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255 One end of a long rod 3 cm in diameter is inserted into a furnace...

255 One end of a long rod 3 cm in diameter is inserted into a furnace with the (3 outer end projecting into the outside air.

255 One end of a long rod 3 cm in diameter is inserted into a furnace with the (3 outer end projecting into the outside air. Once the steady state is reached the temperature of the rod is measured at two points, 15 cm apart and found to be 140°C and 100°C, when the atmospheric air is at 30°C with convection coefficient of 20 W/m2.K. Calculate the thermal conductivity of *.the rod material جابت 265 Consider a stainless steel spoon(k = 15.1 W/m.K), partially immersed in the (4 boiling water at 95°C in a kitchen at 25°C. The handle of the spoon has a cross-section 0.2 cm x 1 cm and it extends 18 cm in the air from the free surface of the water. If the heat transfer coefficient on the exposed surface of the spoon is 15 W/m2.K, calculate the temperature difference across the exposed surface of the spoon handle. The spoon handle may be treated as a * fin of insulated tip جاتے دند A hot surface at 100°C is to be cooled by attaching 3 cm long. 0.25 cm (5 diameter aluminium fins(k = 237 W/m.K) to it, with a centre to centre distance of 0.6 cm. The temperature of surrounding air is 30°C and heat transfer coefficient on surface is 35 W/m2.K.Calculate the rate of heat transfer from the surface for almx 1m section of the plate. Also determine the overall * .effectiveness of the fins إجان
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91 Given Tooh Т. Tz . do 3cm a 0.03 m Ti= 140 c Taa luoc K To 0.5m X2-x,= 15cm-0.15m ha 20w1m²K Too = 30°c To find Thermal coT-To (x) T-T m “Х Ti-To ., m (x2-x ) г Т2-Т-140-30 0.15 X m. 100-30 0.15xm: en (40)= 0.45198 : mo 3,013 4h kd 4 x 20 KX0.03 = (3.0133² Ans.t- :. k = 293.7 w/mk

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