Answer Happy

A 10 cm outer diameter copper pipe is used in a heat exchanger. The pipe wall is 0.5 cm thick and the pipe is 2 m long. Water at a mean temperature of 27°C flows into the pipe. The water mean inlet velocity in the pipe is 10 m/s. Because of lack of maintenance, a 2 cm thick scale has formed inside the pipe, similar to the illustration below. Steam at 100ºC flows over the pipe, and its associated convection coefficient is 600 W/m²K. Assume all water properties can be approximated as water properties at 300K. Assume the scale thermal conductivity is kscale = 5 W/ mK and that the copper thermal conductivity is kcopper = 350 W/m.K a) Draw the equivalent thermal circuit b) Evaluate the convection coefficient of the internal flow c) Calculate the exit mean temperature of the water