heat sheet2 dr solved problm ahmedawad
DESCRIPTION
' MANF 475: Heat TransferNew Engineering ProgramsManufacturing DePartmentDr. GamilW. YounanSheet (2): Conduction Heat Transfer From Extended Surfacesi.. A very long copper rod (k=372 W/m.K) 22mm in diameter has one end maintained at90"C. The rod is exposed to a fluid whose temperature is 40"C and h=3'5W/^'.X.How much heat is lost by the rod. 5' t r\ -Z. Two long copper rods (k=380 Wm.K) of 10mm diameter are soldered together endto end with solder having a melting point of 650"C. The rods are in the air at T-=25"Cand h=10 W/m2.K. Calculate the minimum power input needed to effect thesoldering.3. lTwo copper rods having 10mm diameter and length of 150mm and 300mmhaving melting point at 650"C. The two rods are exposed to ambient temperatureT*=25"C and h=10 W/m2.K. Neglecting the heat transfer from rod ends (tips)calculate the minimum power input needed to affect the solder and determine thetemperature at the free ends of the rod.4. One end of a circular poker is places in a fire. The poker is made of steel (k=55W/m.K)and it has a diameter of 10mm. The end of the poker in the fire is 350"C, the airaround the poker is at 80"C with h=25 W/m2.f. lf the length of the poker betweenthe fire and the hanille is 0.6m Iong, calculate the temperature of the handle of thepoker.- 5. A very long pin fin of 5mm diameter has a base temperature of 200oC. The pin\* surrounding surface is exposed to air at 25o C with h=100 W/m2.tloss througt rf,u fin and the fin effectiveness. Also estimate how long the fin musthave to be making assumption of "Very Long Fin " yields to accurate estimation forheat loss calculation. Take for fin material k=335 W/m'K.6. A straight fin of rectangular profile is made of stainless steel (k=L6.3 W/m.K), has alength of 75mm and 2.5mm thickness. The base temperature is maintained at l-00"Cwhile the fin is exposed to ambient temperature T-=20"C with h=45 W/m2.K.Calculate the heat loss by the fin per meter width, the fin effectiveness. Alsocalculate the tip temperature of the fin, consider the end is adiabatic tip.7. ln an arrangement for measuring the thermal conductivity of solid material, a longrod lraving diameter of 25mm is introduced inside a furnace such that half of it wasinside the furnace, while the other half extended hori,zontally in ambient air at 25"Ctemperature was found to be 150"c and 90"c respectively a while the two points are at distance of 75mm from each other. Find the thermal conductivity of the rod material.B' consider two long solid rods A and B of same diameter but different materiars. one end of each rod is attached to the same base surface maintained at 100-c while the surfaces of the rods are exposed to air at 20"c. By traversing the length of each rod with thermocouples, it was observed that the temperature of the rods were equal at positions Xn=15cm and Xr=/.5cm, where X is measured from the base surface.- If kn=70 W/m.K, determine ks9' A brass srab is 20mm thick (k=110 w/m.K) has gases on one side Tr=560"c with hr=15wm2'K, whire a riquid frows on the other side which Tz=40"C with hz=Zaoow/m''K' calculate the rate of heat transfer from the gases to the liquid through the bare slab. lt is advised to add brass fins of 1mm thick, 10mm long and 10mm apart on centers to increase the heat transfer rate from;;;, to liquid. Determine where better to add these fins (on gases side or on liquid side)? And calculate the percent increase in the heat transfer rate for the better ."ru .nor"n.10' Determine the percentage increase in heat transfer rate associated with attaching aluminium fins (k=237 w/m.K) of rectangular profile to plane wall. The fins are 50mm long' 0'5mm thick and are equally spaced at distance of 4mm (250 fins/meter). The convection coefficient with the base wail is 40 w/mr.K, whire tt,rt *itn fins is 30 w /m2.x11' An annular fins of rectangular cross section surrounds at 25mm outer tube diamTRANSCRIPT
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