Homework Answers
Answer:
Gas temperature is 3000 C
Convective coefficient, h = 75 W/m2. K
Initial temperature is 250 C
Sphere diameter is 75 mm
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Gas at a temperature of 300°C with a convective coefficient h=75 W/m2 K flows through a...
Superheated steam flows steadily through steel tubing (k 35 W/m-K) applying a tube inner surface temperature...
Superheated steam flows steadily through steel tubing (k 35 W/m-K) applying a tube inner surface temperature of 575°C. The tubing has an inner diameter of 300 mm and a wall thickness of 30 mm. Insulation (k 0.10 W/m-K) is applied to the outer surface of the tube while thin aluminum sheet is applied around the insulation as a protective covering. The ambient air at 27°C provides a convection coefficient of 6 W/m2-K. Determine the minimum insulation thickness necessary (mm) to...
Thermal energy storage systems commonly involve a packed bed of solid spheres through which a hot...
Thermal energy storage systems commonly involve a packed bed of solid spheres through which a hot gas flows when the system is being charged. In the charging process heat is transferred from the hot gas to the spheres and it increases the thermal energy stored in the spheres. Here are some variables that are important - the convection coefficient between the particle surface and the gas is h (W/m2 K) and the particle thermophysical properties are k (W/m K), Cp...
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...
NE Steel tubes (k =35 W/m2.K) of 400-mm inner diameter and 30-mm wall thickness are used...
NE Steel tubes (k =35 W/m2.K) of 400-mm inner diameter and 30-mm wall thickness are used to route superheated steam from the boller to the turbine in a power plant. Safety and economic concerns make it practical to add a 200-mm layer of Insulation (k =0.1 W/mK) to each tube, which is wrapped in a thin sheet of aluminum with an emissivity e =0.15. The air (with a convective coefficient h =5 W/m2K) and wail temperatures of the plant are...
5.61 Spheres A and B are initially at 800 K, and they are simultaneously quenched in...
5.61 Spheres A and B are initially at 800 K, and they are simultaneously quenched in large constant temperature baths, each having a temperature of 320 K. The follow- ing parameters are associated with each of the spheres and their cooling processes. Sphere A Sphere B Diameter (mm) Density (kg/m) Specific heat (kJ/kg .K) Thermal conductivity (W/ m K ) Convection coefficient (W/m²K) 300 1600 0.400 170 5 30 400 1.60 1.70 50 (a) Show in a qualitative manner. on...
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...
a) Given the properties below, what is the average convective mass transfer coefficient of the second scenario? b) What is the Sherwood # of scenario 2? Gas X is at a temperature of 44°C is m...
a) Given the properties below, what is the average convective
mass transfer coefficient of the second scenario?
b) What is the Sherwood # of scenario 2?
Gas X is at a temperature of 44°C is moving in crossflow over an object with s characteristic length of L 0.1 m and surface temperature of 31°C. The system has a Re# of 104 and an average convective heat transfer coefficient of 25 w/m24. The same object is then dipped in liquid Y...
LT An aluminum rod of diameter D 2.5 cm and of length from a wall maintained at T, 300"C. The.coovective heat coefficient h 17 W/m2-K with an ambie.t air temperature T Thermal conductivity k =...
LT An aluminum rod of diameter D 2.5 cm and of length from a wall maintained at T, 300"C. The.coovective heat coefficient h 17 W/m2-K with an ambie.t air temperature T Thermal conductivity k = 204 WmK. Assume there is e luid by convection from the end of the rod, which is at temperature Ta. Using 2. -38c. nergy transfer to the a finite difference method, with Ax = 5 cm, the fo be derived for the solution of the...
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)...
Superheated steam flows steadily through steel tubing (k 35 W/m-K) applying a tube inner surface temperature of 575°C. The tubing has an inner diameter of 300 mm and a wall thickness of 30 mm. Insulation (k 0.10 W/m-K) is applied to the outer surface of the tube while thin aluminum sheet is applied around the insulation as a protective covering. The ambient air at 27°C provides a convection coefficient of 6 W/m2-K. Determine the minimum insulation thickness necessary (mm) to...
Thermal energy storage systems commonly involve a packed bed of solid spheres through which a hot gas flows when the system is being charged. In the charging process heat is transferred from the hot gas to the spheres and it increases the thermal energy stored in the spheres. Here are some variables that are important - the convection coefficient between the particle surface and the gas is h (W/m2 K) and the particle thermophysical properties are k (W/m K), Cp...
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...
NE Steel tubes (k =35 W/m2.K) of 400-mm inner diameter and 30-mm wall thickness are used to route superheated steam from the boller to the turbine in a power plant. Safety and economic concerns make it practical to add a 200-mm layer of Insulation (k =0.1 W/mK) to each tube, which is wrapped in a thin sheet of aluminum with an emissivity e =0.15. The air (with a convective coefficient h =5 W/m2K) and wail temperatures of the plant are...
5.61 Spheres A and B are initially at 800 K, and they are simultaneously quenched in large constant temperature baths, each having a temperature of 320 K. The follow- ing parameters are associated with each of the spheres and their cooling processes. Sphere A Sphere B Diameter (mm) Density (kg/m) Specific heat (kJ/kg .K) Thermal conductivity (W/ m K ) Convection coefficient (W/m²K) 300 1600 0.400 170 5 30 400 1.60 1.70 50 (a) Show in a qualitative manner. on...
a) Given the properties below, what is the average convective
mass transfer coefficient of the second scenario?
b) What is the Sherwood # of scenario 2?
Gas X is at a temperature of 44°C is moving in crossflow over an object with s characteristic length of L 0.1 m and surface temperature of 31°C. The system has a Re# of 104 and an average convective heat transfer coefficient of 25 w/m24. The same object is then dipped in liquid Y...
LT An aluminum rod of diameter D 2.5 cm and of length from a wall maintained at T, 300"C. The.coovective heat coefficient h 17 W/m2-K with an ambie.t air temperature T Thermal conductivity k = 204 WmK. Assume there is e luid by convection from the end of the rod, which is at temperature Ta. Using 2. -38c. nergy transfer to the a finite difference method, with Ax = 5 cm, the fo be derived for the solution of the...
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)...
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