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Waste can contribute to environmental issues, but it also contains potential resources that can be generated and used by the community. Previous research indicates that the composition of household and similar waste is dominated by organic waste accounting for 50-60%. The organic waste can be converted into compost, which can be used to enrich agricultural soil. A perforated brick construction method (Bata Terawang) with the open windrow principle is a well-known composting method in Indonesia, where the supply of oxygen and moisture must be an essential consideration. The aeration system in the composting with the perforated brick construction is typically accomplished in two ways: by creating hollows in the brick construction or by placing perforated pipes crosswise in the middle of the composter tube. This research was conducted to produce a design for composting organic waste systems that can be used in households and industries. The method used in this research is using an experimental approach. This study attempted to place a perforated pipe into the aeration process and periodically add airflow from a blower. The results show that adding airflow will speed up the composting process, while the quality of the compost produced is drier due to the lower water content. [ABSTRACT FROM AUTHOR]

Effective ventilation is vital for indoor air quality and occupant comfort. However, room layout and furniture placement can influence ventilation distribution, leading to inconsistent airflow. This study investigates the relationship between ventilator placement and ventilation profiles in a room. Experimental simulations were performed using the computational fluid dynamics (CFD) with varying placements of ventilator fans were conducted. The 8 different placements were made at high and medium height configurations across the walls either opposite or perpendicular to the inlet section in the enclosed space which in this case, is a room. The boundary conditions set at ambient atmospheric pressure of 101325 Pascals and the ambient temperature is set at a room temperature of 293.2 K. The results show that ventilator placement significantly affects ventilation distribution, with some areas experiencing inadequate or inconsistent airflow and ventilation coverage. The results obtained had determined that the higher placement of ventilator and located strategically at the opposite of the inlet section would be the most optimized configuration where the air flow will have a more complete distribution and coverage of the space in the enclosed space. These findings would promote better room designs to optimize ventilation and enhance occupant comfort. [ABSTRACT FROM AUTHOR]

The use of solar air heaters is efficient as solar energy is converted into thermal energy, which then is transferred to a fluid in order to be used for heating. Solar energy is collected at the surface of the absorber plate, transformed into thermal energy, and then used. It has been determined that the low effectiveness of the flat plate SAH is caused by a low convective HT coefficient. Increasing the effectiveness of the SAH by including roughened components on the bottom of the absorbing area is the strategy that has shown to be both the most popular and the most successful. An increase in the radiation intensity that is received by the absorber plate as well as an efficient removal of heat contribute to an increase in the SAH's thermal performance. The findings of the experiments conducted for this study reveal that the HT of the absorber plate can be amended by intentionally roughening the side of the plate that faces the air flow. HT coefficient and thermal efficiency properties of SAHs were tested in the field using artificial roughness created in the form of discrete double arc reversal on the plate. The parameters employed were W/H = 8, p/e = 10, e/Dh = 0.027, α = 60°, and Re = 2975-13739. In addition, the solar radiation intensities during the outdoor test ranged from 860 W/m2 to 895 W/m2 and lasted from eleven in the morning (just before noon) until two in the afternoon. Thermal efficiency and coefficient of HT across the smooth duct were increased by 1.16 and 2.8 times respectively. [ABSTRACT FROM AUTHOR]

Double skin facade systems are greatly used in buildings designed by famous architects and are described as a typical "green" building approach. In the present study, the exhausted air of the Heating, Ventilation and Air Conditioning (HVAC) system was used and passed through the air cavity. A numerical investigation was established to estimate the influence of the cavity of width 0.2 and 0.3 m and the airflow velocities of 0.9, 1.25, and 1.5 m/s on the temperature distribution and reducing the cooling load for buildings. A double skin facade system was used in this study using a glass sheet with a thickness of 6 mm. The computational domain was numerically modeled and solved utilizing the ANSYS19-Fluent software. The results demonstrated that, by using the exhausted air from the HVAC system, the small cavity width is more efficient in reducing the cooling load and saving more energy. The reduction in DSF indoor wall temperature was about 21% for the cavity of width 0.2 m compared with that of width 0.3 m. In addition, the effect of velocity in the cavity with a small gap of 0.2 m width has no significant impact on the temperature distribution through the cavity. [ABSTRACT FROM AUTHOR]

