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Rekayasa: Jurnal Penerapan Teknologi dan Pembelajaran
Published by Universitas Negeri Semarang
ISSN : -     EISSN : 25276964     DOI : https://doi.org/10.15294/rekayasa
Core Subject : Education,
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REKAYASA journal publishes exciting articles from all fields of research and Engineering Science. The journals primary focus is on research practice and engineering processes utilizing biomass or factory waste. The engineering journal is an open-access peer-reviewed journal that publishes articles from all areas of Engineering and Science research.
Arjuna Subject : Umum - Umum
Articles 5 Documents
 1 
Search results for , issue "Vol. 22 No. 2 (2024)" : 5 Documents clear
Ultrafiltration Technology for Batik SME Wastewater Treatment: Column-Based Materials with Zippers for Plant Irrigation Water Supply Zakia, Maulida; Mahatmanti, F. Widhi; Wati, Safna Rahma; Rahmalia, Berliana Putri; Rengga, Wara Dyah Pita
Rekayasa Vol. 22 No. 2 (2024)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v22i1.17184

Abstract

Textile batik wastewater discharged into drains can contaminate groundwater and harm ecosystems and human health. This study focuses on reducing hazardous heavy metals in sewage through physical and chemical filtration. Heavy metals in the wastewater can poison aquatic organisms, disrupt food chains, and contaminate water sources. The goal is to analyze the heavy metal content, pH, and colour of batik wastewater to make it safe for plant irrigation. The filtration process uses silica sand, activated carbon, and zeolite for mechanical filtration and ion exchange. Ultrafiltration is added to remove fine particles, heavy metals, and organic matter more effectively while resisting fouling. These materials are placed in zipper bags for easy replacement and regeneration. The wastewater passes through a filtration column consisting of two tanks: Tank 1 for fresh wastewater and sedimentation, and Tank 2 for overflow from Tank 1. Tests were conducted for Cr, Cu, Pb, and Zn using AAS, pH with a universal pH meter, and colour through organoleptic analysis. Cr levels initially exceeded quality standards, while Cu, Pb, and Zn were within safe limits. After filtration, reductions of Cr, Cu, Pb, and Zn were 81%, 8%, 22%, and 85%, respectively. The pH decreased from 10–11 to 7–8, and water color improved from murky greenish-brown to clearer. The results demonstrate the potential of ultrafiltration in reducing heavy metals, stabilizing pH, and improving water clarity. Wastewater treated through this process meets safety standards and can be used for plant irrigation.
Alternative Design of a Pneumatic Conveying Machine for Rice Husk as A Coal Substitute for Rotary Kiln Fuel in Cement Factories Permanadewi, Indrasukma; Febry Ibrahim, Ahmad; Azzahra Putri Solihin, Syifa; Aldiansyah, Rizky
Rekayasa Vol. 22 No. 2 (2024)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v22i1.18907

Abstract

The reduced amount of coal transported to cement factories is being diverted to rice husk, which is biomass, to facilitate the use of increasingly expensive coal. This transition is necessary due to the different characteristics of rice husk compared to coal. Additionally, the combustion process in rotary kilns requires extremely high temperatures (1,400–1,500°C). However, a significant portion of the generated energy is lost through the kiln walls, exhaust gases, and heat radiation. These heat losses reduce thermal efficiency and increase fuel consumption. Coal, fuel oil, and natural gas are the primary energy sources for cement kilns, which are not only expensive but also have negative environmental impacts. The fluctuation in fossil fuel prices further affects overall cement production costs. To address these challenges, cement factories must design an efficient rice husk conveying system from storage to the rotary kiln. Transporting rice husks with air ensures no unintended reactions while allowing smooth flow through closed horizontal and vertical transport pipes commonly used in the industry. This study aims to design a pneumatic conveying machine with a closed air pressure system to transport biomass (rice husks) at a capacity of 7 tons/hour as an alternative fuel for rotary kilns in the cement industry. The design method follows several stages, including practical work experience, literature review, material selection, design considerations, conceptual design, calculations, and technical drawings. The proposed system utilizes the dilute phase method, with a blower power of 49.26523 kW pushing the rice husks toward the hopper. The pipeline flow parameter, measured as the pressure drop, is 132.9673 kPa. The selected materials include galvanized iron pipes with two elbows to connect horizontal and vertical sections.
Aerodynamic Performance Enhancement of Electric Vehicles Using Selig 1223 Airfoil Wing-Type Spoiler: A Computational Fluid Dynamics Study Fajar Rizqi Sandi Pratama; Aldias Bahatmaka; Amin, Muklis; Hyung, Cho Joung
Rekayasa Vol. 22 No. 2 (2024)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v22i2.25166

