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Heat transfer

Choose the correct answer Water flows at 20°C at 8kg through the diffuser having 3 cm diameter at the entrance and 70 cm diameter at its ext. The fluid Reynolds number at the inlet and *edit of the diffuser are 336105143530 337105.144530 338105, 145530 ооооо Not all the above 339105.146530 5 A fan provides air speed upto 8 50 m/s. is used in low speed wind tunnel with atmospheric arat 27°C. If this wind tunnel is used to study the boundary layer behaviour over a flat plate upto Re = 10'6. What should be the minimum plate length ? At what distance from the leading edge would transition occur.if critical Reynolds number is (Re)critical * ?x105 31.72 m, 0.159 31.92 m, 0.150 m Not all the above ооооо 31.82m 0.150 m 32 m, 0.17 m. US The temperature of road (9 surface at 9 am was S'C to a good depth. From 9am to 12 noon the surface is exposed to solo radiation of 650 Wim2 of which 0.4 times is absorbed. Determine the temperature at a depth of 4 cm. (Thermal diffusivity) = 3.26 *.10-7m2/s, -0.552 Wink 37.8°C. O 39°C. O Not all the above ооооо 40°C 38.6°C. O

Answer 1

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Di = 3cm = 0.03m. Entry 0.07 m V 1 2 At I D Exit D2 = 7cm = in = 8kg/s Density of water 3 = 1000 kg/m3 20°c, Dynamic viscosity of water 4= 1.0024103 Pa.s crossection area of diffeuses at entry and exit are А, 4 = 7.068X104. 3.848 810 4 And mass flow rate is given in = SANI = SA₂ V₂ velocity of flow at entry and exit m 8 -4 = 11.3186 m/s SAI 1000x 7.068x10 A DE 4 T(0:03) m2 2 Az m2 = m V2 8 2.078 m/s SAL 1000 x 3-848 X10-3 therefore Re, M Reynolds number at we inlet and exit are SV,DI lood x 11. 3186 X 0.03 338880.8 1.002 x 103 3V₂D₂ looo x 2.078 X 0.07 = 145169.66 M 1.002 x 10 Rez 3 Choose Not all the above