At the peak of the solar radiation, the efficiency of the photovoltaic module and the energy output decrease due to the high temperature of the PV panel, which leads to the loss of energy produced by the photovoltaic panels. The present research includes a study to increase the efficiency of the photovoltaic unit by hybrid cooling using fins and water flow together. The PV module is cooled by naturally flowing air over the surface of the fins installed beneath the back surface of the photovoltaic panel, and water flows over the PV panel surface at 1, 2, 3, and 4 liters per minute. The experiments were conducted with three 50W solar panels installed on the roof of a steel structure one meter high to provide space for cooling air. The back of each of two panels was connected to the aluminum heat sink and the distribution is located in the PV1 staggered and PV2 in-line. These two panels were tested with hybrid cooling, while the third PV0 was installed without cooling. This article presents an experimental investigation according to the meteorological conditions of the city of Babylon, Iraq. The results indicate that the cooling of inline arrangement PV2 is better than that of staggered one PV1 in the two cases of presence and absence of water. The average temperature of the PV2 was reduced to 22°C, 18°C, 15.6°C, and 18.5°C with a flow rate of 1,2,3, and 4 l/m, respectively. Consequently, the electrical efficiency was improved from 11.5% to 12.3%, 13.3%, and 12%, at flow rates of 1, 2, 3, and 4 l/m, respectively. [ABSTRACT FROM AUTHOR]

Airfoils, which are basically the wings of an aeroplane, are an essential part of aerodynamics and aviation, greatly influencing the lift and drag properties of an aircraft. Aerodynamic performance can be strongly affected by flow separation, a phenomenon where the airflow over an airfoil separates from its surface. The paper uses MATLAB numerical simulations to examine the effectiveness of many flow separation control strategies. A significant challenge in aviation is flow separation, which has an impact on the lift-to-drag ratio and overall aerodynamic efficiency. Many strategies have been researched to tackle this problem, including active and passive control approaches. Leading-Edge Blowing, Boundary Layer Suction Control, and Angle of Attack Control are some of these methods. The paper's two main goals are to evaluate how different strategies affect airfoil performance and to pinpoint the most efficient way(s) to increase aerodynamic efficiency. Using a range of airfoil designs, flow conditions, and simulations at different angles of attack and Reynolds numbers, the process entails numerical research. Every control method has a mathematical model that has been carefully created and put into practice in MATLAB. The research paper's observations provide important new information on how well flow separation control strategies works. The data, graphs, and analysis that are provided show how various methods affect important aerodynamic factors including lift, drag, and pressure distribution. Even with flow separation's drawbacks, this study highlights how creative control strategies can improve airfoil performance. These results add to the growing body of knowledge in the field of aerodynamics, deepen our understanding of flow separation control, and lay the groundwork for further investigations aimed at improving aviation efficiency and safety. [ABSTRACT FROM AUTHOR]

In the article, the need to study the indicators of the movement of dangrous air currents in motion and to limit the spread of these movements in the environment, to determine the parameters of aspiration currents in the environment, is scientifically justified. "Improving the tactics of localization and elimination of emergency situations using the coefficient of aspiration flow" and localization, taking into account the additional air flows absorbed during combustion, in particular, through solutions based on the results of research, which are becoming one of the most urgent issues in the field of fire safety to prove. [ABSTRACT FROM AUTHOR]

Since the inception of the automobile industry, the incremental improvements in the Internal Combustion Engines have been observed. The IC Engine run vehicles are bulky, have many components and create air pollution, which is a major issue throughout the world. Now a day's technological advancement in the field of electric vehicle provides solution to every problem in a much more efficient way. This paper describes the design and optimization of the electric motorcycle chassis. In this work, optimization of chassis frame has been carried out to reduce the battery changing time. Air flow over chassis is used for cooling the batteries by forced convection. Proposed chassis design is validated using the results of structural and computational fluid dynamic analysis study. The optimized proposed model has achieved 40% of weight reduction of the electric motorcycle chassis. The flow rate of air through batteries was increased for the optimized chassis and battery module. [ABSTRACT FROM AUTHOR]

This study aims to determine the effect of material on heat distribution in the design of battery pack cases in the Garuda Kencana 2022 electric car. The type of research used is experimental research with the subject material used in battery pack cases on the Garuda Kencana 2022 electric car. It uses SolidWorks Flow Simulation software to determine the airflow that helps heat distribution from the battery to the battery pack case material. Three materials were tested: Aluminum, Magnesium, and Zinc. The data analysis technique used to process the test data is descriptive analysis. The results of this study indicate the distribution of heat in the material, with the presence of airflow that helps heat distribution. The material that can experience the best heat distribution is Aluminum, with a maximum temperature of 49.69°C at a battery temperature of 60°C [ABSTRACT FROM AUTHOR]

