EPI International Journal of Engineering

The Assessment of Indoor Thermal Comfort Of University Classrooms in Hot and Humid Area

Rahmi Andarini, Muhammad Dzaky Al-Haidar, Vincentius Rayza Lee — Sun, 23 Feb 2025 12:57:10 +0000

Thermal comfort is a description of the mental satisfaction experienced by humans regarding the temperature conditions in the surrounding environment. Appropriate thermal comfort conditions will have a positive influence on the occupant such as increasing productivity. This research was carried out to determine the level of thermal comfort in classrooms of the Universitas Multimedia Nusantara. There are two methods applied in this study, firstly by measuring indoor air quality parameters, and the second method is by surveying the occupants' acceptance of the indoor air condition. The measurement of indoor air parameters consists of two different methods, those are by installing Internet of Things monitoring systems, and manual measurement. There were 2 classrooms and 1 student lounge surveyed, and the measured parameters were indoor air temperature and relative humidity. The results of the measurements show that the average indoor air temperature of the conditioned classrooms was 26^OC and the average temperature of the student lounge during unconditioned was 29^OC. With the same condition, the measured relative humidity in the classrooms was found at 55% and the student lounge was at 70%. Regarding the thermal comfort condition, 68% of occupants of Student Lounge felt just comfortable,17% felt very comfortable and 15% felt uncomfortable. The opinion regarding this choice is affected by the sitting position of the respondents. At the classrooms D1509 and D1510, 64% of the respondents felt just comfortable, 28% felt very comfortable, 8% felt uncomfortable, which means that the majority of the respondents felt comfortable.

Computational Fluid Dynamic Analysis on Double-Type Drying Machine Design

Waleed Waleed, Mona Nur Moulia, Athoillah Azadi — Wed, 16 Apr 2025 06:51:42 +0000

The design of a double-type dryer with tray and rotary will be designed to be able to dry chips and grains commodities in one time process for energy and time-saving. In the designing process, Computational Fluid Dynamic (CFD) simulation is used to analyze the distribution of hot air and minimize failures in the design. The purpose of this study was to determine the pattern of hot air flow distribution and determine the best design of the drying machine. The parameters used in the CFD input have a temperature of 60 ^oC, air velocity 1 m/s, and a pressure 1.01325 bar with a constant time. This study used 2 treatments, namely the outlet position parameter (A) with dimension 60 mm x 60 mm and the number of holes in the bulkhead between the tray and rotary have the gap type (L) with dimension 540 mm x 70 mm with a total of 21 treatments. This research begins with pre-processing for made geometry and boundary condition input, next is solver process with average iterations 298 with 36 s interval, and the last is post-processing for having air contour. The results showed that the best treatment based on temperature pattern is the A2L1L2 treatment, with the output A2 and 2 limiting gaps, on gaps 1 and 2. This treatment had an average temperature distribution of 56.69 ^oC, deviation 3,55^oC, air velocity 1.57 m/s, and turbulence 0.021 m/s.

Evaluation of Articulated CAT 745 Fuel Ratio Based on Haul Road Geometry at PT Hillconjaya Sakti Site PT Adhi Kartiko Pratama Tbk

Aryanti Virtanti Anas, Wahyuni S, Rini Novrianti Sutardjo Tui, Rizki Amalia — Wed, 16 Apr 2025 13:25:59 +0000

The distance for transporting overburden at PT Hillconjaya Sakti reaches hundreds of meters. Based on actual conditions, Articulated CAT 745 queues often occur on certain haul road segments due to unsuitable haul road conditions so the fuel ratio value is in the low performance category. The purpose of this study is to evaluate the fuel ratio value and provide recommendations for improving the geometry of haul roads to meet the established fuel ratio value standards. Multiple linear regression analysis using Eviews 12 VS was used to determine the variables that significantly affect the fuel consumption of hauler based on haul road geometry. Road grade, total resistance, travel time and speed of the hauler are independent variables, while fuel consumption is the dependent variable. Based on the results of data processing, a fuel ratio value of 1.85 was obtained and the parameters that had a significant effect on fuel consumption were total resistance and travel time. Improvement of haul road conditions based on ESDM Decree No. 1827 K/30/MEM/2018 and AASHTO Manual Rural High Way Design. The fuel ratio value after repairs decreased to 0.60 and was in the best performance category based on PT Hillconjaya Sakti's standard fuel ratio value.

Preliminary Design and Energy Production of a Mobile Floating Structure (MFS) for Offshore Wind Turbines in Indonesian Waters

Tue, 22 Apr 2025 11:09:42 +0000

The Mobile Floating Structure (MFS) is an innovative floating wind turbine concept that utilizes a catamaran hull design to enhance mobility and operational efficiency. Unlike stationary platforms, the MFS can relocate to areas with higher wind energy density, making it a promising solution for optimizing wind energy harvesting in offshore environments. This study focuses on the preliminary design and energy production of the MFS. Maxsurf is used to analyze hydrostatics and assess the hydrodynamic performance of the MFS hull after the dimension of the MFS is determine with key considerations including rotor diameter and the weight of the wind turbine. Furthermore, four wind turbines are installed in the MFS. Those aspect were integrated into the design process to ensure realistic operational adaptability. As result. the resulting dimensions of the MFS were determined utilizing Maxsurf. Moreover, different with the previous study that use satellite data, the present study employs reanalysis data to estimate the energy density and power production of MFS. the energy density map is also produced in the present study to determine the monthly location of the MFS. The energy production of the MFS with four turbines has been calculated, and the energy production map is also drawn. Finally, the energy production of the MFS in the chosen location has also been estimated. The energy production map can be utilized to develop MFS in other location.

