the velocity of air flow in the live section of the heat sink of a given design, which leads to an increase in the heat transfer coefficient. This, in turn, makes it possible to reduce the temperature drop at a given design of the system for ensuring thermal modes. The possibility of control of reliability indicators, namely, relative intensity of failures and probability of failure-free operation of thermal mode systems of different designs (current modes, number of thermocouples, surface area of the heat sink) at a given cooling level (medium temperature, thermal load, geometry of thermocouples) under changing conditions of heat exchange of the heat sink with the medium is considered.

Performance evaluation of solar-assisted humidification dehumidification system for seawater desalination: An experimental approach

Humidification/dehumidification desalination presents a promising method for small-scale water production due to its ability to utilize solar energy and minimal technological requirements. This research examines the performance of solar-assisted humidification/dehumidification (SA-HDH) desalination system, which is designed to treat seawater from Dumas Beach in Surat city of India. The system integrates a solar air heater, a packed humidifier, and a dehumidifier with an indirect evaporative cooler. Through comprehensive energy, exergy, sustainability, and economic assessments, the study aims to assess system efficiency and viability. Results demonstrate that increasing airflow rates significantly enhances heat transfer efficiency within the humidifier and dehumidifier, boosting system performance and increasing yield by 5.4–7.7 %. The average energy efficiency of 35.5 % is observed at an airflow rate of 125 kg/h. The system effectively removed 99.7 % of total dissolved solids, total hardness, and chloride from the seawater, producing high-quality freshwater. The cost of water production ranging from 0.025 to 0.028 $/L, with a sustainability index ranging from 1.052 to 1.064. These findings underscore the SA-HDH system’s potential as an efficient, sustainable, and cost-effective solution for mitigating water scarcity.

Cadmium sequestration with MgCuAl-layered double hydroxide@montmorillonite nanocomposite in batch and circulated fluidized bed column experiments

In this study, montmorillonite cationic clay coated with MgCuAl-Layered double hydroxide nanoparticles was investigated for its capacity to adsorb cadmium ion (Cd2+) from aqueous solutions. Montmorillonite, MgCuAl−LDH, and a novel MgCuAl-Layered double hydroxide@montmorillonite nanocomposite (MCA−LDH@MMt) were characterized using various mechanisms including BET surface areas, XRD, TEM, FTIR, and SEM/EDS analysis. The adsorption behaviour of MCA−LDH@MMt towards Cd2+ ion was studied using batch and continuous flow systems. pH, contact time, initial Cd2+concentration, MCA−LDH@MMt dose and particle size, agitation speed, and temperature were examined in the batch system. The higher removal efficiency of Cd2+was reported at pH 5 at 70 mg/l initial concentration and 0.2 g/100 ml best adsorbent dose with 150 rpm. The adsorption of Cd2+ on MCA−LDH@MMt followed Langmuir model and yielded a maximum adsorption capacity of 129.82 mg/g. While the pseudo-second-order model better simulates the cadmium kinetics data, and adsorption rate parameters values showing that the adsorption process was chemisorption and the rate-determining step of controlling cadmium adsorption onto MCA−LDH@MMt not intra-particle diffusion. A three-phase, commonly known as gas-liquid-solid circulated fluidized bed column was used to continuously eliminate Cd2+. Four influencing parameters were studied: liquid and air flow rate, bed height, and initial Cd2+concentration. The adsorption efficiency of Cd2+in a continuous system increased when the liquid flow rate decreased and the bed height increased. The time required for MCA−LDH@MMt to reach saturation increases as the bed height and the air flow rate increase. Column data were described using Bohart-Adams, Thomas, and Yoon and Nelson models of adsorption for given experimental conditions. The Bohart-Adams could represent the initial regime of the breakthrough curves, while the Thomas model was better at describing the whole curve of metal ion adsorption for a given experimental condition.

Modeling of hexavalent chromium removal onto natural zeolite from air stream in a fixed bed column

The increasing use of hexavalent chromium (Cr(VI)) has exposed large populations to this environmental and occupational carcinogenic agent. Therefore, researchers have been interested in removing this substance through adsorbents. This study aimed to investigate the efficiency of natural zeolite in the direct adsorption of Cr(VI) from airflow and its adsorption modeling. In this study, a nebulizer device produced the Cr(VI) mist. The efficiency of natural zeolite in Cr(VI) adsorption from airflow, modeling of fixed column adsorption, and the effective parameters on adsorption efficiency including the initial concentration of chromium, airflow rate, and adsorption bed depth were studied. To facilitate the prediction of the performance of natural zeolite’s adsorption column, Yoon–Nelson, Thomas, BDST, and Buhart–Adams models were used. The results showed that the adsorption capacity diminished with increased airflow rate and initial concentration, while it increased with elevated height of the adsorption bed. Yoon–Nelson, Thomas, and BDST models corresponded to experimental data with a correlation coefficient of 0.9933, but the information of the Buhart–Adams model had a lower correlation coefficient (around 0.6677). In conclusion, natural zeolite can be used as an efficient low-cost adsorbent for directly Cr(VI) removing from the airflow in a fixed bed column.

