During the daytime, water is drawn from an upper reservoir and is run through a turbine on its way to a lower reservoir in order to produce power for a town. At night, the water is pumped back up to the upper reservoir in order to replenish the upper reservoir. Assume that the heat loss rate due to friction is 65 hp (going either up or down) and that the internal energy change is negligible. Required:
a. Find the power extracted by the turbine if the downward volume flow rate is 15,000 gallons per minute.
b. What would the upward volume flow rate have to be in order for the system to "break even"?

A3-mm-thick panel of aluminum alloy (k 177 w/m-k, c 875 j/kg-k and ? = 2770 kg/m) is finished on both sides with an epoxy coating that must be cured at or above t,-150°c for at least 5 min. the production line for the curing operation involves two steps: (1) heating in a large oven with air at ts,0-175°c and a convection coefficient of h, 40 w/m2. k, and (2) cooling in a large chamber with air at 25°c and a con- vection coefficient of he 10 w/m2.k. the heating portion of the process is conducted over a time interval te which exceeds the ime required to reach 150°c by 5 min (h = r + 300 s). the coating has an emissivity of ? = 0.8, and the temperatures of the oven and chamber walls are 175 and 25°c, respectively. if the panel is placed in the oven at an initial temperature of 25°c and removed from the chamber at a safe-to-touch tempera ture of 37°c, what is the total elapsed time for the two-step curing operation?