Studi Eksperimental Pengaruh Jumlah Baffle terhadap Kinerja Microbubble Generator Venturi
Luluk Fitri Yani, Dr. Ir. Khasani, S.T., M.Eng., IPM. ; Prof. Dr. Ir. Deendarlianto, S.T., M.Eng. ; Prof. Dr. Ir. Indarto. DEA., IPM. ; Dr. Hifni Mukhtar Ariyadi, S.T., M.Sc.
2023 | Tesis | S2 Teknik Mesin
Dalam budidaya ikan terdapat beberapa faktor yang menentukan keberhasilan pembenihan yaitu kualitas benih, pengolahan, dan kualitas air yang meliputi suhu air, salinitas, pH, dan oksigen terlarut. Oksigen terlarut atau Dissolved Oksigen (DO) merupakan zat yang dibutuhkan oleh makhluk hidup di dalam air untuk melangsungkan kehidupan. Oksigen terlarut diperlukan untuk pernapasan, dan proses metabolisme atau pertukaran zat yang kemudian menghasilkan energi untuk pertumbuhan dan pembiakan. Sehingga oksigen terlarut menjadi tolak ukur terhadap kualitas air. Microbubble generator sebagai aerator dapat meningkatkan konsentrasi oksigen terlarut di dalam air untuk menambah laju pertumbuhan ikan dan tumbuhan. Penelitian ini mengembangkan model baru microbubble generator tipe venturi dengan modifikasi bagian inlet yaitu dengan pebambahan swirl baffle. Studi eksperimental dilakukan untuk menginvestigasi pengaruh jumlah baffle microbubble generator venturi terhadap distribusi ukuran microbubble, koefisien perpindahan massa volumetrik, dan kinerja microbubble generator venturi. Fabrikasi microbubble generator dilakukan dengan 3D printing, dengan konstruksi utama yaitu konvergen, throat, dan divergen. Bagian throat berdiameter 9 mm dan terdapat sebuah lubang bagian atas throat berdiameter 3 mm digunakan untuk mengalirkan udara ke dalam microbubble generator. Pada bagian inlet dan outlet microbubble generator venturi juga dipasang pressure tabs berukuran 1 mm untuk mengukur tekanan bagian inlet dan outlet microbubble generator. Swirl baffle di tempatkan pada inlet microbubble generator dengan tebal 2,5 mm dan Panjang 6 mm. Variasi jumlah baffle berjumlah 2 dan 3 dengan sudut 60 derajat. Air bersih digunakan sebagai fluida cair dan udara pada tekanan 1 atm sebagai fluida gas. Seksi uji berada di kolam aquarium berbahan kaca dengan Panjang 280 cm, lebar 60 cm, dan tinggi 60 cm. Air diisi sampai mencapai ketinggian 40 cm. Microbubble generator venturi diletakkan pada 20 cm dari dasar kolam. Air disirkulasikan tertutup dengan menggunakan pompa 1 fasa. Sirkulasi debit air ditentukan variasi alirannya dengan cara mengatur pompa menggunakan valve dan diukur menggunakan water flowmeter dari 40 - 60 lpm. Sedangkan Debit udara diatur variasinya mengunakan air flowmeter dari 0.1 - 0.7 lpm. Pengukuran distribusi microbubble generator venturi diamati menggunakan kamera berkecepatan tinggi merk Phantom Miro M310. Output rekaman ditransfer ke komputer melalui aplikasi Phantom Control kamera. Data diolah menggunakan image processing menggunakan perangkat lunak MATLAB R2023a untuk menghasilkan data kuantitatif distribusi diameter bubble. Pengukuran oksigen terlarut dalam air menggunakan Dissolved Oxygen meter yang diletakkan 110 cm dari output microbubble generator venturi. Distribusi ukuran bubble hasilnya menunjukkan diameter terkecil yang dihasilkan sebesar 73 ?m. Kenaikan debit air menyebabkan kurva probabilitas semakin meningkat dan distribusi bubble yang lebih seragam. Pengaruh jumlah baffle terhadap distribusi ukuran bubble menyebabkan baffle 3 memiliki nilai probabilitas yang lebih tinggi dibandingkan dengan baffle 2. Hasil pengukuran koefisien perpindahan massa volumetrik didapatkan oksigen terlarut meningkat seiring dengan kenaikan debit air dan debit udara. Kinerja microbubble generator venturi ditinjau dari parameter pressure drop, hydraulic power, dan bubble generation efficiency. Diperoleh hasil sebagai berikut: bertambahnya debit air menyebabkan terjadinya peningkatan nilai pressure drop dan peningkatan nilai hydraulic power. Terjadinya peningkatan nilai hydraulic power menyebabkan menurunnya nilai bubble generation efficiency. Penambahan baffle pada bagian inlet microbubble generator venturi menyebabkan baffle 3 memiliki nilai pressure drop, dan hydraulic power yang lebih tinggi dibandingkan dengan baffle 2, sedangkan bubble generation efficiency lebih rendah dibandingkan dengan baffle 2.
