Increasing Air Flow Rate Research Articles

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.

A novel recurrence-based approach for investigating multiphase flow dynamics in bubble column reactors.

In chemical industries, multiphase flows in a bubble column reactor are frequently observed. The nonlinearity associated with bubble hydrodynamics, such as bubble-bubble and bubble-liquid interactions, gives rise to complex spatiotemporal patterns with increased gas or liquid velocities, which are extremely difficult to model and predict. In the current study, we propose a new, computationally efficient recurrence-based approach involving the angular separation between suitably defined state vectors and implement it on the experimental multiphase flow variables. The experimental dataset that consists of image frames obtained using a high-speed imaging system is generated by varying air and water flow rates in a bubble column reactor setup. The recurrence plots using the new approach are compared with those derived from conventional recurrence, considering standard benchmark problems. Further, using the recurrence plots and recurrence quantification from the new recurrence methodology, we discover a transition from a high recurrence state to a complex regime with very low recurrence for an increase in airflow rate. Determinism exhibits a rise for the decrease in airflow rate. A sharp decline in determinism and laminarity, signifying the quick shift to complex dynamics, is more prominent for spatial recurrence than temporal recurrence, indicating that the rise in airflow rate significantly impacts the spatial location of bubbles. We identify three regimes that appeared as distinct clusters in the determinism-laminarity plane. The bubbly regime, characterized by high values of determinism and laminarity, is separated by an intermediate regime from the slug flow regime, which has low determinism and laminarity.

Обоснование дебита свежего воздуха для нижних горизонтов рудника «Интернациональный» АК «АЛРОСА» (ПАО)

Today, the issue of providing consumers of the lower horizons of the «International» mine of ALROSA Diamond-Mining Company (PJSC) with fresh air is at the top of the agenda. The measures to ensure sustainable airflow in mines by using mining machines with a hybrid or electric drive, as well as by using air reserves and preventing in-shaft leaks of inflowing air were taken earlier. At the same time, it is still possible to improve the situation significantly by redistribution of fresh airflows in the ventilation network. The article provides data on the arrangement of efficient ventilation for the horizons 0/+130 m of block № 2 by the termination of aerodynamic connection with the main ventilation network of the mine. The proposed measures require the installation of the main ventilation system in the auxiliary ventilation shaft and the supply of fresh air via the existing portal overlooking the open pit. The fresh air supplied for ventilation is to be heated by air curtains. The basic parameters of the recommended engineering solution have been determined via the simulation of the ventilation process using the «Aeroset» software. The data obtained show that the proposed arrangement of the mine ventilation network will enable to increase the volume of fresh air supplied for ventilation of lower horizons from 120 to 196,7 m3/s; i.e., by 63.9 %. The solution does not require the correction of performance of the main ventilation system in the skip shaft, jobs to substantiate the increase of airflow rate in the shafts exceeding the scheduled rate, and the measures to enlarge the cross-section of main air-supply and air-outlet developments.

Application of biomass-based wood shaving packing in a liquid desiccant dehumidification system – a source of sustainable energy

ABSTRACT The present work focuses on the construction of a counter flow dehumidification test rig where calcium chloride liquid is used as the desiccant and is made to spray on the novel organic packing made of wood shaving with different densities and porosities. The mass flow rate of the air is varied and the performance parameters such as moisture removal rate (MRR), dehumidification effectiveness, coefficient of performance (COP), sensible heat factor (SHR) and mass transfer coefficient have been investigated. Results demonstrated an increase in the relative humidity, mass transfer coefficient and drop in the COP, MRR and dehumidification efficiency with the increase in the flow airflow rate. On increasing the CaCl2 concentration, dehumidification performance parameters such as MRR, COP and mass transfer coefficient are found to be increased. Out of the three different densities tested, 500 kg/m3 shows best performance with MRR, ΔRH and dehumidification effectiveness being 9.7%, 18.7% and 4.9% lower than the Celdek pad when measured at 5 m/s of air velocity for 30% desiccant concentration. Optimisation of the input parameters has been done and the results revealed that air velocity should be maintained within the range of 4–5 m/s to minimise energy consumption and optimum performance.

