Karakterisasi Perpindahan Panas Konveksi Alami Pada Elliptical Tubes Di Dalam Ronggga Asimetri Termal Dengan AR = 2,5; CR = 0,4 DAN 0,64;T ref. = 55oC, 65oC & 75oC SERTA PR = 3a

Laelyani, Nabila Amelita (2018) Karakterisasi Perpindahan Panas Konveksi Alami Pada Elliptical Tubes Di Dalam Ronggga Asimetri Termal Dengan AR = 2,5; CR = 0,4 DAN 0,64;T ref. = 55oC, 65oC & 75oC SERTA PR = 3a. Undergraduate thesis, Institut Teknologi Sepuluh Nopember.

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Abstract

Konveksi natural adalah sebuah fenomena penting yang banyak dijumpai. Aplikasi yang paling banyak dijumpai adalah pada kulkas yang menggunakan Kondensor tipe hot-wall yang dipasang di sisi dalam dinding terluar kulkas. Analisis dilakukan sebagai alternatif penggunaan elliptical tube sebagai pengganti tube lingkaran pada suatu heat exchanger. Aspect Ratio (AR) dari elliptical tube yang paling optimal adalah 2.5 dengan orientasi sumbu disusun mayor vertikal, didapat dari penlitian – penelitian terdahulu.
Variasi yang digunakan pada tugas akhir ini ada dua yaitu, variasi jarak Clearence Ratio, CR = x/Y dan Temperatur Termokopel Referensi, Tref. Parameter tetap yang digunakan dalah Pitch Ratio PR = St/a. Variasi CR adalah 0.4 dan 0.7 dan variasi Ts yaitu 55oC, 65oC dan 75oC sedangkan jarak PR adalah tetap yaitu 3. Susunan tiga tube di letakan didalam asymmetrical thermal cavity bebentuk balok yang didalamnya terdapat 3 sisi terinsulasi. Pemasangan kabel termokopel diletakan pada titik awal terjadinya plume, stagnasi aliran dan separation poin. Pengambilan data temperatur dilakukan menggunakan arduino dan ditampilkan secara simultan untuk setiap titik pengambilan data pada lembar kerja Excel. Metode perhitungan data dilakukan berdasarkan 3 korelasi perhitungan yaitu vertical flat plate, cavity, dan q” aktual.
Hasil penelitian menunjukan temperatur permukaan ellips tertinggi terjadi pada Tube 3 CR 0.4 – T ref. 75ºC saat α = 180º adalah 58.85 ºC, temperatur udara tertinggi terjadi diantara tube 1 dan 2 adalah 67.74 ºC dan selisih ΔT tertinggi terjadi pada Tube 2 CR 0.4 – T ref. 75 ºC saat α = 27º adalah 28.83 ºC. Nilai h lokal tertinggi berdasarakan korelasi vertical flat plate adalah 7.35 pada Tube 2 CR 0.4 – T ref. 75 ºC saat α = 27º, berdasarkan korelasi cavity adalah 7.86 pada Tube 3 CR 0.64 – T ref. 55 ºC saat α = 333º, dan q” aktual adalah 13.23 pada Tube 1 CR 0.64 – T ref. 55 ºC saat α = 27º. Perbedaan terbesar hasil h lokal terjadi antara korelasi vertical flat plate dan q” aktual perhitungan adalah 8.03 pada Tube 1 CR 0.64 – T ref. 55 ºC saat α = 0º. Selisih tersebut terjadi karena pada korelasi q” aktual ΔT berbanding terbalik dengan h lokal.
============= Natural convection is an important phenomenon that have been found. The most common application of this phenomenon is on refrigerators that use a hot-wall type condenser mounted on the inside of the outer wall of the refrigerator. The analysis was performed as an alternative of elliptical tubes utilization instead of circular tube on a Heat Exchanger. The most optimum aspect ratio (AR) of the elliptical tube is 2.5 with the major axis arranged vertically, obtained from previous research.
There were two variations used in this final project, which were, the Clearence Ratio distance variation, CR = x/Y and Thermocouple Reference Temperature, Tref. Pitch Ratio, PR=3a was used as a fixed parameter. The variation of CR had a value of 0.4 and 0.64 then the variation of T ref. had a value of 55oC, 65oC and 75oC. The three tubes array were placed inside the beam shaped asymmetrical thermal cavity which have 3 insulated walls inside. The thermocouple cables was positioned at the starting point of the plume, flow stagnation point and point of separation. Temperature data retrieval was performed using arduino and was displayed simultaneously for each point of data retrieval on the Excel worksheet. Data calculation method was done based on three empirical correlations that were vertical flat plate, cavity, and q "actual.
The result shows that the maximum elliptical surface temperature occured on Tube 3 CR 0.4 – T ref. 75ºC when α = 180º was 58.85 ºC, the maximum ambient air temperature occured between Tube 1 and Tube 2 was 67.74 ºC and the maximum temperature difference betwee ambient air and tubes surface ΔT was occurred on Tube 2 CR 0.4 – T ref. 75 ºC when α = 27º that was 28.83 ºC. The higest value of local h based on vertical flat plate correlation was 7.35 from Tube 2 CR 0.4 – T ref. 75 ºC when α = 27º, based on cavity correlation was 7.86 from Tube 3 CR 0.64 – T ref. 55 ºC when α = 333º, and based on q” actual correlation was 13.23 from Tube 1 CR 0.64 – T ref. 55 ºC when α = 27º. There was the maximum error result between calculation between vertical flat plate correlation and q” actual correlation which was 8.03. The error occurred because th calculation based on the q” actual correlation has the ΔT inversely proportional to local h.

Item Type:	Thesis (Undergraduate)
Uncontrolled Keywords:	Natural convection, elliptical tube, pitch ratio, clearance ratio, aspect ratio, cavity, Konveksi natural, elliptical tube, pitch ratio, clearance ratio, aspect ratio, cavity
Subjects:	T Technology > TJ Mechanical engineering and machinery > TJ263 Heat exchangers
Divisions:	Faculty of Industrial Technology > Mechanical Engineering > 21201-(S1) Undergraduate Thesis
Depositing User:	Nabila Amelita Laelyani
Date Deposited:	02 Aug 2018 03:57
Last Modified:	02 Aug 2018 03:57
URI:	http://repository.its.ac.id/id/eprint/57156

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