Inovasi Manajemen Termal Berdasarkan Kinerja Termohidrolik dan Mekanisme Transisi Aliran Dua Fase Sirkulasi Alami Menggunakan Nanofluida Al2O3 pada Sistem Pendingin Pasif Nuklir
Dwi Yuliaji, Prof. Dr. Ir. Deendarlianto, S.T., M.Eng., Prof. Dr. Ir. Indarto, DEA, IPM, ASEAN Eng., Prof. Dr. Ir. Mulya Juarsa, S.Si., MESc.
2026 | Disertasi | S3 Teknik Mesin
Pendingin
sirkulasi alami saat ini menjadi fitur di dalam sistem keselamatan reaktor
Pembangkit Listrik Tenaga Nuklir (PLTN) yang terus dikembangkan melalui inovasi
manajemen termal. Penelitian ini bertujuan untuk melakukan investigasi pengaruh
sifat fisis fluida kerja akibat perubahan daya terhadap kinerja termohidrolik,
ketidakstabilan aliran (mode aliran, tipe osilasi, dan peta pola aliran) dan
mekanisme fisik transisi pola aliran dua fase.
Penelitian
dilakukan dengan metode eksperimen pada open loop passive containment
cooling system (OL-PCCS) dengan rasio geometri NG skala
rendah. Loop menggunakan pipa SS 201 berdiamater dalam
0,023 m dengan panjang total loop 3,24. Bidang
pengamatan posisi vertikal menggunakan pipa pyrex dengan
diameter dalam 0,023 m. Data akuisisi menggunakan casing NI cDAQ 9188, sensor
temperatur menggunakan termokopel tipe K dengan perekaman modul arus NI 9214,
sensor tekanan menggunakan pressure transmitter dengan
perekaman modul tegangan NI 9203. Visualisasi pola aliran menggunakan foto
makro dengan image type JPEG, RAW. Periode perekaman data
temperatur, tekanan, dan foto makro dilakukan per detik. Kontrol daya pemanas
menggunakan regulator voltage pada enam variasi, yaitu
880, 966, 1056, 1150, 1248, dan 1350. Untuk
memvariasikan sifat fisis fluida kerja (densitas, viskositas dinamik, kalor
spesifik, dan konduktivitas termal) dispersan nanopartikel alumunium
oxside (Al2O3) berukuran 40 nm dicampur
ke fluida dasar menggunakan magnetic stirrer dengan persentase
berat 0,025, 0,05, dan 0,1. Data eksperimen dianalisis
menggunakan korelasi yang diperoleh dari literatur, selanjutnya didukung dengan
analisis statistik menggunakan probability distribution function (PDF), power
spectral density (PSD), dan wavelet transforms.
Pengaruh daya
pemanas dan sifat fisis fluida kerja terhadap kinerja termohidrolik, mode
aliran, tipe osilasi, pola aliran, dan mekanisme fisik transisi pola aliran dua
fase telah berhasil dilakukan. Penambahan dispersan nanopartikel
memberikan dampak baik terhadap kinerja termohidrolik dan mampu
menekan ketidakstabilan aliran. Mode aliran yang berhasil ditemukan antara
lain, geysering, compound flashing instability, boiling
instability, dan stable boiling flow. Tipe osilasi yang
berhasil diidentifikasi antara lain, tipe osilasi intermitten, sinusoidal,
dan tipe osilasi sirkulasi aliran stabil pada kondisi subcooled
boiling. Peta pola aliran dua fase pada pipa vertikal untuk sirkulasi
alami yang berkerja pada tekanan atmosfer juga telah berhasil dipetakan.
Mekanisme fisik transisi pola aliran dua fase berdasarkan nilai tegangan geser
dinding dan nilai tegangan geser antar muka juga telah diperoleh, serta nilai
distribusi aliran dan drift velocity menggunakan dua korelasi
pembanding
Natural
circulation cooling systems have become an essential feature in the safety
systems of Nuclear Power Plants (NPPs), continuously developed through
innovations in thermal management. This study aims to investigate the effect of
power variation on the thermophysical properties of the working fluid and its
impact on thermohydraulic performance, flow instabilities (including flow
regimes, oscillation types, and flow pattern maps), as well as the physical
mechanisms governing two-phase flow pattern transitions.
The research was
conducted by experimental method on open loop passive containment cooling
system (OL-PCCS) with low scale geometry ratio. The loop uses SS 201 pipe
with an inner diameter of 0.023 with a total loop length of 3.24. The
vertical position observation plane uses a pyrex pipe with an inner diameter of
0.023. Data acquisition using NI cDAQ 9188 casing, temperature sensor using K
type thermocouple with NI 9214 current module recording, pressure sensor using
pressure transmitter with NI 9203 voltage module recording. Visualization of
flow patterns using macro photos with image type JPEG, RAW. The recording
period for temperature, pressure, and macro photos is per second. Heating power
was controlled using a voltage regulator at six variations, namely
880, 966, 1056, 1150, 1248, and 1350. To vary the
physical properties of the working fluid (density, dynamic viscosity, specific
heat, and thermal conductivity) 40 nm aluminum oxide (Al2O3)
nanoparticle dispersant was mixed into the base fluid using a magnetic stirrer
with weight percentages of 0.025, 0.05, and 0.1. The
experimental data were analyzed using correlations obtained from the
literature, further supported by statistical analysis using probability
distribution function (PDF), power spectral density (PSD), and wavelet
transforms.
The effects of
heating power and the thermophysical properties of the working fluid on
thermal-hydraulic performance, flow regimes, oscillation types, flow patterns,
and the physical mechanisms of two-phase flow-pattern transitions have been
successfully classified. The addition of nanoparticle dispersants provides
beneficial impacts on thermal-hydraulic performance and effectively suppresses
flow instabilities. The identified flow regimes include geysering, compound
flashing instability, boiling instability, and stable boiling flow. The
observed oscillation types consist of intermittent oscillations, sinusoidal
oscillations, and stable circulation-flow oscillations under subcooled boiling
conditions. The two-phase flow-pattern map for vertical natural-circulation
flow operating at atmospheric pressure has been successfully established. The
physical mechanisms of two-phase flow-pattern transitions, governed by the
dynamic variation of wall shear stress and interfacial shear, have also been
clarified. In addition, the distribution parameter and drift velocity have been
obtained using two comparative correlations.
Kata Kunci : Open loop passive containment cooling system (OL-PCCS), Al2O3, thermohidrolik, Discrete wavelet transform, Ketidakstabilan aliran, Mekanisme transisi aliran dua fase
