Air Stream Research Articles

Vapor kinetic energy for the detection and understanding of atmospheric rivers

Poleward water vapor transport in the midlatitudes mainly occurs in meandering filaments of intense water vapor transport, spanning thousands of kilometers long and hundreds of kilometers wide and moving eastward. The water vapor filaments are known as atmospheric rivers (ARs). They can cause extreme wind gusts, intense precipitation, and flooding along densely populated coastal regions. Many recent studies about ARs focused on the statistical analyses of ARs, but a process-level understanding of ARs remains elusive. Here we show that ARs are streams of air with enhanced vapor kinetic energy (VKE) and derive a governing equation for Integrated VKE to understand what contributes to the evolution of ARs. We find that ARs grow mainly because of potential energy conversion to kinetic energy, decay largely owing to condensation and turbulence, and the eastward movement is primarily due to horizontal advection of VKE. Our VKE framework complements the integrated vapor transport framework, which is popular for identifying ARs but lacks a prognostic equation for understanding the physical processes.

Near-Field Mixing in a Coaxial Dual Swirled Injector

AbstractImproving mixing between two coaxial swirled jets is a subject of interest for the development of next generations of fuel injectors. This is particularly crucial for hydrogen injectors, where the separate introduction of fuel and oxidizer is preferred to mitigate the risk of flashback. Raman scattering is used to measure the mean compositions and to examine how mixing between fuel and air streams evolves along the axial direction in the near-field of the injector outlet. The parameters kept constant include the swirl level $$S_e = 0.67$$ S e = 0.67 in the annular channel, the injector dimensions, and the composition of the oxidizer stream, which is air. Experiments are carried out in cold flow conditions for different compositions of the central stream, including hydrogen and methane but also helium and argon. Three dimensionless mixing parameters are identified, the velocity ratio $$u_e/u_i$$ u e / u i between the external stream and internal stream, the density ratio $$\rho _e/\rho _i$$ ρ e / ρ i between the two fluids, and the inner swirl level $$S_i$$ S i in the central channel. Adding swirl to the central jet significantly enhances mixing between the two streams very close to the injector outlet. Mixing also increases with higher velocity ratios $$u_e/u_i$$ u e / u i , independently of the inner swirl. Additionally, higher density ratios $$\rho _e/\rho _i$$ ρ e / ρ i enhance mixing between the two streams only in the case without swirl conferred to the central flow. A model is proposed for coaxial swirled jets, yielding a dimensionless mixing progress parameter that only depends on the velocity ratio $$u_e/u_i$$ u e / u i and geometrical features of the swirling flow that can be determined by examining the structure of the velocity field. Comparing the model with experiments, it is shown to perform effectively across the entire range of velocity ratios $$0.6 \le u_e/u_i \le 3.8$$ 0.6 ≤ u e / u i ≤ 3.8 , density ratios $$0.7 \le \rho _e/\rho _i \le 14.4$$ 0.7 ≤ ρ e / ρ i ≤ 14.4 , and inner swirl levels $$0.0 \le S_i \le 0.9$$ 0.0 ≤ S i ≤ 0.9 . This law may be used to facilitate the design of coaxial swirled injectors.

The Geysers Is a Unique Geothermal Resource Presenting Equally Unique Challenges to Drillers

_ For drillers, The Geysers is a unique sort of hell. It is one of the only places on Earth where a shallow well can reach a highly fractured reservoir so hot that it only produces steam. That steam powers 18 power plants generating 835 MW of electricity, making this 45-square-mile area the world’s most prolific geothermal power producer. High drilling costs there also stand out. Drilling a well requires 60 days or so and generates a lot of damaged drill bits and drillpipe. The drilling rigs have the size and power of modern onshore rigs, but a close look reveals there’s no topdrive. Below the rig floor there is a rotary table, known as a Kelly drive because it can spin drilling pipe without being in the line of fire of the steam flowing out when running slotted casing into the steam-production zone. When they get to that zone, they switch from drilling fluid and mud to injecting a high-pressure stream of air because of the enormous fluid losses anticipated when they reach that highly fractured level. A drill bit that lasts 500 ft in this harsh, highly fractured rock has had a long run. And the rugged terrain—mountains to a Texan but hills to a Californian—makes this a hard place to move a rig. “The Geysers is its own animal, for sure,” said Sam Noynaert, a Texas A&M professor who was a key member of a team of drilling experts and scientists that drilled a well in The Geysers to test if faster drilling methods from the oil business could work there. The two upper sections went pretty well, considering. As they went deeper, they repeatedly had to deal with severe fluid losses. Still, they had shaved nearly 6 days off the average drilling time. But when they reached the highly fractured steam-producing payzone and their drilling method changed to air drilling, things got worse with drill bits failing after runs as short as 21 ft. As a Geysers drilling paper presented at the Stanford Geothermal Workshop earlier this year delicately put it: “The air section proved to be more challenging.” The Blob The Geysers has a long history. The heat source is “a large blob of silica-rich magma (which) forced its way through Earth’s crust beneath the Coast Range,” according to the description of an image from NASA. That flow about 1.3 million years ago from deep within the earth heated the overburden, making the rock brittle and prone to fracturing. Over time, water seeped into those hot fissures, creating hot springs that were awed by Native Americans and later attracted tourists to a nearby resort hotel. By the 1960s drillers were tapping the steam in those payzones for commercial power generation, which peaked at 2,000 MW in 1987. It declined from there as steam production depleted the reservoir. Eventually, the output was stabilized at its current level by injecting water from sewage-treatment plants into the production zone.

