After heat treatment, the 2-cm-thick metal plates
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HEAT+MASS TRANSFER:FUND.+APPL.(LOOSE)
- 7.43 Liquid sodium is to be heated from 500 K to 600 K by passing it at a flow rate of 5.0 kg/s through a 5-cmID tube whose surface is maintained at 620 K. What length of tube is required?arrow_forwardIn the effort to find the best way to cool a smooth thin-walled copper tube, an engineer decided to flow air either through the tube or across the outer tube surface. The tube has a diameter of 6 cm, and the surface temperature is maintained constant. Determine the convection heat transfer coefficient when air is flowing through a thin-walled tube at 25 m/s with bulk mean temperature of 50°C. _____ w/m^2karrow_forwardTo cool a storehouse in the summer without using a conventional air-conditioning system, the owner decided to hire an engineer to design an alternative system that would make use of the water in the nearby lake. The engineer decided to flow air through a thin smooth 10-cm-diameter copper tube that is submerged in the nearby lake. The water in the lake is typically maintained at a constant temperature of 15°C and a convection heat transfer coefficient of 1000 W/m2?K. If air (1 atm) enters the copper tube at a mean temperature of 30°C with an average velocity of 2.5 m/s, determine the necessary copper tube length so that the outlet mean temperature of the air is 20°C.arrow_forward
- Determine the convection heat transfer coefficient (in W/m2∙K) for the flow of water at a velocity of 5 m/s in an 8-cm-diameter and 10-m-long tube when the tube is subjected to uniform heat flux from all surfaces. The tube is maintained at a constant temperature of 95°C. Take the properties of water at 25°C. For water at 25°C: ρ = 997 kg/m3; cp = 4180 J/kg∙K; k = 0.607 W/m∙K; ? = 0.891×10-3 kg/m∙sarrow_forwardAir enters a 20-cm-diameter 12-m-long underwater duct at 50°C and 1 atm at a mean velocity of 7 m/s, and is cooled by the water outside. If the average heat transfer coefficient is 85 W/m2 °C and the tube temperature is nearly equal to the water temperature of 5°C, determine the exit temperature of air and the rate of heat transferarrow_forwardThe nose section of the rocket is made up of a 6 mm thick stainless steel plate (p = 7800 kg/m°, c = 460 J/kg°C, k = 55 W/m°C). It is held initially at a uniform temperature of " T = 47°C. When the rocket enters the denser layers of the atmosphere at a very high velocity the effective temperature of the air surrounding the nose region attains the value 2150 °C; the surface convective heat transfer coefficient is estimated as 3395 W/m?°C. If the maximum metal temperature is not to exceed 1100°C, determine: (i) Maximum permissible time in these surroundings. (i) Inside surface temperature under these conditions.arrow_forward
- Engine oil enters a straight tube with a flow rate of 1 kg/s. The tube has a diameter of 5 mm and the surface temperature of the tube is maintained at 150˚C. The engine oil has an inlet temperature 52˚C and it is desired to heat the oil to a mean temperature of 80˚C at the exit of the straight tube. The properties of the engine oil are k = 0.139 W/m.K, Pr = 834, cp = 2072 J/kg.K and μ = 5.62 x 10-2 N.s/m2 Assume the flow is at fully developed region, determine:(a) The required length of the tube. (b) The rate of heat transfers from the tube to the engine oil.arrow_forwardHot engine oil at 150°C is flowing in parallel over a flat plate at a velocity of 3.30 m/s. Surface temperature of the 1.800-m long flat plate is constant at 50°C. The properties of engine oil at Tf = (150°C + 50°C)/2 = 100°C are k = 0.1367 W/m∙K, v = 2.046 × 10−5 m2/s, Pr = 279.1. Determine the local convection heat transfer coefficient at 0.200 m from the leading edge and the average convection heat transfer coefficient. The local convection heat transfer coefficient at 0.200 m from the leading edge is ___ W/m2·K. The average convection heat transfer coefficient is ___ W/m2·K.arrow_forwardPulverized coal particles are used in oxy-fuel combustion power plants for electricity generation. Consider a situation where coal particles are suspended in hot air flowing through a heated tube, where the convection heat transfer coefficient is 100 W/m2·K. If the average surface area and volume of the coal particles are 3.1 mm2 and 0.5 mm3, respectively, determine how much time it would take to heat the coal particles to two-thirds of the initial temperature difference.arrow_forward
- Layers of 23 cm-thick meat slabs ( k = 0.47 W/m*C and a=0.13*10 m/s) initially at a uniform temperature of 7 C are to be frozen by refrigerated air at -30 C flowing at a velocity of 1.4 m/s. the average heat transfer coefficient between the meat and the air is 20 W/m*C. Assuming the size of meat slabs to be large relative to their thickness, determine how long it will take for the center temperature of the slabs to drop to -18 C, Also, determine the surface temperature of the meat slab at that timearrow_forwardA cylindrical fuel rod of 2 cm in diameter is encased in a concentric tube and cooled by water. The fuel generates heat uniformly at a rate of 150 MW/m3. The convection heat transfer coefficient on the fuel rod is 5000 W/m2∙K, and the average temperature of the cooling water, sufficiently far from the fuel rod, is 70°C. Determine the surface temperature of the fuel rod and discuss whether the value of the given convection heat transfer coefficient on the fuel rod is reasonable.arrow_forwardHot air at atmospheric pressure and 80°C enters an 8-m-long uninsulated square duct of cross section 0.2 m * 0.2 m that passes through the attic of a house at a rate of 0.15 m3/s . The duct is observed to be nearly isothermal at 60°C. Determine the exit temperature of the air and the rate of heat loss from the duct to the attic space.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning