Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Impacts of Lateral Boundary Condition Resolution in Tropical Urban Climate Modelling for Kuala Lumpur
Get PDFChoosing the best LBCs is still debated among researchers due to the errors resulted. However, several recommendations have been documented to control the errors propagated by LBCs. One of the recommendations is employing higher resolutions LBCs. In the present, many LBCs are developed with various resolutions; spatially and temporally, for many applications but no claims regarding the best LBCs for tropical climate modelling have yet been documented. Therefore, this study intends to analyse the impacts of lateral boundary condition resolution during numerical downscaling within a tropical city. This study serves as a site-specific investigation to determine the suitable LBCs for the focused study area. Two widely used LBCs with different resolutions were utilized to initiate the Weather Research and Forecasting (WRF) simulation model. The performances of the two LBCs were compared using statistical tests and analyses. The study has found that the LBC with higher resolutions excels the other LBC during inter-monsoon season. Nevertheless, it was identified that both LBCs were able to provide reliable reconstruction of the tropical climate condition of the Kuala Lumpur City as portrayed by similar results obtained. Thus, it is concluded that both LBCs can be employed in numerical downscaling for tropical urban regions similar to the Kuala Lumpur City
Effective Solar Light Photocatalysis by Graphene Sheets (GSs) Addition on the Composite TiO2/SiO2
Get PDFThis study investigated the synthesis of TiO2/SiO2 by using a sol-gel method with the addition of difference of the mass ratio of Titanium (Ti):Graphene Sheets (GSs) (1:0; 1:0.04; 1:0.07; 1:0.14) and the variation of calcination temperature (Tcal) (400 ℃; 450 ℃; 500 ℃). The synthesized composites were analyzed by X-ray powder diffraction (XRD) and Scanning electron microscope and energy dispersive X-ray spectrometer (SEM-EDS). The TiO2/SiO2/GSs XRD pattern shows anatase and rutile phases as well as graphite at the near point of 2θ (26°-27°). The tendency of anatase phase according to GSs ratio and Tcal variables is decreasing with an increase in the GSs ratio and Tcal. The crystal size was in the range of 24 – 41 nm. The decolorization of methylene blue was done under four conditions: dark, UV lamp, LED, and solar light. The photocatalytic activity result under solar light is comparable with UV light. The photocatalyst with a ratio at 0.07 and Tcal at 450 ℃ gave the maximum efficiency of MB decolorization under solar light with 97.83 % within 3 hours. The reusable TiO2/SiO2/GSs show a slight fall in efficiency after four cycle times
Parametric Optimization of NACA 4412 Airfoil in Ground Effect Using Full Factorial Design of Experiment
Get PDFThis investigation emphasizes the changes of the lift-to-drag ratio of an airfoil with the variation of ground clearance and angles of attack. Various ground clearances and angles of attack with a fixed speed of 30 m/s are applied to the NACA 4412 airfoil. Computational fluid dynamics (CFD) is used to calculate the aerodynamic coefficients acting on it. To study the influence of these two factors on the lift-to-drag ratio, 32 factorial design based on Design of Experiments (DOE) is utilized. A total of 9 numerical experiments were carried out with Ansys Fluent. When the angle of attack decreases, lift coefficient increases and drag coefficient decreases resulting in a high lift-to-drag ratio: also, the lower the ground clearance, the higher the lift-to-drag ratio. It shows the effectiveness of ground clearance and angle of attack. The analysis shows that either increasing ground clearance or using a higher angle of attack gives a decrement in the lift-to-drag ratio, but there is no interaction between them
Numerical Heat Transfer Investigation in a Solar Receiver Heat Exchanger Channel with Punched Elliptical-Winglet Vortex Generators
Get PDFThermal performance in a solar receiver heat exchanger (SRX) channel with punched elliptical-winglet vortex generator (P-EW) mounted on the absorber plate is numerically examined for Reynolds number (Re) ranging from 4000 to 24,000. In the present simulation, the P-EW characteristics included three ratios of winglet pitches (PR = 2.0, 1.5 and 1.0) including four sizes of the perforated-holes (nondimensional hole diameter, dR= 0.0, 0.25, 0.417 and 0.583) at one value of the attack angle (a =30°) and relative height (BR= 0.48). The computation reveals that employing P-EW generally yields considerably large friction factor (f) and Nusselt number (Nu) than the flat-plate channel alone. The use of smaller hole size causes the rise in Nu and f. It is noticeable that counter-spinning vortices pairs generated by the multiple P-EW can induce the impinging flow onto the absorber plate together with the air jet coming out of the hole, leading to the rise in the heat transfer rate greater than the smooth flat-plate channel. The highest thermal performance of about 1.9 was seen for the one with PR = 1.5 and dR = 0.417
