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Heat Transfer Problem:
A sphere of pure aluminum weighing 6 kg and initially at a temperature...
3. A large, 5-cm thick plate of pure aluminum initially at a uniform temperature of 200°C...
3. A large, 5-cm thick plate of pure aluminum initially at a uniform temperature of 200°C is suddenly exposed to a convection environment in which the fluid temperature is 50°C and the heat- transfer coefficient is 1200 W/ m K. Calculate the temperature of the plate at a depth of 1.5 cm from one of the surfaces after 3 min. How much heat is lost from the plate during this time? Ans: Tplate = plane
4-79 White potatoes (k0.50 W/m-K and 0.13 X 10-6 m/s) that are initially at a uniform temperature of 25°C and have an a...
4-79 White potatoes (k0.50 W/m-K and 0.13 X 10-6 m/s) that are initially at a uniform temperature of 25°C and have an average diameter of 6 cm are to be cooled by refrigerated air at 2°C flowing at a velocity of 4 m/s. The average heat transfer coefficient between the potatoes and the air is experimentally determined to be 19 W/m2.K Determine how long t wl take for the center temperature of the potatoes to drop to 6°C. Also, determine...
The heat transfer coefficient for hydrogen flowing over a sphere is to be determined by observing...
The heat transfer coefficient for hydrogen flowing over a sphere is to be determined by observing the temperature–time history of a sphere fabricated from pure copper. The sphere, which is 20.0 mm in diameter, is at 70°C before it is inserted into the gas stream having a temperature of 27°C. A thermocouple on the outer surface of the sphere indicates 50°C 97 s after the sphere is inserted into the hydrogen. Find a) What is the value of the specific...
The heat transfer coefficient for hydrogen flowing over a sphere is to be determined by observing...
The heat transfer coefficient for hydrogen flowing over a sphere is to be determined by observing the temperature–time history of a sphere fabricated from pure copper. The sphere, which is 20.0 mm in diameter, is at 90°C before it is inserted into the gas stream having a temperature of 27°C. A thermocouple on the outer surface of the sphere indicates 40°C 97 s after the sphere is inserted into the hydrogen. Step 1 What is the value of the specific...
B4: The steel sphere from the unsteady heat transfer experiment is initially at 20 °C. The...
B4: The steel sphere from the unsteady heat transfer experiment is initially at 20 °C. The sphere is placed in a water bath at 80 °C. After one minute the centerline temperature is 70 °C. Estimate the Biot number for this sphere and determine the convection coefficient, h.
Problem 2: A hot metal ball 0.00245 W/m°C; α-0151* 10-s m2/s; d 18 cm) initially at...
Problem 2: A hot metal ball 0.00245 W/m°C; α-0151* 10-s m2/s; d 18 cm) initially at a unifom temperature of 310°C is cooled by placing it in air at 29 C is flowing at a constant 4 m/s. In order to continue on in the manufacturing process, the temperature at the center of the ball must be 70°C. (μ. = 1.872*10-5 kg m-s). The air You mav assume that the properties of air may bem odeled as V = 1.608...
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...
Problem #2: The surface temperature of a sphere with volume of mR", density of 8000 kg...
Problem #2: The surface temperature of a sphere with volume of mR", density of 8000 kg mº, specific heat of 450 J/kgK and mass of 20 kg is initially at 350 °C. The sphere's surface temperature eventually drops to 200 °C due to air flowing over it with a velocity of 3 m/s. Determine: a. average heat transfer coefficient b. how long it will take for this cooling process.
Cold conditioned air at 10°C is flowing inside a 1.5 cm thick square aluminum (k = 240 w/mK) duct...
Cold conditioned air at 10°C is flowing inside a 1.5 cm thick square aluminum (k = 240 w/mK) duct of inner cross section of 25x25cm at a mass flow rate of 1.0 kg/s. The duct is exposed to air at 35°C with a combined convection-radiation heat transfer coefficient of 15 W/m2K. The convection heat transfer coefficient at the inner surface is 75 W/.m2.K. If the air temperature in the duct should not increase by more than 1°C determine the maximum...
3. A large, 5-cm thick plate of pure aluminum initially at a uniform temperature of 200°C is suddenly exposed to a convection environment in which the fluid temperature is 50°C and the heat- transfer coefficient is 1200 W/ m K. Calculate the temperature of the plate at a depth of 1.5 cm from one of the surfaces after 3 min. How much heat is lost from the plate during this time? Ans: Tplate = plane
4-79 White potatoes (k0.50 W/m-K and 0.13 X 10-6 m/s) that are initially at a uniform temperature of 25°C and have an average diameter of 6 cm are to be cooled by refrigerated air at 2°C flowing at a velocity of 4 m/s. The average heat transfer coefficient between the potatoes and the air is experimentally determined to be 19 W/m2.K Determine how long t wl take for the center temperature of the potatoes to drop to 6°C. Also, determine...
B4: The steel sphere from the unsteady heat transfer experiment is initially at 20 °C. The sphere is placed in a water bath at 80 °C. After one minute the centerline temperature is 70 °C. Estimate the Biot number for this sphere and determine the convection coefficient, h.
Problem 2: A hot metal ball 0.00245 W/m°C; α-0151* 10-s m2/s; d 18 cm) initially at a unifom temperature of 310°C is cooled by placing it in air at 29 C is flowing at a constant 4 m/s. In order to continue on in the manufacturing process, the temperature at the center of the ball must be 70°C. (μ. = 1.872*10-5 kg m-s). The air You mav assume that the properties of air may bem odeled as V = 1.608...
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...
Problem #2: The surface temperature of a sphere with volume of mR", density of 8000 kg mº, specific heat of 450 J/kgK and mass of 20 kg is initially at 350 °C. The sphere's surface temperature eventually drops to 200 °C due to air flowing over it with a velocity of 3 m/s. Determine: a. average heat transfer coefficient b. how long it will take for this cooling process.
Cold conditioned air at 10°C is flowing inside a 1.5 cm thick square aluminum (k = 240 w/mK) duct of inner cross section of 25x25cm at a mass flow rate of 1.0 kg/s. The duct is exposed to air at 35°C with a combined convection-radiation heat transfer coefficient of 15 W/m2K. The convection heat transfer coefficient at the inner surface is 75 W/.m2.K. If the air temperature in the duct should not increase by more than 1°C determine the maximum...
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