Experimental investigation on the impact of air flow rates and back pressures on kerosene microscopic spray characteristics discharged from an air-assisted pressure-swirl atomizer

The air-assisted pressure swirl atomizer has attracted considerable interest owing to its exceptional capacity to generate fine droplets and precisely regulate spray characteristics. The primary objective of the study was to investigate the impact of auxiliary air flow rate, orifice diameter, and ambient back pressure on the kerosene spray cone angle, droplet size and distribution. The results indicate that employing a nozzle with a smaller orifice size leads to a larger spray cone angle. The spray cone angles of the other two orifice sizes exhibit an increasing trend as the auxiliary air flow rate increases. Also, increasing the auxiliary air flow rate effectively reduces the Sauter Mean Diameter (SMD). Additionally, as the auxiliary air flow rate gradually increases, the peak of the particle size distribution shifts towards smaller diameters. Furthermore, as the environmental back pressure increases, there is a noticeable decrease in the SMD. With an increase in ambient backpressure, there is a consistent shift of the peak particle size towards smaller diameters. At an elevated ambient pressure of 1.4 MPa, an increase in the axial distance from the nozzle results in a decrease in the volume percentage of the peak diameter, while simultaneously causing the particle size distribution range to broaden.

Effects of hydrogen blending on combustion and pollutant emission of propane/air in a model furnace with a rotary kiln burner

A rotary kiln burner is one of the critical equipment in various industrial processes, particularly in the field of material calcination. This study focuses on the effects of hydrogen blending in a rotary kiln burner operating with propane as a fuel. The primary objectives are to explore the effects of key parameters, such as hydrogen blending ratio, fuel hole size, and air flow rate, on the combustion and emission characteristics under the ignition condition. Results reveal that a hydrogen blending ratio of 10% leads to a 3.4% and 1.5% reduction in COx and NOx emission indexes, respectively. The hydrogen can be mixed with propane while maintaining the same total heat release, reducing carbon and nitrogen oxide emissions. Although adjusting the fuel hole size allows the flow characteristics after hydrogen blending to be restored to their pre-blending state, the combustion characteristics would be changed. With a 30% increase in air flow rate under fuel-rich ignition conditions, the propane consumption rate witnesses a 20.8% growth, accompanied by a parallel rise of 6.8% in both COx and NOx emission indexes. These numerical results can be a reference in designing kiln burners and selecting operating conditions.

Comprehensive assessment of double skin façades: A mathematical model for evaluating influence of KL ratio on electrical and thermal performances, and indoor conditions

The present study proposes a mathematical model to evaluate the electrical and thermal performance of a novel Double Skin Façade (DSF) system and its impact on indoor conditions. DSF system comprises opaque PV and transparent Glass panels integrated as an exterior skin. Further, the cavity between the DSF’s exterior and interior skins provides airflow that increases PV efficiency and delivers preheated air into the room for space conditioning. The mathematical model is based on energy balance equations written, considering the DSF as an integral part of the room. This system of energy balance equations is then solved analytically under quasi-steady-state conditions for developing a mathematical model in terms of DSF’s design and climatic parameters. The model is employed to investigate multiple design parameters of DSF, including KL ratio (proportion of PV façade height to total façade height), Glass façade transmissivity, PV packing factor, cavity dimensions, and airflow rate. Montreal (Canada) is considered a pilot location for the study. The results indicate that increasing the KL ratio reduces room temperature and increases electrical output. For a fixed KL ratio, the room temperature can also be modified by adjusting the transmissivity of the exterior and interior glass façade without impacting the electrical output. A 20 % increase in the interior façade’s transmissivity results in a 2.3 ˚C rise on a winter design day and a 2.6 ˚C rise on a summer design day. Additionally, the room temperature increases with an increase in the mass airflow rate up to a certain value, after which it decreases. This behavior is attributed to the interplay between the increased convective heat transfer coefficient (which tends to increase room temperature) and the reduced flow rate factor (which tends to decrease room temperature).

