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Unformatted text preview: Click to edit Master subtitle style 8/13/11 Packed Beds and Internal Flow Chapter 7 Section 7.7,8 8/13/11 A pebble bed nuclear reactor is cylindrical of length 10 m and diameter 3 m. The chamber is filled with spherical uranium pellets of core diameter Dp = 50 mm. Each pellet generates thermal energy in its core and is coated with a layer of nongenerating graphite of uniform thickness 5 mm. Both the uranium oxide and graphite have a thermal conductivity of 2 W/mK. The porosity ε = 0.4. Pressurized helium at 40 bar is used to absorb the thermal energy from the pebbles. It enters the packed bed at Ti = 450o C with a velocity of 3.2 m/s. The properties of helium are c = 5193 J/kgK, k = 0.3355 W/mK, l = 2.1676 kg/m3, ’ = 4.214 X 105 kg/sm, and Pr = 0.654. If q(dot) is 125 MW, what is the mean outlet temperature of the helium leaving the bed and the amount of thermal energy generated by each pellet? 8/13/11 A pebble bed nuclear reactor is cylindrical of length 10 m and diameter 3 m. The chamber is filled with spherical uranium pellets of core diameter Dp = 50 mm. Each pellet generates thermal energy in its core and is coated with a layer of non generating graphite of uniform thickness 5 mm. Both the uranium oxide and graphite have a thermal conductivity of 2 W/ mK. The porosity ε = 0.4. Pressurized helium at 40 bar is used to absorb the thermal energy from the pebbles. It enters the packed bed at Ti = 450o C with a velocity of 3.2 m/s. The properties of helium are c = 5193 J/kgK, k = 0.3355 W/mK, & = 2.1676 kg/m3, & = 4.214 X 105 kg/sm, and Pr = 0.654. If q(dot) is 125 MW, what is the mean outlet temperature of the helium leaving the bed and the amount of thermal energy generated by each pellet? Plan: a) Find To using simplified steadyflow thermal energy equation b) Find number of pellets c) Find energy generated per pellet 8/13/11 A pebble bed nuclear reactor is cylindrical of length 10 m and diameter 3 m. The chamber is filled with spherical uranium pellets of core diameter Dp = 50 mm. Each pellet generates pellets of core diameter Dp = 50 mm....
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 Fall '10
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