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Journal : Rotasi

Pemodelan dan Optimasi Multiobjektif Refrigerator Kompresi Uap Menggunakan Metode Meminimalkan Pembangkitan Entropi Dwinanto, Matheus
ROTASI Vol 23, No 2 (2021): VOLUME 23, NOMOR 2, APRIL 2021
Publisher : Departemen Teknik Mesin, Fakultas Teknik, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/rotasi.23.2.36-42

Abstract

The vapor compression refrigerators have many applications for cooling and freezing. The advantage of this system has good performance, and can meet the needs of a relatively large cooling capacity with a small system size. But behind its advantages, the energy consumption of this system is high so that energy saving is the main goal of optimization and this will continue to be done in a sustainable manner in the future. In this article, thermodynamic design optimization is presented to minimization entropy generation, minimization total power input, maximization the efficiency of the second law, and maximization the performance coefficient, simultaneously. A multi-objective genetic algorithm is used during the optimization process, and based on the Pareto frontier a decision-making strategy is obtained and then used to determine the final solution. The optimization results show that the method of minimization entropy generation can experience a paradox, where minimizing the entropy generation number of the system will not automatically result in the maximum efficiency of the second law but there is an optimal point which indicates that the generation of entropy is minimum. From the results of thermodynamic design optimization of the refrigerator, the total input power is 0.281 kW, the second law efficiency is 0.311 and coefficient of performance is 2.95.
Analisis Energi dan Eksergi Modul Surya 50 WP Tipe Polikristalin Dwinanto, Matheus
ROTASI Vol 23, No 1 (2021): VOLUME 23, NOMOR 1, JANUARI 2021
Publisher : Departemen Teknik Mesin, Fakultas Teknik, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/rotasi.23.1.%p

Abstract

In this modern era, electricity has become a basic necessity so it is very necessary to sustain people lives and encourage economic growth in a region. The solar photovoltaic module has been used as a power plant in remote area thereby increasing the electrification ratio. In its operation the solar photovoltaic module generates electrical energy and thermal energy from the intensity of the solar radiation absorbed. One type of the solar photovoltaic module that is widely used is polycrystalline. This paper aims to examine the energy and exergy analysis of 50 WP solar photovoltaic module polycrystalline type based on sunny weather conditions for 4 days in October 2019 in Kupang. Experimental data is used to calculate the output power, exergy input, thermal exergy, electrical exergy, exergy loss, energy efficiency and exergy efficiency of the system. Increased the intensity of the solar radiation will increase the output power and exergy input but result in the exergy loss greater than thermal exergy and electrical exergy. The module surface temperature has a great influence on exergy efficiency. Energy efficiency is relatively constant, ranging from 19.6% to 19.9%. In contrast, the exergy efficiency is quite fluctuating, ranging from 42.09% to 54.19%
Pengaruh Temperatur Kondensasi terhadap Kinerja Siklus Rankine Organik yang Menggunakan R245fa, R600a, R1234yf, dan R1234ze Dwinanto, Matheus
ROTASI Vol 23, No 4 (2021): VOLUME 23, NOMOR 4, OKTOBER 2021
Publisher : Departemen Teknik Mesin, Fakultas Teknik, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/rotasi.23.4.28-34

Abstract

The organic Rankine cycle (ORC) is an unconventional technology and has been widely used to conversion of thermal energy at low temperatures into electrical energy on a small scale. For this reason, the use of more environmentally friendly hydrocarbons and hydrofluoroolefins has become a demand and a central issue in the future. This paper presents a performance study of using R600a, R1234yf and R1234ze as drop-in replacement to R245fa in an ORC system. The system performance is based on the variation of the condensation temperature using Genetron Properties software with the evaporation temperature being held constant. The important quantities analyzed are mass flow rate, pumping power, heat absorption, heat rejected, turbine outlet temperature, turbine outlet superheat temperature, turbine pressure ratio, and thermal efficiency. The results show that the condensation temperature is very influential on system performance. It is not easy to determine the optimal performance for each working fluid used in the system independently so that the cycle simulation approach with a thermodynamic model while comparing the three working fluids with R245fa is the most common way. The results of this study indicate that the studied hydrocarbons and hydrofluoroolefins working fluid candidates have the same thermal efficiency as R245fa.
Pengaruh Rasio Tekanan Kompresor Turbocharger Terhadap Kinerja Mesin Diesel dan Emisi NOX Matheus Dwinanto
ROTASI Vol 24, No 4 (2022): VOLUME 24, NOMOR 4, OKTOBER 2022
Publisher : Departemen Teknik Mesin, Fakultas Teknik, Universitas Diponegoro

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.14710/rotasi.24.4.41-48

Abstract

The use of a turbocharger in large diesel engines has become a demand because it can increase engine output and efficiency by utilizing exhaust gas from combustion (exhaust gas). Turbocharger is a device to increase the intake of air into the cylinder by utilizing the energy of exhaust gases from combustion. The purpose of this study is to analyze the effect of differences in the turbocharger pressure ratio on diesel engine performance using Diesel-RK software. The diesel engine under study is model 4D56 2.5L which uses a single turbocharger with maximum power of 136 PS at 4000 rpm and maximum torque of 324 N.m at 2000 rpm. The compressor pressure ratio under study was only 1.5 and 2.5 compared to a diesel engine without a turbocharger or natural aspirated engine (NA). The engine capacity is 2477 cc, 4 cylinders, and the compression ratio is 18:1. The fuel used is SME Biodiesel (Soya Methyl Ester, C15H28) with a cetane number of 56.5. The results of this study indicate that the use of a turbocharger will lead to an increase in engine power, especially at a high compressor pressure ratio due to the larger air filling when compared to the NA diesel engine for the engine speed range of 750 rpm to 5000 rpm. For diesel engines that use a turbocharger, the BSFC will decrease with increasing engine speed. NOx emissions increase with increasing turbocharger compressor pressure ratio when compared to NA diesel engines, and this occurs over the entire engine speed range (750 rpm – 5000 rpm). NOX emissions decrease as engine speed increases