Studi Numerik Pengaruh Nozzle Exit Position (NXP) terhadap Unjuk Kerja Ejector dengan Variasi NXP -10 mm, 0 mm, 10 mm, 20 mm, 30 mm, dan 40 mm

Hadyandhika, Aryasatya Naufal (2026) Studi Numerik Pengaruh Nozzle Exit Position (NXP) terhadap Unjuk Kerja Ejector dengan Variasi NXP -10 mm, 0 mm, 10 mm, 20 mm, 30 mm, dan 40 mm. Other thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Sistem pendingin berbasis siklus transkritikal CO2 masih menjadi salah satu alternatif refrigeran ramah lingkungan untuk menggantikan HFC yang memiliki Global Warming Potential (GWP) tinggi. Penggunaan ejector dalam siklus ini berpotensi mengurangi kerugian ekspansi dan meningkatkan efisiensi sistem. Salah satu parameter geometri yang berpengaruh terhadap unjuk kerja ejector adalah Nozzle Exit Position (NXP), yaitu posisi ujung motive nozzle terhadap inlet mixing chamber. Penelitian ini bertujuan uuntuk menganalisis pengaruh variasi NXP terhadap unjuk kerja dan karakteristik aliran ejector dua spesies CO2-N2 menggunakan pendekatan Computational Fluid Dynamics (CFD). Simulasi dilakukan secara tiga dimensi menggunakan perangkat lunak ANSYS Fluent 2024 R1 dengan model turbulensi k-e RNG dengan Enhanced Wall Treatment, dan model Species Transport. Variasi NXP yang diterapkan adalah -10 mm, 0 mm, 10 mm, 20 mm, 30 mm, dan 40 mm dengan kondisi batas mass flow inlet pada kedua inlet. Hasil simulasi menunjukkan bahwa NXP 0 mm menghasilkan unjuk kerja terbaik dengan efisiensi sebesar 18,70% dan ΔP sebesar 126,76 Pa. Seiring bertambahnya nilai NXP, efisiensi dan ΔP menurun secara bertahap hingga mencapai nilai terendah pada NXP 40 mm dengan efisiensi 9,86% dan ΔP 68,68 Pa. Analisis distribusi tekanan, kecepatan, pola aliran, dan fraksi massa CO2-N2 menunjukkan bahwa pergeseran posisi nozzle yang semakin jauh ke arah suction chamber menyebabkan energi kinetik jet primer terdisipasi lebih awal sehingga transfer momentum antara fluida primer dan sekunder di dalam mixing chamber menjadi kurang efektif.
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The CO₂ transcritical refrigeration cycle remains one of the environmentally friendly refrigerant alternatives to replace HFCs, which have a high Global Warming Potential (GWP). The use of an ejector in this cycle has the potential to reduce expansion losses and improve system efficiency. One of the geometric parameters that influences ejector performance is the Nozzle Exit Position (NXP), which is the position of the motive nozzle tip relative to the mixing chamber inlet. This study aims to analyze the effect of NXP variation on the performance and flow characteristics of a CO₂–N₂ two-species ejector using a Computational Fluid Dynamics (CFD) approach. Simulations were performed in three dimensions using ANSYS Fluent 2024 R1 with the RNG k-ε turbulence model with Enhanced Wall Treatment, and a Species Transport model. The NXP values applied were -10, 0, 10, 20, 30, and 40 mm with mass flow inlet boundary conditions at both inlets. Simulation results show that NXP = 0 mm produces the best performance with an efficiency of 18.70% and ΔP of 126.76 Pa. As NXP increases, both efficiency and ΔP decrease gradually, reaching their lowest values at NXP = 40 mm with an efficiency of 9.86% and ΔP of 68.68 Pa. Analysis of the pressure, velocity, flow pattern, and CO₂–N₂ mass fraction distributions indicates that shifting the nozzle position further toward the suction chamber causes the kinetic energy of the primary jet to dissipate earlier, resulting in less effective momentum transfer between the primary and secondary fluids inside the mixing chamber.

Item Type:	Thesis (Other)
Uncontrolled Keywords:	Ejector, Nozzle Exit Position (NXP), CO2, N2, Unjuk Kerja, Species Transport, Ejector, Nozzle Exit position (NXP), CFD, CO2, N2, Performance, Species Transport
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) > TA357 Computational fluid dynamics. Fluid Mechanics T Technology > TC Hydraulic engineering. Ocean engineering > TC173 Orifices. Nozzles. Jets T Technology > TJ Mechanical engineering and machinery > TJ903 Pumping machinery.
Divisions:	Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21201-(S1) Undergraduate Thesis
Depositing User:	Aryasatya Naufal Hadyandhika
Date Deposited:	28 Jul 2026 01:27
Last Modified:	28 Jul 2026 01:27
URI:	http://repository.its.ac.id/id/eprint/138206

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