Bio-inspired soft pneumatic actuator based on a kresling-like pattern with a rigid skeleton

IntroductionBiomimetic soft pneumatic actuators (SPA) with Kresling origami patterns have unique advantages over conventional rigid robots, owing to their adaptability and safety. ObjectivesInspired by cloning and moving behaviors observed from salps, we proposed an SPA based on a Kresling-like pattern with a rigid skeleton. The elongation and output force were tested, and the effectiveness of the applications with the SPA was evaluated. MethodsThe proposed SPA consists of rigid skeletons and a soft skin. The rigid skeletons are constructed using layers of Kresling-like patterns, while a novel extensible inserting structure is devised to replace the folds found in conventional Kresling patterns. This innovative approach ensures that the SPA exhibits axial contraction/expansion motion without any twisting movement. To mimic the bionic characteristics of swimming and ingesting progress of salps, the proposed SPA can perform an axial contraction motion without twisting and a controllable bending motion based on multi-layered Kresling-like patterns; to mimic the cloning and releasing life phenomena of salps, the number of layers of Kresling-like patterns is changeable by adding or reducing skeleton components according to the practical needs. ResultsThe experimental elongation results on the SPA with multiple layers of Kresling-like patterns show that the elongation can increase to above 162% by adding layers; the experimental output force results show that the three-layer SPA can provide 6.36 N output force at an air flow rate of 10 L/min, and the output force will continue to increase as the number of layers of Kresling-like pattern increases or the air flow rate increases. Further, we demonstrate the applications of the SPA in soft grippers, scissor grippers, claw grippers and pipe crawlers. ConclusionOur proposed SPA can avoid twisting in the radial contraction motion with high elongation and output force, and provide the practical guidance for bio-inspired soft robotic applications.

Experiments and CFD modelling of bubble formation at a lateral hole in a top-submerged nozzle

Top-submerged nozzles with lateral holes find applications as passive mixing devices in radiochemical/hazardous industries. We report the mechanism of bubble formation and detachment at a lateral hole in such a nozzle for the first time. Three distinct phases – a growth phase, an elongation phase and finally a rise/detachment phase – could be observed during bubble formation. Effect of gas flow rate, diameter of lateral hole (1, 2 and 3 mm) and physical properties of liquid-liquid system on bubble detachment time and bubble equivalent diameter are reported. Three different liquid-liquid systems (DM water, 2 N and 4 N nitric acid) have been considered. Bubble diameter first reduced, reached a minimum and then started to increase in an oscillatory manner with increase in air flow rate. Before the onset of oscillatory behaviour an increase in hole diameter was seen to reduce bubble diameter. Such a behaviour is typical to bubble formation at lateral hole and is not seen for top-submerged nozzles with central opening. A detailed analysis of the results was carried out and it was observed that inertial forces played a major role. The work also reports a fundamental criterion which must be achieved for onset of oscillations in bubble diameter with flow rate. We also report a 2D CFD model that can simulate bubble formation dynamics at a lateral hole. The model was validated qualitatively as well as quantitatively against the experimental data.

CFD modeling of optimal airflow rates for safe production in isolated mining faces with high methane concentration and coal spontaneous combustion

From the perspective of airflow rate adjustment for disaster prevention, controlling methane concentration and reducing spontaneous combustion zone in the goaf naturally contradict. Generally, an increased airflow rate is beneficial in reducing methane concentration but also increases the risk of coal spontaneous combustion. Coal pillars on both sides of an isolated mining face are broken to form air leakage passages, which connect its goaf and the two sides of the goafs to form triple goafs. Especially for triple goafs of the isolated mining faces with high methane concentration and coal spontaneous combustion tendencies, the lack of air leakage law and knowledge of the distribution of methane and oxygen concentrations makes disaster prevention and control difficult. To solve the above problem, this study adopts a computational fluid dynamics (CFD) modeling method to construct a physical model containing triple goafs and investigate the optimal airflow rates for safe production, with an isolated mining face in a mine in Guizhou taken as an object. Results show that the air leakage paths in the triple goafs of the isolated mining face mainly consist of “U–shaped” and “semi–U–shaped”. The optimal airflow rates to maintain methane concentration at safety limits and to minimize the spontaneous combustion zone in the triple goafs are 1800 m3/min to 2000 m3/min. In consideration of economic efficiency and workload, the optimal installation spacing of the dynamic barriers is determined as 15.0 m–20.0 m. The study results provide scientific concepts and practical guidance for the prevention and control of methane and coal spontaneous combustion hazards in triple goafs of isolated working faces.

