Now showing 1 - 6 of 6
  • Publication
    Statistical Analysis on The Near-Wake Region of RANS Turbulence Closure Models for Vertical Axis Tidal Turbine
    The flow field in the near wake region (up to six turbine diameters downstream) of a tidal current turbine is strongly driven by the combined wake of the device support structure and the rotor. Accurate characterisation of the near-wake region is important, but it is dominated by highly turbulent, slow-moving fluid. At present, limited number of researches has been undertaken into the characterisation of the near-wake region for a Vertical Axis Tidal Turbine (VATT) device using the Reynolds Averaged Navier Stokes (RANS) model in the shallow water environment of Malaysia. This paper presents a comprehensive statistical analysis using the Mean Absolute Error (MEA), Mean Squared Error (MSE) and Root Mean Squared Error (RMSE) on the near-wake region for shallow water application by comparing numerical solutions (i.e., different types of RANS turbulence models using Ansys Fluent) with published experimental data. Seven RANS turbulence models with a single VATT, represented by using a cylindrical object, were employed in the preliminary study. The statistical analysis performed in this study is essential in exploring and giving a detailed understanding on the most suitable RANS turbulence model to be improved, specifically on its near-wake region. In this study, the near wake region is defined as D ≤ 6, where D is the device diameter. The analysis shows that the RANS numerical solutions are unable to accurately replicate the near-wake region based on large statistical errors computed. The average RMSE of near-wake region at z/D = [2, 3, 4, 6] are 0.5864, 0.4127, 0.4344 and 0.3577 while the average RMSE at far-wake region z/D = [8, 12] are 0.2269 and 0.1590, where z is the distance from the cylindrical object along the length of domain. The statistical error values are found to decrease with increasing downstream distance from a cylindrical object. Notably, the standard k–ε and realizable k–ε models are the two best turbulent models representing the near-wake region in RANS modelling, yielding the lowest statistical errors (RMSE at z/D = [2, 3, 4, 6] are 0.5666, 0.4020, 0.4113 and 0.3455) among the tested parameters.
  • Publication
    Fracture behavior of intermetallic compound (IMC) of solder joints based on finite elements’ simulation result
    ( 2017-01-01)
    Eang Pang Ooi
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    ; ; ;
    Sulaiman M.H.
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    ; ;
    Ahmad Kamal Ariffin
    The development of microelectronic industry has made solder joints failure a major reliability issue. From literature, many researchers have identified that intermetallic compounds (IMC) layer contribute greatly to the fracture of solder joint. This paper presents a finite element modeling of solder butt joints IMC layer failure based on displacement extrapolation method (DEM). Conceptual study on single edge crack of IMC solder joints is presented. A FE analytical model is proposed to be used in difference range of crack length to understand the fracture behavior of solder joint of IMC layer. The simulation results show that soldering material become less tough if greater crack length is present in the joint. It also seen that the thicker IMC has slightly reduced the stress intensity factor on the crack tip but the change from solder to IMC layer decrease the solder joint fracture toughness.
  • Publication
    Experimental investigation on AC unit integrated with sensible heat storage (SHS)
    ( 2017-10-29)
    Aziz N.A.
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    ; ;
    Hussin A.
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    Zhubir S.
    The growth in population and economy has increases the energy demand and raises the concerns over the sustainable energy source. Towards the sustainable development, energy efficiency in buildings has become a prime objective. In this paper, the integration of thermal energy storage was studied. This paper presents an experimental investigation on the performance of an air conditioning unit integrated with sensible heat storage (SHS) system. The results were compared to the conventional AC systems in the terms of average electricity usage, indoor temperature and the relative humidity inside the experimented room (cabin container). Results show that the integration of water tank as an SHS reduces the electricity usage by 5%, while the integration of well-insulated water tank saves up to 8% of the electricity consumption.
  • Publication
    Maximum spreading diameter of a water droplet after impact on a hot surface beyond Leidenfrost temperature
    The impact of liquid droplets on heated surfaces are relevance across a range of applications. The maximum spreading diameter of water droplet during impact on hot surface was experimentally studied. The surface was made of aluminium. The diameter and height of the aluminium block was 70.0 mm and 30.0 mm, respectively. During experiment, the test surface was heated beyond Leidenfrost temperature. A high-speed video camera was used to capture the droplet images from the first impact until the droplet reached maximum spreading condition. The frame rate was set to be 2,000 fps. Distilled water was used as the test liquid. The impact height was set to be about 65.0 mm. From the high-speed images analysis, the droplet diameter was found to be approximately 4.5 mm. The measured droplet maximum spreading diameters were found to have a good agreement with theoretical calculation.
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  • Publication
    Effect of various bending angles on a passive light pipe for eco-daylighting systems
    Daylighting systems is one of alternative to reduce a high energy consumption that caused by artificial lighting. However the use of passive light pipes in daylighting systems with various bending angles may affect the efficiency of light transfer from the sunlight to the room. Thus this paper is proposed to study the effect of various bending angles on a light pipe. Three bending angles of light pipe, which are 0°, 30° and 45°, were analyzed through the experimental works. A test bed room was constructed in order to simulate daylighting in a room. The results were then visualized in graphs based on the efficiency by considering the maximum average internal illuminance achieved by each light pipe. From the results, it shows that when the bending angle increases, the average internal illuminance decreases. And the highest average internal illuminance was achieved by 0° light pipe.
      4  5
  • Publication
    Performance power evaluation of DC fan cooling system for PV panel by using ANSYS CFX
    A research has been conducted to find the optimum combination for DC fan air cooling system of photovoltaic (PV) panel. During normal operation of PV panel, it is estimated that only 15 % of solar radiation is converted into electrical energy. Meanwhile, the rest of the solar radiation is converted into heat energy which affects the performance of the PV panel. Therefore, the aim of this research is to investigate the performance power evaluation of DC fan cooling system for PV panel by using ANSYS CFX. The effect of airflow configuration of DC fan has been investigated. This is to analyze whether the airflow circulation of DC fan cause a change towards the maximum temperature of PV panel. Besides, the impact of varying number of DC fans attached at the back of PV panel is evaluated. The result of airflow circulation of DC fan has been discussed. Meanwhile, with the increment number of DC fans, the PV panel temperature drops significantly. As a conclusion, the optimum number of DC fans is two with the combination of inlet airflow.
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