A 6-in.-OD pipe is buried with its centerline 50 in. below the surface of the ground [k of soil is 0.20 Btu/(h ft ?F)]. An oil having a density of 6.7 lb/gal and a specific heat of 0.5 Btu/(lb ?F) flows in the pipe at 100 gpm. Assuming a ground surface temperature of 40?F and a pipe wall temperature of 200?F, estimate the length of pipe in which the oil temperature decreases by 10?F.GIVENAn oil filled pipe buried below the surface of the groundPipe outside diameter (D) = 6 in. = 0.5 ftDepth of centerline (z) = 50 in.Thermal conductivity of the soil (k) = 0.20 Btu/h ft ?FSpecific gravity of oil (Sp. Gr.) = 0.8Specific heat of oil (cp) = 0.5 Btu/lb ?FFlows rate of oil m = 100 gpmThe ground surface temperature (Ts) = 40?FThe pipe wall temperature (Tp) = 200?FASSUMPTIONSSteady state conditionTwo dimensional heattransfer

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T-40°F Z- 50 In. D= 6 In. To- 200°F