A methodology for selection of solid desiccants in energy recovery ventilators

Controlling indoor humidity levels is essential for maintaining acceptable indoor air quality in buildings. The use of energy recovery ventilators (ERVs) is an energy-efficient way to regulate indoor air humidity. Fixed-bed regenerators and rotary wheels are widely used ERVs because of their high sensible and latent effectiveness. These ERVs are made of desiccant-coated substrates, which enable them to transfer moisture between the supply and exhaust air streams. However, the moisture transfer ability of ERVs depends on the physiochemical and sorption properties of desiccants. Extensive, full-scale experiments are required to determine the best desiccant material for these systems. This paper presents a simplified method of selecting suitable desiccant materials for ERVs. The methodology involves important characterization methods, literature correlations for performance prediction, and cost-effective testing methods prior to full-scale testing, and full-scale test methods are discussed in detail. Furthermore, the performance of a few newly derived materials is evaluated and compared with that of conventional desiccants such as silica gel and molecular sieves. The highest latent effectiveness was obtained for composite of super absorbent polymer (SAP) with potassium formate (SAP-HCO2K-50 %), all-polymer porous solid desiccant (APPSD) and metal organic framework (MOF)–MIL–101 (Cr), followed by activated carbon fibre felt (ACF) Silica sol-LiCl30, SAP, silica gel, MOF–303, and molecular sieve. Researchers and manufacturers would benefit from the proposed methodology and presented data in developing new desiccant materials for ERV applications.

Exergy Efficiency and Energy Efficiency of Double Air Pass Solar Tunnel Air Dryer: A CFD Analysis

This work presents, the computational fluid dynamics simulation of a forced convection double air pass solar tunnel drying system to study the temperature distribution, the flow behaviour of the air stream, and the exergy performance. Realizable k-epsilon non-equilibrium wall function turbulence model, discrete ordinate radiation model, and species transport were used. The average temperature, thermal efficiency, and exergy efficiency were found to 59.2 oC, 30%, and 9.41%, respectively. The result revealed that the uniform temperature and velocity distribution throughout the heating and drying chamber. Therefore, the newly developed double air pass solar tunnel dryer enhances the air temperature and the exergy performance leads to the increment of drying rate and reduction of drying period.

Innovative Electrostatic Precipitator Solutions for Efficient Removal of Fine Particulate Matter: Enhancing Performance and Energy Efficiency

The removal of particulate matter (PM) from air streams is essential for advancing environmental technologies and safeguarding public health. This study explores the performance of an electrostatic precipitator (ESP) in eliminating fine and ultra-fine PM under varied experimental conditions. It uniquely examines the influence of PM size and feed rate on ESP removal efficiency. The system’s use of low voltages enhances energy sustainability, while its innovative design improves corona discharge, leading to significant reductions in fine and ultra-fine PM emissions. Plants using electrical devices are increasingly being incorporated into material processing lines to reduce pollution in the surrounding work area, as well as to collect particle emissions in the atmosphere. It is also possible to recycle some raw materials in this way with low energy consumption. This cleaning technology increases the added value of industrial equipment, which affects its competitiveness and its impact on sustainable manufacturing. The experimental results indicate a steady electrostatic field voltage of 15.1 kilovolts, with an airflow maintained at 0.8 m/s through a doser at 2.5 bar, eliminating the need for a fan. The PM feed rate varied between 2 and 20 mm/h, with six trials conducted to ensure the data were consistent. Preliminary studies devoid of ESP intervention demonstrated little PM removal, since buildup on the chamber walls distorted the results. The installation of the ESF markedly enhanced the removal efficiency, achieving up to 95.5%. Further analysis revealed that ESP performance depended on PM concentration in the agglomeration chamber, achieving a clearance rate exceeding 98% under optimal conditions. Fine PM (0.35 to 8.7 µm) was more efficiently removed than ultra-fine PM (0.2 to 0.35 µm). The highest removal efficiency was observed at a feed rate of 0.962 mg/s, while the lowest occurred at 0.385 mg/s. A strong positive correlation between particle concentration and removal efficiency (Pearson value up to 0.829) was observed, particularly at feed rates of 0.128, 0.641, and 1.283 mg/s. The study’s findings confirm that the ESP is highly effective in removing particulate matter, particularly fine and ultra-fine particles, with an optimal feed rate, significantly enhancing the system’s performance.

