Search

The research aims to investigate the kinetic characteristic of microwave-assisted pyrolysis of palm kernel shells using microwave output power (800, 600, 450, and 300 watts). The research consists of three steps; thermogravimetry analysis, microwave-assisted pyrolysis, and kinetic study analysis. This research showed that increased output power affected the decreasing activated energy, increased heating rate, and accelerated pyrolysis. The findings showed that microwave output power significantly affected kinetic characteristics and the production yield of microwave-assisted pyrolysis. Microwave-assisted pyrolysis ran optimally at 800, 600, and 450 watts but had not yet entirely run at 300 watts. The shells produced high solid products because they had a high lignin content (38.76 wt.%). The shell had a volatile matter content of 67.84 wt. %. Analysis using GC-MS showed that the liquid product contains an aromatic compound which was acetic acid and phenol. [ABSTRACT FROM AUTHOR]

Microwave absorber and microwave output power plays an important role in the microwave-assisted pyrolysis of aseptic packaging waste in view of its significant influence on the type, quantity, and quality of product yields. The pyrolysis experiments were carried out at microwave output power ranging from 300 W to 800 W and using two different microwave absorbers (activated carbon and silica carbide). The chemical composition of the wax product obtained from microwave pyrolysis was investigated in this study by Fourier Transform Infrared Spectroscopy (FTIR). The result showed that if activated carbon was used as the absorber, the lowest output power of 300 W could produce the highest char of 57.01wt.% because of the slow heating process. For the wax product, the highest amounted to 27.19wt.% was obtained at the highest output power (800 W), while the highest gas product (66.54wt.%) was obtained at 600 W. The use of silica carbide absorber can increase the final temperature achieved. Meanwhile, the carbon absorber can extend the residence time of volatile in the hot zone so that it can produce a higher gas product. The variation in the output power of 300 W shows a smooth spectrum of carbonyl compounds, this means that the content is lower than the wax produced at other output variations. The model established in this study revealed that the quantity and quality of the products obtained from microwave pyrolysis highly depended on the process conditions, which were significantly influenced by the microwave absorber and microwave power output. [ABSTRACT FROM AUTHOR]

This paper gives an overview of several published current studies concerning heat transfer enhancement on the double pipe heat exchanger. Since double pipe heat exchanger has drawn much consideration due to simplicity and wide-range utility. The flow manipulation technique to enhance heat transfer in a double pipe heat exchanger has been frequently cited. Also, various research addressing working fluid on a double pipe heat exchanger has been discussed in detail. Another technique is known as surface modification that has an infrequent investigation comparing the other techniques. Correlation of Nusselt number and pressure drop coefficient shown in this overview. Future research opportunities are mentioned. [ABSTRACT FROM AUTHOR]

This study aims to visualize the non-premixed flames in a radial flow burner equipped with swirl vanes and to analyze the stability of flames. The study was carried out using concentric pipes, an air pipe 2 inch in diameter and a fuel pipe 6 mm in diameter. Fuel was injected through 3 holes with diameter of 1.5 mm. The fuel used is LPG and the air is supplied from a blower with a speed range of 3.8-6.6 m/s. The air passed a swirl vane with angles Ø=10°, 30°, 50°. The stability limits of the flame at fixed air velocities were obtained by increasing the fuel velocity until the flame blowed out. The fuel velocity were then plotted into a flame stability diagram. Furthermore, structures of the flame were visualized from ignition until the flame blows out using video camera with 240 fps. The results show that in general larger angle of the swirl vane increases levels of flame stability. At relatively low air speeds, the swirl with Ø=50° shows the broadest stability limits compared to Ø=10° and 30°. While at higher air velocity the stable flame area of the swirl with Ø=50° is narrower compared to Ø=30°. At the blade angle Ø=10° and Ø=30 ° increase in air velocity causes an expansion in flame stability, whereas at Ø=50° increase in air velocity causes a decrease in flame stability. [ABSTRACT FROM AUTHOR]

Water tunnel (WaTu) visualization techniques have been in high demand to analyze aerodynamic characters in the delta-aircraft model because of clearer and more detailed results. The visualization was used to observe the aerodynamic characteristic of the rolled-up vortex phenomenon on delta-wing. The difference in fluid and flow parameters became an issue of the accuracy of the results. Therefore, testing parameters need to be analyzed so that the results of the WaTu test have been able to represent the real conditions. This research has varied the velocity to investigate the delta-wing aerodynamic characteristics using GAMA water tunnel. The results were compared with computational fluid dynamics (CFD) results based on WaTu and real (subsonic) conditions, as well as several other references. The results showed a similarity in the vortex breakdown location (VBL) at all flow rates in the WaTu and CFD. The CFD results also showed that the coefficient of pressure (Cp) on the wing had the same results in all tests, both based on WaTu and real conditions. Likewise, for a lift and drag coefficient (Cl-Cd), values for all states approached the same amount with a difference of less than 5%. Finally, the uses of the WaTu method has been able to represent the actual conditions in vortex dynamics cases in delta aircraft with the optimum velocity to produce the best visualization around 0.1 m/s. [ABSTRACT FROM AUTHOR]