Energy and exergy analysis for a laboratory-scale closed-loop spray drying system: Experiments and simulations

Improving exergy efficiency is crucial to the drying process, especially in reducing costs and carbon dioxide emissions. A closed-loop drying system with a condenser-reheater system was built and analyzed using a numerical simulation to explore the optimal drying conditions, such as inlet air temperature and the air flow rate. Heat-loss coefficients in the simulation were fitted to experimental measurements. The study found that increasing the inlet temperature led to an increase in energy inflow and exergy loss in the system. With an increase in air flow rate from 0.005 to 0.01 kg/s, the exergy loss of the chamber decreased (0.07–0.04 kW), and the exergy efficiency increased (69–92%). The exergy loss was mainly concentrated in the drying chamber, that is, the drying process, and the newly connected condenser and reheater had good exergy efficiencies, exceeding 60%.

Passive ventilation for building not subjected to solar radiation

Some small-height buildings are not exposed to direct solar radiation due to shading from neighboring buildings. Therefore, for these buildings to be ventilated naturally, it was necessary to develop a method using a thermal chimney. This is done by using hot water resulting from the solar heater at the top of the building to heat the base of the chimney instead of direct solar radiation. In this paper, the solar chimney system used to generate power, using some modifications, to be used in ventilation operations is investigated. The effect of different variables on the airflow rate inside the chimney ventilation air drawn was studied. From the experimental result, the ventilation air flow rate increase with the chimney height and diameter. Also, the increase of heated plate area and the heater capacity increases the ventilation air flow rate. Increasing the inlet air gap thickness decreases the ventilation air. For the divergent chimney, the ventilation air increases with the increase of the conical angle.

Experimental Study on Two-Phase Countercurrent Flow Limitation in Horizontal Circular Pipes

The two-phase countercurrent flow limitation (CCFL) in horizontal channels is important in relation to nuclear reactor safety. In this study, we aim to investigate the CCFL characteristics and the flow behaviors in horizontal circular pipes with small diameters. The effects of pipe diameter and the water head in the upper plenum on CCFL characteristics are experimentally studied. An image-processing technique and statistical treatments are implemented to analyze the horizontal countercurrent flow. The results show that the CCFL characteristics for the horizontal circular pipes with small diameters can be well correlated using the dimensionless parameters, which are based on adding fluid viscosity to the Wallis parameters. The CCFL characteristics are significantly affected by the pipe diameter and are slightly affected by the water head above the horizontal pipe. The gas–liquid interface fluctuates with certain periods, and flow pattern transitions happen in the horizontal air–water countercurrent flow. As the air flow rate increases, the occurrence location of the liquid slug appears to shift towards the water entrance. In addition, the further away from the water entrance, the lower the average of liquid holdup.

Dispersion and migration characteristics of multisource respirable dust in development panels during tunnelling processes

Underground miners in Australia are facing continued threats from dust-related diseases. To address these issues, improved knowledge of airflow migration patterns and respirable dust dispersion characteristics within a continuous-miner-driven heading under an exhausting ventilation system is required. Based on site-specific conditions of a development heading in New South Wales, a three-dimensional computational fluid dynamics (CFD) model was constructed and validated with onsite dust monitoring data, where a good agreement was achieved. Three scenarios of coal cutting at the middle, floor and roof positions were considered and simulated, with dust generated at four different sources. The simulation results indicated that the operators on the left-hand-side (LHS) with the extraction duct should be equipped with fit-for-purpose personal protective equipment and stay behind the ventilation duct inlet during coal cutting process, while miners standing at the right-hand-side (RHS) of the continuous miner for roof and rib bolting and machine operating should stay immediately behind the roof and rib bolting rig where dust concentration is relatively low. In addition, an increase in airflow rate through the exhausting ventilation duct or a reduction in the distance from the duct inlet to the heading face assisted in reducing dust levels within the heading, particularly at the LHS of the continuous miners. Finally, compared to the scenario of the current ventilation scheme, an on-board exhausting ventilation system could improve dust removal performance, with dust concentration at the breathing level reducing by approximately 43.6%. This modelling study can advance the understanding of multi-source dust diffusion characteristics in the heading face and provide guidance on dust mitigation, thus improving the health and safety of miners and creating a cleaner underground working environment.