A heat exchanger is a component that is able to maintain equipment temperature effectively. Several efforts have been made so that the heat exchanger can work more efficiently, one of which is highlighted in this research, namely the use of AC wastewater as a liquid in the heat exchanger. AC waste water will flow inside the air cooler generator to cool the walls of the fins so that the temperature of the air passing through the air cooler generator becomes lower. The water cycle will continue to rotate so that the temperature of the flowing water can be maintained. The average values for the heat transfer rate for regular water are 3097.8 J/s, while for AC wastewater, it is 2937.9 J/s. So it can be concluded that AC waste water can be used as cooling water. [ABSTRACT FROM AUTHOR]

Sustainability, efficiency and optimized constructions have been unique characteristics of nature which inspires modern age designers and engineers to solve complex engineering problems in an innovative way using nature inspired design. Nowadays, with the commercialization of additive manufacturing, referring to nature as a source of inspiration for solving simple to complex engineering problems has been one of the greatest advantages to designers. An attempt has been made in this regard to optimize the performance of a residential ceiling fan seeking inspiration from nature. Ceiling fans are generally used for cooling and to improve the thermal comfort of the residents in a closed room. They consume less energy and have very negligible maintenance cost as compared to their counterparts like air conditioners and air coolers. However, there are some limitations that the conventional fans have; concerning the area, they circulate the air in, which reduces with distance from the fan. This research proposes to optimize these performance characteristics of fan blades inspired from a sycamore seed. The design results are validated by a software simulation that demonstrates a better air circulation and distribution in a given room with a greater speed over a larger area for the same power being consumed as that of a conventional fan. [ABSTRACT FROM AUTHOR]

The effect of air velocity V in the channel on the dissociation of Freon R-134a hydrate at atmospheric pressure was studied experimentally. An increase in the velocity V led to an increase in the dissociation rate J, the surface temperature of the granules, and the temperature along the height of the Freon hydrate layer. An increase in velocity V from 0 to 2.5 m/s led to an increase in J by 2-2.1 times. [ABSTRACT FROM AUTHOR]

Solar photovoltaic with thermoelectric air conditioners are better and suitable for remote locations, particularly those with direct power source from the sun. Thermoelectric air-conditioning systems have demonstrated promising advantages over conventional air-conditioning systems on the other hand the thermoelectric peltier has low coefficient of performance. In this work the exergy and energy of new thermoelectric solar assisted air-cooling integrated duct are experimentally studied for two cases by using two values of operating current. First case used maximum current while the second case used fixed current of (2.7A). the air cooler duct used in this work is an integrated type that has two side one is for the cold air and the other is for hot air flow. The goal of this research is to evaluate the exergy and energy of the thermoelectric air-conditioning to obtain optimum operation technique for the system and better COP values. The average value of COP was (0.38) for both maximum current case and (2.7A) case. The exergy efficiency of maximum current case ranged between maximum value (1.03%) and minimum value (0.44%) with average value of (0.59%). While the second case maximum value was (0.26%) a minimum value (0.08%) with average of (0.12%). regardless the lower COP value in maximum current case the exergy efficiency improved by (79%) which mean that using maximum current value leads to better performance. [ABSTRACT FROM AUTHOR]

The new design of the sun simulator offered a wide range of solar flux according to the outside data recorded by the Iraqi Meteorological Organization and Seismology for Baghdad in 2020. This study consists of two parts: experimental and numerical work. Three mass flow rates (0.01531, 0.02321, and 0.02937 kg/s) were tested experimentally, as well as three months of intensity data. order to confirm the accuracy of the numerical work, A mathematical model was built using a finite volume scheme. SIMPLE algorithm was utilized to solve three dimensions of steady state, turbulent, and forced convection flow. The maximum air temperature difference was 20, with the air mass flow rate of 0.01531 kg/s and the solar radiation of 950 W/m2 in July. Also, the greatest thermal efficiency was obtained at 47.4% in mass flow rate of 0.02937 kg/s and maximum intensity of 950 W/m2. There was an acceptable difference in results between the numerical and experimental tests. [ABSTRACT FROM AUTHOR]

