To cool a summer home without using a vapor compression refrigeration cycle, air is routed through a plastic pipe (k=0.15 w/m*k, d_inner=0.15m, d_outer=0.17m) that is submerged in an adjoining body of water. the water temperature is nominally at t_infinity=17 degrees celsius and has a convection coefficient of h=1500w/m^2*k is maintained at the outer surface of the pipe. if air from the home enters at t_m, i=29 degrees celsius and a volumetric flow rate of v_i=0.025 m^3/s, what pipe length, l, is needed to provide a discharge temperature of t_m, o=21 degrees celsius?

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?