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A nanocatalyst of CaO supported by Fe3O4 magnetic particles was prepared by a chemical precipitation method. It was characterized by various techniques including X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM); Fourier transforms infrared spectroscopy (FTIR), and Hammett indicator. It has been found that the catalyst consists of CaO and Fe3O4 accompanied by CaFe2O4. This composite catalyst was used for the catalytic transesterification of palm seed oil. The results revealed that the highest biodiesel yields for palm seed oil of 69.7% can be obtained under the conditions of (65 °C reaction temperature, 300 min reaction time, 20 methanol/oil molar ratio, and 10 wt.% of CaO/Fe3O4 catalyst loading). The physicochemical properties of the biodiesel produced from palm seed oil were further studied and compared with the ASTM and the EN biodiesel specifications. The results showed that the properties of the biodiesel produced comply with the international standard specifications.

The melting of a phase change material (PCM) inside a horizontal concentric two-pipe heat exchanger is experimentally investigated. The PCM RT-42 (Rubitherm) is contained in the annular space between the inner tube of diameter 25 mm and outer insulated shell of diameter 75mm. The hot water as a heat transfer fluid (HTF) flows inside the inner tube at different temperatures, 60, 70 and 80 °C. The experimental setup involves twelve thermocouples to record the transient temperatures of PCM at different locations. Also, the progress of the solid-liquid front during the melting process is tracked photographically by a digital camera. The experimental findings revealed that the heat conduction, accompanied by the same melting rate around the inner tube of the heat storage unit, is predominant at the beginning of the melting process. As time progresses, the natural convection role is strengthened and causes a higher melting at the top part than is shown at the lower part, which is still dominated by conduction. Also, the melting rate is directly affected by the temperature of the HTF. The melting time is reduced by about 27% and 46% when the HTF temperature varies from 60 to 70°C and 80°C, respectively. The variation of the Nusselt number during the melting process is evaluated. There is a positive influence of the HTF temperature on the energy stored by the PCM.