Spray Drying of Inca Peanut Meal Protein Hydrolysate to Produce Protein Powder Drink Mix

The optimal conditions (maltodextrin concentration and inlet air temperature) for spray drying Inca peanut meal protein hydrolysate (IMPH) were determined. The maltodextrin concentration was varied at 5, 10 and 15 % by weight, and inlet air temperature was varied at 150, 160 and 170 °C. The IMPH was subjected to spray drying, where the feed solution was atomized into fine droplets and exposed to a hot air stream, leading to rapid drying and the formation of powder. The moisture, protein, yield, water activity and water solubility index (WSI) of IMPH powder were analyzed. The optimal condition for spray drying IMPH powder utilized 10 % maltodextrin and an inlet air temperature of 160 °C. Under these conditions, the moisture, protein, yield and WSI of IMPH powder were 2.93, 36.93, 38.95 and 99.59 %, respectively, while water activity was 0.41. IMPH powder particles were spherical and non-agglomerate. Inca peanut meal protein powder drink mix (IMPD) with cocoa flavor was the most acceptable. The IMPD with cocoa flavor could be promoted as a high protein and high dietary fiber product. It could be kept at 35 ± 2 °C for 12 weeks, whilst retaining good microbiological properties. HIGHLIGHTS The optimal conditions for spray drying Inca peanut meal protein hydrolysate (IMPH) were determined to be 10% maltodextrin and an inlet air temperature of 160 °C. This resulted in high yield, protein content, and water solubility, while keeping moisture and water activity low. IMPH powder had spherical, non-agglomerated particles, and cocoa-flavored Inca peanut protein powder drink mix (IMPD) was the most preferred in sensory evaluations. The IMPD with cocoa flavor was identified as a high-protein, high-dietary-fiber product, suitable for storage at 35 °C for up to 12 weeks while maintaining good microbiological quality. The study highlights the nutritional benefits of the cocoa-flavored IMPD, which includes essential amino acids, omega-3 fatty acids, and antioxidant properties. GRAPHICAL ABSTRACT

Porous Monolithic Perovskite Structures for High-Temperature Thermochemical Heat Storage in Concentrated Solar Power (CSP) Plants and Renewable Electrification of Industrial Processes

A novel approach towards thermal energy storage of surplus renewable energy (RE) is introduced via a hybrid thermochemical/sensible heat storage concept implemented with the aid of porous structures made of redox metal oxides, capable of reversible reduction/oxidation upon heating/cooling in direct contact with air, accompanied, respectively, by endothermic/ exothermic heat effects and demonstrating fully reversible dimensional changes under cyclic operation. The proposed modular storage units can be heated during the day to a level exceeding the metal oxide’s reduction onset temperature either by hot air streams from air-operated Concentrated Solar Power (CSP) tower plants or via surplus/cheap RE-electricity from photovoltaics, wind, or other renewable sources (“charging”/energy storage step). When this RE sources become non-available or upon demand, the fully charged system can transfer its energy to a controlled airflow that passes through the porous oxide block and initiates the exothermic oxidation of the reduced metal oxide. Thus, a hot air stream is produced which can be used to provide electricity or exploitable heat for industrial processes. The present work elaborates on the operating principles and the potential application of this concept and reports progress in the preparation and shaping of reticulated porous ceramics (RPCs also known as “ceramic foams”) from CaMnO3-based perovskite compositions and their preliminary testing with respect to cyclic reduction-oxidation.

