Reference no: EM131512467

Question: Computer analysis of Prob. with to=f(x) and constant fluid properties: Calculate the flow, starting with inital conditions of flat velocity and temperature profiles at the inlet. Compare the computer results with the analytical results.

Problem: Let air at 21°C and 1 atm pressure flow at a Reynolds number of 50,000 in a 2.5 cm diameter circular tube. The tube wall is insulated for the first 75 em, but for the next 125 cm the tube surface temperature is constant at 40°C. Then it abruptly increases to 50°C and remains constant for another 125 cm. Plot the local heat-transfer coefficient h as a function of an axial distance. Does the abrupt increase in surface temperature to 50°C cause a significant change in the average heat-transfer coefficient over the entire 250 cm of heated length? In simple heat-exchanger theory a mean heat-transfer coefficient with respect to tube length is generally employed. In this case how much does the mean differ from the asymptotic value of h?