Studi eksperimental koefisien perpindahan kalor aliran dua fasa air-udara bentuk gelembung aliran berlawanan arah dalam pipa annulus vertikal

ARBIYANTORO, Ir. Purnomo, MSME, Ph.D

2008 | Tesis | S2 Teknik Mesin

Studi eksperimen koefisien perpindahan kalor aliran fluida dua fasa yang terdiri atas air dan udara aliran berlawanan arah dalam pipa annulus telah diteliti. Pipa annulus vertikal terbuat dari tembaga diameter dalam 22,6 mm dan panjang 1200 mm. Bagian tengah pipa digunakan stainlees steel sebagai core annulus dengan diameter 6,3 mm. Pipa tembaga dililiti elemen pemanas sepanjang 900 mm, untuk mengukur temperatur dinding pipa dan fluida dipasang termokopel pada tujuh titik dengan jarak masing-masing 135 mm. Air dialirkan dengan pompa melalui planum pipa bagian atas dan udara diinjeksikan dengan nosel melalui center annulus bagian bawah. Fluk kalor listrik divariasi 812.62 W/m2, 1415 W/m2, 2239 W/m2, 3194 W/m2, dan 4384 W/m2. Selama penelitian, fenomena aliran dijaga bentuk aliran gelembung, hasil penelitian menunjukkan bahwa koefisien perpindahan kalor meningkat dengan meningkatnya debit udara. Koefisien perpindahan kalor juga menunjukkan penurunan jika terjadi kenaikan debit air. Koefisien perpindahan kalor maksimum adalah 2063 W/m2 pada ReSL 272.544 dan ReSG 285, pada fluk kalor listrik 1415 W/m2. Peningkatan nilai koefisien perpindahan kalor dapat meningkatkan efisiensi energi

Experimental study of heat transfer coeffisient of two phases fluid flow that is water and air annulus pipe with counter current flow was examined. The vertical annulus pipe is made from copper with inner diameter 22.6 mm and the length is 1200 mm. In the middle of pipe, stainlees steel used as a core or center annulus with outer diameter 6.3 mm. The vertical annulus copper pipe is coiled by heater element with the length of flux heater element is 900 mm and seven thermocouples are attached to the pipe and gap annulus inside the wall of the pipe with each has the distance 136 mm. Water is pumped from the top planum of the pipe and air is injected by nozzle into the water stainless steel as center annulus pipe. Electrical flux are varied 812.62 W/m2, 1415 W/m2, 2239 W/m2, 3194 W/m2 and 4384 W/m2. From the result, phenomenon of bubble flow occurred during observation, heat flux coefficient tends to increase if air debit increase. Changing in heat flux coefficient also show reduction if water debit increase. Heat transfer coefficient maximum 2063 W/m2oC at ReSl 272.544 and ReSG 285. at electric heat flux 1415 W/m2. Increasing heat transfer coefficient can be resulting in high efficiency of energy.

Kata Kunci : Perpindahan kalor dua fasa berlawanan arah,Aliran gelembung, Heat Transfer Coefficient, Two Phases, Bubble Flow, Counter Current