Flow dynamics and heat transfer analysis of a sweeping air jet – An experimental approach

Technological and environmental constraints are driving the development of enhanced heat transfer alternatives. In this context, the scope of this study encompasses sweeping jets generated by fluidic oscillators, which offer considerable potential for enhancing heat transfer. Initially, an experimental setup was developed to measure the flow velocity using a Laser Doppler Anemometer (LDA) and the heat transfer onto a target surface using a flux sensor. Moreover, videos capturing the free jet under various flow regimes were recorded using a Nikon® D850 camera. Concerning the flow dynamics of the sweeping jet, an upward trend in the estimated deflection angle of the jet and its oscillation frequency was noted at higher air flow rates. Heat transfer measurements on a surface indicated that an increase in air flow rate leads to improved heat transfer effectiveness of the jet. Finally, a comparison between the sweeping jet and the industry standard jet for surface cooling was carried out. This comparison revealed that the sweeping jet is highly sensitive to the flow regime at a distance from the plate of H/D= 6. In laminar flow, the sweeping jet outperforms the impinging jet in heat transfer performance. However, as the jet transitions to turbulent flow, the impinging jet exhibits superior thermal characteristics for enhancing heat transfer.

Analysis of Thermoacoustic Instabilities Using the Helmholtz Method in a Swirled Premixed Combustor

The Helmholtz method is developed to predict the self-excited thermoacoustic instabilities in a gas turbine combustor, combining flame describing functions, the measured damping rates under the firing condition, and the non-uniform spatial distributions of the physical parameters. The impact of the hydrodynamic and geometrical parameters on the thermoacoustic instabilities is investigated. The measured damping rates show lower values under a hot condition compared with those in a cold state. The experimental results indicate that the relative errors of the predicted eigenfrequencies and the velocity fluctuation levels are below 10%. The pressure amplitude decreases and the phase increases in the axial direction, indicating a typical 1/4-wavelengh mode. At a higher equivalence ratio, the mode shape in the axial direction becomes steeper due to the elevated fluctuation amplitude at the pressure antinode after enhancing the thermal power. When the air flow rate increases, the discrepancies between the pressure shape on the flame tube side and that on the plenum side are reduced. The velocity fluctuation level increases as the combustor length increases at a constant damping rate. In fact, the velocity fluctuation level first increases and then declines, caused by more significant damping rates when employing longer flame tubes. Self-excited thermoacoustic instabilities can be well predicted using the proposed method.

Effect of perforation density distribution on production of perforated horizontal wellbore

To address the issue of horizontal well production affected by the distribution of perforation density in the wellbore, a numerical model for simulating two-phase flow in a horizontal well is established under two perforation density distribution conditions (i.e. increasing the perforation density at inlet and outlet sections respectively). The simulation results are compared with experimental results to verify the reliability of the numerical simulation method. The behaviors of the total pressure drop, superficial velocity of air-water two-phase flow, void fraction, liquid film thickness, air production and liquid production that occur with various flow patterns are investigated under two perforation density distribution conditions based on the numerical model. The total pressure drop, superficial velocity of the mixture and void fraction increase with the air flow rate when the water flow rate is constant. The liquid film thickness decreases when the air flow rate increases. The liquid and air productions increase when the perforation density increases at the inlet section compared with increasing the perforation density at the outlet section of the perforated horizontal wellbore. It is noted that the air production increases with the air flow rate. Liquid production increases with the bubble flow and begins to decrease at the transition point of the slug–stratified flow, then increases through the stratified wave flow. The normalized liquid flux is higher when the perforation density increases at the inlet section, and increases with the radial air flow rate.

Effect of airflow rate on CO2 concentration in downflow indoor ventilation

We perform direct numerical simulations to study the effect of increasing airflow rate on CO2 concentration in downflow and displacement ventilation in a room with one occupant. Often, CO2 concentration is used as a proxy for the concentration of bio-aerosols of respiratory droplets, and therefore, tracking the CO2 concentration in ventilation strategies can be useful to understand and quantify the risk of spread of communicable respiratory illnesses. At low to moderate airflow rates, the flow in the downflow setup is not mixed, but stratified. The CO2 concentration in the upper and lower layers is determined by the strength of the thermal plume originating from the occupant. We provide a simple theoretical model to predict the height of the stratified interface, the volumetric flux of the ascending plume, and the CO2 concentration in the lower and upper layers. At very high airflow rates, the flow is well-mixed and the average CO2 concentration in the room can be predicted with the mixing ventilation assumption. We demonstrate that at low to moderate airflow rates, displacement ventilation more effectively maintains lower CO2 concentrations in the lower layer compared to downflow ventilation.

