Answer Happy

Name: Page 5 3. An oil cooler consists of a straight tube of 20 mm O.D. and a wall thickness of 2 mm enclosed within a pipe and concentric with it. The external pipe is well insulated. Oil flows through the tube at 0.05 kg/s, while cooling liquid flows in the annulus in the opposite direction at a rate of 0.1 kg/s (Cp = 4000 J/kg-K). The oil enters at 180°C and leaves at 80°C, while the cooling fluid enters at 30°C. It is known that the heat transfer coefficient of the water in the annulus is 4000 W/m²-K. Find the length of the cooler. Neglect: the resistance due to the tube wall and fouling the effect of entrance length and variable property effects The hot fluid properties are as follows: Cp=3561 J/kg-K, k = 0.380 W/m-K, μ = 2.172x10 kg/m-s, p = 1006 kg/m³. (20 points)