Luga Martin Simbolon

Penelitian berupa simulasi CFD yang dilakukan di “LG VRF System Training Center Classroom 2” pada jurusan teknik refrigerasi dan tata udara Politeknik Negeri Bandung. Simulasi CFD dilakukan dengan menggunakan software bernama Ansys Fluent. Proses simulasi CFD dibagi menjadi tiga bagian besar yaitu pre-processing, solver, dan post processing. Proses validasi merupakan proses memastikan keakuratan hasil simulasi dengan cara membandingkan data pengukuran dengan hasil simulasi. Nilai error validasi temperatur memiliki nilai terkecil sebesar 1,128% dan error terbesar sebesar 2,710%. Hasil simulasi vector pada ruang kelas, nilai udara yang keluar dari diffuser menghasilkan udara berkecepatan 2 m/s lalu menurun hinga 0 m/s. pada supply dan return FCU dengan menggunakan menghasilkan udara berkecepatan 1,95 m/s. Hasil simulasi contour berupa visualisasi distribusi temperatur udara pada diffuser mengeluarkan udara bertemperatur 24,7 °C. FCU mengeluarkan udara bertemperatur sebesar 24,7°C yang ditahan oleh tembok bagian timur yang bersuhu sekitar 26,5°C.

Until now, R134a is still used as a working fluid in automotive air conditioning (A/C) even though it has a very high global warming potential (GWP), which is 1430. Refrigerant R600a is an alternative working fluid as a substitute for R134a in automotive (A/C). This environmentally friendly substitute refrigerant is also expected to produce a better system performance, for which it is necessary to analyse energy and exergy. During work, each AC component generates friction, heat loss, and pressure drop which causes irreversibility in each component. The irreversible quantity of each component is calculated by exergy analysis. Because automotive A/C is driven by engine rotation, its performance is also affected by engine rotation. In this study, the engine rotation to be evaluated is 1000, 1500, 2000, 2500, and 3000 rpm. The evaporating and condensing temperatures of automotive A/C in this study were 5oC and 45oC, respectively. Based on the energy analysis it was found that replacing R134a with R600 enhanced COP, for example at 2000 rpm for R134a and R600a respectively were 3.59 and 3.69, or an increase in COP of about 3%. Based on the exergy analysis, the greatest irreversibility occurred in the compressor, namely 72.1% and 78.6% for R134a and R600a, respectively, for 2000 rpm. This means that there is a potential to enhance the COP improvement using R600a by reducing the irreversibility on the compressor.

Kota Baru Parahyangan is located between Cimahi City and Padalarang. As an area designed as a satellite city, Kota Baru Parahyangan has various facilities including a business centre. In the present study, PM10 and PM2.5 will be measured at three business centres and one residential location located at the southernmost point for comparison. Data collection was carried out on 2 weekdays, namely Monday and Tuesday, and 2 weekends, namely Saturday and Sunday. The data collection time is from 08:00 to 15:30, where data collection is carried out every 30 minutes. Based on these measurements, PM10 and PM2.5 concentrations in three business centre locations and 1 residential location are still under the PPRI No. 22 of 2021 standards. Meanwhile, when evaluated using Kepmen LHK No. 14 of 2020, the API level for PM10 in three business centre locations and 1 residential location is in the "Good" category. However, the API level for PM2.5 in three business centre locations and 1 residential has reached the "Moderate" category. This means that the concentration of PM2.5 in business centre and residential in Kota Baru Parahyangan should be seriously considered by developer and local government. Because it is confirmed that PM2.5 concentrations will continue to increase over time with increasing activity and an increase in the number of vehicles passing through a region.

Dimethyl ether is one of the derivative products of coal that will be used as a household fuel substitute for LPG in Indonesia. In addition, it can also be used as a working fluid in a refrigeration system. To understand the behavior of this refrigerant, a simulation was carried out to determine the flow pattern of dimethyl ether in a horizontal evaporator. This study was applied in an evaporator of an air conditioner with inside diameter of 6.3 and 7.9 mm and cooling capacity of 2.64 and 5.28 kW. By varying the evaporation temperature from -20 to 5°C it was observed that the flow pattern was dominated by annular flow when the evaporation temperature was set at higher value. Simulation using pipe diameter of 7.9 mm and cooling capacity of 2.64 kW showed that at the evaporator inlet the flow pattern is combination of stratified-wavy and wavy-annular for all range of evaporation temperature. When the pipe diameter was reduced to 6.3 mm, stratified wavy at the evaporator inlet was only found at evaporating temperature of -15 and -20°C. All stratified wavy flow vanishes when the cooling capacity was doubled to 5.28 kW. Annular flow is dominant under this condition.