Question

Tomato soup is flowing through a double-pipe heat exchanger (3 cm ID, 4.2 cm OD), with saturated steam at 112°C on the outside of the pipe. The convective heat transfer coefficient between the soup to the pipe is 323 W/m² K and the convective heat transfer coefficient between the steam to the pipe is very large. The thermal conductivity of the soup and pipe are 0.89 W/m K and 15.6 W/m K, respectively.

1. For this system:

A. The overall heat transfer coefficient for the inside of the pipe is smaller than the overal heat transfer coefficient for the outside of the pipe

B. Since the convective heat transfer coefficient between the steam and the pipe is very large, U=h_i

_C. The steam provides heat by converting from vapor to liquid

D. The log mean temperature difference for co-current and counter-current flow are the same, regardless of the inlet and outlet temperatures of the soup

2.The temperature of the soup at a certain point in the pipe is 55°C. If the pipe wall is at the same temperature as the steam, what is the rate of heat transfer between the pipe wall and the soup in kW/m²?

3. If the heat exchanger is 70 m long, what is U_i?

Answer 1