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Heat and Mass Transfer: Fundamentals and Applications
- In a ball bearing production facility, steel balls (k=50 W/m.K, c=0.460 kJ/kg.K, ρ=7865 kg/m3) that are each of 13,99 mm in diameter are annealed by first heating them to 870 oC and then slowly cooling in air to 125 oC. If the cooling air stream temperature is 60 oC, and it has a convective heat transfer coefficient of 35 W/m2.K), determine the time [s] required for the cooling.arrow_forwardA refrigeration plant stored 10 metric tons of eggs at a temperature of 15°C. To preserve the eggs by not spoiling them, they have to be cooled at -8°C. What is the refrigerating capacity of the plant in TOR if it is cooled for 12 hours? The specific heat of the eggs above and below freezing are 0.95 kcal/kg-°C and 0.4 kcal/kg-°C, respectively. The latent heat of fusion is 68.5 kcal/kg The freezing temperature is -3°C.arrow_forwardPlasma spraying is a process used to coat the surface of a material with a protective layer to prevent material degradation. In a plasma spray process, the protective coating in powder form is injected into a plasma jet. The powder is then heated until the droplets coalesce and are propelled over the surface of the material. Once deposited on the surface of the material, the molten droplets solidify and form a protective coating layer. Consider a plasma spray process using alumina (k = 30 W/m K, ρ = 3970 kg/m³ and cp = 800 J/kg K) powder that is injected into a plasma jet at T∞ = 15,000 ° C and h = 10,000 W/m²·K. Alumina powder is made up of spherically shaped particles with a mean diameter of 60 μm and a melting point of 2300 °C. Determine the amount of time it would take for the particles, with an initial temperature of 20 °C, to reach their melting point from the time they are injected into the plasma jet. Note: Give the solution from fundamental concepts of how the heat flow…arrow_forward
- Plasma spraying is a process used to coat the surface of a material with a protective layer to prevent material degradation. In a plasma spray process, the protective coating in powder form is injected into a plasma jet. The powder is then heated until the droplets coalesce and are propelled over the surface of the material. Once deposited on the surface of the material, the molten droplets solidify and form a protective coating layer. Consider a plasma spray process using alumina (k = 30 W/m K, ρ = 3970 kg/m³ and cp = 800 J/kg K) powder that is injected into a plasma jet at T∞ = 15,000 ° C and h = 10,000 W/m²·K. Alumina powder is made up of spherical-shaped particles with a mean diameter of 60 μm and a melting point of 2300 °C.Solving, the amount of time it would take for the particles, with an initial temperature of 20 °C, to reach their melting point from the time they are injected into the plasma jet is 5,25x10 -4 s. Explain how the heat flow behaves in the system, using the…arrow_forwardPlasma spraying is a process used to coat the surface of a material with a protective layer to prevent material degradation. In a plasma spray process, the protective coating in powder form is injected into a plasma jet. The powder is then heated until the droplets coalesce and are propelled over the surface of the material. Once deposited on the surface of the material, the molten droplets solidify and form a protective coating layer. Consider a plasma spray process using alumina (k = 30 W/m K, ρ = 3970 kg/m³ and cp = 800 J/kg K) powder that is injected into a plasma jet at T∞ = 15,000 ° C and h = 10,000 W/m²·K. Alumina powder is made up of spherical-shaped particles with a mean diameter of 60 μm and a melting point of 2300 °C.Solving, the amount of time it would take for the particles, with an initial temperature of 20 °C, to reach their melting point from the time they are injected into the plasma jet is 5,25x10 -4 s. Give a solution from fundamental concepts of how the heat flow…arrow_forwardQuestion -) Consider a stainless steel spoon (k = 15 W/m·K) partially immersed in boiling water at 95°C in a kitchen at 25°C. The handle of the spoon has a cross section of 0.2cm x 1.2 cm, and extends 18 cm in the air from the free surface of the water. If the heat transfer coefficient at the exposed surfaces of the spoon handle is 15 W/m2·°C, determine the temperature difference across the exposed surface of the spoon handle. State your assumptions.arrow_forward
- Example 9: A 2-kW resistance heater wire whose thermal conductivity is k = 15 W/m ·°C has a diameter of D = 4 mm and a length of L = 0.5 m, and is used to boil water. If the outer surface temperature of the resistance wire is Ts = 105°C, determine the temperature at the center of the wire.arrow_forwardConsider a stainless steel spoon (k = 15 W/m·K) partially immersed in boiling water at 95°C in a kitchen at 25°C. The handle of the spoon has a cross section of 0.2cm x 1.2 cm, and extends 18 cm in the air from the free surface of the water. If the heat transfer coefficient at the exposed surfaces of the spoon handle is 15 W/m2·°C, determine the temperature difference across the exposed surface of the spoon handle. State your assumptions.arrow_forwardConsider the process of baking potatoes in a conventional oven. Can the hot air in the oven be treated as a thermal energy reservoir? Explain.arrow_forward
- In a manufacturing facility, 2-in-diameter brassballs (k = 64.1 Btu/h·ft·°F, r = 532 lbm/ft3, and cp =0.092 Btu/lbm·°F) initially at 250°F are quenched in a waterbath at 120°F for a period of 2 min at a rate of 120 ballsper minute. If the convection heat transfer coefficient is42 Btu/h·ft2·°F, determine (a) the temperature of the balls afterquenching and (b) the rate at which heat needs to be removedfrom the water in order to keep its temperature constant at120°F.arrow_forwardSteam in the condenser of a steam power plant is to be condensed at a temperature 500C (hfg = 2383 kJ/ kg) with cooling water (Cp = 4180 J/kg) from a nearby lake, which enters the condenser at 180C and leaves at 270C. The surface area of the tubes is 42 m2 and the overall heat transfer coefficient is 2400 W/ m2 .0C. Determine: (i) The mass flow rate of cooling water needed (ii) The rate of condensation of steam in the condenser.arrow_forwardThe condenser of a steam power plant operates at a pressure of 0.95 psia. The condenser consists of 144 horizontal tubes arranged in a 12 * 12 square array. Steam condenses on the outer surfaces of the tubes whose inner and outer diameters are 1 in and 1.2 in, respectively. If steam is to be condensed at a rate of 6800 lbm/h and the temperature rise of the cooling water is limited to 8°F, determine (a) the rate of heat transfer from the steam to the cooling water and (b) the average velocity of the cooling water through the tubes.arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning