No abstract

The limitation of fossil fuel sources and negative environmental impact persuade scientists around the world to find a solution. One possible solution is by using renewable fuel to replace fossil fuel with an inexpensive, fast, and effective production process. The objective of this study is to investigate the biodiesel production from crude Reutealis trisperma oil using the conventional and the ultrasonic bath stirrer method through the esterification and transesterification process. The result shows that the most effective reaction time with an optimum condition for the esterification and transesterification of Reutealis trisperma oil is at 2 h 30 min by using the ultrasonic bath stirrer method. The optimum conditions at a temperature of 55 °C for the esterification and at 60 °C for transesterification with 2% (v/v) of sulphuric acid with catalyst concentration of 0.5 wt.% were a methanol-to-oil ratio of 60%, and agitation speed of 1000 rpm. This optimum condition gives the highest yield of 95.29% for the Reutealis trisperma biodiesel. The results showed that the ultrasonic bath stirrer method had more effect on the reaction time needed than using the conventional method and reduced half of the conventional method reaction time. Finally, the properties of Reutealis trisperma biodiesel fulfilled the ASTM D6751 and EN 14214 biodiesel standards with density, 892 kg/m3; pour point, −2 °C; cloud point, −1 °C; flash point, 206.5 °C; calorific value, 40.098 MJ/kg; and acid value, 0.26 mg KOH/g.

The reduced production of fossil energy, especially petroleum, has encouraged researchers to continuously increase the role of new and renewable energy as part of energy security and independence. A Tesla turbine is a device that can be used to recover wasted energy from exhaust gases, thereby increasing the overall energy use. The purpose of this study was to assess the performance of a Tesla turbine using various parameters such as engine speed, the gap between the disks, the diameter of the disks, and the number of disks. In this study, the performance of a Tesla turbine was simulated using computational fluid dynamics (CFD). The reference dimensions of this Tesla turbine are made with a slit diameter of 44 mm, a hole diameter of 10 mm, disc diameter of 140 mm, a disc width of 1.5 mm, a disc gap of 35 mm, a disc gap width of 4 mm, and a shaft length of 50 mm. The results of this study were in the form of torque and pressure drop values. In the variation of engine speed, the highest torque was at 1800 rpm with a torque value of 0.422 Nm, and the highest pressure drop was at 1800 rpm with a pressure drop value of 79161.5 Pa. In the disk gap variation, the highest torque is at a 7 mm disk gap with a torque value of 0.54 Nm and the highest pressure drop is at a 4 mm disk gap with a pressure drop value of 79161.5 Pa. In the variation of disk diameter, the highest torque was found on the disk with a diameter of 180 mm and a torque value of 0.831 Nm, and the highest pressure drop was on a disk with a diameter of 180 mm and a pressure drop value of 86753.5 Pa. In the variation of the number of disks, the highest torque was found at eight disks with a torque value of 0.765 Nm, and the highest pressure drop was found at eight disks with a pressure drop value of 82031.3 Pa. After performing this simulation, it can be concluded that at variations in engine speed, the higher the engine speed, the higher the value obtained and the variations in the disk gap, disk diameter, and number of disks. There are several values of torque that increase and decrease because the input value given cannot always increase the torque value in these variations.

The combination of building materials and PCM is an efficient way to increase thermal energy storage capacity in building components. In this study, a study of the use of beeswax/bentonite PCM on the concrete walls of the building had been carried out. This investigation intended to ascertain the amount of concrete compressive strength if coarse aggregates were replaced in part by PCM beeswax/bentonite. The use of PCM-beeswax in the concrete has not been able to increase the strength of concrete. Even worse, their existence proof to decreased the compressive strength of PCM mixture concrete. Heat absorption test shows that PCM beeswax/bentonite is capable of decreasing the concrete temperature up to 6,67% compared to concrete without PCM. It also means that the PCM proposed in this study shows great potential for application as a phase change material in lightweight concrete.

Thermal energy storage using Phase Change Materials (PCM) is now widely applied to wall buildings. In general, PCM which is used for applications on building walls is organic PCM and has temperature range from 0? to 65oC. Beef tallow and coconut oil is a type of organic PCM known as Bio PCM needs to characterize by using the T-History Method. The T-History method is more accurate than Differential Scanning Calorimetry (DSC) and Differential Thermal Analysis (DTA). This study aimed to determine the thermal properties of beef tallow/coconut oil PCM using the T-History method. The beef tallow and coconut oil as bio PCM material was used in this study with the variation are respectively: 100%, 70+30%, 60+40%, and 50+50%. Tests are carried out using the T-History method. From the results of testing and analysis obtained supercooling temperature, melting temperature, specific heat, and latent heat for bio PCM beef tallow/coconut oil. The effect of adding coconut oil mixture to beef tallow caused a decrease in melting temperature and supercooling temperature, while the specific heat and latent heat of bio PCM of beef tallow/coconut oil ranged from 2.96-2.19 kJ/kg.? and 101.05-72.32 kJ/kg. The result obtained that this bio PCM material of cow beef tallow/coconut oil can apply, as additional material in wall building applications.