In this paper, the effect of injecting micro bubbles of air into a flowing water stream in copper tube of 8-meter length with a wavy design and a diameter of 0.0125 meter has been studied. The solar collector's inner surface moreover, coated with matte black paint that includes thermal die and 5% of TiN (Titanium Nitrate) nanoparticles to enhance the ability of solar radiation absorption. The solar collector's performance was evaluated. The experimental rig was designed and built in Karbala-Iraq, latitude (32.6160 oN) and longitude (44.0249 oE) within the first four months of the year. The air was introduced into the tubes through a venturi device, which mixed with the water and then flowed together inside the solar water collecting tube. The first section of the experiment involved only four various levels of water flow (0.5, 1, 1.5, 2) L/min, while the second section involved a water flow with injection of air bubbles at three different levels (0.25, 0.35) L/min. The result showed that as the rate of mass flow is reduced, the outgoing temperature rises, resulting in a rise the difference in temperature between the entrance and the output temperatures in both the incoming and departing systems. The largest temperature difference was 6.6 oC for opened system and 9.1 oC for closed system. But the small flow rate showed that the collector efficiency is decrease. Also, the results shows that the best efficiency for opened system at 1 liter per minute and 2 liter per minute for closed system. The average efficiency in the closed system was (65.57 %) at water and air bubble flow rate of 2 L/min and 0.35 L/min, respectively. The average efficiency of the opened system was (39.27 %) for water and air bubble flow rate of 1 L/min and 0.25 L/min, respectively. [ABSTRACT FROM AUTHOR]

A historic school building was recently retrofitted. Due to its high architectural quality, the building is listed as National Architectural Patrimony, and therefore the rehabilitation process has met very challenging requirements regarding its conservation to maintain the original layout. In view of its age, the building is done with thick stone walls which help energy conservation and enhance thermal inertia. Its primitive architecture enables natural lighting, increases solar radiation gains, and favors natural ventilation, assuring, consequently, an improved energy efficiency. The implemented rehabilitation actions tried to preserve the original architecture and the building restorations were designed to conserve as much as possible the ancient distinctive architectural style. Given the imposed constraints, matters like Indoor Air Quality (IAQ) and thermal comfort in rooms and offices for administration and staff were not met. The current situation has resulted in justifiable complaints from the building users, reporting poor rooms IAQ due to a lack of air renovation. Because of the impossibility to install mechanical ventilation ducts, the building rooms are operated through natural ventilation, which makes the adoption of constant air flow regimes difficult to implement. To evaluate the problem and promote measures to deal with it, an experimental campaign to assess IAQ and building thermal comfort was implemented during the Winter of 2022. In the framework of the campaign, two identical rooms with similar occupancy, size, volume, building typology, heating regime, and with the same equipment installed, were measured in situ for 3 months, by monitoring continuously the following variables: indoor radon concentration, air temperature and relative humidity, under distinct regimes of ventilation. By using statistical analysis of the experimental data, the results show, as expected, that the room with a permanent air renovation has an improved IAQ than the other monitored room, operated with a restricted ventilation schedule, without jeopardizing the energy efficiency. Based on the results, natural ventilation in a steady state mode is the key to balancing IAQ and energy efficiency. [ABSTRACT FROM AUTHOR]

The aim of the present study is to investigate the air flow and temperature distributions of two-seater tandem vehicle cabin. The air flows and temperature distribution in the cabin must be designed to reach acceptable passenger thermal comfort while at the same time minimizing the energy of mechanical cooling efficiently. The model is two-seater tandem vehicle cabin with a volume of 1.7 m3. The heat load from internal and external source is applied into the calculation, and the outdoor environment is assumed in tropical climate. We evaluate the thermal comfort of the passenger using PMV model based on temperature distribution in the cabin. Two conditions inside cabin, are implemented, there are at peak and lowest heat load. [ABSTRACT FROM AUTHOR]

