Eflita Yohana

Tea ( Camellia sinensis ) is one of the most widely consumed beverages, popular for centuries globally, including in Indonesia. The productivity of tea processing is supported by equipment such as spray dryers, which produce tea in powdered form. This study investigates the effect of adding a...

A solar air heater generates heated air using solar energy. This system has a relatively simple design, which reduces the initial cost and facilitates maintenance compared with other solar systems. However, its thermal conversion efficiency is limited by the poor thermal conductivity of air. Previous studies have improved thermal efficiency by enhancing either the heat transfer area or the heat transfer coefficient, but most have applied only one of these approaches. In this work, a novel solar air heater with longitudinal fins and blocks, designed to simultaneously enhance the heat transfer area and heat transfer coefficient, is investigated for various block shapes (rectangular, forward-chamfered, backward-chamfered, and triangular blocks) utilizing computational fluid dynamics. Compared to the smooth fin channel, heat transfer is enhanced by a maximum of 1.61 times with the backward-chamfered block, while the corresponding enhancement factors for the rectangular, forward-chamfered, and triangular blocks are 1.52, 1.46, and 1.54, respectively. The thermo-hydraulic performance parameter, which simultaneously evaluates heat transfer augmentation and frictional penalty, further indicates that the backward-chamfered block is most effective at Reynolds numbers below 6000, while the rectangular block performs best above 9000.

Integrating Phase Change Material (PCM) in Photovoltaic Thermal (PVT) systems is an effective solution to improve the cooling efficiency of solar panels. This study modeled and analyzed three configurations of paraffin-based PCM containers using the Computational Fluid Dynamics (CFD) approach, with radiation intensities of 300, 600, 900, and 1200 W/m². The temperature distribution analysis showed that Model 1, with its design lacking additional partitions, produced a more homogeneous heat distribution and maintained lower PV-cell temperatures than Models 2 and 3. Model 1 recorded a maximum temperature of 27.4°C at its highest intensity, while Model 2 and Model 3 reached 28.5°C and 27.5°C, respectively. Efficiency evaluations show that the Model 1 also produces the highest thermal efficiency, reaching 11.7% at 1200 W/m², compared with the Model 2 at 10.5% and the Model 3 at 11.2%. The Model 1's superior performance is attributed to the PCM's ability to absorb latent heat effectively, slow the rise in PV cell temperature, and maintain stable energy conversion efficiency. Based on these results, Model 1 is recommended as the optimal configuration for PVT-PCM systems to improve thermal efficiency, maintain PV-cell performance, and extend the operational life of solar collector systems.

Steam power plants are a type of electricity generator that can be relied on because of their capability to generate significant amounts of power. Similarly, PT. XYZ is capable of producing 625 MW of power. However, there are problems at PT. XYZ, so there is no detailed calculation analysis of energy and exergy in multistage turbines. Furthermore, PT. XYZ lacks a software-based simulation process for analyzing the steam power plant's performance. This study examines the energy and exergy produced by multistage turbines composed of a HPT, an IPT, and a LPT at various load conditions, starting at 50%, 75%, 80%, 90%, 99%, and at commissioning. HPT and IPT is a backpressure turbine and LPT is a condensing turbine. The research was conducted using the HYSYS simulation software fluid package Peng-Robinson EoS, which can analyze energy and exergy in alongside efficiency in a steam power plant. This research allows companies to determine the best steps to improve turbine performance. The simulation results show the power generated by each multi-stage turbine. HPT generates the most power, followed by IPT and HPT. The highest power produced by HPT was 179 MW. IPT is the most efficient, followed by HPT and LPT. IPT has a maximum efficiency of 92% at 50% load and a minimum of 84% at 80% load. LPT had the greatest energy loss compared to the others, reaching 58.2 MW. IPT has a lower energy loss than LPT and IPT, with the lowest value at 7.82 MW. LPT causes the most exergy destruction, followed by HPT and IPT. The highest exergy destruction in LPT occurred during the commissioning load, with a value of 860.1 kJ/kg. The research data successfully demonstrated that further analysis and improvements are required for the LPT turbine to maximize exergy because it has the highest exergy destruction while having the lowest efficiency when compared to other turbine stages.

Vortex generator is a component that has a significant impact on aircraft performance. The function of the vortex generator is to create vortices that can optimize the aerodynamic performance of aircraft wings by avoiding air flow separation and increasing lift at high angle of attack. Vortex generator can provide increased lift during take-off and landing due to the increased wing angle of attack. Although the use of vortex generator can be carried out using an experimental approach, a computational fluid dynamic approach to determine the influence of geometric parameters and placement of the vortex generator needs to be carried out. The aim of this research is to determine the effect of parameters like placement on the wing chord, height of the boundary layer, length, shape, angle of incidence and distance between pairs on the lift and drag. The model used as a computational fluid dynamic calculation model is the Spalart Allmaras transient model. As a result, vortex generator does not always have a good effect on aerodynamics. All configurations have a negative influence on the lift and drag values, but the flow separation phenomenon can be reduced significantly. Of all the configurations, the best configuration is obtained by exhibiting an ogive shape, positioned at 13.8% of the chord length, set at a 13o angle of incidence. The vortex generator should have a height closely matching the boundary layer, with a length 6.5 times the height and a pair spacing of 6.7 times the height

Computational Fluid Dynamics (CFD) has been widely used to study Circulation Fluidized Bed (CFB) combustion processes. Analysis of mixed fuel between coal and biomass from PKS (palm kernel shell) in the combustion process that occurs in the boiler at West Kalimantan power plant is carried out by mixing the addition of PKS fuel by 20%, 40%, 60%, and 80%. The simulation uses model set-up data, material properties, and boundary conditions according to PJB (Pembangkitan Jawa Bali) Ketapang's experimental data. Then an analysis was carried out with a fluid flow velocity of 3.2 kg/s and particle sizes of 150 μm, 300 μm, 400 μm, and 500 μm on the erosion rate that occurs on the furnace walls due to sand particles present in the combustion process material at the Steam Power Plant (PLTU). Based on the simulation results of mixing fuel between coal and PKS variations of 20% - 80%, the temperature decreased from 1180℃ – 920.03℃ due to differences in fuel heat. Whereas the erosion rate in the simulation has increased from 0.000189 kg/s – 0.001886 kg/s due to differences in the size of the sand particles and the velocity of the mass flow rate of the particles.

Increasing electricity production must continue to be pursued to meet the increasing electricity needs of the community. One of the efforts that engineers can make is to improve the performance of the main suppliers of electricity needs. It is impossible to separate the role of the system's components from the performance of the gas turbine generator. This journal discusses exergy and energy analysis in the gas turbine generator of X combined cycle power plant through simulation with Cycle-Tempo software. The simulation results show that the highest system energy efficiency is owned by the gas turbine generator unit 2.3 of 35.541%, with a system exergy efficiency of 34.069%. The lowest system energy efficiency is owned by the gas turbine generator unit 2.1 of 31.669%, with a system exergy efficiency of 30.355%. The gas turbine generator component with the lowest exergy efficiency occurs in the combustion chamber of the gas turbine generator unit 2.2 of 76.81%, with exergy destruction of 92.581 MW. Meanwhile, the gas turbine generator component with the highest exergy efficiency occurred in the turbine of the gas turbine generator unit 2.3 of 96.81%, with exergy destruction of 9.762 MW. The simulation results that have been carried out show that the performance of the components in the gas turbine generator is still in good performance, with the lowest exergy efficiency above 75%.