Full-Loop Study of a Pilot-Scale Dual Fluidized Bed Cold Flow System: Hydrodynamic Simulation

Computational particle fluid dynamics (CPFD) simulations of three-dimensional cold-flow gas-solid flow were performed for a pilot-scale dual-circulating fluidized bed (DCFB) using Barracuda Virtual Reactor® 17.4.0. This DCFB system is a fluidized bed gasifier used in a calcium-loop gasification process to produce a hydrogen-rich gas with CO2 capture. The effects of different bubble bed inlet airflow rates and different solid inventories on the full-loop pressure distribution and particle concentration distribution were compared. The increase in the bubble bed inlet airflow rate significantly increases the pressure in the bubble bed and lift pipe, and the increase in the solids inventory significantly increases the pressure where the solids are tightly packed. For long-term operation, the appropriate combination of parameters should be found to maintain a stable particle seal at the loopseals.

An evacuated tube solar bubble column liquid desiccant regenerator

Liquid desiccant air conditioners (LDAC) are environmentally friendly, require less energy, and can improve air quality. These systems are composed of two main parts: a dehumidifier and a regenerator which are heat and mass exchanger devices that are the main bottlenecks on the overall performance of LDAC systems. Despite their numerous advantages over conventional regenerators, bubble column regenerators have only been studied adiabatically. To address this gap in the literature, an internally heated bubble column regenerator is proposed that is heated with an evacuated tube solar collector while also eliminating the previous issues with corrosion. A prototype was constructed, and the effect of various values of air flow rate, air injection depth, and initial desiccant concentration was studied experimentally in 10 cases (8 modified cases, 2 conventional cases). The results showed that initial concentration has the highest impact on the device’s performance. Increasing air flow rate led to higher water extraction. Air injection depth had no significant impact on the device’s output. In Case 10 (10 L/min air flow rate, 50 cm hose depth, and 30 % initial desiccant concentration), a maximum of 576 g of water was removed from the desiccant. The maximum improvement over the conventional case was 139 % which was achieved in Case 5 (10 L/min air flow rate, 50 cm hose depth, and 35 % initial desiccant concentration). The exergy efficiency for Case 10 was the highest, reaching 8.5 % at the end of the experiment.

Experimental study on dynamic thermal characteristics of novel thermosyphon with latent thermal energy storage condenser

Emergency cooling systems are an essential part of data centers. A water tank is usually used as an emergency cooling source to provide cold thermal energy; however, tanks are bulky and additional uninterrupted power supplies (UPSs) are needed. For flexible emergency cooling, a novel thermosyphon integrated with a latent thermal energy storage condenser (TLTESC) is developed and experimentally studied. The effects of the refrigerant filling ratio and inlet conditions on the dynamic thermal performance are analyzed. With an increase in the refrigerant filling ratio from 48.7% to 82.5%, the cooling capacity decreases; the maximum cooling capacity decreases from 4.68 to 2.03 kW. The superheating temperatures for all cases are always zero, indicative of the two-phase refrigerant being at the evaporator outlet. During the entire operating period, the refrigerant temperatures at the vapor line are considerably higher than those at the liquid line. Moreover, the refrigerant pressure at the evaporator inlet is the highest. Under the optimal filling ratio, the outlet air temperature increases and the maximum cooling capacity increases from 3.6 to 4.8 kW with the inlet air temperature increasing from 30 to 40 °C. The cooling capacity increases with air flow rate during the first half, after which the situation is reversed. The accumulated energy increases slightly as the air flow rate increases. The thermal performance is investigated to promote the application of TLTESC in data center.

