Cold conditioned air at 12°C is flowing inside a1.5-cm-thick square aluminum (k 5 237 W/m·K) duct ofinner cross section 22 cm 3 22 cm at a mass flow rate of0.8 kg/s. The duct is exposed to air at 33°C with a combinedconvection-radiation heat transfer coefficient of 13 W/m2·K. The convection heat transfer coefficient at the inner surfaceis 75 W/m2·K. If the air temperature in the duct should notincrease by more than 1°C determine the maximum length ofthe duct.

Ahouse has the following electrical appliance usage (1) single 40w lamp used for 4 hours per day (2) single 60w fan used for 12 hours per day (3) single 200w refrigerator that runs 24 hours per day with compressor run 12 hours and off 12 hours find the solar power inverter size in watt with correction factor of 1.25.

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.

Fluids at rest possess no flow energy. a)- true b)- false