A fine wire of diameter D is positioned across a passage to determine flow velocity from heat transfer characteristics. The current is passed through the wire to heat it, and the heat is dissipated to the flowing fluid by convection. The resistance of the wire is determined from electrical measurements and the temperature is known from the resistance. For a fluid of arbitrary Prandtl number, develop an expression fro its velocity in terms of the difference between the temperature of the wire and free stream temperature of the fluid. What is the velocity of an airstream, in m/s at 1 atm and 25∘C, if a wire of 0.5 mm diameter achieves a temperature of 40∘C while dissipating 39 W/m?

Ashielded metal arc-welding operation is accomplished in a work cell by a fitter and a welder. the fitter takes 5.5 min to load components into the welding fixture at the beginning of the work cycle, and 1.5 min to unload the completed weldment at the end of the cycle. the total ength of the weld seams 1200 mm, and the travel speed used by the welder averages 300 mm/min. every 600 mm of seam length, the welding stick must be changed, which takes 0.8 min. while the fitter is working, the welder is idle (resting): and while the welder is working the fitter is idle. (a) determine the average arc-on time as a fraction of the work cycle time. (b) how much improvement in arc-on time would result if the welder used flux-cored arc welding (manually operated), given that the spool of weld wire must be changed every 10 weldments, and it takes the welder 5.0 min to accomplish the change? (c) what are the production rates for these two cases (weldments completed per hour)? attach your work and solutions.