Part A: A single pass heat exchanger has 12 tubes that are 1 cm inside dia x 1 m long. A fluid is flowing through the tubes at the rate of 50 L/min. At its mean fluid temperature, the density and viscosity of the fluid are 0.9 g/mL and 0.8 cP. Calculate the Reynolds number for the flow. 10 pts.

Part B: A counter current single-pass shell and tube heat exchanger is used to recover heat from a wastewater stream in a commercial facility. Table 1 displays performance of the heat exchanger.

Table 1: Performance of the single pass shell and tube heat exchanger STREAM - Temperature, oC Waste water hot stream in - 140 C Waste water hot stream out - 100 C Process water cold stream in - 30 C Process water cold stream out - 60 C

Your supervisor feels there is opportunity to recover more heat from the waste stream. To save on engineering cost, s/he prefers adding an identical heat exchanger in series to the existing heat exchanger. How would the change affect the overall heat transfer coefficient U, the area for heat exchange and the log mean temperature difference? The possible ranges, A-D, for the proportional change in the rate of heat transfer, Q, are listed below

A: / 1 : 1 < /< 2 : / = 2

: 2 < / Choose the right answer and justify it qualitatively. Assume the fluid properties do not vary over the temperature range/