Indonesia has an opportunity in developing the coffee processing industry, because apart from having a large market, it is also supported by potential raw materials. Therefore, strategic efforts are needed, such as downstream in order to increase added value and increase production capacity (Kemenperin, 2019). To determine the quality of the coffee can be seen based on two tests namely physical quality testing, and taste. Moisture value of coffee beans the maximum is 12.5%. One form of control is an increase in coffee processing technology, namely roasting machines (Maulid et al, 2021). This research focuses on forced convection hot air flow by a blower whose speed is engineered using the help of a dimmer speed controller to obtain optimal heat and mass transfer results by experimentally varying airflow and heat transfer then obtaining optimal speed and temperature values. Temperature also affects the value of the forced convection coefficient. The largest convection coefficient is found in the variation of the highest temperature value test, namely 297.5 ᵒC with a value of 43.66 W/m2 ᵒC. The lowest convection coefficient value lies in the experimental variation with an air flow velocity value of 11.4 m/s at a temperature of 297.5 ᵒC with a convection coefficient value of 28.38 43.66 W/m2 ᵒC. The convection heat transfer value (Q) will increase when the flame temperature (T) and air flow velocity increase (v). The greatest electric power will increase when the air flow velocity increases with a low flame temperature value. Effect of airflow velocity (v) and flame temperature (T) simultaneously on the final roasting temperature of 87.5%. [ABSTRACT FROM AUTHOR]

The work has been carried out to study the temperature distribution and air flow variation inside the food compartment of domestic refrigerator. Effect of natural convection and forced convection modes of operation on secondary air flow and temperature distribution has been studied numerically. Also, effect of placement of evaporator in the natural circulation mode of operation has been studied. Commercial CFD software ANSYS FLUENT is used to model and simulate the food compartment of the refrigerator. Radiation effect has been considered into account while carrying out the simulation. Temperature and air flow distribution contours along with air velocities at specific locations have been presented and analyzed. It is observed that forced convection mode of operation results in better refrigeration effect. It also concluded that radiation plays a vital role in the temperature distribution. [ABSTRACT FROM AUTHOR]

This paper focuses on the effect of airway narrowing caused by the disease tracheal stenosis in the respiratory tract of human. A circular model of the human respiratory airway was constructed, and a 50% constriction was considered in the trachea to mimic the tracheal stenosis. Airflow pattern, pressure distribution, and their effect on drug transport and deposition are numerically investigated using Computational Fluid Dynamics analysis. The inhalation rate for resting condition (15L/min) and laminar flow model were considered in the present analysis. Velocity contours and pressure drop around the upstream and downstream of the stenosis constriction were obtained. The presence of tracheal stenosis alters the flow patterns significantly downstream of the stenosis, which can be observed in the velocity contours. There are large recirculation zones after the stenosis constriction indicating the possibility of large residence time of particles in those areas. The upstream of the stenosis imparts high resistance to the airflow producing significant pressure drop, which supports the evidence that airway constriction can cause drastic and relatively rapid rise in breathing impairment. [ABSTRACT FROM AUTHOR]

The article is devoted to the development of a universal and energy-efficient design of the air transport system of semi-trailed cotton-picking machines. The principles of operation and the development trend of air transport systems of cotton picking machines were studied various modifications, including with spindle devices. As is known, the main unit in the air transport system is a centrifugal fan. The airflow generated by the fan allows the cotton to be transported, collected by the harvester, into the bunker of the machine. Calculations are given for the effective use of the area of the ellipsoidal side inlet for flow air flow through the fan. Based on our research on improving the air system of a semi-trailed cotton-picking machine justified recommendations for the development of its universal design. [ABSTRACT FROM AUTHOR]

Airflow sensor is an important component in medical ventilators. It measured the air flow rate, tidal volume, and minute volume delivered to the patient. During the COVID-19 pandemic, airflow sensors were not locally available due to international demand; also, their design and fabrication for this medical application require complex processes and standards. This work aimed to develop flow sensors for medical ventilators. Two types of airflow sensors have been created: orifice-based flow sensors and venturi-based flow sensors. Methods for flow sensor development include defining design specifications, developing CAD design, choosing the material for housing, 3D printing, flow sensor assembly, testing, and calibration. Performance analysis was performed for accuracy, precision, and linearity across the desired flow range encountered in mechanical ventilation. The prototypes of flow sensors have also been compared their performance to commercially available flow sensors. Using a statistical analysis t-test, it was observed that there was no difference in performance between the prototypes and the commercial flow sensors. These airflow sensors had been installed in the automatic airbag ventilator #BPPT3S-POLY for measuring the tidal volume and minute volume delivered to the patients. [ABSTRACT FROM AUTHOR]