Airflow Resistance of Solid-Separated Dairy Waste for Drying and Storage

The resistance of solid-separated solid wastes (SSDWs) to moderate airflow ranging from 0.05 to 0.30 m3/s-m2 was measured at various bed depths and moisture levels. The pressure drop across a loose-fill fixed bed column was observed to increase more rapidly with increasing airflow rates than with increasing bed depths. An increase in the moisture content (10 percentage points) caused a decrease in the pressure drop by an average of 13.2–17.0%, evaluated within a 10–40% moisture content (MC) range. A full-factorial model analysis using standard least squares was used to describe the main effects and interactions of the test parameters in predicting the pressure drop. The Hukill and Ives nonlinear model was able to accurately describe the airflow resistance data of SSDWs at various MCs. Empirical curves describing the SSDW resistance to airflow were developed to aid in the preliminary design of ventilation systems for drying and storage.

The role of capsule aperture size on the dispersion of carrier-based formulation at different air flowrates

The effect of capsule aperture size on the aerosol performance of lactose blend formulation was studied using Foradil® (containing 12 μg of formoterol fumarate (FF11A list of all acronyms used in this paper can be found in the section “Abbreviations & Symbols.”.) and 24 mg of lactose) dispersed with a powder inhaler Aerolizer® at increasing air flowrates. Apertures sizes of 0.4, 1.0, 1.5, 2.5, and 4.0 mm were introduced at the opposite ends of the capsule. The formulation was dispersed into a Next Generation Impactor (NGI) at 30, 60 and 90 L/min, with the fine particle fractions (FPFrec and FPFem) measured by chemical assay of FF and lactose using high-performance liquid chromatography. Particle size distribution (PSD) of FF particles dispersed in wet media was also characterized by laser diffraction. FPFrec showed a stronger dependency on the flowrate than the capsule aperture size. The most efficient dispersion was achieved at 90 L/min. At a given flowrate, FPFem remained broadly constant across different aperture sizes. The laser diffraction studies demonstrated the presence of large agglomerates.

Experimental and Numerical Investigation of Thermal Performance of an Air-Cooled Battery Module Under High Ambient Temperature Conditions

Abstract Lithium-ion batteries (LiBs) are widely used in electric vehicles due to their high energy and power density. The operating temperature has a significant impact on the thermal performance and longevity of LiBs. The thermal performance of an air-cooled battery module containing 16 (4S4P) high-energy density LiBs has been investigated through a series of experiments and numerical simulations. At varying transverse and longitudinal cell spacing, airflow rates, ambient temperatures, and discharge C-rates, the thermal performance of a battery module with aligned battery cells was analyzed. For the thermal performance evaluation, the average temperature rise, temperature non-uniformity, and maximum temperature of the module’s battery cells are utilized. During discharge cycles, the rate of temperature increase is linear but becomes nonlinear at the end of the discharge cycle. In the current architecture of the battery module, a minimum space utilization ratio of 0.38 is necessary to limit maximum temperature and temperature non-uniformity to safe battery thermal management temperatures. The thermal performance was significantly affected by the airflow rate. Increasing airflow rate decreases temperature but increases pressure drop substantially. The maximum cell temperature is greatly affected by the inlet air temperature, increasing from 62.8 °C to 76.6 °C when the inlet air temperature is increased from 30 °C to 45 °C. At high ambient temperatures (over 40 °C), LiB temperatures exceed permissible limits, and air cooling alone is inadequate. This study examines the thermal performance of an air-cooled battery module working at high temperatures.

Experimental study and modeling analysis of sewage sludge smoldering combustion at different airflow rates

Sewage sludge is a major by-product of wastewater treatment, and its unfavorable properties are frequently a key restriction of disposal technologies, resulting in high costs and ineffective waste management. Smoldering combustion is a new technique for disposing of organic solid waste with high moisture content, which efficiently recovers energy with minimal igniting energy requirements. The objective of this study is to investigate the effects of airflow rate on sewage sludge (SS) smoldering combustion by combining experimental and modeling analyses. Results show that air channeling easily forms at the reactor's edge, intensifying the smoldering reaction and forming a concave smoldering front. The minimum airflow rate required for self-sustaining smoldering is 0.3 cm/s. As the airflow rate increases, convective heat transfer becomes dominant over conduction and radiation, resulting in a surge in smoldering temperature and velocity at 0.6 cm/s, followed by a linear increase. The maximum airflow rate at which the smoldering process can propagate stably during SS disposal is 8 cm/s. The expressions of the smoldering characteristics are obtained by using the activation energy asymptotic approach, and the calculated and experimental values show the same trend of variation, with good agreement at low airflow rate conditions. Sensitivity analysis shows that porosity φ is the most crucial parameter affecting smoldering temperature and velocity.

