Flux-cored arc-welding is used to butt weld two austenitic stainless steel plates together. The welding voltage = 20 volts, and the current = 175 amps. The cross-sectional area of the weld seam = 45 mm2 , and the melting factor of the stainless steel = 0.60. Using tabular data and equations in this and the preceding chapter, determine the value for travel speed in the operation.

To save energy, the air supply to a 2000 ft office has been shut off overnight and the room temperature has dropped to 40°f. in the morning, the thermostat is reset to 70°f and warm air at 120 f begins to flov in at 200ft'/min. the air is well mixed within the room, and an equal mass flow of air at room temperature (changing with time) is withdrawn through a return duct. the air pressure is nearly 1 atm everywhere. ignoring heat transfer with the surroundings and kinetic and potential energy effects, estimate how long it takes for the room temperature to reach 70°f. plot the room temperature as a function of time.