Process Yields Improvement of Filter Presses in Rabies Immunoglobulin Production
Get PDFThe objective of this study is to improve the performance of the Equine Rabies Immunoglobulin (ERIG) process by using the caprylic acid as a single precipitated agent and the replacement plan for the filter press machine to support higher demand in ERIG. The experiments based on the face-center central composite design are performed to investigate the relationship of yield recovery with 1. the concentration of caprylic acid used in the purification process, 2. the flow rate, and 3. the pore size of the filter press machine used in the filtration process. The regression analysis shows no relationship on linear, quadratic, or interactions between yield recovery and the three factors. Fortunately, according to the Analysis of Variance (for comparing means), there is a significant effect of interaction between the flow rate and pore size and the main effect of concentration of caprylic acid on the yield recovery at a 90% confidence level. From the interaction plot, at a flow rate of 10.5 ml/s with a filter media pore size of 6-15 micron, the process has the maximum yield recovery of 15.5% that is significantly superior to those of the other two sizes of filter media at the same flow rate. With a flow rate of 16.8 ml/s, the yield recovery is not significantly different for any pore size. At a flow rate of 4.2 ml/s, the yield recovery is higher when using the pore size of 4-9 and 6-15 micron than those from 5-12 micron. Nevertheless, with a 90% confidence interval for average yield recovery by Tukey comparison, the average yield recovery received from 16.8 ml/s at every pore size and 4.2 ml/s at 4-9 micron are not statistically different. Therefore, with the current size, 5-12 micron, of filter media used in the current process, the flow rate is suggested to be 16.8 ml/s whereas, the caprylic acid concentration of 1% is preferred due to the highest yield recovery compared to other concentration levels and the lowest production cost
Well Plan Parameter Guideline for Directional Drilling in the Gulf of Thailand
Get PDFComplex structured reservoir in the Gulf of Thailand (GOT) dictates directional drilling design requirement. Torque and drag analysis is used in determination of drill ability from the planned well trajectory. A set of well construction and typical reservoir data in GOT provide constraints for well plan parameters. Both typical 2-dimension (2D) and 3-dimension (3D) well profiles are studied. Each well profile requires different well plan parameters, namely kick off points, build up and drop off rates, inclinations, turn rates, and turn degrees. Sets of well plan parameter guideline for each well type are provided for pre-check drill ability of the designs. For each well profile types, the maximum first inclinations are shown as results for given sets of well plan parameters. The deeper kick off point for 2D well profile benefits on torque and effective tension limits than shallower one. For 3D well design, kick off point and the first inclination have strong effects on torque and effective tension whereas turn degree, build up rate, and turn rate have weaker effects. In addition, high turn degree is drillable with deep kick off point, low build up rate and high turn rate combined
Deterioration in Sulfuric Acid of Cement Pastes incorporating High CaO and Low CaO Fly Ashes
Get PDFThis research studies the deterioration in sulfuric acid solution (pH 1) of cement pastes with fly ash. Effects of three major factors affecting the acid attack behavior are described. First, for the water to binder ratio, it was found that cement pastes with a higher water to binder ratio (w/b of 0.40) have a lower mass loss in sulfuric acid solution than those with a lower water to binder ratio (w/b of 0.25). In addition to the known mechanism of higher porosity in higher w/b pastes which makes the higher w/b pastes to be able to accommodate more gypsum, another mechanism was described based on the different abilities of calcium ion and sulfate ion to diffuse out of and into the pastes, respectively. Second, the type and content of binder provide a great influence on the degradation of cement pastes. The test of cement pastes with 30% and 50% fly ash replacement demonstrated that the fly ashes decrease the deterioration of pastes in sulfuric acid solution. In addition, it was observed that fly ash with low calcium oxide provided better resistance to sulfuric acid attack than fly ash with high calcium oxide did. Finally, the characteristics of the deterioration of paste specimens due to sulfuric acid attack was found to correlate well with CaO/SiO2 ratio
