Chapter 11, Problem 11.43P

A shell-and-tube heat exchanger (1 shell pass, 2 tubepasses) is to be used to condense 2.73 kg/s of saturatedsteam at 340 K. Condensation occurs on the outer tubesurfaces, and the corresponding convection coefficient is $10,000{\text{ W/m}}^2\cdot \text{K}$ . The temperature of the cooling water entering the tubes is $15°C$ , and the exit temperature is not to exceed $15°C$ . Thin-walled tubes of 19-mm diameter are specified, and the mean velocity of waterflow through the tubes is tobe maintained at 0.5 m/s.

1. What is the minimum number of tubes that shouldbe used, and what is the corresponding tube lengthper pass?
2. To reduce the size of the heat exchanger, it is proposed to increase the water-side convection coefficient by inserting a wire mesh in the tubes. If themesh increases the convection coefficient by a
   factor of two, what is the required tube length perpass?