Pengujian Karakteristik Perpindahan Panas dan Penurunan Tekanan dari Sirip-Sirip Pin Diamond Susunan Segaris dalam Saluran Segiempat

This research was conducted to investigate the characteristics of heat transfer and pressure drop as well as the thermal performance of diamond pin fin array in the rectangular channel which air was passed through it as coolant fluid. The pin fins were arranged in inline manner. Dimension of base plate in which pin fins attached was 150 mm x 200 mm x 6.5 mm. The average temperature of base plate surface was kept constant at 60oC. Pin fins were made of duralumin having the dimension of  75 mm of height, its sides 12.7 and 12.7 mm respectively, and the distance inter-fin picth in the spanwise direction was kept constant at Sx/D = 2.95. The parameters of this research were Reynolds number (Re) 3,123 – 37,847 based on averaged inlet air velocity and hydraulic diameter, and the distance between the inter-fin pitch in the streamwise direction (Sy/D = 1.97 – 3.94). The research result  shown that increasing Reynolds and decreasing the distance Sy/D increased Nusselt number, that means increased heat transfer rate where it reach maximum at Sy/D = 2.36. The values of pressure drop (DP) and friction factor (f) decreased with increasing Sy/D. The value of the thermal performances (h) varied between 0.77 – 1.22. At Sy/D = 1.97 for Re > 25,000, and Sy/D = 3.94 for all values of Re, the values of h were less than 1, i.e. the used of diamond pin fin would cause an energy loss rather than gain. The net energy gain (h was greater than 1) was only at Sy/D = 1.97 for Re < 18,830, Sy/D = 2.36 for Re < 25,000 and at Sy/D = 2,95 for Re < 3,150. Increasing Reynolds number would decrease the thermal performance (h) for all Sy/D. A net energy gain up to 22% was achieved for Sy/D = 2.36 and Re = 3,123. Keywords: diamond pin fin, Reynolds number, friction factor, thermal performanc

STUDI EKSPERIMENTAL TENTANG PENGARUH VARIASI RAPAT ARUS PADA HARD CHROME ELECTROPLATING TERHADAP KARAKTERISTIK PERMUKAAN BAJA KARBON RENDAH

The objective of the research is to investigate the effect of  hard chrome electroplating on low carbon steel surface characteristic. This experimental research used low carbon steel as  material  that has been coated by hard chrome electroplating,  chromium powder, and Pb alloy as cathode.  The instrument for the research were rectifier, hardness testing machine LECO M-400-H1, optical microscope and  digital camera. This research had been performed by making variation of current ((15 A/dm2, 30 A/dm2, 45 A/dm2 and  60 A/dm2).The result of this research shows that the maximum hardness of low carbon steel after coated by hard chrome electroplating was 576,50 VHN, when hard chrome electroplating had been performed on current 45 A/dm2. Beside that, on the same current (45 A/dm2) also gained maximum chrome layer (38,65 µm).Keywords: low carbon steel, hard chrome electroplating, hardness,  deep of coated