Assignment Chapter 6 Sol PDF

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ME-531 HEAT TRANSFER – I

7th of July 2020

Assignment Chapter 06

Instructor:

Student:

Dr. Ahmad Abbas

Ahsan Tanveer

AP FME, GIKI, Swabi.

ME-1959

Questions 6–11 The upper surface of a 50-cm-thick solid plate (k=237 W/m·K) is being cooled by water with temperature of 20°C. The upper and lower surfaces of the solid plate maintained at constant temperatures of 60°C and 120°C, respectively. Determine the water convection heat transfer coefficient and the water temperature gradient at the upper plate surface. 6–17 A metal plate is being cooled by air (kfluid=0.259 W/m·K) at the upper surface while the lower surface is subjected to a uniform heat flux of 1000 W/m2. Determine the temperature gradient in the air at the upper surface of the metal plate. 6–18 The top surface of a metal plate (kplate=237 W/m·K) is being cooled by air (kair=0.243 W/m·K) while the bottom surface is exposed to a hot steam at 100°C with a convection heat transfer coefficient of 30 W/m2·K. If the bottom surface temperature of the plate is 80°C, determine the temperature gradient in the air and the temperature gradient in the plate at the top surface of the plate.

6–38 Consider fluid flow over a surface with a velocity profile given as

Determine the shear stress at the wall surface, if the fluid is (a) air at 1 atm and (b) liquid water, both at 20°C. Also calculate the wall shear stress ratio for the two fluids and interpret the result. 6–45 Consider fluid flowing with a free stream velocity of 5 m/s over a flat plate, where the critical Reynolds number is 5x105 . Determine the distance from the leading edge at which the transition from

laminar to turbulent flow occurs for air (at 1 atm), liquid water, methanol, and engine oil, all at 20°C, and mercury at 25°C. 6–58 Consider a 5-cm-diameter shaft rotating at 4000 rpm in a 25-cm-long bearing with a clearance of 0.5 mm. Determine the power required to rotate the shaft if the fluid in the gap is (a) air, (b) water, and (c) oil at 40°C and 1 atm....