Recent Advancement of Sustainable and Renewable Energy in Osmotic Power Generation
Get PDFInvestment in clean energy is demand in this century due to abundance of CO2 accumulation in the world to cause several environmental issues. Therefore, harvesting clean energy may assist in reducing carbon footprint in the world to create a green environment for sustainable living. The salinity gradient energy is one of the clean energies with the concept of mixing both salt concentration water from the ocean and fresh water from the river to create an osmotic pressure to power-up the generator for the production of electrical energy. Salinity different between the oceanic salt water and fresh water could produce an equilibrium osmotic pressure that achieve up to 27 bars equivalent from resulting pressure under the water for 200 to 300 meters. The potential of the power production through osmosis power generator is capture at the value of 2000 TWh per year, where in 2018 the world energy consumption was growing 2.3%, in which twice the number compare to the average rate of the growth. The major energy consumption is contributed from fossil fuel and consequently resulted from emissions of CO2 increased to 33.1 Gt to the atmosphere. This work explained the advantage of using salinity gradient energy and the fundamental principle of blue energy from pressure-retarded osmosis (PRO). Thus, the osmotic power by using different salinity gradient to create energy is widely known as blue energy, in which it is green and sustainable to produce electricity to the local communities
Energy Consumption Reduction by High Solar Reflective Paint
Get PDFHigh solar reflective paint has been widely used nowadays. It is claimed that it can substantially reduce heat gain through building envelope and energy consumption of houses. This study investigated energy saving from using high solar reflective paint compared with conventional paint. The chosen color tone was dark brown. Actual energy consumption was measured from two houses. One house was painted with high solar reflective paint. The other one was painted with conventional paint. Both houses were identical: 4 m wide x 6 m long x 3.16 m high with 24 m2 floor area. The houses were located in Samut Prakan, Thailand. From actual measurements during March and September 2019 which were in the hot and rainy seasons of Thailand, it was found that high solar reflective paint could reduce exterior surface temperature by as high as 8.1oC and save energy by 31.24% from decreasing cooling load due to less heat gain through the envelope. The energy simulation using the EnergyPlus software showed 32.69% saving which agreed well with the actual results
Micro-Raman Spectroscopic System for in situ Evaluation of Tube Wall Type Catalyst
No full textA Raman micro-spectrophotometer was applied to perform in situ characterization of silica supported platinum catalyst. A custom-designed catalytic microcatalytic reactor cell for Raman observation was fabricated and dehydrogenation of cyclohexane was carried out as a model reaction. Surface of silicon microchannel was oxidized to make SiO2 support layer and platinum catalyst was supported on the surface. The in situ catalytic microreactor cell with inlet/outlet ports was prepared using Pyrex glass cover that served as the viewing window. The reaction temperature inside the cell was controlled by plate heater set on the Raman microscope stage. The spectra were collected under the reaction conditions and outlet gas was analyzed by GC.
Without platinum catalyst component, no reaction of either reactant or products were observed at 393 K. When Pt catalyst was supported on the SiO2 reactor wall, GC analysis showed that dehydrogenation reaction has carried out at 393 K and Raman spectra of 1,450 cm-1 which was identified as π-allylic intermediates were observed. At the same time, peaks at 1,600 and 1,350 cm-1 were observed. These could be identified as graphitic carbon and amorphous carbon, respectively. These carbon materials on the surface might be resulted in the subsequent reaction and caused the deactivation of the catalyst. All the Raman peaks were easily removed by N2 gas purging at 393 K.