Setiawan, Angga Tegar (2019) Studi Numerik Dan Eksperimental Perpindahan Panas Konveksi Alami Pada Elliptic Tubes Axis Ratio 2.5 di dalam Rongga Asimetrik Termal dengan Variasi Pitch Ratio dan Clearance Ratio. Masters thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Perpindahan panas konveksi alami atau free convection dalam rongga asimetri termal dipengaruhi oleh perbedaan temperatur antara sumber panas dan dinding rongga, jarak antara sumber panas dan dinding rongga, serta jarak antar sumber panas. Sumber panas dapat dihasilkan dari suatu bluff body yang ditempatkan di dalam rongga. Penelitian ini menggunakan cylindrical tube berpenampang elips (elliptical tube) yang dipanaskan sebagai sumber panas di dalam rongga. Elliptical tube memiliki aspect ratio (AR) 2,5 yaitu nilai perbandingan antara major axis (2a) dan minor axis (2b) sebuah penampang ellipse > 1. Penelitian ini menggunakan tiga horizontal elliptical tubes yang disusun secara vertikal sebagai sumber panas. Panas dalam elliptical tubes dibangkitkan oleh elemen pemanas listrik yang menghasilkan fluks panas seragam 11.870 Watt/m2 dan temperatur permukaan tube dipertahankan pada variasi 55, 65 dan 75 oC. Asimetri termal rongga terbentuk karena tiga sisi rongga terinsulasi sementara satu sisi lainnya terpapar konveksi dengan udara ruang.
Parameter jarak susunan tube ke dinding terinsulasi atau clearance ratio (CR) divariasikan sebesar x/y = 0,4 dan x/y = 0,6 dengan x adalah jarak susunan tube terhadap dinding terinsulasi sedangkan y adalah lebar rongga yang bernilai enam kali minor axis (12b). Sementara itu jarak antartabung (pitch ratio) divariasikan sebesar PR = 2,5a, PR = 3a, dan PR = 3,5a. Penelitian ini akan menganalisis karakteristik perpindahan panas yang terjadi dari permukaan elliptical tube ke udara di sekitarnya secara eksperimen dan numerik.
Dari hasil penelitian diperoleh perpindahan panas konveksi alami yang baik pada CR 0.4 jika dibandingkan dengan CR 0.6. Hal ini juga ditunjukkan pada kontur distribusi temperatur cavity pada CR 0.6 cenderung lebih memiliki gradien temperatur tinggi yang lebih luas. Selain itu, PR 3.5a memiliki nilai koeffisien konveksi paling baik jika dibandingkan dengan yang lain. Hal ini juga ditunjukkan pada kontur distribusi temperatur cavity yang cenderung memiliki gradien temperatur tinggi yang lebih sempit. Selain itu, vektor kecepatan pada CR 0.4 cenderung lebih tinggi jika dibandingkan dengan CR 0.6. hal ini menunjukkan beda temperatur yang tinggi pada CR 0.4 menyebabkan fluida lebih cepat bergerak sehingga perpindahan panas konveksi alami cenderung lebih baik. Dari semua variasi CR maupun PR yang telah dilakukan, perpindahan panas konveksi alami yang paling baik terjadi pada PR 3.5a dan CR 0.4.
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Natural convection heat transfer or free convection in the cavity of thermal asymmetry is influenced by temperature differences between the heat source and cavity wall, the distance between the heat source and the cavity wall, and the distance between the heat source. The source of heat can be produced from a bluff body placed inside the cavity. This research uses cylindrical elliptical tube which is heated as a heat source inside the cavity. Elliptical tube has aspect ratio (AR) 2.5, which is the value of a comparison between the major axis (2a) and the axis minor (2b) a cross section of the ellipse > 1. This study uses three horizontal elliptical tubes arranged vertically as heat sources. Heat in the elliptical tubes is generated by an electric heating element which produces a uniform heat flux of 11,870 Watt/m2 and the surface temperature of the tube is maintained in variations of 55, 65 and 75 oC. The thermal asymmetry of the cavity is formed because three sides of the cavity are insulated while the other side is exposed to convection with space air.
The parameters of the distance of the tube arrangement to the insulated wall or the clearance ratio (CR) are varied by x/y = 0.4 and x/y = 0.6 with x is the distance of the tube arrangement to the insulated wall while y is the width of the cavity which is worth six times the axis minor (12b). While the distance between the pitches (pitch ratio) varied by PR = 2.5a, PR = 3a, and PR = 3.5a. This study will analyze the characteristics of heat transfer that occurs from the surface of the elliptical tube to the surrounding air experimentally and numerically.
From the results of the study obtained a good natural convection heat transfer in CR 0.4 when compared with CR 0.6. This is also shown in the contour of the 0.6 0.6 cavity temperature distribution which tends to have a wider high temperature gradient. In addition, PR 3.5a has the best convection coefficient value compared to the others. This is also shown in the contours of cavity temperature distribution which tend to have narrower high temperature gradients. In addition, speed vectors in CR 0.4 tend to be higher when compared to CR 0.6. this shows that the high temperature difference in CR 0.4 causes the fluid to move faster so that natural convection heat transfer tends to be better. Of all the CR and PR variations that have been done, the best natural convection heat transfer occurs in PR 3.5a and CR 0.4.
| Item Type: | Thesis (Masters) |
|---|---|
| Additional Information: | RTM 621.402 5 Set s-1 2019 |
| Uncontrolled Keywords: | free convection, natural convection, elliptical tube, aspect ratio, vertical cavity, clearance ratio, pitch ratio. |
| Subjects: | T Technology > TJ Mechanical engineering and machinery T Technology > TJ Mechanical engineering and machinery > TJ263 Heat exchangers |
| Divisions: | Faculty of Industrial Technology and Systems Engineering (INDSYS) > Mechanical Engineering > 21101-(S2) Master Thesis |
| Depositing User: | Angga Tegar Setiawan |
| Date Deposited: | 19 Nov 2021 17:37 |
| Last Modified: | 19 Nov 2021 17:37 |
| URI: | http://repository.its.ac.id/id/eprint/61419 |
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