Natural convection and structural impact of rectangular PCM storage units through the modular expansion

To increase the storage capacity and air flow rate of the rectangular thermal energy storage unit (RTESU) for enhancing its application capability, three modular units with air flow rates of 60 m3/h, 120 m3/h, and 180 m3/h for heights of 150 mm, 300 mm, and 450 mm are proposed. Besides, the effect of natural convection (NC) on the charging and discharging process is examined during the modular expansion of the RTESU. The melting performance including melting duration and phase change process is numerically investigated by varying the configurations such as module configuration, non-uniform, and eccentric tube arrangements. The results show that NC has a significant impact on the charging process. It is further demonstrated that the charging process can be enhanced by about 14.58 % and 13.61 % when non-uniform and eccentric tube arrangements are implemented, respectively, as they both increase the area dominated by NC. However, the non-uniform tube arrangement for acceleration of the melting process is gradually enhanced with the increase in storage unit height compared to that of the eccentric tube arrangement. It is worth noting that the Nusselt number (Nu) is introduced for examining heat transfer performance during the melting process with different unit configurations. And the correlation between the dimensionless numbers is applied to predict the liquid fraction for different configurations. For the heat release process, the performance including air outlet temperature, heat extraction, and heat release efficiency of the modular RTESU is evaluated. It is found that the NC has a negligible effect on the discharging process, which is dominated by heat conduction. With the modular expansion, an increase in air flow rate and heat storage capacity as well as the maintenance of a higher heat release efficiency of about 84.97 % can be achieved in the RTESU.

Measurement of liquid water distribution in GDL under cross-flow-inducing parallel flow field using operando synchrotron X-ray radiography

Baffles in flow field channels for air in a polymer electrolyte fuel cell are known to enhance the performance by inducing convective flow through the gas diffusion layer (GDL) with smaller pressure loss than interdigitated flow fields. This work experimentally correlates performance enhancement with the amount of liquid water in a GDL. A parallel flow field (PFF) that has different inlet and outlet opening sizes is applied to induce cross-flow in the GDL under the rib between adjacent air channels. Operando synchrotron X-ray radiography experiments are conducted to compare the amount of water in the GDL with that for a PFF having the same inlet and outlet sizes. The performance enhancement by application of different opening sizes increases with decreasing relative humidity and increasing air flow rate. A significant performance enhancement is observed when the amount of water in the GDL substrate under the rib becomes almost zero. No performance enhancement is observed under over-humidified conditions, although a decrease in the amount of water in the GDL is still observed, which suggests that the performance becomes insensitive to the difference in the liquid water saturation as the saturation increases.

Swirling flow and capillary diameter effect on the performance of an active dry powder inhalers

For patients with lung disease, dry powder inhalers (DPI) are profoundly beneficial. The current study introduces and develops a series of dry powder inhalers (DPIs). A capsule-based (size 0) active DPI was considered. The study aims to investigate whether swirling flow and outlet capillary diameter (dc_out) affect the percentage of emitted doses (ED) released from the capsule. Spiral vanes were added to the capillary inlet to produce a swirling flow. Computational fluid dynamics (CFD) was applied to simulate the problem. The results were compared with previous in vitro and numerical studies to validate the results. Based on the derived results, the small swirl parameter (SP) enhances the secondary flow and recirculation zone. It increases the central jet flow, which increases the ED value by about 5–20% compared to no-swirl flow. However, as the airflow rate increases, the recirculation zone enlarges, vorticities become dominant, and asymmetrical flow patterns emerge. Consequently, ED % drops significantly (more than 50%). As dc_out decreases, the vorticities around the outlet capillary become more potent, which is undesirable. Indeed, the emptying of the capsule does not happen ideally. The research provides a perspective on the device's design and DPI performance.