Performance analysis of natural draft power plant cooling tower: Mathematical modeling of cross-flow type, application in capital cities of Iranian provinces

Cooling towers are heat exchangers that reduce the hot water temperature produced by process equipment through heat and mass transfer between water and air stream. This study investigates the performance of cross-flow cooling towers under various geometrical, physical, and environmental conditions. For this purpose, thermodynamic modeling of the cross-flow cooling tower was conducted, and the governing equations were numerically solved using the finite difference method. Unlike previous studies, the effects of water droplet deformation into an elliptical shape during its fall along the cooling tower were also considered. This deformation, which influences the drag coefficient, Reynolds number of the water droplets, droplet surface area, and its cross-section area, along with the incorporation of buoyancy force in the droplet momentum equation, led to an improvement in the results. Consequently, the maximum computational error in this case was reduced to 1.97 %, compared to the scenario where droplet deformation and buoyancy force were neglected. The change in geometrical parameters of the tower in Tehran and Rasht was investigated, revealing that increasing the outlet radius of the tower from 20 m to 22.5 m decreased the outlet water temperature by 1.21 °C and 0.67 °C and increased the thermal efficiency of the tower by 4.94 % and 2.88 % respectively, while increasing the tower height from 100 m to 120 m, only decreased the outlet water temperature by 0.47 °C and 0.26 °C, and increased the thermal efficiency of the tower by 1.89 % and 1.09 % respectively. Additionally, the cooling tower performance was assessed in the centers of different provinces .of Iran. Results showed that with an initial droplet radius of 1 mm and an inlet water temperature of 50 °C, the maximum and minimum temperature reductions occurred in Shahrekord by 20.16 °C and Bandarabbas by 12.37 °C, respectively.

Numerical study of influencing geometry of separator elements for cleaning dust of food production on its efficiency

At modern food enterprises, the task of providing high-quality air cleaning from dust is relevant. The paper proposes an original dust separator, the peculiarity of which is the presence of structural elements of different shapes, arranged in a chess order. This design solution ensures the formation of a wave-like structure of the gas-dust flow within the device. The separation of solids from air is due to inertial and centrifugal forces. The aim of the work is to evaluate the fractional efficiency of this separator with structural elements of different geometric shape during the dust capture process. The paper considers I-shaped, P-shaped, arc-shaped and V-shaped structural elements. The study is carried out by numerical simulation at a gas dust flow rate of 0.5 to 3 m/s and a particle size of 10 to 200 ?m. During the work it has been found that the shape of the structural elements largely determines the efficiency of separation of dust material from the gas stream. The V-shaped design elements have shown the highest average separation efficiency compared to other shapes under other equal conditions. This is due to the fact that in such a separator the particles are directed to their apex, where the velocity of the particles decreases contributing to their subsequent settling into the bunker. The maximum efficiency for V-shaped elements is on average 80.1 % at a gas dust inlet velocity of 0.5 m/s. The lowest efficiency is observed for I-shaped elements, as particles return to the air stream after rebounding from the walls.

Highly resolved peta-scale direct numerical simulations: Onset of Kelvin–Helmholtz Rayleigh–Taylor instability via pressure pulses

The study presents a comprehensive numerical investigation of the Kelvin–Helmholtz Rayleigh–Taylor Instability (KHRTI) onset using highly resolved peta-scale direct numerical simulations by solving the compressible Navier–Stokes equations (NSE). The numerical framework incorporates a three-dimensional (3D) cuboidal domain with differential heating applied to two air streams, fostering the development of the KHRTI. A novel numerical methodology with selective mesh refinement near critical regions is employed with the help of a non-uniform compact scheme to capture small-scale phenomena accurately. Analysis of pressure disturbances during early KHRTI stages reveal distinct wave propagation patterns influenced by Rayleigh–Taylor (RT) and Kelvin–Helmholtz (KH) mechanisms. Enstrophy dynamics are quantified through the compressible enstrophy transport equation (CETE), highlighting dominant contributions from viscous stresses during early receptivity stages. The study provides insights into KHRTI evolution, shedding light on shear-buoyancy-driven instabilities and their implications for transition to turbulence.

