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There is a small sphere with volume, V, surface area, As, and specific heat, c. The sphere was in...
Consider a solid body having mass m, volume V, density = 10000 kg/m3 , specific heat...
Consider a solid body having mass m, volume V, density = 10000 kg/m3 , specific heat capacity at constant pressure Cp = 600 J/(kg.K), and its initial temperature Ti = 200oC. Assume the system losses heat to the environment by convection at temperature T = 40oC and heat transfer coefficient h = 12 W/(m2 .K). (a) Start with applying the energy balance, and use the concept of the simplified lumped system analysis to derive an expression for the change of...
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...
Solve the differential equation analytically Suppose a thermocouple is to be used to measure the temperature of a hot gas flowing through a duct. The thermocouple junction is initially at ambient tem...
Solve the differential equation analytically
Suppose a thermocouple is to be used to measure the temperature of a hot gas flowing through a duct. The thermocouple junction is initially at ambient temperature Ti-25°C before it is inserted into the gas stream. Hot duct wall Tsur 400°C Gas stream Junction, Tt) 1,-25°C, D p 8500 kg/m3 T 200°C 0.7 mm 400 Jkg.K Approximating the thermocouple junction as a sphere and using the lumped capacitance model, an energy balance on the thermocouple...
Problem 3 A portable thermocouple is used to measure the air temperature inside of a sauna....
Problem 3 A portable thermocouple is used to measure the air temperature inside of a sauna. The sauna is unbearably hot and a person can only stay for 20 seconds, during which the temperature reading keeps on changing and a steady temperature is not reached. Leaving the thermocouple reader in the sauna for extended period of time has been deemed too risky for an electronics device Fortunately, a transient heat transfer model can be used to extract the temperature in...
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...
5. A flaked cereal is of thickness 2L=1.2 mm (or the characteristic length Lc = V/A=...
5. A flaked cereal is of thickness 2L=1.2 mm (or the characteristic length Lc = V/A= 0.6 mm). The density, specific heat, and thermal conductivity of the flake are p 700 kg/m3,cp = 2400J/kg K, and k = 0.34 W/m K, respectively. The product is to be baked by increasing its temperature from Ti = 20 °C to Tr = 220 °C in a convection oven, through which the product is carried on a conveyor. If the oven is Lo...
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.
1 = Consider a part with volume V = 5 x 10-6 m’, surface area A...
1 = Consider a part with volume V = 5 x 10-6 m’, surface area A = 1x10-3 m², mass density P 5000 kg m-3, heat capacity Cp 500 J kg-1 K-1. The part initially has a uniform temperature of Tp : 500 °C. It is suddenly immersed in a fluid at To 25 °C with a heat transfer coefficient of h 20 W m = = -2 K-1 = Based on a control volume that encompasses the part and...
(1) A sphere of decaying radioactive material of radius ro produces heat at a rate of q"" (W/m3)....
(1) A sphere of decaying radioactive material of radius ro produces heat at a rate of q"" (W/m3). The sphere is contained in a spherical shell of graphite of outside radius r1. The outside surface of the graphite is cooled uniformly by flowing air of temperature To. The heat transfer coefficient at the outside surface is h. The constant thermal conductivities of the radioactive material and the graphite are ko and ki, respectively. Densities and heat capacities are ρο, co...
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.
Solve the differential equation analytically
Suppose a thermocouple is to be used to measure the temperature of a hot gas flowing through a duct. The thermocouple junction is initially at ambient temperature Ti-25°C before it is inserted into the gas stream. Hot duct wall Tsur 400°C Gas stream Junction, Tt) 1,-25°C, D p 8500 kg/m3 T 200°C 0.7 mm 400 Jkg.K Approximating the thermocouple junction as a sphere and using the lumped capacitance model, an energy balance on the thermocouple...
Problem 3 A portable thermocouple is used to measure the air temperature inside of a sauna. The sauna is unbearably hot and a person can only stay for 20 seconds, during which the temperature reading keeps on changing and a steady temperature is not reached. Leaving the thermocouple reader in the sauna for extended period of time has been deemed too risky for an electronics device Fortunately, a transient heat transfer model can be used to extract the temperature in...
5. A flaked cereal is of thickness 2L=1.2 mm (or the characteristic length Lc = V/A= 0.6 mm). The density, specific heat, and thermal conductivity of the flake are p 700 kg/m3,cp = 2400J/kg K, and k = 0.34 W/m K, respectively. The product is to be baked by increasing its temperature from Ti = 20 °C to Tr = 220 °C in a convection oven, through which the product is carried on a conveyor. If the oven is Lo...
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.
1 = Consider a part with volume V = 5 x 10-6 m’, surface area A = 1x10-3 m², mass density P 5000 kg m-3, heat capacity Cp 500 J kg-1 K-1. The part initially has a uniform temperature of Tp : 500 °C. It is suddenly immersed in a fluid at To 25 °C with a heat transfer coefficient of h 20 W m = = -2 K-1 = Based on a control volume that encompasses the part and...
(1) A sphere of decaying radioactive material of radius ro produces heat at a rate of q"" (W/m3). The sphere is contained in a spherical shell of graphite of outside radius r1. The outside surface of the graphite is cooled uniformly by flowing air of temperature To. The heat transfer coefficient at the outside surface is h. The constant thermal conductivities of the radioactive material and the graphite are ko and ki, respectively. Densities and heat capacities are ρο, co...
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.
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