Advances in Science and Technology Vol. 127

Abstract: Desiccation is the process of extreme drying that results in cracking in materials such as soils. Cracking is a complex process that has the potential to spread and penetrate deeper into the soil, which could lead to instability in earth structures like embankments. A number of desiccation tests were conducted to observe the crack behaviour of manufactured kaolin clay at laboratory scale. All samples were prepared at variation of initial water content and desiccation tests carried out using aluminium desiccation trays. Their crack behaviour was monitored at different thickness and comparison made to the samples tested on different base materials such as ceramic, steel and wood plates. The drying process, crack propagation and pattern were measured and observed daily. A digital image is captured and the crack intensity factor (CIF) calculated manually using a grid system. It was found that a sample of kaolin clay that was 5 mm thick had the highest CIF with rapid propagation and produced non-orthogonal patterns. It also discovered that the thickness of the samples, type of plates utilised and soil state at the start of the test have an impact on the formation and propagation of cracks.

Abstract: This paper presents the regression model for predicting the maximum dry density (MDD) and optimum moisture content (OMC) for sedimentary residual soil mixed with bentonite. The empirical models were developed in accordance with the statistical validity steps and conditions. The laboratories were conducted to determine the physical properties of mixed samples with bentonite such as Atterberg limit and particle size distribution. Meanwhile the compaction testing was performed on the mixed soil samples with bentonite to determine the MDD and OMC values at different compaction energies. The data obtained from laboratories and secondary data were used to develop an empirical model. The results showed there is significant relationship between the particle size, compaction energy and bentonite content to the OMC. Meanwhile there is a relationship between the OMC, bentonite content and compaction energy to the MDD. Reasonably good regression coefficients are obtained in case of both model which R² = 82% for MDD model and R² = 72% for OMC model. Meanwhile the determination coefficient and mean square error (MSE) for validated model between predicted model and empirical model were given R² = 89.5% with MSE = 0.065% for MDD model and R² = 79.5% with MSE = 5.9% for OMC model. Therefore, the models developed present a good predicting for MDD and OMC values.

Abstract: An ambient air vaporizer (AAV) is an industrial heat exchanger equipment used in the vaporization process of liquefied gases before supplying to consumers. AAV utilizes the simple heat transfer principle that uses surrounding ambient air to vaporize the liquefied gases. Liquefied Natural Gas (LNG) is one of the liquefied gases commonly associated with AAV applications. Due to a significant temperature difference between cryogenic fluid of LNG and ambient air, frost formation is inevitable to reduce the heat transfer rate. Fins geometry contributes a substantial impact on the performance of AAV and is the main element of heat transfer for AAV. This study aims to design a model of an AAV with a star 6-finned tube vaporizer with hexagon shape and to simulate the fluid flow on the vaporizer model to demonstrate the LNG vaporization process. The hexagon vaporizer model is designed using Solidworks, and heat transfer model is simulated using computational fluid dynamics (CFD) tool, Ansys Fluent solver. Parameters such as fin geometry, LNG flowrate and wind speed were referred from previous studies. Methane and air are assumed as working fluids inside and outside of the vaporizer model. Wind temperatures of 300K (27°C), 303K (30°C), and 306K (33°C) are utilized in the simulation process based on geometrical weather in Malaysia. In the simulation model, methane entered from the bottom of the tube, while air entered horizontally at x-direction from the right side. The temperature contour shows that as the temperature of methane that flowed inside the tube increased as it entered the tube, the air temperature reduced as it entered and flowed passes through the finned tube. The analysis from the simulation model shows that higher air temperature with substantial wind speed can increase the outlet temperature of methane (LNG), thus improving the performance of AAV.

Abstract: Lubrication is one of the important factors for a journal bearing to function well. Therefore, the use of bio-lubricants such as coconut oil and vegetable oil are highly recommended for their high level of biodegradability to reduce the risk of environmental pollution. Vegetable oil like coconut oil has a great lubricating quality including low friction coefficient and improved oxidation stability which is very suitable to be used as a lubricant. The performance assessment of journal bearings utilizing coconut oil as a bio-lubricant and varying angular velocity and eccentricity ratio will be the main emphasis of this study. The behavior of the journal bearing with coconut oil as the lubricant will be examined using the Computational Fluid Dynamics (CFD) program, ANSYS Fluent. Using ANSYS Fluent, the pressure distribution of pure coconut oil is analytically studied. To evaluate the efficacy of each lubricant with a varied value of angular velocity utilized by the journal in journal bearings, average viscosity, viscosity index, and produced maximum pressure can be discovered under the lubrication of the journal bearing. Using the values of angular velocity with the same value of dynamic viscosity and density as properties for the coconut oil were used to run the simulation for the journal bearing. The result obtained from the simulation for eccentricity ratio of 0.2 with an angular velocity of 5000rpm is 205926.1 meanwhile the result for eccentricity ratio of 0.8 with same angular velocity value is 9661441. Each result signifies those different value of angular velocity with different value of eccentricity ratio that effects the bearing design itself occurs different result.