Steel balls 12 mm in diameter are annealed by heating to 1100 K and then slowly cooling to 390 K in an air environment for which ?T?= 325 K and h= 20 W/m2·K. Assuming the properties of the steel to be k= 40 W/m·K, ?= 7800 kg/m3, and c= 600 J/kg·K, estimate the time required for the cooling process.
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Steel balls 12 mm in diameter are annealed by heating to 1100 K
and then slowly...
QUESTION TWO Carbon steel balls (p 7833 kg/m3, k-54 W/m K, cp 0.465 kJ/kg.0C and a-1.474...
QUESTION TWO Carbon steel balls (p 7833 kg/m3, k-54 W/m K, cp 0.465 kJ/kg.0C and a-1.474 x 10-6 m2/s) 10 mm in diameter are annealed by heating them first to 900'C in a furnace and then allowing them to cool slowly to 100°C in ambient air at 35°C. If the average heat transfer coefficient is 75 W/m2 K, determine how long the annealing process will take. If 2500 balls are to be annealed per hour, determine the total rate of...
A long steel bar of radius R=2.5 cm, k =50 W/(m °C), p= 7800 kg/m), and...
A long steel bar of radius R=2.5 cm, k =50 W/(m °C), p= 7800 kg/m), and c = 0.5 kJ/(kg. . °C) is to be annealed by cooling slowly from 800.°C to 100.°C in an environment at temperature 50.°C. If the heat transfer coefficient between the environment and the surface of the bars is h = 45 W/(m .°C), determine the time required for the annealing process using lumped system analysis.
Metal bearings with diameter of 10 mm are initially at equilibrium at 400?C in a furnace....
Metal bearings with diameter of 10 mm are initially at equilibrium at 400?C in a furnace. At t = 0 the bearings are removed from the furnace and cooled slowly in air with h = 150 W/m2K and temperature of 20?C to control the mechanical properties of the metal. Calculate the time required for the center of the sphere to reach a temperature of 335?C. Thermophysical properties are ? = 3000 kg/m3 , k = 20 W/m·K, and c =...
4- A steel strip of thickness 6-12 mm is annealed by passing it through a large fumace whose wall...
4- A steel strip of thickness 6-12 mm is annealed by passing it through a large fumace whose walls are maintained at a temperature Tw corresponding to that of combustion gases flowing through the fumace (Iw Tp). The stip, whose density, spcific thermal conductivity, and emissivity are 79 kg/m3, cp -640 J/kg K, k 30 W/m K and 0.7, respectively, is to be heated from 300°C to 600°C Furnace walls, Combustion gases For a unifom convection coefficient of h-100 W/m2...
Steel is sequentially heated and cooled (annealed) to relieve stresses and to make it less brittle....
Steel is sequentially heated and cooled (annealed) to relieve stresses and to make it less brittle. Consider a 100-mm-thick plate (k = 45 W/m.K, p= 7800 kg/m3, cp = 500 J/kg.K) that is initially at a uniform temperature of 180°C and is heated (on both sides) in a gas-fired furnace for which T. = 700°C and h= 500 W/m2.K. How long will it take for a minimum temperature of 550°C to be reached in the plate? sec. It will take...
Problem 2. A long 6.5 cm diameter solid cylinder steel (K 16.3 W/m. K,p 7817 kg/m3,...
Problem 2. A long 6.5 cm diameter solid cylinder steel (K 16.3 W/m. K,p 7817 kg/m3, Cp 460 J/kg.k). It's initially at a uniform temperature of T 150°C. It is suddenly exposed to a convection environment with h-285 W/m2 K and Too 50°C. Calculate the temperature at 1.) the axis of the cylinder, and 2.) a 2.5 cm radial distance after 5 min of exposure to the cooling flow. (20%)
Q2 (a) A 12 mm diameter mild steel sphere (k = 42.5 W/m K) is exposed...
Q2 (a) A 12 mm diameter mild steel sphere (k = 42.5 W/m K) is exposed to cooling airflow at 27 "C resulting in the convective coefficient, h = 114 W/m' K. The relevant properties of mild steel are given as follows: Density p= 7850 kg/m . Specific heat c = 475 J/kg K and thermal diffusivity a = 0.043 m/hr Determine: (i) Time required to cool the sphere (lumped parameter system) from 540 °C to 95°C. [7 marks] (ii)...
Please help solve these parts. Thanks After leaving the furnace at temperature 900°C, steel balls of...
Please help solve these parts. Thanks
After leaving the furnace at temperature 900°C, steel balls of radius 1.5 cm are being placed in a moving belt of speed u=1 cm/s and cooled slowly in air (Too = 30°C, h = 100 W/m²K); these balls are then collected Furnace Air, 35°C after moving a distance of L = 4.5 m. Choose steel: ks = 900°C 50 = 0.465 kg.K Air: ka = 0.025 Pa = 1.2800 kg,ca = 0.718 k] The...