The use of solar air heaters for building in European countries is important as it helps in making the rooms hot during the winter. Due to the low energy conversion efficiency of passive solar air heaters, a constant flow of air is required. This flow can be achieved with the help of an airflow pump which is driven by electricity. The alternate source for providing the electricity to pump is a thermoelectric generator that generates the electricity with the help of solar radiation. The positioning of the thermoelectric generator is a new task that is investigated in the present work, two configurations, one on the placement of the thermoelectric generator over the absorber plate and the other at the house walls are investigated. A simulation model is developed in COMSOL Multiphysics 5.5 with the measurement of the temperature of thermoelectric material at different positions calculated. The results indicated that the placement of a thermo-electric generator at the absorber plate generates a temperature of 325 K which is more in comparison to when placed over the walls i.e., 312 K. [ABSTRACT FROM AUTHOR]

Decomposition of organic matter is sensitive to air flow, humidity and temperature, thus appropriate conditions are needed for effective composting which are achieved through a correct composter design. The paper focuses on a simulation analysis for the injection molding process of the bottom part of a composter. Contemporary injection molding machines require fine tuning to ensure successful mold filling and the attainment of satisfactory product quality. Addressing plastic product design from a manufacturing perspective helps ease challenges related to injection molding process and mold design. Process optimization commonly involves variables such as injection pressure, injection time, packing pressure, packing pressure holding time, melt temperature, mold cavity temperature and features of the cooling system. To ensure consistent product quality, it's crucial to optimize process parameters for specific cases due to substantial variability among injection molding input parameters. The use of Moldex3D software aids in identifying locations of critical values of defects, such as shrinkage and warpage. Warpage and shrinkage defects are minimized by Design of Experiments (DOE) optimization method. The results show that simulation, combined with optimization techniques, significantly improves product quality and process efficiency. Reducing warpage is achievable by extending the packing pressure time and using a lower coolant temperature. However, while extending the packing pressure time and reducing the melt temperature have a marginal effect on reducing shrinkage, higher cooling temperatures, as predicted, results in diminished shrinkage. [ABSTRACT FROM AUTHOR]

Iraq, daytime load consumption exceeded midnight due to the country's all-year increase in summer power demand. Building air conditioning is the main cause of this. Thus, one way to lower the peak demand would be to generate and consume power at night while storing cold thermal energy to lower the demand for air conditioning during the day. We Suggest a new radiant floor cooling system using two types (spiral and counter geometry) of thermal energy storage (TES) filled with phase-changed materials (PCMs) with night re-cooling using air conditioning (A/C) in the summer of Iraq. This study aims to save and shift energy from nighttime to daytime for two test rooms full-size prototypes made from sandwich panels of dimension (length 2.25 x width 2.95 x height 2.95) m situated in Kirkuk-Iraq, also to clarify the steps to guarantee the thermal storage effect of the suggested cooling system during the day for two test rooms within a very small diurnal temperature range, focusing primarily on the thermal characteristics of PCMs. We investigated the connection between the suggested system's heat flows and indoor air temperature distributions. The results showed a decrease in the room temperature was about 1 when using forced water cooling for the floor room, while it was 2.8 °C using the PCM. The evaporative cooling used in Test 1 to cool the floor and increase the COP of the air conditioner resulted in a 40.2% and 34.79 % for spiral and counter design respectively, reduction in energy use for the entire summer compared to Test 3 and a 28.2 % and 23.55 % for spiral and counter design respectively, reduction in energy compared to Test 2. It is clear from the results that the energy saving of the counter design is (6%) more than that of the spiral design. [ABSTRACT FROM AUTHOR]

Water cooling in the circulating water supply systems is common in different industries. A closed-circuit cooling tower is developed with indirect gas-liquid contact by means of an internal tube heat exchanger with an inline tube arrangement. The purpose of the work is a numerical study of the thermal characteristics of the developed cooling tower. The heat transfer coefficients on the different tubes of the heat exchanger were found to vary significantly depending on the mean air velocity in the cooling tower unit and the location of the tubes. The obtained results of numerical calculation were verified by comparison with an analytical solution based on the various criterion equations describing the transverse air flow around a tube bundle with a corridor arrangement of tubes. [ABSTRACT FROM AUTHOR]