Computational study of the coaxial air and fuel jet through a 3-lobe strut injector for efficient fuel mixing in a supersonic combustion chamber

In this article, comprehensive simulations of the compressible air stream inside the combustion chamber are done to disclose the mixing and circulation performance of the 3-lobe injector behind the strut. The computational approach is employed to visualize the jet flow with/without the inner air jet released at supersonic flow. The main focus is the importance of lobe shape nozzle on the fuel diffusion into the main stream behind the strut. The role of the shock waves and their contact with the fuel jet flow is also investigated in the present work. Free stream velocity inside the combustion chamber is Mach = 4 while the hydrogen fuel jet is injected via sonic speed. A comparison of single and 3-lobe nozzles indicates that the lobe configuration of the nozzle increases the circulation behind the nozzle. Besides, the usage of the internal air jet increases the contact of the fuel jet with the shear layer initiated from the edge of the strut.

Technical Analysis of the Possibility of Burning Hydrogen in Furnaces of the Metallurgical Sector

This article analyses the possibility of using hydrogen as fuel in furnaces used in the metallurgical industry. The research was conducted for a selected continuous furnace. For this purpose, based on actual measurements, a heat balance of the furnace was prepared to determine its energy indicators. These values were used to verify the developed numerical model in IPSEpro 7.0 software. Numerical calculations were performed for three variants: pure natural gas; 30% hydrogen, 70% natural gas; and 100% hydrogen. The determined values of gas and combustion air streams allowed for achieving the assumed charge temperature in the heating technology. Calculations of the impact of the excess combustion air ratio on process parameters were also carried out. It was found that no changes are required in the exhaust gas removal system, but verification of the fan supplying air to cool the exhaust gases before the recuperator is necessary. The amount of hydrogen required to fuel the continuous furnace also increases significantly (nearly threefold), which may also affect operating costs. At the same time, the emission of carbon dioxide into the atmosphere is completely reduced, which may be an important criterion when considering modernization options for heating furnaces in the metallurgical industry.

Ablation resistance of C/C–Hf1-xZrxC composites under an oxyacetylene flame at above 2700 °C

To the better application of C/C composites in thermal components of vehicles above 2700 °C, C/C–Hf1-xZrxC composites were prepared by CLVD, and the ablation behavior of composites was investigated. The results show that C/C–Hf0.5Zr0.5C has excellent ablation properties with linear and mass ablation rates of −0.23 μm/s and −0.31 mg/(s·cm2), respectively. ZrO2 molten phase and HfxZr1-xO2 particles are generated on the surface of C/C–Hf1-xZrxC composites during ablation. During the ablation process, defects are healed by the ZrO2 molten phase due to its mobility, which inhibits the diffusion of oxygen into the substrate. The ZrO2 molten phase is stabilized by the pinning effect of the HfxZr1-xO2 particles, which makes the ZrO2 molten phase better resistant to the scouring of the air stream. A relatively complete oxide layer is generated on the C/C–Hf0.5Zr0.5C surface, with a moderate amount of HfxZr1-xO2 exerting a pinning effect to hold the ZrO2 molten phase.

Analysis of Thermo-Acoustic Instabilities Induced by Hydrogen Swirling Flames

Abstract A considerable research effort has been concerned combustion dynamics of systems fed with hydrocarbon fuels. The case of pure hydrogen/air flames deserves to be specifically considered because hydrogen is highly reactive, has a tendency to develop thermo-diffusive instabilities, is envisaged in many future applications, most notably in gas turbines, and is less well documented. Thermo-acoustic instabilities of pure hydrogen flames are here investigated in a configuration where hydrogen is injected in-crossflow in a swirling stream of air. The study is focused on operating conditions that lead to oscillatory regimes. Using Abel-transformed phase-averaged images of OH* emission and visible light emission in burnt gases, it is shown that the OH* signal evolves approximately in phase with the heat release rate. This signal is then used to determine the local Rayleigh source term that feeds acoustic energy in the oscillation. The contributions of this term are examined using a space–time analysis based on an integration of the source term in the transverse direction. This procedure allows a detailed analysis of the processes that contribute to the acoustic energy in the system, showing, in particular, that a strong positive addition of acoustic energy results from a roll-up of the flame tip and from the quick cyclic back propagation of the flame to the injector tip. A global integration of the Rayleigh source term is then used together with a volume-integrated acoustic energy to estimate the growth rate associated with these driving processes and estimate the damping rate. A special experimental method is then exploited to determine the effective growth rate of the instability. The system allowing a sweep in frequency, self-sustained instabilities obtained at different frequencies are used to extract the specific instability frequency band of the burner. Finally, the flame is externally forced in order to measure its flame-describing function.

