Ga copper pipe (kc = 400 w/m·k) with inner diameter of 20 mm and wall thickness of 0.025 m is used for carrying liquid oxygen to a storage tank. the liquid oxygen flowing in the pipe has an average temperature of -200°c and a convection heat transfer coefficient of 120 w/m2·k. the condition surrounding the pipe has an ambient air temperature of 20°c and a combined heat transfer coefficient of 20 w/m2·k. if the dew point is 10°c, determine the thickness of the insulation (ki = 0.05 w/m·k) around the copper pipe to avoid condensation on the outer surface. assume thermal contact resistance is negligible.

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.