This study aims to determine the mechanism of breaking bubbles into small size in a Swirl type microbubble generator (MBG) with variations in water discharge (QL) at the distance of the air nozzle to the MBG outlet of 1mm. Observations were made using a Phantom Miro M310 high speed video camera with a maximum resolution of 1200×800 to record the microbubble phenomenon. All measurements were taken at a frame rate of 3000 fps. The spatial resolution and frame rate used in this study allow the behavior of the microbubbles to be observed in detail. The focal length and lens aperture are 85 mm and 2.8 mm, respectively. The length between the lens and the viewing area is 350 mm. A wide measuring field and a narrow depth of field were obtained, which is about 2 mm. Its field of measurement is 40.3 mm x 85 mm, and it was found that the 1 pixel of the camera represents 89,55 µm. The results of the investigation showed that the mechanism of the bubbles breaking into smaller sizes starts with bubbly flow in the mixing chamber channel, then forming ligaments at the MBG outlet, before finally bursting into small bubbles. At higher QL and constant air flow (QG), more bubbles were produced and more uniform with smaller size. [ABSTRACT FROM AUTHOR]

Utilization of geothermal energy is still dominated by indirect use for electricity generation, beside geothermal energy can also be used for direct application. Direct use is mostly using a low enthalpy geothermal resources (<150°C), one of the applications of low enthalpy geothermal energy is for drying process. Drying is a post-harvest method that aims to improve the quality of agricultural products by removing some of the water to an agreed an d safe limit, while microorganisms unable to grow and multiply. Coffee is one of the important commodity which has an important role in economic sector in Indonesia. In this study, the Computational Fluid Dynamics (CFD) method is used to determine and predict the drying chamber's temperature and air flow distribution patterns. The simulation process is carried out by varying the thermosiphon heat temperature (50, 60, and 70 °C) and the air inlet velocity (0.2, 0.4, and 0.6 m/s). The simulation results show the uniformity of temperature in the drying chamber, with the highest drying air temperature is 57.72°C, where the air temperature is influenced by the thermal temperature of the thermosiphon and the large air flow velocity. Based on the simulation conditions, the highest amount of heat needed in the drying process is 118.79 kJ/kg at temperature condition of 50°C with velocity 0.6 m/s and the lowest is 117.41 kJ/kg. [ABSTRACT FROM AUTHOR]

Hot air rising (or convective airflow) is transparent gases (fluids) and invisible. The visualization of fluid dynamics is of considerable interest due to its widespread applications. Background-oriented schlieren (BOS) as an optical method offers numerous advantages in the visualization since this method can provide simple, non-contact, non-invasive, and non-intrusive measurements. The performance of the BOS method strongly depends on the background patterns. Implementing the BOS method usually use random dot patterns as a background and the digital image correlation (DIC) algorithm as a software tool for image processing. However, this algorithm can also analyze the regular pattern background. So far, the experimental BOS using regular patterns background and the DIC algorithm are rarely developed. In this paper, three types of regular patterns, including a checkerboard (crossed fringes), vertical and horizontal fringes patterns, have been proposed as the background in the experimental BOS. During the experiment, a camera is continuously focusing on the background patterns. At the same time, a convective airflow is in the position between the background and the camera. The digital camera records the change of background patterns with and without a convective airflow, giving them distorted and undistorted (reference) images. By comparing both images, the DIC algorithm estimates the pixel displacements. Finally, the interpolation method reconstructs the pixel displacements field into an image resembling the convective airflow. For calibration purposes, the developed BOS uses the known deflection angle of a wedge prism as a standard to assess the accuracy. As a testing, the calibrated BOS visualize the convective airflow induced by a hot object as a heat source, such as candle flame and hot plate. The results show that all the types of backgrounds in the experimental BOS has created image, visualized and distinguished the fluid dynamics of convective airflow. Also, the developed BOS can calculate quantitatively the magnitude of pixel displacements that are proportional to density (or refractive index) gradients of the convective airflow. Thus, the developed BOS can detect an invisible phenomenon and potentially measure density (or refractive index) fluids and other transparent materials. [ABSTRACT FROM AUTHOR]

Flow separation is when the air flow gets detached from the surface of the object which was travelling through the flow. Several studies are going on. In attempt to improve this airflow, we utilize a vortex generator and a passage vane type in this research, which permits the air to remain connected to the surface without being detached. By studying NACA 5 series 23013 designing part is done by using Catia to make 3D model of the selected airfoil and the model which is used is K-e SST for analysis in ansys 19.1 workbench tool with the velocity 10m/s and varying the angle of attacks. This review aims at comparing about the analysis of air flow over a surface with vortex generators and passage vane created. The computational results are compared with respect to lift and drag variation. [ABSTRACT FROM AUTHOR]