Abstract

The performance of electric vehicles (EVs) is significantly influenced by aerodynamic forces, which directly affect energy consumption and vehicle stability. One of the main challenges in this regard is the increase in lift and drag forces at higher speeds, which compromises efficiency and handling. This study investigates the impact of a wing type rear spoiler, designed using the Selig 1223 airfoil, on the aerodynamic behavior of EVs. A comparative computational fluid dynamics (CFD) simulation was conducted on two vehicle models: one without a spoiler and another equipped with the Selig 1223 spoiler mounted at a 15° angle of attack. Both models were tested under five speed conditions ranging from 40 to 120 km/h. The simulation results demonstrated a notable improvement in aerodynamic performance. The spoiler produced an average reduction in the lift coefficient (Cl) of approximately 110%, while the drag coefficient (Cd) showed only a slight increase, with the highest recorded rise being 13.3% at 120 km/h. Pressure distribution analysis revealed a substantial increase in static pressure at the rear of the vehicle (Point P3), rising from 37.47 Pa to 660.859 Pa, indicating enhanced downforce. Additionally, streamline and velocity contour plots confirmed improved airflow regulation and reduced turbulence behind the vehicle when the spoiler was installed. These findings indicate that the Selig 1223 airfoil spoiler effectively enhances EV stability and safety with minimal aerodynamic penalties, making it a promising aerodynamic enhancement for future electric vehicle designs.
A Simple Method in Evaluating the Performance of H2S Scrubber at Existing Biogas Plant Akbar, Ramavi; Hanif Ardhiansyah; Muhammad Wasim Ikram
Rekayasa Vol. 22 No. 2 (2024)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v22i2.30454

Abstract

Biogas as one of the renewable energy sources contains hydrogen sulfide (H₂S) which causes equipment corrosion and gives negative impacts on the environment. To study some factors that affect the H2S removal efficiency, evaluation was done on the performance of existing H2S scrubber. For the case study, it was found that the existing scrubber performance did not reach the target (< 200 ppm-v H2S) with 1,450 Nm3 biogas/h and 2,550 ppm-v H2S inlet (-10 mbarg and 35oC). Scenarios were made by varying the design parameters of the H2S outlet scrubber (0 - 1,140 ppm-v), H2S inlet scrubber (2,550 and 3,000 ppm-v), and biogas flow (1,450 and 1,700 Nm3 biogas/h). Based on the analysis results, it was found that the initial design had already considered an overdesign factor of at least 52 times. Through solubility and residence time analysis, favorable scrubber operation is to run at low liquid spray flow (~ 70 m3/h). In addition, low flow liquid spray could help activate the bacteria on the bio-packing media surfaces so that they are not eroded by the high erosive spray velocity. This study’s results are expected to be a reference for the biogas industry in evaluating the performance of H2S scrubbers.
Analyzing the Total Resistance and Wave Pattern of Purse Seine Vessels with Photovoltaic-Powered Naryanto, Rizqi Fitri; Bahatmaka, Aldias; Wibowo, Muhammad Yusuf; Ghyferi, Andi Abdullah; Fahmi, Fiqri Fadillah; Hyoung Cho, Joung
Rekayasa Vol. 22 No. 2 (2024)
Publisher : Universitas Negeri Semarang

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.15294/rekayasa.v22i2.10634

Abstract

With 64.97% of its territory consisting of sea, Indonesia is one of the world's largest maritime nations and produces approximately 8.02 million tons of fish annually. Traditional fishing vessels play a crucial role in supporting livelihoods, yet their design is often based on hereditary methods rather than hydrodynamic optimization. This study uses catamaran hull forms as a design reference to analyze the total resistance and wave patterns of purse seine vessels with photovoltaic-powered systems. Computational methods are employed to predict vessel performance efficiently. The resistance analysis applies the Slender Body approach and Savitsky's mathematical model, supported by comparative studies for validation. Particular attention is given to the influence of chine configurations on resistance characteristics and wave formation. Results indicate that the addition of chines increases the Froude number and contributes to reducing total resistance. Among the variations, single chine geometry demonstrates the lowest resistance, making it the most efficient configuration for catamaran fishing vessels. While chine modifications affect the wave pattern, the hull maintains a relatively clean wake distribution. These findings highlight the potential for improving vessel design through careful chine geometry optimization combined with computational modeling. The study underscores the importance of modern hydrodynamic analysis in advancing traditional fishing vessels toward higher efficiency and sustainability. Future research is recommended to incorporate more advanced computational approaches, such as Computational Fluid Dynamics (CFD), examine water-hull interactions and enhance vessel performance under operational conditions.

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