Aspherical gas-storage tank with an inside diameter of 7.9 m is being constructed to store gas under an internal pressure of 1.79 mpa. the tank will be constructed from steel that has a yield strength of 275 mpa. if a factor of safety of 3.1 with respect to the yield strength is required, determine the minimum wall thickness tmin required for the spherical tank.

Apipe with an outside diameter of 15 cm is exposed to an ambient air and surrounding temperature of -20°c. the pipe has an outer surface temperature of 65°c and an emissivity of 0.85. if the rate of heat loss from the pipe surface is 0.95 kw per meter of length, the external convective heat transfer coefficient (h) is: (a) 12.5 w/m"k (b) 18.6 w/mk (c) 23.7 w/mk (d) 27.9 w/mk (e) 33.5 w/mk