The air-conditioning system shown utilizes a 16-in diameter galvanized drainage pipe buried at a depth where the soil maintains the pipe surface at 60°f. air is forced through the pipe at a volumetric flow rate of 1200 cfm. the indoor air is maintained at a steady temperature of 72°f. if 63°f cooling air is desired, what length of pipe is required? what is the heat transfer? assume that the pipe has a roughness of 0.10 inch. how can the length of pipe be reduced and still achieve the same heat transfer?

Aloaded platform of total mass 500 kg is supported by a dashpot and by a set of springs of effective stiffness 72 kn/m. it is observed that when the platform is depressed through a distance x = 12.5 cm below its equilibrium position and then released without any initial velocity; it reaches its equilibrium position in the shortest possible time without overshoot. find the position and velocity of the loaded platform 0.10 sec. after its release. if a further load of 400 kg is added to the platform, find, i) the frequency of damped vibrations, and i) the amplitude of vibration after 2 complete oscillations, given that the initial amplitude is 15 cm.