3.48 A thin electrical heater is wrapped around the outer sur- face of a long cylindrical tube whose inner surface is maintained at a temperature of 5°C. The tube wall has inner and outer radii of 25 and 75 mm, respectively, and a thermal conductivity of 10 W/m K. The thermal con- tact resistance between the heater and the outer surface of the tube (per unit length of the tube) is R = 0.01 m K/W. The outer surface of the heater is exposed to a fluid with To = -10°C and a convection coefficient of h= 100 W/m² K. Determine the heater power per unit length of tube required to maintain the heater at T, = 25°C.

5) Which statement is true about the friction factor in the Moody diagram (shown below). Moody Diagram 0.1 0.09 Transition Region 0.08 0.07 0.05 0.04 0,06 0.03 0.05 0.02 0.04 0.015 0.01 0.03 0.005 0.002 0.001 5x10-4 2x10-49 10-4 5x10-5 10-5 5x10-6 10-6 Friction Factor 12---- Laminar Flow 64 Material Concrete, coarse 0.25 0.025 Concrete, new smooth Drawn tubing 0.0025 Glass, Plastic Perspex 0.0025 Iron, cast 0.15 Sevens, old 3.0 0.1 Steel, mortar lined Steel, rusted 0.5 Stoel, structural or forgod 0.025 Water mains, old Friction Factor=AP. 1.0 Smooth Pipe 3000 10³ 10¹ 105 106 107 108 Reynolds Number, Re - Vd P a) The lines for different relative roughness in the turbulent regime correspond to Darcy-Weisbach model b) The lines for different relative roughness in the turbulent regime correspond to Nikuradse model c) The lines for different relative roughness in the turbulent regime correspond to Hazen-Williams model d) The lines for different relative roughness in the turbulent regime…

(i) A pump manufacturing company has to assemble bearing on the shaft in large quantities. The time study shows 134 seconds as an observed time for the assembly operation. Determine the standard time with fatigue and personal allowance as 8% and 5%respectively. Level factor for this time study is 0.8.

What is the scale of this diagram? 1cm to what?