Evaluation of bubble column dehumidifier using magnesium chloride desiccant

With growing emphasis on indoor air quality and energy conservation, the development of sustainable and efficient dehumidification systems has become increasingly crucial across various industries. Liquid desiccant dehumidification system (LDDS) offers a more efficient alternative to conventional methods by utilizing low-grade waste heat. Most direct-contact liquid dehumidification systems use expensive desiccants such as LiCl and LiBr. Our research focuses on exploring MgCl2, prevalent in saltwater bitterns, as a cheaper, less toxic alternative. The core principle of this system involves passing air through a column filled with the MgCl2 aqueous solution, leveraging the hygroscopic properties of MgCl2 to remove moisture from the air stream effectively. Various parameters such as hole size, air flow rate and desiccant concentration are investigated. We further developed a numerical model for the dehumidification process considering the rise time of the bubbles in the desiccant solution and mass transfer in the bubble. After dehumidification, the diluted desiccant solution can be revived using low-grade heat. Use of seawater bitterns, with major component as MgCl2, shows potential for building an environmentally friendly and cost-effective dehumidification system.

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.

Spraying Wheat Plants with a Drone Moved at Low Altitudes

On a mounted laboratory stand, comparative tests were carried out on the effectiveness of spraying wheat plants with liquid using a multi-rotor drone. The study was undertaken with and without propeller rotations. The lack of rotations simulated spraying by a ground sprayer. The height of the drone’s displacement above the plants was similar to that of the nozzles above the plants used when spraying with field sprayers, 0.5 m and 1.0 m. The speed of the drone movement was 0.57 and 1.0 m·s−1. The effects of the height and speed of the drone’s movement and the impact of the airflow on the volume and uniformity of the liquid application on the plants were assessed. In addition, changes in the transverse distribution of liquid volume in the droplet stream and the transverse distribution of the air velocity in its stream were evaluated. The liquid was sprayed at a constant pressure of 0.2 MPa. The study’s results show that the low height of the drone displacement not only had a strong effect on increasing the liquid volume applied to the plants but also improved the uniformity of application at plant levels. It was also noticed that, at a height of 0.5 m, there was a significant irregularity in the air stream under the drone.

Rotary kiln simulation for energy recovery: The precalciner cement kiln case

Cement production process is energy intensive both in terms of the thermal and electrical energy. In fact, energy demand accounts for about 40 % of operational costs. Significant heat losses are present even in modern plants, affecting negatively both on production costs and emissions. These losses are mainly due to the sensible heat in the hot flue gases and exhaust air streams used for cooling down the clinker (35 % of the process heat losses). Given the good quality of the available sensible heat in these streams (temperatures above 280 °C), a heat recovery system can be considered to increase the overall efficiency of the cement plant. The aim of this work is to create a simplified model of a cement rotary kiln to study the heat recovery optimization. Results were consistent with the temperature, pressure and flowrates ranges indicated in the literature. The model here proposed can be adapted to simulate other processes involving a rotary kiln. As a result of the study of the proposed case scenario, the plant was found to potentially generate 3.2 kWh/ton of clinker of electricity, equivalent to approximately 20 % of the total plant electrical consumption.

Microcontroller-based integrated data logging system for solar air heater performance assessment

ABSTRACT Efficiency curves for assessing solar air heater (SAH) performance are determined by measuring different parameters under certain operating conditions recommended by different test standards such as American Society of Heating, Refrigerating and Air-Conditioning Engineers. In this work, development and testing of a low cost integrated datalogging system for tracing efficiency curves are presented. Pyranometer (CMP11) and temperatures sensors (DS18B20) are integrated with microcontroller (AT89S52) for continuous data recording at desired time interval. Switching devices are integrated to automatically control operations of electric heater for maintaining inlet air stream temperature as per testing requirements. Using the system, efficiency curves of a 1.46 m2 SAH installed in Tezpur University, India, are determined at two mass flow rates of air. Results are comparable with published literatures revealing negative slope (energy loss component, F R U L ) and positive intercept (energy absorption component, F R (τα) n ) of efficiency curves. SAH shows better performance at lower mass flow rate of air (0.0235 kg/m2-s), with F R U L as 13.5 W/m2-K compared to operation at 0.0430 kg/m2-s mass flow rate of air where slope increases by around 23% with same intercept. Higher slopes of the SAH demonstrate its highest sensitivity to prevailing wind compared to three previously published designs. Present study shows that the integrated system can replace individual traditional measuring instruments for respective parameters like solar irradiance and temperatures as well as additional control equipment required to maintain desired test conditions. Further development of the system can lead to a modular and portable efficiency curve tracer for SAH performance assessment.