The improvement of the performance of fighter aircraft is always made by engineering the flow around the fuselage; one way is by the addition of a canard. The addition of a canard with delta configuration will bring about the appearance of a roll-up vortex, with a vortex core that has a speed higher than its free velocity, from the canard to the main wing. This vortex core, which keeps the flow above the main wing, remains streamlined and delays a stall, thus increasing the aircraft's maneuverability. The interaction of the vortex core from the canard with the airflow over the main wing is strongly influenced by the canard position against the main wing. Investigations needed to be done to see the effectiveness of the flow interactions. A visualization method using a water tunnel gave the advantages of a detailed flow review due to the density and mass diffusion being greater than air, yielding a better visualization. However, this suffered from limitations in getting quantitative data in detail, so that there was a need for computational fluid dynamics (CFD) techniques. The results of this study indicated the effectiveness of canard position on the flow interaction, having a good lift coefficient (Cl) for the canard position on the top and front side of the main wing, with the Cl increased by up to 5%-12.1%. While at a high angle of attack (AoA), the canard position that was closer or coincides with the wings was capable of delaying the stall to 5-10 deg of AoA. [ABSTRACT FROM AUTHOR]

The paper would report the aerodynamic CFD model characteristic studies of backward 3-D wind turbine blades in operation. It is found that the blade lip of the bottom section is suffered from strongly decelerated disturbance, while the upper section are accelerated. The region influenced by radial disturbance starts radially from the top toward the bottom part of the blade, from lightly disturbed to weakly disturbed region. Original radial source of disturbance, caused by centrifugal and Corriolis force, are still persist. Q-criterion was used to benchmark for the quality of computation to justify the most sensitive outcome, to determine the largest size for the smallest computational cell. Compare to structured grids, the unstructured grids gives significant results errors. [ABSTRACT FROM AUTHOR]

The use of delta wings is widely used for high-speed aircraft such as fighter aircraft. In the delta wing, there is a pressure difference that causes the vortex flow and forms a vortex core with a very low pressure that will lead to the addition of lift force. Increased angle of attack will raise the vortex core speed so that the force will also rise, but under certain conditions, the vortex core structure will be destroyed, or there is a vortex breakdown that will remove the lift force. The analysis of the occurrence of vortex breakdown becomes very important to maintain lift force on the wing. Vortex breakdown analysis can be done through visualization techniques. The use of water tunnel as a visualization test facility has been widely used and has advantages in detail visualization. This research will be testing the character of vortex breakdown on delta wing by using GAMA water tunnel facility. For comparison and validation would be used computational fluid dynamics (CFD) technique. The results of the research show that the GAMA water tunnel facility can show the vortex breakdown phenomenon and the aerodynamic forces that occur on the delta wing. These results have conformity with the test using CFD and other references where the vortex breakdown was affected by the angle of attack and the change of the sweep angle. [ABSTRACT FROM AUTHOR]

Latent heat storage (LHS) has been widely used for energy storage. Compare to sensible heat storage, LHS has several benefits because of its high energy density, small unit sized and operating at low temperature. This paper is aimed to investigate the melting characteristic of phase change material (PCM) implemented in concentric double pipe heat exchanger. The investigation is carried out by both simulation as well as validation. The simulation is conducted using ANSYS FLUENT with double pipe shape of heat storage. The geometrical shape of the storage is double pipe heat exchanger, the PCM is stored in the inner tube meanwhile hot water is circulated in the outer tube. The dimension of the inner tube are 5 cm of diameter and 50 cm length. The diameter of outer tube is 10 cm and 60 cm length. The hot liquid is circulated from the inlet port and withdrawing from the outer port. The inlet and outlet ports are located away at the distance of 5 cm from the edge of the outer tube. The inlet and outlet ports are constructed at the bottom and upper part of the outer tube. The simulation is carried out at temperature 60oC of the hot liquid and flow rate at 4 liters per minute. The validation is also conducted at the same configuration with that on the simulation. The tweaked parameters are number of mesh and mushy-zone value. Results revealed that validation is numerically accepted at deviation less than 5% for melting time deviation. The validation is obtained at number of mesh is 144,000 and mushy-zone value is 1.4x107. On the evaluation of temperature distribution similarity, all of coefficient correlation are obtained greater than 0.8 between simulation and experiment. Being a valid simulation model, it is enabled to be enhanced for predicting melting of phase change materials on the heat energy storage system. [ABSTRACT FROM AUTHOR]

A popular method to recycle plastic wastes is pyrolysis, where oil, gas and char can be produced. These products can be utilized as fuels because they are basically hydrocarbons. The research investigates char properties, including their performance as fuel briquettes. There are 13 char samples from PE (Polyethylene) pyrolyzed at temperatures of around 450 oC, with and without a catalyst. Some of the samples were obtained from PE mixed with other types, such as Polystyrene (PS), Polypropylene (PP), Polyethylene Terephthalate (PET), and Others. Char properties, such as moisture, ash, volatile matter, and fixed carbon contents, are revealed from the proximate analysis, whereas calorific values were measured with a bomb calorimeter. Briquettes are made by mixing 4 g of char with 0.5 - 1 g binder. Briquettes are hollow cylinders with an outer and inner diameter of around 1.75 cm and 0.25 cm, respectively. Combustion is carried out in a furnace with wall temperatures of about 230oC and a constant air velocity of 0.7 m/s. Five out of 13 char briquettes are not feasible because they melt during combustion. Briquettes made from 100% PE wastes burn in substantially shorter duration than those from mixed plastic wastes. Char #1 and #5 are excellent due to their highest energy release, whereas #10 show the worst performance. [ABSTRACT FROM AUTHOR]