Design of Quasi-isotropic Rectangular Plates for Optimizing the Fundamental Mode of Bending Vibration

Yoshihiro Narita — Thu, 09 Apr 2026 00:00:00 +0000

This study is the first work to demonstrate that quasi-isotropic laminated composite plates can be optimized for bending vibration through appropriate stacking-sequence design. A quasi-isotropic plate is defined as a laminated composite plate exhibiting isotropic in-plane stiffness. Owing to this constraint, such plates have traditionally been excluded from stacking-sequence optimization. The present work clarifies why optimization remains feasible despite the in-plane isotropy requirement and outlines a systematic procedure for maximizing or minimizing the fundamental natural frequency with respect to ply orientation angles while preserving isotropic in-plane behavior. Numerical results are provided for square and rectangular plates under various classical boundary conditions, and the corresponding maximum and minimum fundamental frequencies are identified. In particular, the ratio of maximum to minimum fundamental frequency is evaluated; for example, it reaches 2.17 for a cantilevered quasi-isotropic square plate.

Inventory Model Simulation to Reduce Bullwhip

Mujaddid Mujaddid, Sapta Asmal, Saiful Mangngenre — Sun, 12 Apr 2026 11:55:45 +0000

One of the issues that frequently arise in the supply chain is the bullwhip effect. The bullwhip effect is simply the presence of a distant intersection of supply and demand. To address this issue, inventory management must be implemented in order to provide products or services at the appropriate time and location. The goal of this study is to reduce the occurrence of the bullwhip effect, increase service level, and consider total cost and profit. The method used is the RQ policy. RQ policy is a fixed replenishment point inventory policy / fixed replenishment quantity policy referred to as an RQ policy. When the inventory level drops below the fixed replenishment point (R), the product's fixed replenishment quantity (Q) is ordered, which is simulated in anylogistix software to determine the optimal inventory policy and design. The optimal simulation results are R:15,000 and Q:30,000 with an inventory capacity of 30,000, a bullwhip effect value of 1.62 to 1, indicating no bullwhip effect, and a service level of 0.90 to 1, indicating that all orders can be fulfilled. with the right timing and profits ranging from Rp. 74.400.000 to Rp. 101,450,000.

THERMAL PERFORMANCE OF DE’DIBA KULONG RUMA BULONGAN FOR RESIDENTS COMFORT

Icha Anggriani — Fri, 22 May 2026 02:35:01 +0000

The Bulungan Stilt House which in local language is called De’diba Kulong Ruma Bulongan has various floor heights of around 30cm, 50cm and 100cm. The difference in stilted floor height is expected to yield different thermal performance that affects occupant comfort. This study aims to: (1) explain the architectural characteristics of De’diba Kulong Ruma Bulongan and the existing conditions of thermal comfort of the occupants, and (2) analyze the effect of the floor height of De’diba Kulong Ruma Bulongan on the thermal comfort based on measurements and occupants perceptions, (3) explain the floor height performance on occupant thermal comfort as a function of climatic and environmental conditions. This research is quantitative, with a survey method using both qualitative and quantitative data. Data were collected through observation, thermal measurements, and distribution of questionnaires to 43 respondents who lived in 9 samples of Bulungan stilt houses. The analysis technique used PMV and PPD through the CBE thermal comfort tools, as well as cross-tabulation of questionnaire data. The results of the analysis of the psychrometric chart and the effective temperature chart at 13:00–14:00 WITA show that the highest average effective temperature in all measured stilt houses is in the range of 25.5-29°C. PMV analysis using the CBE thermal comfort tool shows that houses on stilts are most compliant with Ashrae 55 at a height of 100cm with PMV = 0.02 and PPD feel 5 % of a neutral value with an operating temperature of 25.5 - 27°C. Questionnaire analysis shows the most comfortable thermal reception according to the respondent’s characteristics, namely occupants who are women, elderly (> 54 years old), and those who wear long loose gowns called gamis. The analysis of the occupants' perception shows that the most comfortable thermal reception at the four measurement points of the house on stilts is a house on stilts with a height of subsequently 100, 50, and 30 cm. This study concludes that the floor height affects thermal comfort in which the higher the stilted floor height in the architecture of the De'diba Kulong Ruma Bulongan the more comfortable for the occupants. This study also verifies that thermal comfort is influenced by climatic and environmental conditions.

Characteristics Of Filament From Extrusion Result Of Low Density Polythylene Plastic Waste Using Extrusion Method For 3d Printing Filament Applications

muhammad ali chandra — Fri, 22 May 2026 03:25:07 +0000

Low-Density Polyethylene (LDPE) plastic is a material that is widely used by the industry as packaging. Worse, the manufacturing industry players do not place environmental issues as the main focus in the supply of products. This study aims to analyze the characteristics of LDPE plastic waste that is formed into filaments for 3D printing filament applications. The research variables analyzed were the temperature of the test sample at 170 °C, 180 °C, 190 °C, 200 ºC, 210 °C, and 220 °C. The filament analysis process is to form LDPE plastic waste into 3D printing filaments using a plastic waste extrusion machine. The hardness test was then carried out using a digital Shore A Durometer Hardness tool. Furthermore, a microstructure test was also carried out using SEM (Scanning Electron Microscope). The results of the hardness test obtained show that the specimen temperature of 210 °C has the highest hardness value, which is in the range of 83–89.5 HA. In the meantime, specimens at 180 °C had the lowest hardness values, ranging from 59.5 to 71.5 HA. In addition, the SEM test resulted in the sample surface not being very flat at temperatures of 170 °C, 180 °C, and 190 °C, while the sample surface was quite flat at temperatures of 200 °C, 210 °C, and 220 °C.