Pengaruh geometri pengganggu (obstraksi) terhadap fenomena flooding pada saluran vertikal

YUNIARTO, Tonny, Prof. Dr. Ir. Indarto, DEA

2008 | Tesis | S2 Teknik Mesin

Fenomena flooding terjadi pada peralatan-peralatan industri seperti kondensor, evaporator, kolom destilasi, reaktor kimia gas cair, dan reaktor nuklir, dimana fenomena ini akan mempengaruhi kinerja peralatan tersebut. Penelitian ini bertujuan mengamati pengaruh bentuk permukaan geometri pengganggu terhadap permulaan flooding aliran udara-air pada saluran vertikal. Model pengganggu yang dipakai dalam penelitian ini disesuaikan dengan aplikasi dalam industri berupa sambungan pipa maupun endapan kerak yang menonjol. Penelitian dilakukan pada daerah pola aliran film, menggunakan pipa plexiglass berdiameter dalam 32 mm, panjang seksi uji 3000 mm, dengan inlet cairan berpori dan outlet tajam (sharp). Pengganggu berbentuk cincin berpenampang persegi yang ujung bagian tajam dichamfer, berdiameter dalam 28 mm, dengan variasi geometri pengganggu melingkar 1200, 2400, serta 3600 dan pengganggu cincin tunggal dan ganda (jarak 6 mm dan jarak 20 mm). Hasil penelitian menunjukkan bahwa semakin besar sudut melingkar Pengganggu pada saluran uji maka mekanisme flooding semakin cepat. Mekanisme awal flooding terjadi di pengganggu pada pengganggu dengan sudut melingkar penuh (3600). Pada Pengganggu melingkar 2400, mekanisme awal flooding dapat terjadi di pengganggu pada L/D = 78,125 , dan mekanisme awal flooding terjadi di outlet cairan pada L/D = 15,625. Sedangkan pada pengganggu melingkar 1200, mekanisme awal flooding terjadi pada outlet cairan. Pada saluran uji dengan pengganggu cincin tunggal dan ganda (jarak 6 mm dan jarak 20 mm) menunjukkan bahwa tidak terjadi perbedaan secara signifikan terhadap kecepatan flooding cairan dan gas. Hal ini disebabkan bahwa posisi cincin pengganggu paling depan terhadap aliran cairan lebih dominan menimbulkan gelombang pada permukaan lapisan film cairan. Mekanisme flooding yang terjadi pada pengganggu ditandai dengan naiknya gradien tekanan pada pengganggu.

A flooding phenomena is occurred on some industrial equipments like condensor, evaporator, destilation column, gas liquid chemical reactor, and nuclear reactor, where this phenomena will influence the equipment activities. The objective of this research is to observe the influencing of the surface geometry obstruction to the flooding of liquid-gas flow in the vertical channel. The obstruction model which is used in this research has been appropriated with the application in the industrial as pipeline connecting and scalling. Experiments were conducted in a film flow of patern area and used a plexiglass pipe which had 32 inch of inside diameter and the experiment section length is 3000 mm, with the liquid porous inlet and sharp outlet. The obstruction, that was shaped like a ring, had a rectangle longitudinal section section which had chamfered sharp edge. The inside diameter was 28 mm with the disturbing geometric variation was going around 1200, 2400, and 3600 and for the obtruction both of singular and double (the distances were 6 mm and 20 mm). The result of experiment shows that if the obstruction angle on the experiment line is bigger, the flooding mechanisn is so faster. The flooding initial mechanism is occured in the obstruction which has full rounded angle (3600). In the rounded obtruction 240, the flooding initial mechanism is occured in the obstruction on L/D = 78,125 and the flooding initial mechanism is occured in the liquid outlet on L/D = 15,625 . Whereas on the twist obstruction of 1200 , the flooding initial mechanism is occured on the fluid outlet. On the experiment line with the double and single obstruction (for the distance are 6 mm and 20 mm) shows that there is no significant difference for the gas and fluid flooding velocity. This is occurred because of the position of an earliest obstruction for fluid flow is more dominant and it appears a wave on the fluid film surface. The flooding mechanism, which happened on the obstruction, is shown with the increasing of the pressure gradient on the obstruction.

Kata Kunci : Flooding,Pengganggu,Sudut melingkar, Flooding, Obstruction, Rounded Angle