Now showing 1 - 4 of 4
  • Publication
    Modeling of the aerodynamics of the integrated four blades (VAWT) having movable vanes
    ( 2020-03-25)
    Suffer K.H.
    ;
    Hussain A.K.
    ;
    One of the economic problems facing all the public at present is the increasing demand for energy. Because of industrial development, fossil fuel depletion is on the increase, so the use of renewable energies as an alternative to fossil fuels has become apparent. In addition to solving problems caused by fossil fuels on the climate. Wind power is one of the most important renewable energies; the wind turbine is the machine that converts wind energy into mechanical energy. Which is used to pumping water, grind grain and generate electricity. The aim of this work is to study the aerodynamic performance by using Computational Fluid Dynamics (CFD) of a model of a vertical axis wind turbine, which has four integrated blades (each of which consisted of a vertical movable vane with Darius-type airfoil). The objective from combining the airfoil with the vanes comes to solve the low starting torque of the airfoil. The (SST) k-ω turbulence model and finite volume method were used with ANSYS FLUENT 16.1 software. The results concluded from the present numerical simulation give that the drag coefficient Cd is in maximum value at the positive side at 90° angular position, and Cd is decreased to the minimum value in the negative side at 45° angular position. The drop in the static pressure on the positive side is higher than on the negative side. The aerodynamics characteristics results represented by the static and dynamic pressures distributions and velocity distribution show that the air exerted to the turbine blade on the negative side is easily passes without any resistance. Therefore, it can be concluded that the addition of the vertical movable vanes with straight airfoil in one construction of a vertical wind turbine blade helps to solve the Darrieus straight airfoil starting torque and increases the rotation of the turbine rotor.
  • 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.
  • Publication
    Prediction of maximum spreading time of water droplet during impact onto hot surface beyond the Leidenfrost temperature
    ( 2021-12-01) ; ;
    Rahim Y.A.
    ;
    ; ;
    Ismail K.A.
    ;
    Ani M.H.
    When a water droplet impacts on a heated surface in the film boiling regime, it will spread, recede, and finally bounce off from the heated surface. These unique liquid-solid interactions only occur at high surface temperatures. Our main objective in this research is to measure the maximum spreading and residence time of the droplet and the findings were compared to theory. We focused our study in the film boiling regime. Brass material was selected as the test surface and was polished until it became a mirror polished surface. The temperature range for this experimental work was between 100 °C up to 420 °C. Degassed and distilled water was used as the test liquid. The high speed video camera recorded the images at the rate of 10,000 frames per second (fps). As a result, it was found that the experimental value of maximum spreading and residence time agreed closely with the theoretical calculation. A new empirical formula that can be used to predict the maximum spreading time in the film boiling regime is also proposed.
      2
  • Publication
    Critical heat flux and Leidenfrost temperature on Electrical Discharge Machining (EDM) - constructed hemispherical surface
    ( 2021-10-01) ; ;
    Rosman N.A.
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    ;
    Shaiful A.I.M.
    ;
    Ismail K.A.
    ;
    Ani M.H.
    This paper reports a Leidenfrost temperature on hemispherical surface constructed by Electrical discharge machining or known as EDM. We focus our study on the droplet evaporation lifetime to investigate and identify the Leidenfrost temperature. Three (3) different types of materials were selected i. e such as Brass (Br), Aluminum (Al) and Copper (Cu). Meanwhile, ethanol liquid has been chosen as the test liquid. Ethanol liquid was elected due to its low boiling point of approximately 78 °C. The droplet impact velocity and droplet diameter was approximately 1.129 m/s and 3.476 mm, respectively. As a result, we finally succeeded in determining the Leidenfrost temperature for all materials mentioned above. On top of that, all the Leidenfrost temperature results, TL were close to the superheat limit temperature of ethanol liquid, TSL which is about 197.8 °C.
      2