4. Hardening of ball bearings made from Type 440C stainless steel, one of the hardest stainless...
4. Hardening of ball bearings made from Type 440C stainless steel, one of the hardest stainless steels, is accomplished by heating the bearings to 1010 to 1065 °C then quenching (rapidly cooling) them in oil Consider bearings 24 mm in diameter at an initial uniform temperature of 1050 °C, cooled in an oil bath at 50 °C in which the convective heat transfer coefficient is 600 W/(m2 K). Properties of Type 440C Stainless Steel:t Density, 7800 kg/m3 Thermal conductivity, 24...
7. (20 pts) A sphere with 30 mm in diameter initially at 800 K is quenched...
7. (20 pts) A sphere with 30 mm in diameter initially at 800 K is quenched in a large bath having a constant temperature of 320 K with a convection heat transfer of 75 W/m2.K. The thermophysical properties of the sphere material are: p=400 kg/mº, c=1600 J/kg-K, and k=1.7 W/mK. (Use characteristic length Lc=VIA to determine applicability of lumped method; Use radius of the sphere for one term approximation) a) Calculate the time required for the surface of the sphere...
QUESTION TWO Carbon steel balls (p 7833 kg/m3, k-54 W/m K, cp 0.465 kJ/kg.0C and a-1.474 x 10-6 m2/s) 10 mm in diameter are annealed by heating them first to 900'C in a furnace and then allowing them to cool slowly to 100°C in ambient air at 35°C. If the average heat transfer coefficient is 75 W/m2 K, determine how long the annealing process will take. If 2500 balls are to be annealed per hour, determine the total rate of...
A long steel bar of radius R=2.5 cm, k =50 W/(m °C), p= 7800 kg/m), and c = 0.5 kJ/(kg. . °C) is to be annealed by cooling slowly from 800.°C to 100.°C in an environment at temperature 50.°C. If the heat transfer coefficient between the environment and the surface of the bars is h = 45 W/(m .°C), determine the time required for the annealing process using lumped system analysis.
4- A steel strip of thickness 6-12 mm is annealed by passing it through a large fumace whose walls are maintained at a temperature Tw corresponding to that of combustion gases flowing through the fumace (Iw Tp). The stip, whose density, spcific thermal conductivity, and emissivity are 79 kg/m3, cp -640 J/kg K, k 30 W/m K and 0.7, respectively, is to be heated from 300°C to 600°C Furnace walls, Combustion gases For a unifom convection coefficient of h-100 W/m2...
Steel is sequentially heated and cooled (annealed) to relieve stresses and to make it less brittle. Consider a 100-mm-thick plate (k = 45 W/m.K, p= 7800 kg/m3, cp = 500 J/kg.K) that is initially at a uniform temperature of 180°C and is heated (on both sides) in a gas-fired furnace for which T. = 700°C and h= 500 W/m2.K. How long will it take for a minimum temperature of 550°C to be reached in the plate? sec. It will take...
Problem 2. A long 6.5 cm diameter solid cylinder steel (K 16.3 W/m. K,p 7817 kg/m3, Cp 460 J/kg.k). It's initially at a uniform temperature of T 150°C. It is suddenly exposed to a convection environment with h-285 W/m2 K and Too 50°C. Calculate the temperature at 1.) the axis of the cylinder, and 2.) a 2.5 cm radial distance after 5 min of exposure to the cooling flow. (20%)
Q2 (a) A 12 mm diameter mild steel sphere (k = 42.5 W/m K) is exposed to cooling airflow at 27 "C resulting in the convective coefficient, h = 114 W/m' K. The relevant properties of mild steel are given as follows: Density p= 7850 kg/m . Specific heat c = 475 J/kg K and thermal diffusivity a = 0.043 m/hr Determine: (i) Time required to cool the sphere (lumped parameter system) from 540 °C to 95°C. [7 marks] (ii)...
Please help solve these parts. Thanks
After leaving the furnace at temperature 900°C, steel balls of radius 1.5 cm are being placed in a moving belt of speed u=1 cm/s and cooled slowly in air (Too = 30°C, h = 100 W/m²K); these balls are then collected Furnace Air, 35°C after moving a distance of L = 4.5 m. Choose steel: ks = 900°C 50 = 0.465 kg.K Air: ka = 0.025 Pa = 1.2800 kg,ca = 0.718 k] The...
4. Hardening of ball bearings made from Type 440C stainless steel, one of the hardest stainless steels, is accomplished by heating the bearings to 1010 to 1065 °C then quenching (rapidly cooling) them in oil Consider bearings 24 mm in diameter at an initial uniform temperature of 1050 °C, cooled in an oil bath at 50 °C in which the convective heat transfer coefficient is 600 W/(m2 K). Properties of Type 440C Stainless Steel:t Density, 7800 kg/m3 Thermal conductivity, 24...
7. (20 pts) A sphere with 30 mm in diameter initially at 800 K is quenched in a large bath having a constant temperature of 320 K with a convection heat transfer of 75 W/m2.K. The thermophysical properties of the sphere material are: p=400 kg/mº, c=1600 J/kg-K, and k=1.7 W/mK. (Use characteristic length Lc=VIA to determine applicability of lumped method; Use radius of the sphere for one term approximation) a) Calculate the time required for the surface of the sphere...
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