In fish farming, there are several factors that determine hatching success, namely seed quality, processing, and water quality which includes water temperature, salinity, pH, and dissolved oxygen. Dissolved Oxygen (DO) is a substance needed by living creatures in water to sustain life. Dissolved oxygen is needed for respiration, and metabolic processes or exchange of substances which then produce energy for growth and reproduction. So dissolved oxygen becomes a benchmark for water quality. Microbubble generators as aerators can increase the concentration of dissolved oxygen in the water to increase the growth rate of fish and plants. This research develops a new model of venturi type microbubble generator with modification of the inlet section, namely by adding a swirl baffle. An experimental study was conducted to investigate the effect of the number of baffles of the venturi generator microbubble on the microbubble size distribution, volumetric mass transfer coefficient, and performance of the venturi microbubble generator. Microbubble generator fabrication is carried out using 3D printing, with the main construction being convergent, throat and divergent. The throat section is 9 mm in diameter and there is a hole at the top of the throat with a diameter of 3 mm which is used to channel air into the microbubble generator. At the inlet and outlet of the venturi microbubble generator, pressure tabs measuring 1 mm are also installed to measure the pressure at the inlet and outlet of the microbubble generator. The swirl baffle is placed at the inlet of the microbubble generator with a thickness of 2.5 mm and a length of 6 mm. Variations in the number of baffles are 2 and 3 with an angle of 600. Clean water is used as the liquid fluid and air at a pressure of 1 atm as the gas fluid. The test section is in a glass aquarium pool with a length of 280 cm, a width of 60 cm and a height of 60 cm. Water is filled until it reaches a height of 40 cm. The venturi microbubble generator is placed 20 cm from the bottom of the pool. Water is circulated closed using a single phase pump. Water discharge circulation is determined by variations in flow by adjusting the pump using a valve and measured using a water flowmeter from 40 - 60 lpm. Meanwhile, the variation in air flow is regulated using an air flowmeter from 0.1 - 0.7 lpm. Measurements of the microbubble distribution of the venturi generator were observed using a Phantom Miro M310 high-speed camera. The recorded output is transferred to a computer via the camera's Phantom Control application. The data was processed using image processing using MATLAB R2023a software to produce quantitative data on bubble diameter distribution. Dissolved oxygen in water was measured using a Dissolved Oxygen meter placed 110 cm from the venturi microbubble generator output. The resulting bubble size distribution shows that the smallest diameter produced is 73 ?m. An increase in water discharge causes the probability curve to increase and the bubble distribution to be more uniform. The influence of the number of baffles on the bubble size distribution causes baffle 3 to have a higher probability value compared to baffle 2. The results of measuring the volumetric mass transfer coefficient show that dissolved oxygen increases along with the increase in water discharge and air discharge. The performance of the venturi microbubble generator is reviewed from the parameters of pressure drop, hydraulic power, and bubble generation efficiency. The following results were obtained: increasing water discharge causes an increase in the pressure drop value and an increase in the hydraulic power value. An increase in the hydraulic power value causes a decrease in the bubble generation efficiency value. The addition of a baffle to the inlet of the venturi microbubble generator causes baffle 3 to have a higher pressure drop and hydraulic power value compared to baffle 2, while the bubble generation efficiency is lower than baffle 2.
Kata Kunci : microbubble generator, venturi, oksigen terlarut, perpindahan massa volumetrik