Unwinding the correlation between atmospheric pressure plasma jet operating parameters and variation in antibiotic wastewater characteristics

The influence of plasma operating parameters such as gas medium, electrode distance, applied voltage, gas flow rate, and their interdependency on reactive species generation was investigated. Full factorial design-based response surface methodology (RSM) was used to establish the correlation between the operating parameters. The optimization studies were carried out by taking energy yield and degradation efficiency as response parameters. The operating voltage of 9 kV, the airflow rate of 2 LPM, and the electrode distance of 5 mm are optimum for the system studied. The higher voltage of 9 kV and a flow rate of 2 LPM give maximum yield due to the increased rate of gas atoms undergoing ionization. However, at the low voltage (5 kV), the increase in air flow rate from 0.5 to 2 LPM, the energy yield decreases from 67.5 to 54.2 mg/kWh. These observations are further supported by measuring OH (A-X) intensity in an air medium using optical emission spectroscopy. The studies also reveal that the degradation efficiency is adversely affected by scavenges, with a maximum from isopropyl alcohol, followed by tert-butyl alcohol and methanol. TOC and LC-MS analyses established complete mineralization and its degradation pathway. Phytotoxicity studies suggest that treated effluent, rich in nitrates, is suitable for irrigation, promoting seed germination. In short, the studies provide a strategy to optimize the generation of reactive chemical species in a reactor and how such optimization would help attain optimum energy yield, especially when there is a fluctuation in target pollutant concentration.

Numerical simulation of the dust pollution characteristics and the optimal dustproof air volume in coal washing plant screening workshop

Dust pollution generated during the working process of a screening workshop in a coal washing plant seriously threatens the occupational health of workers. To improve the working environment for workers, we investigated the effects of various airflow parameters on the diffusion of dust particles and pollutants. We established a proportional model of the screening workshop and conducted spatiotemporal analysis of the evolution laws of airflow and particulate matter. We used numerical simulation and on-site measurements to obtain the optimal dust removal air flow rate in a coal washing plant workshop. When the air flow rate is between 360 and 1260 m³/min, the overall dust concentration in the workshop and the average dust mass concentration in the breathing zone decrease significantly as the air flow rate increases. However, if the air flow rate is too high, this can cause re-entrainment of dust, which will pollute the operation area again. The optimum dust removal airflow for the inlet air was 1260 m³/min. This air flow rate decreases the dust at the height of the breathing zone in the working area, and the dust concentration at the sidewalk in the working area decreases by 58.82%. This air flow rate can act as a reference value for workshop ventilation design to provide a clean and safe production environment for coal miners. Our methodology and results are of value the formulation and development of effective dust control and clean production technologies.

Optimization of simultaneous utilization of air and water flow in a hybrid cooling system for thermal management of a lithium-ion battery pack

The present study provides a simulation of a battery pack (BCK) comprising lithium-ion battery cells positioned within an air channel utilizing Finite Element Method (FEM). A tube containing a flowing liquid, which serves the purpose of cooling BCK, sits at center of the BCK. Laminar nanofluids (NFs) or water flow enters tube, and air flows inside channel. A transient investigation is conducted on BCK temperature, heat transfer coefficient (HTC), and air and liquid outlet temperatures by varying airflow rate (AFR). The results demonstrate that raising airflow decreases the BCK's average temperature (TAE) and maximum temperature (TMM). The TAE of the BCK is more sensitive to changes in flow rate. Furthermore, as the AFR increases, the HTC increases because liquid and air leaving the outlet are cooled. Using NFs instead of water in the tube causes the average and TMM of the BCK to decrease and the HTC to enhance. The results show that The TMM and the TAE of the BCK are increased until the first 25 min and then are reduced. Using NFs instead of water reduces the outlet air and water temperature when AFR is low. Using NFs for battery cooling typically results in better performance than water.

Experimental investigation of two solar air heaters, with and without employing PCM

AbstractIn the present study, an experimental test was conducted to investigate the energetic performance of a novel designed solar air heaters (SAHs), with, and without phase change material (PCM). Two identical SAHs were fabricated and tested to compare their performance. The first heater is a jacket‐tube solar air heater (SAH 1), while the second heater is similar to the first but filled with PCM (SAH 2). Experimental results showed that increasing air flow rate increases the daily thermal efficiency. Thermal energy during day hours can be stored in the PCM and used after sunset. SAH 2 gave an additional operating time after sunset for 4 hours at 0.01 kg/s, 2.5 hours at 0.035 kg/s, and 1 hour at 0.06 kg/s. Maximum improvement in the daily thermal efficiency was 15% at SAH 2, more than SAH 1 at 0.01 kg/s air flow rate. Employing PCM, as so as increasing air flow rate can reduce the daily thermal losses.